Indesit Company UK Limited© 2006 Reg. Office: Peterborough PE2 9JB Registered in London: 106725

ServiceInformation

GENERALREFRIGERATIONFUNDAMENTALS

FORREFERENCE

&TRAINING

5403820 Issue 2 Jan. 2006

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Health & Safety Information Applicable to Servicing RefrigerationContaining R12 & R134a

General1. This manual is not intended as a comprehensive repair/maintenance guide to the appliance.

2. It should only be used by suitably qualified persons having technical competence, applicable product knowledge, suitable tools and test equipment.

3. Servicing of electrical appliances must be undertaken with the appliance disconnected. (unplugged from the electrical supply).

4. Servicing must be preceded by earth continuity and insulation checks.

5. Personal safety precautions must be taken to protect against accidents caused by sharp edges on metal and plastic parts.

6. After servicing, the appliance must be rechecked for electrical safety.

Refrigerants R12 and R134a - Safe Handling - Transporting & Storage1. Work areas should be well ventilated and any immediate heat sources turned off.

2. Do not smoke where there is a possibility of refrigerant in the atmosphere. Customer/s should also be advised.

3. Cylinders must not have heat applied, or stand close to a heat source, and should be stored out of direct sunlight.

4. Should a sudden release of refrigerant occur, open windows or outside doors in the immediate vicinity, then evacuate for a few minutes.

5. It is illegal to intentionally vent refrigerant to atmosphere. Follow the Company procedure on collection and reclamation.

6. If a leak is identified, the appliance must be repaired immediately if possible.

7. Where it is not possible to repair an appliance immediately, the customer should be advised.The appliance should be turned off and the refrigerant recovered.

8. Returned compressors must be sealed to prevent the escape of oil and refrigerant. Refer to the Environmental responsibilities for service engineers in your Health and Safety booklet.

9. Cylinders (R134a) being transported must be in an upright position on the floor of the vehicle and prevented from movement.

10. A Green compressed gas label Part No. 8100062 should be displayed on the rear of the vehicle.

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Health & Safety Information applicable to Servicing Refrigeration Products containing Isobutane Refrigerant R600a

General

The following Health & Safety instructions are an addition to other Company Health Safety Procedures already published:-

1. Only engineers who have been trained on the safe handling of Isobutane R600a refrigerant are authorised to transport, store or carry out system repairs.

2. This manual is not intended as a comprehensive repair/maintenance guide to the appliance.

3. It should only be used by suitably qualified persons having technical competence, applicable product knowledge, suitable tools and test equipment.

4. Servicing of electrical appliances must be undertaken with the appliance disconnected. (unplugged from the electrical supply).

5. Servicing must be preceded by earth continuity and insulation checks, plus refrigerant leak detection.

6. Personal safety precautions must be taken to protect against accidents caused by sharp edges on metal and plastic parts.

7. After servicing, the appliance must be rechecked for electrical safety.

8. Smoking, naked flames, or operating gas and/or electrical equipment (including cordless power tools) are forbidden within the storage area, working area and vehicles used to transport Isobutane.

9. The carrying case for the scales and refrigerant must display a red flammability label Part Number 8100063 which should be visible and readable at all times.

10. The vehicle and storage area must be ventilated as far as is reasonably practicable and the aluminium case kept out of direct sunlight. The storage temperature of Isobutane should not exceed 50ºC.

11. The vehicle transporting Isobutane (R600a) refrigerant must display a Red Flammable Gas warning sticker (Part Number 8100063).

12. Engineers should not wear clothes that are liable to cause static discharge ("electrostatic sparking").

13. Avoid working in small rooms.

14. Do not work in cellars.

15. Whenever possible move the appliance into a larger open area away from possible ignition sources.

16. Request the customer to turn off all other electrical and gas appliances in the near vicinity of the repair and note that it is done. Customers should be advised to restrict activity within the near vicinity for a short time.

17. Isobutane refrigerant must be vented to atmosphere, (outside of the premises e.g. via open window through the clear plastic hose supplied).

Continued....

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Health & Safety Information applicable to Servicing Refrigeration Products containing Isobutane Refrigerant R600a

18. Isobutane is heavier than air and must not be vented within 3 metres of the following: sewer cover, cellar, drain or any similar construction lower than ground level, boiler air inlet/outlet, or near any possible source of ignition.

19. Working with a naked flame i.e. soldering or brazing is forbidden. Unless otherwise stated, pipework connections must only be made using the Lokring coupling system.

20. Electronic leak detectors with high voltage tips must NOT be used with any Isobutane (R600a).

21. All equipment used for this activity must be checked regularly and maintained in a safe working condition; parts must be replaced as required.

Information regarding Isobutane Canisters

1. The maximum quantity of Isobutane an engineer should hold or store at any one time is two 420 gramme aluminium canisters, supplied individually as Part Number 2602600.

2. Canisters must be stored inside the aluminium case with the weighing scales for protection from possible damage and heat. The aluminium case must NEVER be placed next to a heat source or in direct sunlight.

3. Isobutane must only be dispensed to the appliance from the 420 gramme aluminium canister placed in an upright position on the weighing scales provided.

4. A blue returns label RS 5647 must then be attached and the individual canister/s left out for the driver to collect and return for disposal.

5. Canisters must not be punctured or the internal valve damaged.

6. Before storing the canister it must have the extraction tap valve removed and the internal valve of the canister checked for leakage using leak detector. (Leak Detector Part Number 5700043).

7. All used canisters and those found to be leaking should be exhausted to atmosphere to ensure they are completely empty in the following manner: Refit the extraction tap if necessary, open the tap and then invert the canister. This must be done outside in open air away from buildings and ignition sources and complying with Item 18 above.

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INDEX

SECTION HEADINGS & INDICATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page No

Introduction and Customer Satisfaction - A guide to good practice. . . . . . . . . . . . . . . . . . . . .6

Refrigeration an Explanation - A basic understanding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

The Domestic Refrigerator - A brief history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

10 Point Preliminary Examination For Poor Performance - Essential guide. . . . . . . . . . . . . .9

The Importance of Cold Storage & Star Ratings - Fundamental . . . . . . . . . . . . . . . . . . . . . .10

Food Storage Temperatures & Temperature Measurements - For accurate diagnosis . . . .11

Temperature Controls (Thermostats) - What type - What they do - How they work . . . . 12 - 13

Heaters in Refrigeration - Where they are used and why . . . . . . . . . . . . . . . . . . . . . . . . 14 - 15

Compressors and Their Controls - What they do - How they work . . . . . . . . . . . . . . . . . 16 - 17

System Components - What type - What they do - How they work . . . . . . . . . . . . . . . . . 18 - 20

System Observations - Undercharged? Overcharged? . . . . . . . . . . . . . . . . . . . . . . . . . . 21 - 22

Ambient Temperatures - How do you know what is acceptable? . . . . . . . . . . . . . . . . . . . 23 - 24

Customer Use and Door Sealing - Some do’s, dont’s and indicators . . . . . . . . . . . . . . . . . . .25

Unusual Heat Loads and Appliance Sounds (Noise) - What is acceptable? . . . . . . . . . . . . .26

Frost Accumulation and Condensation (Internal & External) - What causes it? . . . . . . . . .27

Airflow (Circulation Internal & External) - Essential but often overlooked . . . . . . . . . . . . . . .28

Appliance Location & Miscellaneous Issues - Installing it! Moving it! Leaving it . . . . . . . . . .29

Refrigerants and Environmental Issues - Chemicals their use and effect . . . . . . . . . . . 30 - 31

Diagnostic Checklist - A guide to some common faults and possible causes . . . . . . . . . 32 - 34

Temperature Conversion Chart - Essential information on this chart . . . . . . . . . . . . . . . . . . .35

NOTE

Many of the issues are interrelated, it may therefore be necessary to refer to more than one section to qualify understanding.

INTRODUCTIONThe information contained in this publication has been compiled for reference to enable engineers to clarify understanding and for use as a training aid.

Much of the information is general and can be related to all model types, but there are also sections included where the information is more specific, especially where the fault is unusual or is associated with a particular model type.

The sections include information on component function and operation, temperature control and measurement, cold storage, star rating, food storage temperatures, ambient temperatures, condensation, and frost accumulation, environmental issues, appliance installation and much more.

System repairs are not covered but a detailed section with illustrations to aid diagnosis is included, under system observations.

A diagnostic check list can be found on the last few pages and a temperature conversion chart on page 36.

To find the required section quickly or just view the options, refer to the index on page 5.

A 10 point preliminary examination check list is also included overleaf for use whenever the complaint is related to the performance of the appliance. The check list is in a logical order for many situations. Following the checks in order should ensure that most conditions are considered and therefore, not overlooked.

CUSTOMER SATISFACTION Success in satisfying the customer should begin with paying close attention to the customer’s complaint. Asking questions to find out exactly why the customer has requested a service call.

