Best practice examples of reduced power consumption in building services and refrigeration by...

eColI br I u M • MArCH 2011 30

Best practice examples of reduced power consumption in building services and refrigeration by integrated control of EC fans and motors

dr s. brAdWell, M.AIrAH, ebm-papst Australia and new Zealand

AbstrACtIt is shown that the power consumption of building services and refrigeration can run to over 50% of total power consumption with buildings (1). Of this, a significant proportion is fan and motor applications in HVACR.

This review will detail some examples of best-practice solutions in the application of high-efficiency PMM (permanent magnet motor) based or EC fan technology, and the benefits of speed control in achieving reduced power consumption and hence carbon emissions.

EC-based fan systems are available from a range of manufacturers and the details included within this paper are typical of the high-performance products within the industry.

Examples of integrated fan solutions show power and carbon footprint savings are shown.

Those discussed include:

• 55%fanpowersavingsinairhandlingunits

• 161,000MtonnesC02 savings in condensers

• Constantpressureandconstantvolumeventilationcontrolsystems

• 38,000tonnesCO2 in refrigeration

F O R U M

1. IntroduCtIonPower consumption in fan motors has been estimated to consume 35% of all power in commercial office buildings and up to 60% in commercial supermarkets.

Low efficiency fans and motors are used in:

• Refrigeratingoursoftdrinks

• Ventilatingourrooms

• Supplyingairconditionedenvironmentsinouroffices

• Controllingourhumidity

• Rejectingourheatloadincondensers

• Coolingourcomputers and data centres

• Creatingaircurtains

DC motors and PMM (permanent magnet motors) motors and drives have been used in the automotive market for many years cooling radiators or actuating mechanical movement. Traditional DC motors are inherently power efficient but commonly unreliable due to the carbon brush method of commutation. New electronic commutation (EC) or EC technology has brought together high-efficient DC or PMM motors, Figure 1, with electrical commutation and integrated

speed control, Figure 2 (p.32), providing an approximate uplift of 10% motor/speed control efficiencies in comparison to traditional methods.

In the development of electronics to convert alternating current supply to direct current supply, many other features were made available. The two main features being:

• IntegratedPIDSpeedcontrol–withtheuseof0-10V or PWM supplies EC fans and motors can be controlled over 95% of their speed with minimal loss of efficiency.

• Integratedcommunicationprotocols–RS485connectionsallows remote site control and monitoring. This subsequently encourages both response-based, proactive maintenance (i.e. a failing or aging system can be identified before failure and subsequent system failure) as well as fine tuning of equipment by remote site, dynamic balancing of building service systems.

Speed control is the most significant variable allowing building users to reduce power consumption. According to fan laws, power consumption is proportional to speed to the power three, i.e.

Pa = k.(n)3

Where Pa = power absorbed [W]

K = control factor

n = speed [rpm]

31MArCH 2011 • eColI b r I u M

F O R U M

Integration of EC systems into communication protocols is shown in Figure 3. RS485 outputs from EC fans is used to feed back speed and performance data as well as fault finding

and fault history. This allows fine tuning of the fan systems to be achieved as well as performance monitoring for maintenance. This ensures peak system efficiency for the maximum time.

A more detailed examination of the efficiency differences of EC motor/speed control couples in comparison traditional 3~ motor/VFD couples is shown in Figure 4. Here it can be seen that at part load, the efficiency of the 3~ systems drops dramatically, whereas the EC couple stays relatively constant. The significance of this is dramatic especially 1) when we consider that the significance of speed control on power consumption is the main goal and 2) when systems such as air conditioning will be regulated at part load as is anticipated within the MEPS regulations for air conditioning post 2010.

Although no absolute data is shown here, it is also worth considering the reduction in internal temperatures resultant of this efficiency and its effect on increased life times. This is especially significant in low power product (less that 500W), where shaded pole AC motors are commonly used and where lifetimes can double with the use of higher efficiency air movement products.

Figure 1: The variation of motor efficiency [%] and shaft power [W] for EC motors compared to 3 phase MEPS and HEPS standard motors driven with VFDs (assumed 7% loss in VFD) – Note the comparison is made with 3~ motors with VFD as EC has in built speed control, integral to the motor.

TechnicalPapers

AIRAH is always seeking technical papers of merit for publication in Ecolibrium.

If you are interested in submitting a paper for publication, visit www.airah.org.au and download the AIRAH guidelines for preparing technical papers.

www.airah.org.au

www.bigfootsystems.com.au

the complete solution

Pro Pipe Supplies Pty Ltd, 13-15 Main Street, Beverly, SA5009t: +61 8 8268 8633 [email protected]

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Text Box


F O R U M

2. best PrACtICe of eC In AIr CondItIonIng And refrIgerAtIon

EC, high efficiency is applicable within the refrigeration circuit in both the “cold” or supply and “hot” or heat-rejection circuits.

Best practice in supply systems can utilise a range of both axial and centrifugal (EC plug fan) fan technologies dependent upon the system requirements. EC technology is widely used in evaporator circuits due to the double savings available due to the drop in heat rejected from the motor. The most widely used applied is in domestic or commercial refrigerators as will be highlighted subsequently.

2.1 supply side air conditioning

Some best-practice examples in roof top (RTU) and air handling (AHU) packages as detailed by Lockwood (2) are shown in Figure 5.

By changing the 15 inch by 15 inch (38cm by 38cm) forward curve belt driven fan and applying the backward curved, plug fan EC technology as detailed, it was shown that the fan input power reduced from 6.3kW to 2.78kW. This resulted in an annual saving of approximately 28MWhr per annum.