Once established, write the customer’s complaint on the invoice (or a note pad) and keep it in mind until the call is completed. It could be that the product is not actually at fault, but rather, the customer does not understand how to use the product or how it should perform.

Accordingly, many complaints require only an explanation or reassurance that the product is operating properly.

Customer satisfaction is dependent on many things but correct diagnosis and repair are essential prerequisites. Paying close attention to the customer’s complaint, questioning and evaluating the information helps to introduce you.

When conducted properly, it will confirm to the customer that you are responsive to their concerns, and appear knowledgeable about their particular product.

Plunging in with a screwdriver immediately on entering the home does not demonstrate efficiency or effectiveness, only that you are in a hurry.

INTRODUCTION AND CUSTOMER SATISFACTION

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REFRIGERATION AN EXPLANATIONRefrigeration can be described in the most basic terms as the removal of heat from an object in order to lower its temperature. In order to relate this to a refrigeration system, the following principles must be appreciated.

1. Heat flows from an area of high temperature to an area of low temperature. Hence a warm or hot object can be cooled simply by placing it in contact with a colder object.

2. The temperature at which a liquid boils depends on the pressure - the lower the pressure, the lower the boiling point.The refrigerant R134a used in many domestic refrigerators and freezers has a boiling point of -26.5 C at Atmospheric Pressure.

3. When a liquid boils it absorbs heat from its surroundings.

4. When the heat absorbed by an evaporating or boiling liquid is removed from the resulting vapour, the vapour condenses back into a liquid (Vis:- Refrigerant gas may be returned to its liquid form after the cooling cycle merely by extracting the heat from it).

5. The temperature at which a saturated vapour condenses to a liquid depends on the pressure. By increasing the pressure of the vapour or gas. The temperature can be raised to a level higher than that of its surroundings, at which point its heat will flow into the cooler environment. As the heat leaves the vapour, the vapour condenses back to a liquid at the higher pressure.

TEMPERATURE CONTROLIf a system is simply allowed to run uncontrolled, the temperature inside the cabinet will fall until it reaches a level at which, for various reasons, no more heat can be extracted from the cabinet.

Various aesthetic symbols can be screened around the control knob to aid the customer in selecting the correct position. These maybe numbers where the higher number signifies a colder setting (see note below) or the more precise indicators such as warm, cold etc.

NOTE :-Mistral fridge-freezers use a numbered system, which actually represents the Fridge temperature. ( Select 4 = 4 C )

Satisfactory temperatures should generally be expected when the controls that are adjustable by the customer, are positioned at a setting close to halfway. (eg 3 or 4)

Controls positioned at extreme settings (high or low) usually indicate the customer is attempting to achieve colder or warmer temperatures. This maybe because of climatic change’s but could also be that the appliance was not functioning as expected and the thermostat setting was changed to compensate. (ie: warm/frozen milk, ice cream soft/rock solid)

Internal temperatures can be affected by such factors as the appliance location, ambient temperature, inadequate airflow over the compressor and condenser, frequency and or time the doors are open. Where possible controls should be adjusted to compensate.

Whilst this temperature maybe acceptable for a freezer, frozen milk, eggs and butter are very little use to the housewife. This apart, if the compressor is running continuously, it will become exceptionally hot and may eventually start to cycle on the thermal overload. The temperature is therefore controlled at an acceptable level by means of a thermostat.

REFRIGERATION - AN EXPLANATION

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THE DOMESTIC REFRIGERATORThe domestic refrigerator first appeared around 1850. It was a slate lined, insulated wooden cabinet cooled by blocks of ice, which were cut and stored in the winter period.

In 1923 the electric refrigerator was pioneered by two Swedish engineers who sold the patents to a company in the United States, where production started in 1925.

Poisonous refrigerants such as ammonia and sulphuric acid were commonly used in domestic models during the 1930’s, when safer alternatives began to be developed. (Ammomia is still widely used in commercial cold store installations.)

The first of this group of refrigerants was (R12) Dichlorodifluoromethane, a CFC Chlorofluorocarbon refined from petroleum and coal tar.

It was used in the production of refrigerators until its manufacture was prohibited, as from January 1st 1995, because of its negative effects on the ozone layer and its global warming potential.

The replacement refrigerant is R134a, which is a Hydrofluorocarbon (HFC), it is the principal

refrigerant used in domestic products at thepresent time.

However, many European manufacturers havenow adopted R600a Isobutane as the replacement.Isobutane is a Volatile Organic Compound(Hydrogen HC), it is flammable and combustiblegiven certain conditions.

Manufacturers currently using it regard the risk as infinitesimal due to the minute quantities involved. The real advantage is that it is far more environmentally friendly.

10 POINT PRELIMINARY EXAMINATION

On every call, where the customer complains of "poor performance" a 10 point preliminary examination of the appliance and its surroundings should be made.

Its purpose is to ensure as far as possible that consideration is given to each of the 10 points, covering the most common causes for poor performance.

When the cause of "poor performance" is discovered, an appropriate repair or adjustment should be made. Unless, the need for customer education is required, due too improper use or installation deficiencies.

The first mechanical domestic refrigerator was developed in 1879, and was a modified variant of an industrial model designed six years earlier. Cooling was achieved through the compression and evaporation of ammonia using a steam pump.

THE DOMESTIC REFRIGERATOR

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1. AMBIENT TEMPERATURE Is the room temperature occasionally or perpetually too warm or too cool for the appliance operating temperature class?

2. CUSTOMER USE - Is the usage non-domestic, excessive, heavy or light?Is the freezer compartment mostly full or lightly loaded?

3. FOOD TEMPERATURESAre the temperatures in the various compartments within the limits?

4. TEMPERATURE CONTROL SETTINGSAre the controls set correctly to achieve not just desired, but food safe temperatures? Have the controls been moved, intentionally or inadvertently?

5. COMPRESSOR Is it operating? Is the sound level normal? Is the condenser touch temperature as expected?

6. DOOR SEALINGIs it sealing adequately? Is the seal damaged? Has the door dropped or is it misaligned?

7. UNUSUAL HEAT LOADDo the interior light/s remain on when the doors are closed? Is the icemaker stalled? Is the ambient temperature exceptionally high?

8. FROST ACCUMULATIONDoes the evaporator have an excessive frost accumulation?Is there an automatic defrost system, and if so, is it operating properly?

9. INTERNAL AIRFLOWIs the food load inhibiting airflow? Is the fan operating? Is the evaporator clogged with ice? Is the ducting obstructed?

10. EXTERNAL AIRFLOW Condenser, Front Grille, Rear Cover - Are they clogged with fluff and dust? Is the condenser fan operating?Are clearances around the appliance, or cupboard venting sufficient for air circulation? Is the rear access cover in place? (Foodcentres - Are the cardboard air baffles missing?)

PRELIMINARY CONCLUSION Where the cause for the complaint is debatable, temperature measurements of food stored in the fridge and freezer compartments will provide the most reliable guidance. If the food temperatures are normal in the various compartments, the refrigeration system is performing normally.Where the cause of "poor performance" is not discovered following the 10 point examination, a failure within the refrigeration system should be suspected.Where diagnosis is inconclusive, because the appliance is now working properly, the customer should be advised of any possible intermittent or obscure conditions that may produce a similar occurrence.

For more detailed information on each of the 10 points refer to the individual pages or the index to find information on related topics.

Refer to the sections: Ambient Temperature and Appliance Location, pages 23 & 24and 29.

Refer to the section: Customer Use, on page 25.

Refer to the sections: The Importance of Cold Storage, Star Ratings, Temperature Measurements and Food Storage Temperatures and the Temperature Conversion Chart on pages 10, 11 & 35.

Refer to the section: Temperature Controls, on pages 12 & 13.

Refer to the sections: Compressors and Their Controls and System Observations, on pages 16, 17, 21 & 22.

Refer to the sections: Door Sealing & Frost Accumulation and Condensation, on pages 25 & 27.

Refer to the sections: Unusual Heat Load & Ambient Temperature, on pages 26, 23 & 24.

Refer to the section: Frost Accumulation and Condensation, on page 27.

Refer to the section: Airflow, on page 28.

Refer to the sections: Airflow & Appliance Location, on pages 28 & 29.

10 POINT PRELIMINARY EXAMINATION

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THE IMPORTANCE OF COLD STORAGE Fresh food stored at normal room temperatures will very quickly decay or "go off". This becomes evident as mould or furry growths on food, unpleasant odours from raw meat or curdling of milk.

These various forms of decay are caused by the growth of bacteria. Bacteria are microscopic organisms present in all foodstuffs and, given ideal conditions (warmth and nourishment) they will multiply prolifically. Reducing the temperature will slow the bacteria down to a point where the rate of reproduction is such that it will take a considerable time before decay sets in.

CABINET TEMPERATURES Refrigerators and freezers are designed to comply with British and European StandardsSeparate directives are allied to this standard, and cover other issues such as the minimum and maximum allowable temperatures.

For example. In a 16 C ambient a refrigerator cabinet temperature should not be less than 1 C.Conversely, if the ambient temperature rises to 32 C, the temperature within the cabinet must not exceed 8 C.

These temperatures therefore become the upper and lower limits, but temperatures recorded within this range will vary according to ambient temperature, cabinet loading and thermostat setting. These factors must be taken into consideration when advising on cabinet temperatures.

With a few exceptions it is normally sufficient to simply adjust the thermostat to either a warmer or cooler setting to obtain satisfactory cabinet temperatures.

STAR RATINGS Refrigerators and freezers are rated with regard to their capacity to store or freeze food.

The temperatures for the freezer compartment relating to these star ratings are as follows:

One Star * - Will maintain a temperature of -6 C (21 F). Frozen food can be stored for up to 1 week and ice cream should only be stored for 1 day.

Two Star ** - Will maintain a temperature of -12 C (10 F). Frozen food can be stored for up to 4 weeks and ice cream for 1 week.

Three Star *** - Will maintain a temperature of -18 C (0 F). Frozen food can be stored for up to 3 months and ice cream for up to 1 month.

Four Stars * *** - Three small stars and one large star denote that the appliance has the capacity to freeze a specified quantity of fresh food from +25 C to -18 C in 24 hours without affecting the frozen food already being stored.

The temperature ranges shown in the fridge-freezer illustration below are the normal recommended temperatures for safe food keeping.

The upper temperature limit for safe storage of most food is 8.3 C and domestic refrigerators are designed to maintain a cabinet temperature within the range 7.8 C to 1 C. To store food for longer periods it is necessary to freeze it at temperatures below -18 C at which level the bacteria become completely dormant.

Before this point is reached the food will probably have become inedible due to some other reason - meat or cheese will become hard, vegetables will become soft etc.

These temperatures apply to all domestic fridges and freezers. Refer to the Temperature Conversion Chart inside the back cover.

THE IMPORTANCE OF COLD STORAGE - PLUS STAR RATINGS

Refrigerator

Salad Bins

Chiller

Fast FreezeSection

Freezer

4 to 5 C

0 C to 3 C

-18 C to 23 C

5 to 6 C

10

FOOD STORAGE TEMPERATURES The primary function of a refrigerator or freezer to preserve perishable foods. However, refrigeration does not preserve food indefinitely. Holding food at a low temperature merely reduces the rate at which deterioration takes place.

Ideal Food Temperatures. The ideal food storage temperature will vary, depending upon the nature of the food. Some examples are:

Milk 1 C. Milk will freeze if chilled below 0.5 C.When milk is permitted to reach room temperature, or is contaminated with certain types of bacteria, spoilage may occur quickly even when held at temperatures near 0 C.

Lemons 14 C. Lemons stored at low temperatures develop an undesirable colour. Temperatures above 16 C shorten the storage life.

Fresh Meat 0 C. Fresh meat should be stored at temperatures as near 0 C as is possible without freezing the meat. Bacteria growth in fresh meat, indicated by discolora tion, is more rapid when stored at warmer temperatures.

Lettuce 0 C. Lettuce will freeze if chilled below 0 C but will retain good quality for considerably longer periods at 0 C than at 3.3 C Furthermore, lettuce should not be stored with apples, pears, melons, or other products that give off ethylene gas, thereby causing russet (reddish/brown) spotting.

Ice Cream -15 C. The composition of ice cream varies from one brand to another and from one flavour to another depending upon the butter fat content, sugar content, and other ingredients. However, at -18 C most ice cream is considered hard.

The ideal serving temperature is -15 C to -12 C.At about -11 C the flavour of ice cream will be appreciated more, than at lower temperatures.

Frozen Meat -23 C. A temperature of -18 C or lower is desirable to retain the original taste and flavour of frozen meats. The storage life of all meat products is greatly extended when held at -23 C.

TEMPERATURE MEASUREMENTS Temperature readings should never be taken in free air. Air temperature fluctuates considerably with the on and off cycles and each time the door is opened.

Refrigerator temperature measurements are best taken using a cup of water placed on the centre shelf overnight. Where this is not possible a minimum of 3 hours will be required prior to checking. This should be initiated at the time the customer requests the service call. The customer should also be advised to limit door opening at least 3 hours prior to the engineers’ visit.

Accurate freezer temperature measurements can be achieved by placing the thermometer or digital probe in close contact with the frozen food.

Evaporator plate temperature should be measured by clamping the digital thermometer probe under the thermostat phial clamp, and the results compared to information in the relevant service manual.

It is not possible to diagnose performance faults properly without taking accurate temperature measurements. Where a fridge-freezer performance is questionable, the temperature should always be taken in both compartments.

FOOD STORAGE TEMPERATURES & TEMPERATURE MEASUREMENTS

ThermometerTypes

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THERMISTOR - A thermistor is a resistor in which the resistance changes with temperature. There are two types: - NTC’s & PTC’s.

NTC’s have a Negative Temperature Coefficient. Resistance decreases as the temperature increases, designed for temperature sensing within defined ranges. The change in resistance is compared with set values by the module. When both values are equal a particular function will commence.

MISTRAL FRIDGE FREEZERS PETERBOROUGH PRODUCED

Temperature = Ohms ( )+20 C (Room) 3K

9K11.5K26.0K

+0 C-5 C-20 C

PTC’s have a Positive Temperature Coefficient, where their resistance increases as the temperature increases. They are frequently used for overheat protection and compressor start devices.

THERMOCOUPLE - A thermocouple is a device for measuring temperature, consisting of two dissimilar metal conductors joined together to form a loop. This arrangement generates a minute voltage where its value is dependent on the temperature differential between its two ends. In refrigeration appliances they are usually connected to an electronic control module. The voltage produced by the thermocouple is used to trigger a thyristor or triac and a particular function will commence.

DAMPER CONTROL - A damper control is a mechanical thermostat. Commonly used in frost-free refrigeration to sense temperature and control airflow into the fridge compartment.

The internal temperature of the cabinet is sensed by the capillary phial, located in the air path at one end and the other is joined to the hydraulic bellows in the body of the thermostat. The bellows expands and contracts as the temperature changes and in so doing gradually opens and closes a door or flap linked directly to it.

MOTORISED BAFFLE - The motorised baffle assembly used in the Mistral models (FF80 etc) consists of an electric motor, switch and baffle (door).

When the motor operates the baffle is opened or closed, the switch is also operated each time to indicate to the module the position of the baffle.

Operation is controlled ultimately by a module but is initially selected by a thermistor sensing and controlling the fridge temperature. When the baffle opens the evaporator fan is also selected for operation.

THERMOSTAT - The refrigerator thermostat consists of a set of switch contacts that are opened and closed by means of hydraulic operated bellows.

The internal temperature of the cabinet is sensed by the thermostat capillary phial clamped to the evaporator or cabinet interior at one end a ndjoined to the hydraulic bellows at the other.

The capillary and bellows are charged with refrigerant under pressure, which expands and contracts as the temperature changes.

The bellows are spring loaded (ie: they expand against spring pressure and consequently are spring assisted in contraction) the switch contacts are spring compensated to ensure "snap action" making and breaking.

Operating the switch contacts by the bellows alone would lead to very slow operation with its consequent arcing and reduced contact life

Refer to the section: PTC Start Device on page 17.

TEMPERATURE CONTROLS

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THERMOSTATS - FIXED DIFFERENTIAL Used on freezers and refrigerators without automatic defrost. As the name implies the differential between the cut-in temperature and the cutout temperature remains approximately the same throughout the range of the thermostat.

The freezer version of this type of control generally incorporates a signal lamp facility. The more common method is for a warning light to illuminate if the cabinet temperature rises above a safe storage level, although a variant does exist where the light (green) comes on to indicate that a safe temperature has been attained.

A further variation on this type of control is the push button defrost thermostat where, by depressing a push rod in the centre spindle, the compressor circuit is isolated until the evaporator reaches a predetermined temperature.

When this temperature has been attained the evaporator has defrosted, the defrost push rod then returns to its normal position, and the thermostat resumes cycling at its original setting. The diagrams above show the typical thermal characteristics of this type of thermostat for both fridge and freezer.

THERMOSTAT - CONSTANT CUT- IN There are situations where the variable cut-in setting of the fixed differential control would lead to unsatisfactory temperatures within the appliance. On a twin temperature fridge-freezer it is essential that the freezer compartment is

maintained at a safe temperature (below -18 C)whilst the thermostat cycles to maintain a satisfactory refrigerator temperature.

The constant or fixed cut-in temperature (+3.5 Csensed on the fridge evaporator) ensures that, even at the warmest setting, the temperature in the freezer compartment is maintained below freezing point, and that the fridge evaporator is able to be warmed sufficiently to melt all the ice during the off cycle.