Although the improvement of COP has not been detailed publicly by the end user supermarket, it is anticipated that over the 10-year life time of the plant, the improvements and savings were considerable.

2.2 Condensers

Giles (3) has explored the savings available using high-efficiency condensers utilising EC axial fans.

EC axial fans used in condenser applications can range in sizes from 450mm to 910mm. Reductions in energy requirement can be achieved in two ways; firstly by improvements of specific fan power and secondly by allowing floating head condensing pressure control as shown by Kroger (4).

An analysis of the performance of EC condensers is shown below in Figure 6 by Giles (3). In this graph it can be seen how the noise, refrigeration performance, power and control features of the fan vary with each other. The fan speed is controlled by a simple 0-10V control from the refrigeration or air conditioning controller, and the fan feeds back its performance into the refrigeration controller via a tacho or rs485 feedback loop.

Figure 5: Best practice example of EC plug fans to AHUs and RTUs. (after Lockwood).

Figure 4: A comparison of efficiencies of EC against 3~ 1.1kW 6 pole MEPS motors with VFD at full speed and part load.

Figure 2: An EC motor showing DC or PMM rotor, electronic commutation, power conversion and speed control electronics.

Figure 3: The integration of EC systems into building services systems.

RS485 CONNECTION with Modbus-RTU protocol up to 247 fans/controllers

33MArCH 2011 • eColI b r I u M

F O R U M

This clearly shows the reduction in power consumption and noise available with EC condenser fans.

If we look at the temperature charts for Melbourne in Table 1, the normal design temperature of an ambient of 30°C is only attained for 2% of the hours in a year. Even if the fans were used at 80% speed on average throughout the year, then 50% savings can be simply made.

The recent survey of the refrigeration and air conditioning market by Anderson (5) has surveyed the power consumed by this market sector.

Using the temperature bin data we can thus estimate the power and carbon savings achievable with EC condensers in Australia; these are shown in Table 2.

The total savings available with EC condensers is 185,000 TWhr power savings or greenhouse gas savings of 245,000 Mtonne CO2. This is a major contributor to greenhouse-gas-targeted savings.

Changing from AC to EC condenser fans is a simple process, as proven by existing users. A speed control line is required, but not to have a controller in modern refrigeration circuits is very rare and therefore the application of the EC technology is easy.

3. best PrACtICe of eC In VentIlAtIon sYsteMs

It is common for central ventilation systems to use motorised, backward-curved impellers, as shown in Figure 7, as these are by nature more fitting to Australian systems.

The use of EC backward-curved impellers is now becoming more common as, in combination with pressure-monitoring controllers, required ventilation rates can be specified and maintained irrespective of the number of exhaust vents that are open.

In Figure 7, a physical example of an apartment building lay-out is shown with room ventilation systems discharging into a central system.

In order for the rooms to ventilate at the regulated required rate their ventilation fan must operate against a known and constant back pressure. Commonly, axial fans are used to ventilate apartments and therefore back pressure control is paramount as axial fan performance is particularly sensitive to changes in pressure.

Constant: TD (°K)Variable: Fan speed, control voltage, sound level, air quality, heat rejection (kW), condenser fan power (kW).

Condenser Fan Power Curoe:Use this to establish fan power from the duty point.

Constant: Heat Rejection Capacity (kW)Variable: Fan speed, control voltage, sound level, air quality, T.D., condenser fan power (kW).

Constant: Fan speed, control voltage, sound level, air quality, condenser fan power (kW)Variable: T.D., heat rejection capacity (kW).

EC Condenser performance chart

Figure 6: The EC axial fan and the EC condenser performance chart after Giles (3).

Table 1: Temperature bin table for Melbourne.

Table 2: Power and greenhouse gas (GHG) savings with EC condenser fans.

Temperature bin hours Melbourne

Ambient temperature

Cum h/yr from 20 degrees

Hours per year per bin.

34 54 1533 75 2132 105 3031 138 3330 159 21 1.8%29 220 6128 272 5227 329 5726 407 78

EC condenser fans

Savings 100% load 80% load 50% load

Coldroon [GWhr] 39,804,863 123,978,878 184,694,561

GHG [tonne CO2] 52,940,467 161,172,541 245,643,766

Air conditioning [kW] 601,116 1,872,276 2,789,179

GHG [tonne CO2] 799 2,490 3,709

Total GHG [MtonneCO2] 52,941 161,175 245,647


F O R U M

Traditionally a central ventilation unit is specified for the maximum pressure required when all the bathroom fans are discharging into the central system. The fan runs giving this pressure at all times irrespective of the number of exhaust units operating, and therefore the system is never balanced.

With EC, however, the central ventilation unit can be controlled by measuring pressure in the central system as a differential against atmosphere. The design pressure at maximum ventilation is calculated at the design stages and then this is set in the controller (shown in Figure 8) at commissioning with all the exhaust systems in the building running.

Typically individual exhaust systems in an apartment building operate at varying times of the day dependant upon the occupants. Therefore there will be varying number of axial fans pressurising the central riser at any one time. Using EC, this pressure variation is sensed and the EC fan is reduced in speed maintaining the constant pressure in the system, as shown in Figure 8. This in turn ensures the correct ventilation rates in each room.

By controlling the ventilation system at its design pressure the optimum control is obtained. This means that during periods of non-occupancy, the central ventilation system will reduce in fan speed, as shown in Figure 8.

As outlined previously, typically 50% power savings are available with EC when speed is reduced by 20% – i.e. if 20% of the occupants go to work in the day and turn off their ventilations systems – approximately 50% power savings will be achieved.

4. best PrACtICe of eC In refrIgerAtIon And CoolIng CIrCuIts

In refrigerated cabinets existing shaded pole motors are replaced by single core EC fans. The reduction in energy requirement and improvement in COP is shown in Figure 9.

.

In a 12-month period the power savings per fan is 30W or 262.8 kWh assuming the fans run 24/7. This corresponds to 352kg of carbon per year. It is reasonable to consider the population of shaded pole motors in commercial refrigerators in Australia to be in excess of 150,000. This would suggest that minimum savings of 38,000 tonnes of greenhouse gas (carbon dioxide) can be affected.

If improved COPs are also factored in as shown in the table then further improvement of 16-47% can also be realised on this figure.

5. ConClusIonIt has been shown that power consumption in buildings is significant enough for innovation to be applied. The use of EC fan systems based on high efficiency direct current supply is a high efficiency motor/speed control couple solution.

Integrated PID speed control features available in EC fans allows near fan law control of power consumption.

Examples of best practice use of high-efficient fans include

• thereplacementofbelt-drivenforwardcurvefanssystemswith EC backward-curve plug fans in air conditioning units;Figure 8: EC control in a central ventilation system.

Figure 7: The application of EC in a central ventilation system.

Mandatory disclosure, rising energy costs and concerns about carbon emissions all mean one thing: updating the existing building stock has become the most important of tasks. With up to 50 per cent of a building’s energy dedicated to HVAC&R, and given most of our building stock isn’t new – and not really designed with energy efficiency in mind – it’s high time our older buildings were brought up to speed.

That’s where AIRAH’s Pre-loved Buildings Conference comes in.

The conference will focus on optimising the performance of pre-loved buildings through:

• Retrofittingoccupiedbuildings

• Heritagebuildingrefurbishment

• BIMinexistingbuildings

• Buildingtune-ups

• Optimisingcontrols

• Regulatoryrequirementsandpolicy-drivenincentives

• LearningfromGreenBuildingFundcasestudies

Forspeakerinformationandconferenceregistrationsgoto

www.airah.org.au/preloved2011

ConferenceSponsors:

Table 3: An EC fan for refrigerators and its use therein.

Figure 9: An EC fan for refrigerators and its use therein

Savings Yearly savings per Fan @ $0.12 ø kWh

System COp 1.25 2.0 2.2 2.4

AC Q-motor $58.66 $48.88 $47.40 $46.77

EC W1G200 147% 122% 119% 116%

Mandatory disclosure, rising energy costs and concerns about carbon emissions all mean one thing: updating the existing building stock has become the most important of tasks. With up to 50 per cent of a building’s energy dedicated to HVAC&R, and given most of our building stock isn’t new – and not really designed with energy efficiency in mind – it’s high time our older buildings were brought up to speed.

That’s where AIRAH’s Pre-loved Buildings Conference comes in.

The conference will focus on optimising the performance of pre-loved buildings through:

• Retrofittingoccupiedbuildings

• Heritagebuildingrefurbishment

• BIMinexistingbuildings

• Buildingtune-ups

• Optimisingcontrols

• Regulatoryrequirementsandpolicy-drivenincentives

• LearningfromGreenBuildingFundcasestudies

Forspeakerinformationandconferenceregistrationsgoto

www.airah.org.au/preloved2011

ConferenceSponsors:


F O R U M

• integratedECcondenserslowerspecificfanpowerandallowfloating head pressure control;

• constantvolumecontrolofventilationsystemsallowstuningof ventilation power consumption to occupancy rates

• massivereductionoffanpowerinfridgeswithsubsequentimprovements of COP.

Integration of EC fans into internet and electronic communication networks is simple, and remote site monitoring and effective reactive maintenance without system failure is simple to achieve. ❚

referenCes:1. Atkinson M. 22 July 2008, Building a better

Climate Solution, Financial Review.

2. Lockwood G. 9-10 November 2004, Energy savings by improved application of fans in Air Handling unit, IMechE Events Publications, International Conference on Fans.

3. Giles D. 2007, The Magic of EC condensers, Propeller 21, internal publication, ebm-papst Pty Ltd. – www.ebmpapst.com.au

4. Kroger T. Jan 2003, Heat reclaim v floating condensing pressure, Celsius.

5. Anderson S. June 2007, Cold Hard Facts – The Refrigeration and Air Conditioning Industry in Australia; Australian Government, Dept of Environment and Water and Resources.

AIRAH technical publications

Purchase online at www.airah.org.au

Consult the cornerstone – Consult the DA manual.

The Design Application (DA) series of publications produced by

AIRAH are best practice guidelines to assist HVAC&R practitioners

with their day to day tasks in the design, operation and

maintenance of mechanical building services.