This is achieved using a thermostat incorporating an extra connection for controlling a def rost heater mounted on the evaporator. The heat generated during the defrost cycle not only accelerates defrosting but warms the thermostat capillary phial attached to the evaporator.

This ensures that the thermostat cut-in is prompt and guarantees as far as possible that the on/off cycle is relatively constant and that temperatures in both compartments are maintained.

TEMPERATURE CONTROLS

13

The heaters used in domestic refrigeration products are as varied as their uses. They are normally designed for a specific appliance type, to carry out a necessary function, such as defrost. Occasionally heaters are introduced to a model to combat unusual occurrences (ie: Too cold in a particular compartment or to prevent condensation etc) The more common ones are, Defrost, Gutter, Drip-Tray, Duct, Transom, Anti-Condensation and Low Ambient (referred to as a compensation heater in some manuals). Not so common are Thermostat/Capillary heaters used in some foodcentres.

Defrost Heaters, are used for defrosting evaporators. There are two main types. Larger wattage heaters are used for defrosting evaporators in frost-free models where the frost accumulation builds for a number of hours or days. The frost has to be removed as quickly as possible to ensure that the food temperature is not affected. The duration of the defrost is controlled by a thermostat sensing the temperature close to the defrost heater and opening (generally between 15 C to 20 C).

Control is usually by electro-mechanical timer but may also be electronic.Smaller wattage heaters are used in larderfridges.The frost level should only ever be slight in thesebecause the defrost operation is frequent (10 to 15 minutes is average.Thermostat cycling determines operation as the heater operates during the off cycle.

Anti-Condensation Heaters, as the name implies, are used to reduce or prevent condensation. Usually foamed in around the cabinet front edge of a freezer compartment, where the door seal meets the cabinet. They can be electrical or system pipework. System pipework is commomly routed from the last passes of the condenser around the cabinet,returning to the dryer. It can also start at thecompressor, returning to the input side of thecondenser.

Where an electrical anti-condensation heater is used, normal operation occurs during the compressor off cycle. In some models the customer can select constant operation, by switching from Economy to Humidity. The symbols on this switch were originally ( E) & (H) and are currently (l) & (0) respectively. Constant operation is recommended whilst fast freeze is selected or where humidity is higher than normal. Refer to the section:Condensation, on page 27.

Duct Heaters, are a form of anti-condensation heater designed to reduce or prevent condensation and ultimately ice build-up in the air ducts of some frost-free models. These are foamed-in with some models and are therefore not replaceable.

Drip Tray & Gutter Heaters, are used to ensure that the trays and channels in which the defrost water drains do not re-freeze, before the water is able to drain away.

Heaters are sometimes used or incorporatedin the design of larder fridges and fridge freezersto influence the operation and ensure thattemperatures are maintained. In low ambienttemperatures an appliance may not operate asofter, prolonging the OFF time. This can cause theinternal temperatures to rise, so that even freezertemperatures warm above the recommended -18 C.

The operation of the heater may also have anoverriding control, such as a manual switchoperated by the customer or a thermal switch thatturns the heater on automatically. It might simplybe that the thermostat switches the heater on duringthe compressor OFF period.

The intervals between defrosts can vary from a few hours in some models to more than 60 hours in some Foodcentres.

HEATERS IN REFRIGERATION

14

Thermostat Capillary Heaters are designed to warm the capillary phial close to the body of the thermostat. They are used often where colder air circulating can inhibit thermostat cut-in.

Their purpose is to prevent the thermostat from being influenced from another source and ensure correct thermostat cut-in temperature.

This also guarantees as far as possible that the cabinet temperature does not rise above recommended levels. Various types and shapes are manufactured, the most common ones being heating wire mounted on adhesive backed aluminium foil.

The more elaborate one illustrated above, clips over the capillary where it enters the thermostat. (a GE component)

Note:A temperature control compensator heater should never be used on a cycle defrost refrigerator.

A long off cycle is essential on these model types to allow complete defrosting of the fridge evaporator.

HEATERS IN REFRIGERATION

15

COMPRESSORSThe compressor must operate periodically to provide satisfactory food temperatures. The operating sound will vary from all compressors and one model to another.

When the sound level is determined to be within acceptable limits, the customer should be so advised.

The compressor should not be replaced to appease, as the replacement compressor will most likely produce the same sound as the original.

The compressor is a hermetically sealed compression pump powered by an electric motor. The unit is oil cooled and the motor utilises either a P.T.C. starting device or a relay and overload.

Both of these devices are described in more detail later in this publication.

The schematic diagrams below are intended purely to indicate the function of the compressor, and are not a true representation of the actual workings of the compressor.

R12 and R600a compressors are cooled usingmineral oil which is NOT compatible with R134a refrigerant. R134a compressors use synthetic oil Poly Ester.

COMPRESSOR MOTOR WINDINGS Run Windings - Have a relatively low number of turns in comparison with start windings and consequently comparatively low resistance.

Start Windings - Have the greater number of turns and therefore comparatively high resistance.

Connections to the motor windings are made through three pins on the side of the compressor casing. The configuration of the pins and the internal connections may vary, but a simple resistance check as shown below will identify the internal wiring.

COMPRESSOR - RESISTANCE TESTING (Matsushita 1/6 hp compressor) This particular compressor has start winding resistance of approximately 30 ohms (30 ) and run winding of 17.0 ohms (17 ) at 20 C.Applying these figures to the left hand format above, A-B would give 17.0 ohms. A-C would give 30 ohms and B-C would give 47.0 ohms.

RELAY OPERATION

When the thermostat contacts close, the magnetic field in the relay coil developed by the run winding draws the plunger upwards, closing the start contacts to energise the motor start windings. The motor reaches speed very quickly and consequently the current in the run winding decreases to a point where the magnetic field in the coil is no longer strong enough to hold up the plunger. The plunger drops, which causes the contacts to open disconnecting the start windings, and the motor continues on the run windings alone.

Refer to the section: Refrigerants and Environmental Issues on pages 30 & 31.

COMPRESSORS AND THEIR CONTROLS

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P.T.C. - START DEVICE

As an alternative to the relay, many compressor manufacturers now use the PTC, PositiveTemperature Coefficient thermistor as a compressor starting device.

A PTC will pass current whilst cold, but the flow of current causes a temperature rise which in turn increases the resistance of the device. It is this property that is used in this application.

Referring to the diagram, voltage is applied to both the run winding, and via the PTC, the start winding, and the motor starts.

The temperature of the PTC rises and the resistance increases until it reaches a level at which the start windings are effectively taken out of the circuit and the motor continues to run on the main windings alone. Sufficient current continues to trickle though the device, however, to keep it hot and therefore at high resistance.

RUN CAPACITORS Run capacitors are used increasingly because they improve the efficiency of the compressor resulting in lower consumption figures.The capacitor is wired in parallel with the PTC start device. The effect is that the compressor start windings are left in circuit but out of phase with the run windings.

Note: Many compressors will operate satisfactorily with or without a run capacitor.However some compressors such as the ZEM GL75AH were designed for operation with a capacitor and must therefore always have one fitted.

MOTOR OVERLOAD - EXTERNAL The motor overload is generally clamped to the side of the compressor casing and consists of a bimetallic disc and a heater coil in series with the motor windings. Distortion of the disc will break the circuit to the compressor and this can be caused by heat from one of two sources:-

1. Current rise in the motor causing the heater to energise.

2. Excessive heat radiated from the compressor casing.

Zem and Verdichter compressors now have a single unit overload and PTC start device. See illustration below.

Although the unit appearance is significantly different it functions in the same way as those described above.

Matsushita and Danfoss use (internal) overloads embedded in the motor windings in many of their compressors. This may give rise to excessively long reset time if the overload has tripped due to an overheated motor.

COMPRESSORS AND THEIR CONTROLS

PTC Section

OverloadSection

17

CONDENSERS

The function of a condenser is to remove heat from the hot refrigerant vapour pumped from the compressor so that the vapour can be condensed to a liquid for re-use.

The most common condensers consist of a formed length of small-bore (approx 3mm inside diameter) steel tubing through which the refrigerant gas is pumped at high pressure and temperature.

The condenser tubing is commonly mounted on either a thin louvred steel panel or a wire grid to present as large as possible surface area to aid the dissipation of the heat in the gas.

Compact versions where the tubing is often coiled are also used, but are fan cooled to assist dissipation. Some Chest Freezers are produced with the Condenser bonded to the inner surface of the cabinet, this has the effect of warming the cabinet, reducing the possibility of condensation on the exterior. This type is commonly referred to as a Hot Wall Condenser.

It is essential that the system is free of any moisture or impurities, and to this end a dryer is incorporated between the condenser and the capillary.

DRYER

SYSTEM COMPONENTS

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The dryer consists simply of a cylindrical copper container filled with a desiccant. Two drying agents can be used, Silica Gel or LMS (Linde Molecular Sieve). Silica Gel (very rarely used now) has better moisture absorbent qualities when used at low ambient temperature and is therefore used at the evaporator inlet.