APPLICATION MANUAL

CENTRIFUGAL PUMPS

Australian Institute of Refrigeration, Air Conditioning and Heating

DA01

APPLICATION MANUAL

STEAM AND CONDENSATE


T H E A U S T R A L I A N I N S T I T U T E O F A I R C O N D I T I O N I N G A N D H E AT I N G

DA11

APPLICATION MANUAL

WATER TREATMENT



DA18

APPLICATION MANUAL

NOISE CONTROL



DA02

APPLICATION MANUAL

FANS



DA13

APPLICATION MANUAL

HUMID TROPICAL AIR CONDITIONG



DA20

APPLICATION MANUAL

DUCT WORK FOR AIR CONDITIONING



DA03

APPLICATION MANUAL

AMMONIA REFRIGERATION



DA21

APPLICATION MANUAL

HVAC&R AN INTRODUCTION



DA08

APPLICATION MANUAL

AIR FILTERS



DA15

APPLICATION MANUAL

WATER SYSTEM BALANCING



DA24

APPLICATION MANUAL

AIR CONDITIONING LOAD ESTIMATION



DA09

APPLICATION MANUAL

AIR CONDITIONING WATER PIPING



DA16

APPLICATION MANUAL

INDOOR AIR QUALITY



DA26

DA19 HVAC&R MAINTENANCE Application Manual

••• 20

Application Manual HVAC&R MAINTENANCE DA19

••• 21

EquipmentEconomic life (years)

Air conditioning unit – Room type

7 – 10

Air conditioning unit – Split units (up to 10 kW)

7 – 10

Air conditioning unit – Package (10 kW – 100 kW)

10 – 15

Air conditioning unit – Split package (10 kW – 100 kW)

10 – 15

Air handling unit – Proprietary line central station single or multiple zone20 – 25

Air handling unit – Custom built central station

20 – 30

Air filters – Dry media disposable

0.5 – 1.5

Air filters – HEPA

2 – 5

Air filters – Kitchen hood grease filters

3 – 6

Automatic controls and instrumentation

20 – 25

Boilers – Fire tube

15 – 20

Boilers – Water tube

25 – 30

Boilers – Cast iron

25 – 30

Boilers – Finned copper tube heat exchanger

20 – 25

Boilers – Electrode

15 – 20

Chilled beams

20 – 25

Coils – Cooling and heating

20 – 25

Cooling towers

10 – 25

Ductwork and fittings

20 – 30

Damper actuators (VAV controllers)

20 – 30

Electric motors

20 – 25

Electric storage heaters

20 – 25

Electric strip heaters

8 – 12

Electrical final circuits and outlets

20 – 25

Electrical switchgear and distribution equipment

25 – 30

Electrical mains cables

25 – 30

Evaporative air coolers

10 – 20

Fans

15 – 20

Gas convection heater

15 – 20

Generators

15 – 20

Heat exchangers

20 – 25

Humidifiers

10 – 15

Pipework and valves

20 – 25

Pumps

20 – 25

Radiators – Hot water

20 – 25

Refrigeration chillers – Absorption

20 – 30

Refrigeration chillers – Centrifugal

20 – 25

Refrigeration chillers – Reciprocating

15 – 25

Refrigeration chillers – Screw/Scroll

20 – 25

Tanks

20 – 30

Variable air volume – Terminal units

15 – 25

Table 2.1 Economic (service) life of equipment

Note: The above values are given for guidance only. The assumed life of a plant item may vary depending

on the particular project.

Reproduced from AIRAH Handbook, 4th edition)

3.1 GeneralTo allow the maintenance of plant to be carried out quickly and efficiently it is essential that all of the plant is safely accessible, all items are identified and all services required are available. This should have been resolved during the design and construction period.Maintenance issues need to be considered throughout the lifecycle of an HVAC&R system. As a guide the following list of maintenance considerations should be accommodated during the design, construction and handover stages of a project.

3.2 Design considerationsAll HVAC&R systems should be designed to be as simple, reliable and sustainable as possible while being fit for purpose and providing the required function. This is particularly true of control systems associated with HVAC&R systems.

System designers are best placed to develop the design/maintenance philosophy for a building or system. The maintenance philosophy should be developed based on the maintenance objectives of the owner and the final design should take full account of the maintenance policy, refer section 4.

The maintainability of plant and systems is an important determinant in how energy and water efficient the systems will be over their whole life cycle. Something that is difficult to maintain and tune will be much less likely to operate efficiently and as intended than something that is easier to maintain. Designers should carefully consider the complexity of the systems they conceive with respect to maintenance and operating requirements and the maintenance provider’s ability to properly maintain these services.Maintainability also relates to issues of equipment selection and ongoing maintenance cost and convenience. Consideration should be given to the standardization of common components in a new installation, same make/type of pumps, valves, and the like to reduce the number and type of spare parts that are required to be held or accessed. The ability to readily and cost effectively access

spare parts also needs to be considered during equipment selection to help ensure that the life cycle costs of the systems are minimized.Similarly consideration should be given to the use of specialist or non-specialist plant and local or exotic plant origins. The availability of local maintenance knowledge, equipment (spares), training and support can improve both system maintainability and sustainability. The use of an established technology rather than a new technology in a design may be more appropriate in some cases due to the unavailability of future maintenance skills and resources.Designers can reduce or minimise future maintenance

by using high quality components (reduced mean time between failure), by using components or systems requiring no maintenance (passive systems) or by using duplicate services (run/standby pumps).Designers should consider the commissionability of the system. Commissionability relates to the extent to which the design and installation of HVAC&R systems facilitates system balancing and tuning to required performance.Designers should consider “building in” systems for

monitoring and feedback of plant operation into their designs. Built in monitors can be linked to building management systems and can be associated with future condition monitoring maintenance strategies.

Maintenance in design, installation and handover

3

Project timeline

Rel

ativ

e co

st

OutlineDesign

DetailedDesign

InstallationOperation

Commissioningand handover

Figure 3.1 Relative cost of changes during a construction project

APPLICATION MANUAL

HVAC&R MAINTENANCE

Australian Institute of

Refrigeration, Air Conditioning

and Heating


DA

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NC

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AP

PL

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DA19

Australian Institute of Refrigeration Air Conditioning and Heating

Level 3, 1 Elizabeth Street, Melbourne VIC 3000

Tel: +61 3 8623 3000 Fax: +61 3 39614 8949

www.airah.org.au

APPLICATION MANUAL

CENTRIFUGAL PUMPS


DA01

APPLICATION MANUAL



DA11

APPLICATION MANUAL

WATER TREATMENT


DA18

APPLICATION MANUAL

NOISE CONTROL


DA02

APPLICATION MANUAL

FANS


DA13

APPLICATION MANUAL



DA20

APPLICATION MANUAL



DA03

APPLICATION MANUAL

AIR FILTERS


DA15

APPLICATION MANUAL



DA21

APPLICATION MANUAL



DA08

APPLICATION MANUAL



DA16

APPLICATION MANUAL



DA24

APPLICATION MANUAL



DA09

APPLICATION MANUAL

COOLING TOWERS


DA17

APPLICATION MANUAL

INDOOR AIR QUALITY


DA26

Application Manuals in this series:

DA01 Centrifugal Pumps – selection and application

DA02 Noise Control in and around buildings

DA03 Ductwork for air conditioning

DA08 HVAC&R an introduction

DA09 Load Estimation and psychrometrics

DA11 Steam – distribution and condensate recovery

DA13 Fans – selection and application

DA15 Air Filters – selection and application

DA16 Water Piping for air conditioning

DA17 Cooling Towers

DA18 Water Treatment

DA19 HVAC&R Maintenance

DA20 Humid Tropical air conditioning

DA21 Ammonia Refrigeration

DA24 Water System Balancing

DA26 Indoor Air Quality

DA17 COOLING TOWERS

Application Manual

••• 56

Application Manual

COOLING TOWERS DA17

••• 57

If the stated sound power level is a total cooling tower

sound power level then the free field sound pressure level

at any point around the tower can be determined from:

Lp

= L

w + 10 log10 (Q/4πr 2)

Where;Lp

= Sound pressure level (dB re 2OµPa)

Lw

= Sound power level (dB re 1pW)

r =

Distance from tower (m)

Q =

The directivity factor

The directivity factor Q, if available from the manufacturer,

is specified at a given angle from the centre line of the

tower. Typically Q may be as high as 8 directly opposite

the inlet or outlet, falling to 1 or 0.5 at the sides of the

tower (see Figures 3.15 and 3.16). In practical terms, noise

levels off the cased side of a tower will often be 6 to 12 dB

less than the levels off the louvered side.

Figure 3.15 Directivity factors for induced draft tower

Figure 3.16 Directivity factors for forced draft tower

A correction to the calculated sound pressure level should

be made for any reflective surfaces such as walls, as

described above, when sound pressure levels are stated by

the cooling tower supplier.

Because the noise from a cooling tower with centrifugal

fans is highly directional (see Figure 3.16), walls behind and

at the sides collectively make less than 1dB increase in the

noise to the intake side, but a wall opposite the intake will

increase the noise to the rear and sides by 9dB.

Cooling towers with vertical symmetry give increases of

approximately 3dB for a receiver opposite one wall or

approximately 6dB for a receiver opposite two walls. The

best way of reducing cooling tower noise is to use fan

motor speed controllers. Then the fan speed and fan noise

is reduced during low load (particularly at night). Halving

the fan speed could typically provide a 13 to 18dB noise

reduction.

One way of reducing noise levels from cooling towers

is to select a larger tower with a lower pressure loss or a

larger, slower speed fan. This increases the capital cost but

reduces fan power, and hence fan sound power, and fan

energy operating costs.

Alternatively, discharge stacks and noise attenuators

can be applied to control air outlet noise. Special noise

attenuating louvres can also be applied to air intakes. It

should be noted that lower sound levels often come at the

cost of lower airflow and the resultant effect on tower heat

rejection performance.

3.18. Fire protection

Cooling towers are generally drained when not in use for

microbial management reasons. When dry, cooling towers

may constitute a fire hazard and consideration should

therefore be given to the provision of fire protection by

sprinklers in accordance with AS 2118.

Cooling tower materials can be assessed for their fire

characteristics under the AS 1530 series of test methods.

Casings, louvres, fill and drift eliminators can all be

assessed for fire characteristics such as flammability, smoke

developed and spread of flame. Building regulations may

apply in some applications.

Partition walls between the cells of a multi cell tower can

be fire rated to reduce or retard fire spread in the event

of a fire incident.3.19. Documentation

3.19.1. Operating and

maintenance manuals

Comprehensive operation and maintenance manuals

should be provided with the cooling tower and cooling

water system. AIRAH application Manual DA19 provides

comprehensive details on the possible content and format

of these.3.19.2. Commissioning data

All systems should be fully commissioned and fine tuned

to the specific application. A copy of all commissioning

data should be maintained in the operating and

maintenance manuals.

3.19.3. Certificates

and registrations

A copy of all applicable certificates and registrations should

be maintained in the operation and maintenance manuals.

4.1. Tower location

4.1.1. General

Open circuit towers, closed circuit towers and evaporative

condensers all require good access to ambient air to

achieve their rated performance. Sufficient space needs

to be provided around units to achieve this, at least

the manufacturers recommended minimum. Where

recommendations cannot be achieved the unit may be

susceptible to recirculation and may need to be capacity

derated for the purposes of the particular application.