LMS is more effective at higher ambient temperature and is therefore used at the condenser outlet. The moisture absorbent granules are retained between two wire gauze filters to prevent them being swept around the system and blocking the capillary.

2 STAGE DRYER - FOODCENTRE (R134a)

A special 2 stage dryer was recommended atone time carrying out system repairs on Foodcentres charged with R134a.

It consists of a large filter and a somewhat smaller dryer joined together. The filter has a solid core made of a special porous material that is capable of removing contaminants from the system. (An extra 1/2 ounce or 14 grams of refrigerant must be added to the total charge).

We now recommend the DRS11 Dryer, suppliedby 'Vulkan', Part No. 2090040.

SYSTEM COMPONENTS

CAPILLARY TUBES The main capillary or restrictor tube is a pre-determined length of fine bore tubing inserted in the system between the dryer and the evaporator. Its purpose is to create a restriction and consequently a pressure differential within the system (ie: high and low side) when the compressor is in operation, and to meter the flow of refrigerant. Without this restriction the whole system would be at the same pressure, there would be no high-pressure injection of refrigerant into the reduced pressure evaporator and consequently no refrigeration. Single compressor fridge freezers and freezer fridges also have a larger bore restrictor tube between the two evaporators (primary & secondary) to create another pressure differential.

Refer to the section: Single Compressor Fridge Freezers & Freezer Fridges on page 20.

SUCTION TUBE The suction tube is the return line from the evaporator to the compressor through which the heat laden refrigerant gas is drawn. The capillary or restrictor tube is routed inside the suction tube by most manufacturers, but it can also be soldered to the outside of the suction tube, either way this arrangement forms a heat exchange unit.

The purpose is to aid warming of the suction gases and cooling of the liquid flowing in the capillary. Note: If the restrictor tube (soldered type) becomes detached from the suction tube, temperatures in the fridge and freezer will be warmer.

EVAPORATORS

The evaporator is a heat transfer vessel in which the refrigerant vaporises and in so doing removes heat from the refrigerated space.

Evaporators are designed for specific model applications, and are manufactured in various sizes, shapes, types, and appearance.

Commonly used are wire on tube, (freezer shelving) various finned on tube evaporators (frost-free) and Rollbond (traditional refrigerators and freezers).

The illustration below is a much simplified diagram of a Rollbond evaporator. In reality, areas of the plate would be linked with cross channels to produce an even cooling of the complete area.

The Rollbond evaporator consists of two sheets of aluminium, bonded together to form a series of linked channels into which the liquid refrigerant is injected via the capillary tube.

At the end of the run, before the suction tube exits the evaporator, the channels open out to form a boiler, an area in which any excess liquid refrigerant will collect and "boil off" preventing it returning to the compressor in liquid form.

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SYSTEM COMPONENTS

EVAPORATOR CONFIGURATIONS

Twin Temperature Fridge Freezers, have primary and secondary evaporators. The freezer is the primary evaporator and the small volume secondary evaporator in the fridge is an extension from the last passes of the freezer evaporator. They are connected in series and both evaporators separately remove heat from the respective compartments.

The freezer evaporator must be manually defrosted but the fridge evaporator is defrosted during each off cycle. (Sometimes referred to as a cycle defrost system).

This is accomplished by the thermostat with a constant cut-in (3.5 C to 5 C), temperatures high enough to allow the fridge evaporator to defrost completely. The process is often assisted by a heater attached to the fridge evaporator to aid defrost. This reduces the off time and helps to ensure that the freezer temperatures are maintained.

Single Compressor Fridge Freezers and Freezer Fridges, have primary and secondary evaporators. The primary evaporator is the fridge evaporator with the larger secondary evaporator in the freezer.

They are connected in series, by a length of larger bore restrictor tube (commonly 3mm but will vary, depending on the model) its purpose being to create a pressure differential.

This causes the fridge evaporator to run at a higher pressure and temperature (warmer) than the freezer evaporator.

Most of the refrigerant passing through the fridge evaporator remains as liquid vapour that then evaporates in the freezer. The system is balanced so that when the fridge evaporator is cycling at the correct temperature, the freezer is at or colder than -18 C.

Foamed-In (hidden) Evaporators. The manufacture of the evaporator is usually tube on steel plate construction and is foamed in behind the rear wall of the fridge.

A defrost heater may also be attached to the assembly and will normally operate during the off cycle. (Constant operation is usually selectable.)

Whilst the compressor is operating the rear wall of the fridge will be frosted and will be wet during the off cycle. This arrangement is referred to as Wet Wall design.

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SYSTEM OBSERVATIONS

SYSTEM OBSERVATIONSThe refrigeration system should be carefully examined after all other possible causes of a "poor performance" complaint have been explored and eliminated.

However, before connecting a gauge to the system, make an observation of system components that are easily accessible to distinguish between normal and abnormal circumstances.

Using only the senses of looking and feeling, inspect the condenser, dryer, capillary, and suction tube, when the compressor has been running long enough for the system to stabilise, the following characteristics should be observed.

Normal Operating SystemLiquid refrigerant is present in the last pass of the condenser, dryer, capillary, and in the evaporator. Thus, the condenser is warm throughout - but much warmer (hot) at the inlet than at the outlet.

The dryer and capillary are slightly warmer than room temperature. The suction tube is slightly cooler than room temperature, but not sweating or frosted. However, it is normal for the suction tube to momentarily frost or sweat for a few seconds when the compressor resumes operation after an off cycle.

Undercharged SystemUndercharged System (or a system that has a leak), a lesser amount of liquid refrigerant is present in the condenser and evaporator.

Thus, the condenser is warm but not as warm as normal. The dryer and capillary may be slightly warmer than room temperature (depending upon the extent of the undercharge).

The suction tube is cool (room temperature). When an evaporator has a light accumulation of frost, it is not unusual to observe an incomplete (short) frost pattern. This is not necessarily evidence of an undercharge but rather, a normal circumstance caused by the introduction of warm air or warm food packages.

Overcharged System

A greater amount of liquid refrigerant is in the condenser, overflowing the evaporator, and spilling into the suction tube. Thus, the condenser is warm but the lower portion is not as warm as normal.

The dryer and capillary are cool (room temperature) due to the additional refrigerant accumulating in the lower portion of the condenser.

continued....

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SYSTEM OBSERVATIONS

The suction tube is cold and possibly sweating or frosted (depending upon the extent of overcharge). NOTE If the suction tube is either sweating or frosted, indicating a possible overcharged system, inspect the evaporator for excessive frost accumulation. An excessively frosted evaporator can cause the suction tube to sweat or frost when there is no failure within the refrigerator system.

Refer to section: Frost Accumulation & Condensation on page 27.

Partially Restricted System

In a partially restricted system (usually at the capillary inlet), a greater amount of liquid refrigerant remains in the condenser but a lesser amount is present in the evaporator... caused by the reduced flow through the capillary.

Thus, the condenser inlet is warm but the outlet is cool (room temperature) caused by the unusually high amount of liquid that remains in the condenser.

Consequently, the dryer, capillary, and suction tube are also cool (room temperature). A partial restriction will cause a pressure drop, resulting in sweating or frosting that can be observed at the point of restriction.

Completely Restricted System In a completely restricted system (assumed at the capillary inlet), almost all of the refrigerant is in the condenser and at high pressure due to the completely restricted flow through the capillary.

Accordingly, all of the remaining system components (from the point of restriction back to the compressor) are in deep vacuum. Thus, the condenser, dryer, capillary, and suction tube are cool (room temperature) because the refrigerant is trapped in the condenser.

NOTABLE POINTSSystem pressures will be higher if the internal or external heat load is higher than normal.

For Example: - 1. Following the loading of a large quantity of

fresh food.

2. If the door is open for prolonged periods or customer use is heavy.

3. When the internal or external airflow is poor.

System pressures will be lower if the internal or external heat load is lower than normal.

For Example: -

1. Room temperature lower than normal.

2. Where customer use is lower than normal.

3. Excessive ice accumulation on the evaporator.

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Where an appliance is poorly positioned and as a consequence operates outside its temperature class, system efficiency will be impaired. Furthermore, where the room ambient temperature is regularly outside the appliance temperature class, resiting of the appliance or the introduction of a room heater is to be recommended.

High Ambient Temperature High ambient temperatures increase compressor run time, which can be 100% where ambient temperatures are close too or above the appliance operating class. System pressure and sound will also increase, because the compressor has to work harder pumping higher pressures and may vibrate.

Where ambient temperatures are temporarily high, interim measures can be implemented to reduce the heat load on the system. The customer should minimise use, open windows and doors to improve through draft, close curtains where there is direct sunlight and where possible remove or switch off any other heat source.

continued....