Units are located to prevent warm discharge air entering

building air intakes (mechanical or natural) or flowing

across populated areas. Access is provided for installation,

servicing and maintenance.

The essential points to consider when locating a unit are

the net free area of the air inlet pathways to the tower,

any blockage of tower air intakes or louvres by pipes

or plant and the clearances between the tower and

adjacent walls etc. Any issue that can increase the pressure

drop, cause poor distribution of air or cause or promote

recirculation should be resolved. If the tower manufacturer

recommended velocity limits and required distances can

be achieved, then the tower rating is also achievable.

4.1.2. Interference

Interference, in the form of local heat sources, such as an

adjacent cooling tower upwind of the subject cooling

tower, can artificially elevate the wet bulb temperature

of the entering air, thereby affecting tower performance

(see Figure 4.1). When planning the installation of multiple

cooling towers or an additional cooling tower, proper

tower placement and orientation can minimise this effect.

Figure 4.1 Interference

When considering locating a new cooling tower adjacent

to an existing cooling tower, it may be prudent to measure

wet bulb temperatures at a number of locations at varying

distances from the existing cooling tower, under prevailing

summer wind conditions and so construct a wet bulb

temperature contour map of the site.

The new tower should then be sited to avoid the wind

shadow of the existing cooling tower. If it is necessary to

locate the new tower close by the existing tower, then it

may be necessary to increase the design entering wet bulb

temperature to achieve the required performance. The size

of the tower will then be increased. Figure 4.2 shows the

proper orientation of towers with regard to the prevailing

wind direction to minimise interference.

As a general rule of thumb the distance between

towers should be at least one tower length to minimise

interference effects from one tower to another.

Figure 4.2 Orientation of towers to suit prevailing wind

4.1.3. Recirculation

Recirculation is defined as the mixing of discharge air from

a cooling tower with the ambient air entering the tower.

The discharge air may be visible having formed a saturated

Tower location

and installation

4

Wind

Sector of no interference

1 Tower LengthMinimum

Des

ign

Win

dD

irect

ion

Des

ign

Win

dD

irect

ion

Q = 1

Q = 1

Q = 1

Q = 1

Q = 1/2

Q = 8

Q = 1/2

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APPLICATION MANUAL

COOLING TOWERS

Australian Institute of Refrigeration, Air Conditioning

and Heating

THE AUSTRALIAN INSTITUTE OF REFRIGER ATION, AIR CONDITIONING AND HEATINGDA

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DA17Australian Institute of Refrigeration Air Conditioning and Heating

Level 3, 1 Elizabeth Street, Melbourne VIC 3000

Tel: +61 3 8623 3000 Fax: +61 3 39614 8949

www.airah.org.au

APPLICATION MANUAL

CENTRIFUGAL PUMPS


and Heating


DA01

APPLICATION MANUAL



and Heating


DA11

APPLICATION MANUAL

NOISE CONTROL


and Heating


DA02

APPLICATION MANUAL

FANS


and Heating


DA13

APPLICATION MANUAL



and Heating


DA20

APPLICATION MANUAL



and Heating


DA03

APPLICATION MANUAL

AIR FILTERS


and Heating


DA15

APPLICATION MANUAL



and Heating


DA21

APPLICATION MANUAL



and Heating


DA08

APPLICATION MANUAL



and Heating


DA16

APPLICATION MANUAL



and Heating


DA24

APPLICATION MANUAL



and Heating


DA09

APPLICATION MANUAL

WATER TREATMENT


and Heating


DA18

APPLICATION MANUAL

INDOOR AIR QUALITY


and Heating


DA26

Application Manuals in this series:

DA01 Centrifugal Pumps – selection and application

DA02 Noise Control in and around buildings

DA03 Ductwork for air conditioning

DA08 HVAC&R an introduction

DA09 Load Estimation and psychrometrics

DA11 Steam – distribution and condensate recovery

DA13 Fans – selection and application

DA15 Air Filters – selection and application

DA16 Water Piping for air conditioning

DA17 Cooling TowersDA18 Water Treatment

DA19 HVAC&R Maintenance

DA20 Humid Tropical air conditioning

DA21 Ammonia Refrigeration

DA24 Water System Balancing

DA26 Indoor Air Quality

Order your copy online at www.airah.org.au or email [email protected]

AIRAH’s newly released HVAC Hygiene Best Practice Guidelines are available to purchase in hard copy.

n Establishes the criteria for evaluating the internal cleanliness of HVAC system components

n Clearly determines when cleaning is required, according to the building use

n Describes the components of HVAC systems to be evaluated

n Describes the types of contamination likely to be encountered and includes for post fire and flood damage assessments

n Specifies minimum inspection frequencies for various HVAC systems and components for scheduled maintenance programs

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HVAC HYGIENEAIRAH BEST PRACTICE GUIDELINES

www.airah.org.au

17

HVAC HYGIENE

AIRAH BEST PRACTICE GUIDELINES

www.airah.org.au

If fungal contamination in or on a system component

is suspected, but not readily identifiable through visual

assessment, then surface samples should be taken for

laboratory analysis. Recommended procedures for taking

surface samples for fungal contamination assessment are

detailed in Appendix D.

If a system or component has been confirmed, by

visual observation or analytical assessment, to be

mould contaminated then the affected system or

system components should be decontaminated.

Decontamination or remediation of a mould affected

system should only be undertaken if a thorough

assessment of the system has been undertaken and

not an assessment based on limited samples.