AMBIENT TEMPERATURE

The term "Ambient Temperature" refers to the temperature of the air circulating in a particular area (ie: surrounding a refrigerator).

When the temperature of the air circulating is outside the appliance temperature class, it is often said that there is an "Ambient Temperature Condition", (ie: high or low ambient condition).

All refrigeration appliances are designed for operation in one or more specific ambient temperature classifications. The class symbols are S, SN, ST, & T and can be found on the appliance rating plate.

TEMPERATURE CLASS TABLETemp Class Symbol Ambient CExtended Temperate SN 10 to 32

Temperate N 16 to 32

Sub Tropical ST 16 to 38

Tropical T 16 to 43

The symbol, once confirmed, should be related to the table above to find the ambient operating temperatures (min & max) of an appliance.

It is not unusual to find more than one classrating:e.g. SN / ST - SN = 10 C - ST = 38 C, in thisinstance the appliance operating temperaturewould be 10 C to 38 C.

Important factors in designing a system for a domestic refrigerator are the capacities of the condenser and evaporator plus the density of the foam insulation.

Other considerations are the compressor displacement (cubic capacity), whether heaters are required for defrost, gutter etc.

The design engineer has to weigh all of these factors so that the finished product has the correct balance of temperature in the fridge and freezer sections.

This is in addition to complying with the various standards and regulations and meeting the designated energy band.

Appliances that have an acceptable temperature class for operation in the United Kingdom may not function satisfactorily where the climate is more extreme.

Equally, an appliance that operates perfectly well in our climate can operate inconsistently when the ambient temperature is outside the appliance temperature class.

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AMBIENT TEMPERATURE

Low Ambient TemperatureLow Ambient Temperature affects system performance, reduces run time, and freezing rate, increases off time and freezer temperature. Condenser and dryer temperature will be lower than normal, as will system operating sounds and compressor noise. In cool or colder room temperatures, the compressor may run infrequently.

Where ambient temperatures are (very low)

When temperatures are lower thanThermostat cut-in, operation will of course beprevented.

below cut-in temperatures for standard larderfridge thermostat (e.g. +1 C to +4 C),thermostat operation can can be inhibited.

The above situation is unlikely to be a real problem for a customer with a stand alone larder fridge,although it may cause complaints.

However the temperature of the freezer compartment in some fridge-freezers may increase to a point where it starts to defrost. Where the situation is prolonged, complete defrost can result.

All freezers have a conservation period of some hours which is a safeguard, therefore freezer defrost is an extreme situation, but nevertheless possible.

Where an appliance is installed in a position susceptible to this condition, the customer should be advised that the appliance is incorrectly positioned. When it is not possible to reposition the appliance in a warmer environment, some heat should be introduced to ensure that the minimum ambient temperature for the appliance is achieved.

Manufacturers use various methods to inhibitthe effect or overcome the issue of lowambient temperatures. (Mostly affectinglarder fridges and single compressor fridgefreezers.)

Heaters are sometimes used or incorporatedin the design of larder fridges and fridgefreezers to influence the operation and andensure that temperatures are maintained.In low ambient termperatures an appliancemay not operate as often, prolonging the OFFtime. This can cause the internal temperaturesto rise, so that even freezer temperatures canwarm considerable above the recommended-18 C.

The operation of the heater may also have anoverriding control, such as a manual switchoperated by the customer or a thermal switchthat turns the heater on automatically. It mightsimply be that the thermostat switches theheater on during the compressor OFF period.

Refer to the sections: Thermostat - Constant Cut-in & Defrost Heaters, on pages 13 & 14.

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25

CUSTOMER USE & DOOR SEALING

CUSTOMER USE - GENERALUnder heavy usage conditions, high ambient temperature, a greater demand for ice - (foodcentres), frequent and long door openings, compressor run time will be longer than normal. Fridge temperature will be higher than normal.Freezer temperature can also be higher than normal, especially if the freezer compartment is lightly loaded. With light usage conditions, cool ambient temperature, less demand for ice (foodcentres) infrequent or brief door openings, compressor run time will be shorter than normal and off-cycles longer than normal.

HEAVY USAGEDuring the summer months, higher than normal kitchen temperatures will exist in some homes.

This, in conjunction with a greater demand for ice, increased door openings or duration, can result in long compressor run time with fridge temperatures close to maximum late in the afternoon. Thus, the consumer should be advised to keep the refrigerator door openings to a minimum.

LIGHT USAGEWhen the kitchen is cool (during the winter months) or the refrigerator doors are opened less frequently (no one at home during the day), compressor run time will be shorter than normal. Consequently, the air stratifies (warm air at the top and cold air at the bottom). This may cause the lower sections to become colder than normal.

DOOR SEALINGDoors that are misaligned or door seals that are torn or not sealing adequately will allow warm moisture laden air to enter the food compartments. This will result in longer compressor run time and additional frost accumulation on a fridge evaporator.

Where warm moist air enters a freezer it will condense quickly and a frost line will soon be evident. When air ingress is severe, frosting on the basket fronts and door liner is a possibility. Condensation may also be visible on the cabinet front edge, close to where the seal is damaged.

NOTABLE POINTSFrost-Free Fridge Freezers - Where a fridge section has excessive use, food and liquids not covered as recommended, or where the door is left ajar, greater quantities of warm moist air will bereturned to the freezer. The likely consequence will be, larger than normal frost formation on the evaporator, and possibly in the air return ducting (where used) or any other crevice that will retain moisture.Where the situation exists, performance will be impaired and will result in a service call. In many instances it is not a fault of the appliance, but customer education.

UNUSUAL HEAT LOADS - APPLIANCE SOUNDS (NOISE)

UNUSUAL HEAT LOADS

A heat load such as the interior lights remaining on after the doors are closed, icemaker stalled or a compensation heater operating inappropriately, will result in longer compressor run times.

Air and food temperature may also be higher than normal.

APPLIANCE SOUNDS - NOISE! Modern day refrigerators are designed with more features and manufactured under vastly different conditions than products of a decade ago.

Compressors generally have smaller capacities, run faster and operate more frequently, but are more energy efficient. Frost-free models are much more popular these days and feature additional complex components, which contribute to higher or different sound levels.

For Example:-High Efficiency Compressors. Condenser Cooling Fan. Evaporator Fan. Motorised Baffle. Air Circulation.

The operating sounds that emanate from a refrigeration appliance whilst running can vary considerably. Sounds that are perceived as unacceptable or excessive by the customer can actually be quite normal.

It is therefore important that refrigeration engineers familiarise themselves with the sounds of the various compressors, systems and model types to be able to discuss sound levels with some confidence.

Common Causes - all modelsWhilst operating; the compressor should be the most prominent sound, although this should not be unduly intrusive after the initial running in period.

Other normal sounds are: Refrigerant being injected (slight hissing) into

the evaporator.

Gurgling and or dripping sounds from the refrigerant evaporating and condensing within the system.

Air circulation.

These are usually quite normal but can occasionally be excessive and only the engineer’s experience will determine if the levels are acceptable.

Noisy but repairable sounds:- Touching or rattling pipework.

Evaporator expansion and contraction. (when severe, can result in the occasional loud cracking noise)

Loose or misaligned fan blades or motors. Faulty or damaged compressor.

Frost Free AppliancesFrost Free Appliances can generate a higher incidence of customer queries compared to traditional products, to some extent because of the somewhat different sounds.

Customer concerns may also be elevated because of the higher purchase price and expectations, very often based on their previous product, which in many instances will have been a traditional fridge or freezer.

The fans used to circulate the air internally and externally are often the reason for the customer’s disapproval. The evaporator fan can also operate independently of the compressor, giving another sound and the impression that the appliance is always running.

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FROST ACCUMULATION & CONDENSATION

FROST ACCUMULATIONExcessive frosting may be due to a failure of a component in the defrost system, or simply that the door was left ajar.

Heavy frosting or ice build-up is often due to excessive use, high humidity conditions or occasionally, misuse because the customer does not understand.

Whatever the reason it is the result of warm moist air entering the appliance, condensing andthen freezing. Usually introduced via the door or as part of the food content when food is not covered.

Heavier than normal frosting on an evaporator impairs the efficiency of the system by reducing the ability of the evaporator to absorb heat.

Airflow over and through a frost-free evaporator will also be restricted or stopped. Ice may also prevent the fan from operating.

NOTABLE POINTS Factors that exacerbate the situation are excessive use, poor door sealing or appliance location, uncovered food or liquid, or warm food.

Large regular quantities of fresh food would also contribute considerably.

Chilled or frozen food packages from the supermarket are best transported home in a cool bag to maintain temperature, it will also prevent sweating (condensation).

Condensation on packages loaded into the freezer section of a frost-free appliance can produce a covering of ice, which may result in a complaint.

CONDENSATIONGeneral - Condensation is the conversion of vapour to a liquid through the loss of heat. The results of which are most noticeable where the vapour is in contact with a cold surface and water droplets appear on the colder surface.