Note: Decontamination of a HVAC system due to mould or

microbial contamination is a specialised activity that is

outside the scope of this Guideline. State and Territory

governments may have specific requirements for the

reporting and control of microbial contamination

within HVAC systems. System owners and operators

should ensure that they are familiar with the regulatory

requirements of the jurisdiction in which they operate.

Samples for fungal analysis need to be sent to a

mycological laboratory for testing and assessment, and

identification as a fungal growth site. Details of sample

removal, transport, assessment and analysis should be

coordinated with the testing laboratory.

Fungal species identification may be helpful to

determine whether there is a shift from the indoor

to the outdoor concentration. This is needed in

order to perform a proper risk assessment. Clear

communication between the building owner and

the HVAC cleaner should be established in order

to determine an acceptable fungal level following

cleaning and remediation of the HVAC system.

Once the system has been decontaminated and cleaned

the system hygiene level should be verified, see Section 3.

In particular the presence and source of moisture

supporting any mould growth in the system should

be identified and prevented.

Mould in buildings more generally is covered in the World

Health Organisation (WHO) Guidelines for Indoor Air

Quality, Dampness and Mould.

2.5.4. Asbestos

If HVAC system contamination by asbestos dust or fibres is

suspected then samples should be taken and analysed. If

the presence of asbestos contamination is confirmed the

entire system should be decontaminated by competent

persons.

Note: Decontamination of a HVAC system due to asbestos

contamination is a specialised activity that is outside the

scope of this Guideline.

If potentially friable asbestos containing materials are found

within a HVAC system, the system should be shut down,

the asbestos containing material should be removed by

licensed asbestos removalists and alternative insulation

products installed in its place. This includes the insulation

board surrounding duct mounted electric heaters if it is

verified to contain asbestos.

Note: All asbestos removal work should be carried out in

accordance with NOHSC:2002 – National Code of Practice

for the Safe Removal of Asbestos and all other applicable

state and local government regulations and requirements.

Once all asbestos materials and contamination has

been removed the entire HVAC system should be

cleaned and the system hygiene level should be verified.

The components should be labelled as asbestos-free

and the hazardous materials/asbestos register updated.

2.5.5. Deterioration or

non-porous surfaces

When the surface of non-porous components are

deteriorated and contributing particulates or odours to

the air stream, or otherwise adversely affect the quality

of the air moving through the system, restoration should

be performed and inspection/cleaning of all downstream

components carried out as required.

2.5.6. Deterioration of porous

surfaces and linings

When internal HVAC insulation or lining materials

are found to be deteriorated and traces of the

insulation or lining product found within the system

components, the deteriorated surfaces should be

restored and the affected components of the system

should be cleaned and the entire system inspected

for contaminants and cleaned as required.

2.5.7. Water damage

All HVAC system surfaces and components subjected to

water damage should be evaluated to determine salvage

ability and likely success of any restoration activity. In

particular any internal insulation should be investigated for

evidence of water logging or fungal growth.

Any system components or ducts deemed salvageable

should be thoroughly cleaned and free from microbial

growth. Any water affected or water logged insulation

products should be replaced.

Any water damage due to condensation within the

system also needs to be assessed and the cause of the

condensation identified and mitigated.

Any water leaks (pipes, building structure) need to be

identified and repaired prior to undertaking any HVAC

cleaning or restoration work.

2.5.8. Fire and smoke damage

All HVAC system components subjected to heat or smoke

should be evaluated to determine their integrity and likely

success of any restoration activity. In particular all fire and

smoke dampers and all electric duct mounted heaters

should be assessed for fitness for purpose in accordance

with the survey and maintenance protocols of AS 1851.

Any components or surfaces deemed unable to withstand

proper mechanical cleaning and restoration are beyond

salvage and should be replaced. All porous surfaces

subjected to fire or smoke damage should be evaluated

for friability and odour retention following the cleaning

process. Any areas assessed as friable should be replaced

or resurfaced. Any materials likely to impart odours to the

supply air stream should be replaced.

Any component surface exhibiting damage due to heat

exposure should be restored to an acceptable condition

or replaced. Consideration should be given to any residual

smoke residue that may remain on the internal surfaces of

the system. Certain types of smoke residue can be highly

corrosive and lead to eventual deterioration of the affected

component surface. Some smoke residues can also be

toxic. Any metal surfaces affected by smoke, heat or smoke

residue should be evaluated by competent persons to

determine if restoration will be achievable or effective.

Any components affected by water from fire suppression

activities should be assessed in accordance with 2.5.7.

2.5.9. Building or renovation

contamination

Any HVAC system subject to this contaminant category

should be evaluated to determine the hygiene level of

the system. Any system or components found to have

accumulated general dust and particulate debris greater

than the levels specified in Table 2.3 should be cleaned.

Depending on the type of contamination encountered,

TABLE 2.3 MiniMuM AccEpTABLE sysTEM hygiEnE sTAnDArDs

HVAC system Classification.