The amount of condensation that will actually form is dependent on the temperature difference and the moisture content (relative humidity) of the surrounding air.

Internal CondensationInternal Condensation is the result of relatively warm moist air entering the appliance. This may be due to prolonged door opening, inadequate door sealing, uncovered food or liquid, especially salad vegetables.

The situation will be exacerbated where there is high humidity. Visible condensation on the interior of a refrigerator is quite unusual.

Warm moist air or vapour from food etc entering a traditional refrigerator will usually condense on the evaporator, being the coldest area.

Similarly with a frost-free fridge it will condense where the temperature is coldest. This maybe in the air return ducting at the freezer end or around the evaporator.

The formation of condensation in a freezer is most apparent where the warm moist air enters the compartment.

When it enters via the door seal, it appears on the liner as moisture haze, then as water droplets as it cools still further and finally as ice.

Where the air ingress is relatively small it will appear only in the area where the warm air enters, usually close to the door seal.

Where the air ingress is greater, it will extend further to the door liner and basket fronts.

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External Condensation generally appears more on freezers than refrigerators due to the relatively cold cabinet.

Where freezers are located in garages, outhouses, conservatories etc, the likelihood of condensation on the cabinet exterior is much greater because of the relative damp (ie: a wet car) unheated environment. Some condensation is inevitable where conflicting temperatures prevail.

Colder internal cabinet temperatures will increase the amount of condensation due to the lower temperature of the outer cabinet.

Possible Remedies 1. Check the internal cabinet temperature and

adjust the thermostat position.

2. Where available switch the Humidity button ON. 3. Relocate the freezer

4. Explain to the customer why condensation occurs, it is not detrimental to the performance of the freezer. It is beneficial to periodicallyapply a silicone wax (except to plastic parts)to help preserve the cabinet finish.

AIRFLOW

INTERNAL AIRFLOW - Frost Free Models The evaporator fan operates while the compressor is running to circulate through theevaporator and throughout the freezer and refrigerator compartments. Fan operation is suspended in some models until the evaporator is cold. Refer to the section below

Mistral Fridge - Freezers. The evaporator fan operates with the compressor and also independently to circulate the air and maintain the fridge temperature.

Fan operation is prevented in some models until the evaporator is frosted (ie: temperature normally between -15 C). This reduces the risk of relatively warm air and moisture vapour around the evaporator and gutter from circulating, following the defrost period.

Where there is a fault and the fan for a particular compartment is inoperative, air and food temperature will be higher than normal.

Temperatures will also be higher where the normal airflow is prevented from reaching a particular area or compartment.

The cause can be due to poor food storage (eg tall items in front of air ducts), or overloading of food packages, or simply that the shelf is covered with foil.

However, it may also indicate that there is an ice build-up or perhaps a gutter duct heater has come adrift, blocking the duct and restricting circulation.

Where the freezer temperature is at -18 C or colder and the fridge temperature is noticeably warmer than normal, a system failure should not be suspected.

Note: Instead, re-check the evaporator fan operation, air baffle, damper control and air ducts for a possible blockage.

The above statement does not apply to twin compressor combination models up to and including model type RF60)

Traditional modelsAir circulation internally and externally is also essential. Although, circulation is not fan assisted, much of the criteria that appliesto the frost-free models is also relevant forthese particular products.

EXTERNAL AIRFLOW Poor or restricted airflow over the condenser will result in longer or continual compressor operation. Internal temperatures will be higher than normal.

Possible causes are, blocked or restricted plinth air grille or rear cover, due to excessive fluff and dust, inoperative condenser fan, insufficient clearances, poor venting (missing or poorly fitting air baffles or rear cover will cause similar results with Foodcentres).

If the situation is prolonged it will result in higher than normal air and food temperature, this will be most noticeable in the fridge, although the freezer temperature may also be affected.

28

APPLIANCE LOCATION & MISCELLANEOUS ISSUES

APPLIANCE LOCATION INSTALLATION The location of a refrigeration appliance is usually decided by the design of the kitchen rather than where it would function properly or most efficiently. It should not be placed where the ambient temperature is regularly close to the appliance classification (min or max), or immediately next to a cooker, in direct sunlight, near a radiator or heat vent.

Positioning an appliance in a conservatory, outhouse or a porch where temperatures can be extreme is also best avoided if at all possible.

Clearances - Freestanding Models Clearances must be provided at the top, sides, and rear of most refrigeration appliances for air circulation. Failure to provide the minimum clearances as stated in the handbook will result in poor performance and a reduced operating life.

Clearances - Integrated models All models require cupboard venting for through draft, this is to ensure that the system heat escapes as quickly as possible. Refer to the customer handbook or the installation book for specific model details.

LevelingAn appliance should be firmly positioned on a solid floor. The cabinet should be reasonably level side to side and tilted slightly backward so that the doors swing closed when opened to a 90( position. In addition, failure to level the appliance may result in the cabinet twisting and the door drooping.

Door AlignmentDoors that are misaligned with the outer case or with each other can be a point of dissatisfaction to the customer. The cabinet should be level side to side, tilted slightly to the rear and solidly positioned on the floor.

Door drop (non-hinge side) can in many instances be attributed to the feet not being adjusting adequately during installation, which allows the cabinet to twist.

In most cases the fault can be corrected by adjusting the front foot down on the hinge side

so that it is the primary support for the cabinet. This will reverse the trend and if the foot is adjusted down a little each week over a period the cabinet and doors will return to an acceptable position.

DIFFICULTIES OPENING THE FREEZER DOORDue to improved door sealing, some freezersare virtually airtight, this can make doors very difficult to open. When a freezer door is closed the warm air that entered whilst the door was open, cools and contracts, creating a partial vacuum. This can last for some minutes after the door has been closed.

To overcome the problem until the seal performance diminishes marginally, an adhesive insert can be used. This creates an air path to reduce the effect of the partial vacuum, which allows the door to open more easily. Door handles are also available for many models in white or brown where the customer is Arthritic.

Refer to Technical Bulletin FZ73.

HOLIDAYS - VACATIONS For extended vacations or absences, remove all food, shut of the power to the appliance, move the thermostat control to the off position, clean the interior with a solution of baking soda and water and wipe dry. (15ml = 1 tablespoon to 1 litre of water)

To prevent odours, leave the doors ajar and an open box of baking soda in the appliance. For shorter breaks, remove perishable foods and leave the controls at a suitable setting.

Fridge-freezers susceptible to total defrost in cold ambient temperatures should be treated as for extended holidays. Especially when taking winter breaks.

TRANSPORTING APPLIANCES Appliances should whenever possible be transported in an upright position. Where this is not possible, the appliance should be allowed to stand for up to two hours following delivery and before switching on. This is to allow the oil to return to the compressor.

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REFRIGERANTS AND ENVIRONMENTAL ISSUES

Refrigerant R12 is a CFC, (Chlorofluorocarbon) chemical name Dichlorodifluoromethane, it has a boiling point of -29.8 C at Atmospheric Pressure.

Refrigerant R134a is an HFC, (Hydrofluorocarbon) chemical name Tetrafluoroethane, it has a boiling point of-26.5 C at Atmospheric Pressure.

Refrigerant R22 is an HCFC (Hydrochlorofluorocarbon) chemical name Chlorodifluoromethane it has a boiling point of -40.7 C at Atmospheric Pressure.

Refrigerant R600a is an HC (Hydrocarbon) referred to as Isobutane, it has a boiling point of -11.8 C at Atmospheric Pressure.

IMPORTANT NOTES 1. It is illegal to intentionally vent refrigerants to

atmosphere - refer to your Health and Safety booklet.

2. No attempt should be made to break into a system charged with R22 or R600a, not even for diagnostic purposes.

HEALTH AND SAFETY

R12 - R134a - R22 refrigerants, are odourless, colourless, non-corrosive and non-toxic unless exposed to a naked flame.

R600a Isobutane, refrigerant is colourless, non-toxic, non-corrosive, sweetish odour, it is a Volatile Organic Compound and it is therefore combustible and Highly Flammable.

REFRIGERANT & OIL COMPATIBILITY For a system to run reliably, it must contain oil that is miscible with the refrigerant. This allows the refrigerant to thin the oil and carry it around the system as a vapour. CFC’s, HCFC’s and HC’s are miscible with mineral oil (R12 R600acompressors.HFC’s are only miscible with synthetic oil (Polyol Ester) used in R134a compressors.

REFRIGERANTS & THE ENVIRONMENT The Ozone Layer - Our planets stratospheric ozone layer protects us from excessive exposure to the sun’s ultraviolet rays... radiation that can damage our bodies, stunt the yield of our food crops. Ozone, which is present in the stratosphere, extends from 7 to 28 miles above the earth, it is an unstable form of oxygen, which

is created and destroyed daily through natural processes.