(See 1.5)

HVAC System or Component

(See 1.6)

Minimum hygiene level

(See Table 2.1)

general use systems

AHU

Clean

Supply system – moisture producing

equipment

Clean

Air intakes and exhaustsClean

Supply air system, or

Return air system, or

Outside air system

Pre Filtration – Moderate

Post Filtration – Light

No Filtration – Light

Exhaust air systemModerate

Non-ducted refrigerated a/cLight

Evaporative coolersLight

special use systems

AHU

Clean

Supply system – moisture

producing equipment

Clean

Air intakes and exhaustsClean

Supply air system, or

Return air system, or

Outside air system

Pre filtration – Light

Post Filtration – Clean

No Filtration – Clean

Exhaust air systemModerate

Non-ducted refrigerated a/cClean

Evaporative coolersClean

Note: It should be noted that certain HVAC special use applications such as clean rooms, operating theatres and the like may have

specific requirements for higher levels of HVAC hygiene determined by other governing bodies, manufacturing/processing

activities, regulations and the like. 12

HVAC HYGIENE


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HVAC HYGIENE


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1.8.4. Unusual contamination eventHVAC systems and components should be inspected after

any unusual contamination event such as a fire or flood or

any renovation/building activities. Unusual contamination

events are assessed in accordance with 2.5 of this Guideline.1.9. HVAC restoration

Where HVAC systems or components cannot be

adequately cleaned they should be repaired or replaced.1.10. Best practice hygiene management1.10.1. PrinciplesBest practice HVAC hygiene management can be achieved

through the implementation of a few relatively simple

management practices.• Filter maintenance – Filters are the primary defence

against dust and particulates. System filters should

be regularly inspected and maintained, at least in

accordance with the requirements of AS/NZS 3666.2

and AIRAH DA19 on HVAC&R maintenance. The initial

system assessment should include a review of the

filter specifications to determine if filter application

is optimal for the HVAC system, including the filter

type, filter rating, system airflow and pressure, the

likely contaminant profile and the general quality

of installation and maintenance. Comprehensive

information on the selection and application of air

filters is provided in AIRAH DA15.• Management of moisture – moisture management

is critical for minimising the potential for fungal

contamination and any spills, leaks or wetting of HVAC

systems or components should be dried out and

inspected as soon as is practicable.• Inspection and assessment – All HVAC systems should

be periodically inspected and assessed in accordance

with the recommendations of this Guideline.

• Clean, restore and verify hygiene level – once systems

or components have been identified as contaminated,

cleaning and restoration work should be undertaken

immediately including verifying the cleanliness

of the restored system.• Good housekeeping – HVAC hygiene also requires

a common sense approach to limiting contaminant

generating activities within a building and promptly

responding to any unusual contamination event.

Even everyday tasks such as cleaning (vacuuming,

disinfecting), food preparation and document printing

and copying may be inadvertently introducing

unacceptable contaminants into the HVAC system.

1.10.2. RecordsBest practice HVAC hygiene management requires good

building and system documentation including up to date

operation and maintenance manuals, accurate as installed

system drawings showing access points and original

system commissioning data.The building owner should maintain records of any

conducted HVAC Hygiene Inspection Reports along

with records of any cleaning or remedial works and any

system hygiene verification carried out as a result of such

inspections. Maintaining these records builds up a hygiene

profile of a building or system over time that assists in

HVAC hygiene management.In addition, any reports relating to indoor air quality

assessments or any energy management reports should

also be retained with these records.1.11. HVAC standards and regulationsThe primary design standards for HVAC systems are AS

1668.2 which deals with ventilation requirements (minimum

outdoor air, location of intakes and discharges, exhaust rates)

and AS/NZS 3666.1 which deals with microbial control.

AS/NZS 1668.1 details requirements for fire and smoke

control associated with mechanical ventilation systems.

The primary standard for HVAC systems operation and

maintenance is AS/NZS 3666.2. Its primary focus is the

control of microbiological contaminants such as Legionella

sp. in building water and air handling systems but it also

focuses on general HVAC hygiene.The standard covering the maintenance of the fire and

smoke control features of HVAC systems is AS 1851.

AS/NZS 1668.1, AS1668.2 and AS/NZS 3666 part 1 and part

2 are called up in the Building Code of Australia as primary

referenced standards and are mandatory in all states and

territories of Australia. Apart from building legislation there

may be individual state specific occupational health and

safety legislation and regulations relating to HVAC hygiene

that should be complied with as they are relevant to both

operation and maintenance.The selection and application of general filters are covered

by AS 1324 and minimum application requirements for the

filtration of ventilation systems are specified in AS 1668.2.

HEPA filters are classified in AS 4260.It is not intended that the recommendations of this

Guideline conflict with the requirements of any of these

mandatory standards or with the requirements of any

Commonwealth, State or Territory regulation.

2.1. Hygiene levels definedThe descriptions listed in Table 2.1, provide the HVAC

system hygiene inspector with four hygiene levels to

determine if cleaning is required when assessed against

the minimum acceptable hygiene standards as listed

in Table 2.3.

2.2. Access for inspectionAccess is required in order to inspect the internal surfaces

of all components and a representative portion of the

internal surfaces of the HVAC systems as defined in

1.6.12. AS/NZS 3666 parts 1 and 2 both require adequate

provision of access for maintenance. Inspections and

System inspection and assessment

2

TABLE 2.1 DEFINITION OF HYGIENE LEVELS

Hygiene Level Description1. CleanNo visible dust, debris or other contamination.

2. Light Only slightly visible layer of fine general dust consistent over the component surface with little

to no variations in density.Component surface remains visible beneath the fine layer of dust.

3. Moderate Visible levels of general dust with varying density and limited areas of accumulated fine debris.

Component surface is still visible in some areas beneath the fine dust but in isolated sections may not be.

4. Heavy High levels of visible dust, debris, fibres or any

other contamination that cover the component.

Component surface is barely if not at all visible beneath the contamination.Reference images for the four defined hygiene levels are provided in Appendix F.

HVAC HygieneBEST

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