As early as 1956 researchers discovered a natural anomaly that has been dubbed the "Ozone Hole". In 1974 it was found that chlorine atoms contained in certain compounds would readily combine with an oxygen atom in the ozone molecule, thereby converting ozone into oxygen.Chlorinated compounds were not only used as refrigerants but as aerosol propellants, where they were used far more extensively, and freely vented to atmosphere. Once vented these compounds migrate upwards into the stratosphere where they remain systematically destroying ozone for decades. HCFC’s although containing chlorine, have a lower potential than CFC’s for damaging the ozone. The hydrogen atom in their molecular structure causes it to begin decomposing much earlier.

INTERNATIONAL AGREEMENTS International concerns were eventually acknowledged and this led finally to an international agreement, which was signed in Montreal Canada in 1987. It is known as the "Montreal Protocol". The protocol required a progressive production phase-out, starting with a ceiling on CFC production of 50% of the 1986 total use, with a ban on its production from January 1st 1995, and a total ban from 31st December 1999. (No more reprocessing)HCFC supply levels have been capped from 1st January 95, phase-out will be the 1st January 2003 when it is hoped suitable alternatives will be available. HCFC’s have allowed us to cease with CFC’s earlier than would otherwise have been possible, but have always been regarded as transitional compounds. At present there are no restrictions on HFC’s

Ozone Depletion Potential (O.D.P) - The O.D.P of a chemical is a measure of its ability to destroy the ozone layer. It takes into account how likely it is to reach the ozone layer, how much chlorine it contains or how long it lasts before changing to something less harmful.

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REFRIGERANTS AND ENVIRONMENTAL ISSUES

REFRIGERANTS ODP & GWP CHART

ODP High Med Zero Zero

GWP High High Med Zero

O.D.P - Ozone Depletion Potential G.W.P - Global Warming Potential

R12 R22 R134a R600a

CFC HCFC HFC HC

Hydrocarbons (HC’s) are Volatile Organic Compounds), but they have a zero Ozone Depletion Potential (ODP) and a very low Global Warming Potential (GWP). It is therefore likely to be one of the long-term energy efficient replacement refrigerants.

GLOBAL WARMING POTENTIAL (THE GREENHOUSE EFFECT - GWP)

The greenhouse effect is a natural effect similar to that seen in a greenhouse where higher temperatures are maintained by allowing the suns rays to pass through glass heating the greenhouse during the day but loss of heat at night is reduced by the glass.

A number of gasses in the outer atmosphere contribute to the greenhouse layer of gases including Carbon Dioxide and CFC’s.

Without any greenhouse effect the surface temperature of most of the earth would be too cold for plant life to survive.

Global Warming is a term that refers to the increase in quantity of the greenhouse gases causing the average earth temperature to increase.

This increase in the quantity of the greenhouse gases is a result of the modern industrial world. The discharge of Carbon Dioxide from factory chimneys and power stations is thought to be the main contributor.

Global Warming Potential (G.W.P) The G.W.P of a gas is a measure of its possible contribution to the greenhouse effect. It is interesting to note that though chemicals like R134a & R12 have over 1,000 times the G.W.P of Carbon Dioxide. Carbon Dioxide is exhausted to atmosphere in quantities several million times

that of refrigerants and Carbon Dioxide is still the most serious cause of the Global Warming.

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DIAGNOSTIC CHECKLIST

FAULT POSSIBLE CAUSE

1. Compressor does not start. a. Electrical Supply - check at the compressor. b. Thermostat open circuit. c. Overload, PTC open circuit, poor connection. d. Relay, open circuit, sticking plunger. e. Compressor winding open circuit. f. Low ambient temperature -

(ie: temperature lower than thermostat cut-in).

2. Compressor hums and tries to start a. Overload, PTC - faulty or poor connections. b. Blockage in system - (ie: system not equalised). c. Compressor tight or seized. d. Thermostat out of calibration - (ie: short off

cycle-system not equalised - switch off and wait 10 minutes).

e. PTC too hot, (ie: start winding shorted out - switch the appliance off, wait 10 minutes).

3. Compressor overload tripping. a. Compressor start windings open circuit. b. Compressor tight or seized. c. Overload, PTC faulty or poor connections. d. Relay, open circuit, sticking plunger. e. Thermostat out of calibration - (ie: short off

cycle-system not equalised - switch off -wait 10 mins).

f. System overcharged or blockage

4. Evaporator defrosts intermittently. a. Normal operation for Larder fridges. b. Door not closing properly. c. Thermostat out of calibration or wrong type -

ie: long off cycle. d. Moisture in system freezing and thawing

intermittently or floating blockage. e. Low ambient condition -

(ie: thermostat cut-in inhibited).

5. Compressor runs longer than expected. a. Undercharge, partial loss of refrigerant, partial restriction - cabinet colder than normal.

b. Poor pumping compressor - light but even covering of frost on the evaporator.

c. High ambient temperature - compressor may operate continuously when ambient temperatures are high.

d. Thermostat out of calibration, phial clamp not secure - cabinet colder than normal.

e. Poorly fitting door or door seal.

Continued on next page

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DIAGNOSTIC CHECKLIST Continued

FAULT POSSIBLE CAUSE

6. Cabinet temperature too high. a. Thermostat setting - reset to colder setting. b. Located near a heat source - relocate. c. High ambient temperature - See section on

Ambient Temperature. d. Refrigerant loss. e. Poor air circulation over the condenser and

compressor.f. Poorly fitting door or door seal. More than

normal frost on evaporator - possibly uneven. g. Door not closing or closed properly. h. Interior light permanently on. i. Icemaker seized and or mould heater on. j. Restrictor tube detached from suction tube.

7. Cabinet temperature too cold. a. Thermostat setting- reset to a warmer setting. b. Thermostat out of calibration or contacts welded

together.c. Phial clamp not securely clamped. d. Low refrigerant charge or leak. e. Both flaps in chiller tray open. f. Partial blockage. g. Fast freeze selected.

8. Excessive Frosting - Ice buildup. a. Appliance used excessively (warm moist air entering the appliance?).

b. Door alignment - adjust cabinet feet. c. Door not closing or closed properly. d. Poorly fitting door or door seal. e. Door open for long periods. f. Food or liquids uncovered. g. Pipework or cable entry holes not sealed.

9. Ambient Temperature Conditions High Temp - Above +32 Ca. Abnormal weather - adjust control/s. b. Direct sunlight - drawer curtain/s. c. Poorly positioned - reposition appliance. d. Appliance close to heat source - reposition

appliance.

Low Temp Below +16 Ca. Poorly positioned - reposition appliance.

See Model Temp Class Table on page 23.b. Unheated room - heat room or reposition

appliance.c. Abnormal weather - select fast freeze max 24hrs.

Various remedies similar to those described above can be adopted to overcome temporary ambient temperature conditions. However , appliances should be repositioned where the ambient temperatures are frequently outside the appliance temperature class.

Refer to the section: Ambient Temperatures on pages 23 & 24.

Continued on next page

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DIAGNOSTIC CHECKLIST Continued

FAULT POSSIBLE CAUSE

10. Condensation on appliance. a. Temperature too low in cabinet. b. Economy switch, ( I ) selected, change position

to ( O ) (originally E & H)c. Anti-condensation heaters open circuit. d. Poorly fitting door or door seal. e. Restricted air circulation around the cabinet

front plinth grille or underside of appliance - ie: a thick pile carpet?

f. Appliance in a high humidity area. g. Appliance poorly positioned in a garage,

outhouse, porch etc. h. Insulation breakdown - normally concentrated in

one area and is unusual.i Appliances too close together space 50mm or

use a linking kit.

Refer to section Appliance location - Installation

For more information refer to section: Condensation on page 27.

11. Appliance Sounds (Noise) a. Compressor noise differs between types b. Rattling pipework adjust carefully c. System sounds - refrigerant evaporating &

condensing dripping or gurgling sounds are normal, and not usually a fault.

d. Fan motor/s, evaporator, condenser or humidity.e. Fan blade - loose or catching ice buildup? f. High Ambient - compressor vibration or shake

when stopping.

For more information refer to section: Ambient Temperatures & Appliance Sounds on pages 23, 24 & 26.

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(Calculations to the nearest decimal point)

Celsius FahrenheitC F

25 7720 6815 5910 50 Above This Point Bacteria Growth Is Rapid 8 46 Upper Limit For Safe Food Storage

REFRIGERATOR 6 43 TEMPERATURE 5 41 RANGE 4 39

3 372 361 340 32 Freezing Point Of Water

-1 30-2 28-6 21 * -9 16

-12 10 ** Maximum Temp For Star Rating -15 5

FREEZER -18 0 *** TEMPERATURE -21 -6 RANGE -22 -8

-23 - 9 Storage Life of Meat is Greatly Extended at -23 C

-25 -13-28 -18

TEMPERATURE CONVERSION CHART

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