In the heat of the moment - Eskom Home€¦ · In the heat of the moment Optimise heating,...

In the heat of the momentOptimise heating, ventilation and air conditioning

124537ESKD HVAC brochure.indd 1 2010/09/10 9:52 AM

Energy efficient heating, ventilation and air conditioning (HVAC) 2

1. Introduction 2

2. HVAC basics 2

3. Heating 2

3.1 Heating: opportunities for efficiency improvements 3

4. Ventilation systems 3

4.1 Ventilation systems: opportunities for efficiency and energy saving improvements 3

4.1.1 Replace leaky dampers 4

4.1.2 Use separate make-up air for range hoods 4

4.1.3 Use economiser controls 4

5. Air conditioning and refrigeration 4

5.1 Opportunities for improved efficiency: air conditioning and refrigeration equipment 4

5.1.1 Minimise the temperature difference 5

5.1.2 Reduce the cooling load 5

5.1.3 Optimise cooling towers 5

5.1.4 Adjust control set points 5

5.1.5 Raise evaporator temperature (suction pressure) 5

5.1.6 Lower condensing temperature (discharge pressure) 5

5.1.7 Clean heat exchange surfaces 6

5.1.8 Provide cooler air to the condensers 6

5.1.9 Regular maintenance and monitoring 6

5.1.10 Recommended maintenance procedures specific to refrigeration 6

6. General opportunities for energy efficiency which apply across all HVAC systems 6

6.1 Air handling systems 6

6.2 Fans and pumps 6

6.3 Hot and chilled water piping 7

7. Energy Efficiency Checklist 8

8. Support and advice 9

9. References 9

Contents page


All sectors of the economy can reap major benefits from implementing

energy efficiency policies.

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Energy efficient heating, ventilation and air conditioning (HVAC)

1. Introduction

Throughout commercial, industrial and some residential premises, the use of systems to provide a comfortable living environment is common practice in South Africa today. These heating, ventilation and air conditioning (HVAC) systems consume large quantities of energy, particularly electricity and represent a key target area for improved energy efficiency. HVAC systems provide a key opportunity for optimisation. Achieving optimisation also means operational costs need not spiral out of control despite the possibility of substantial electricity price escalations.

In common with most other countries in both the developed and the developing world, South Africa needs more generation capacity. The extent to which Eskom is able to supply the country’s demand for electric power has a direct impact on economic growth. All sectors of the economy can reap major benefits from implementing energy efficiency policies. By optimising processes and plant efficiency, electricity users reduce input costs and increase their return on investment. As an added benefit, reduced energy consumption means reduced environmental impact, an important part of the “triple bottom line”.

Eskom’s Demand Side Management initiative is helping electricity users to identify various means of reducing their electricity consumption without impacting on their business performance.

This information brochure aims to assist industrial and commercial users of electricity to improve the energy efficiency of HVAC systems. It explains the benefits of energy efficient systems and common problems affecting efficiency, before describing a number of measures to improve operating efficiency and thereby reduce electricity usage and costs. It concludes with a summary checklist and details of free energy efficiency advisory services available from Eskom.

2. HVAC basics

A variety of HVAC systems are used in commercial buildings: however, most have certain major components in common, such as electrical motors (driving pumps, fans or compressors), ducting and filters. Proper maintenance of HVAC system components keeps the system operating at peak efficiency. This not only conserves energy and energy costs; it also helps maintain comfortable conditions, extends equipment life, and prevents costly breakdowns. Maintenance should be performed on a regular scheduled basis. A number of simple maintenance steps can be undertaken in-house. However, more comprehensive maintenance can be obtained by relying on qualified service organisations.

3. Heating

Heating is necessary where industrial or business activity takes place in temperatures that are unsuitably low for workers or for the processes being conducted by the business. In most instances the same units that provide air


conditioning, provide heating; reflecting the fact that changing seasons have an effect on whether air in the workplace needs to be heated or cooled to deliver comfortable conditions.

In more specialised applications, where large-scale heating is required, boilers may be employed which generate heat for dispersal by boiling water. Additionally, electrical heaters can be found in many business settings.

3.1 Heating: opportunities for efficiency improvements

Where boilers are used, simple interventions that support improved operation of equipment also contribute to better reliability. Such interventions should include:

• Inspectboilersforscaledeposits,accumulationofsedimentorboilercompoundsonwatersidesurfaces.

• Inspectelectricalcontactsandworkingpartsofrelaysinordertomaintaingoodworkingorder.

• Checkheaterelementsforcleanlinessandreplaceasnecessary.

• Checkinstrumentationandcontrolsforproperoperation,andrepairandadjustasnecessary.

Where zonal electric heating equipment is being used, the following maintenance activities will support improved efficiency:

• Ensureheattransfersurfacesofallunitsarekeptcleanandunobstructed.

• Makesurethatairmovementinandoutoftheunitsisunobstructed.

• Inspectheatingelements,controlsand,asapplicable,fansperiodicallytoensureproperfunctioningandcleanliness.

• Determineifelectricheatingequipmentisoperatingatratedvoltage.

4. Ventilation systems

Mechanical ventilation systems allow fresh air into buildings mainly to control odours typically caused by smoking, cooking or industrial activity. Ventilation has a significant impact on a building’s total energy consumption. The rate of ventilation, and the difference between outside and indoor temperatures, have a direct bearing on the energy consumed by the heating or cooling system to compensate for the heat gain or heat loss.

A properly functioning ventilation system is essential to the operation of any commercial building. Nonetheless, experience indicates that many buildings are using more ventilation than is minimally necessary. Another concern is that building owners are not taking full advantage of the various control and heat recovery devices that, when applied to the ventilation system, can reduce the energy consumed for heating and cooling. As a result, a substantial amount of energy is being wasted.

4.1 Ventilation systems: opportunities for efficiency and energy saving improvements

Since ventilation systems are driven by fans or pumps and deliver air through ducts, most opportunities for improved performance and reduced electricity consumption relate to optimising these components. This is discussed in more detail in the general opportunities section on page 6.

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4.1.1 Replace leaky dampers Many ventilation systems have low quality outdoor air dampers that do not permit accurate control of airflow. Even when dampers are fully closed, the quantity of air leaking in may exceed minimum outdoor air requirements. Leaky outdoor air dampers can be replaced with high-quality, opposed-blade dampers that have air spats at the blade edges and ends.

4.1.2 Use separate make-up air for range hoodsKitchen equipment exhaust hoods and other process equipment hoods that frequently remove large quantities of conditioned air from a building must be replaced by introducing outside make-up air. To reduce the quantity of energy wasted in pre-conditioning supply air to exhaust hoods it is often possible to install a supply air system that is completely or partially separated from the rest of the building HVAC system.

4.1.3 Use economiser controlsMechanical cooling is often used when outside temperatures are relatively acceptable.

5. Air conditioning and refrigeration

The purpose of refrigeration or air conditioning systems is to move heat from a cooler space to a warmer space. In very simple terms, these systems move heat against its natural direction of flow.

The energy required moving the heat uphill from colder to warmer depends on two things:

• thetemperaturedifferencefromcoldtowarm,and;

• theamountofheatthesystemhastomove(thecoolingload).

5.1 Opportunities for improved efficiency: air conditioning and refrigeration equipment

One attractive characteristic of many air conditioning systems is that the system will deliver the cooling effect required over a wide range of conditions. Unfortunately, the energy consumed in extreme conditions is likely to be more than double that of normal conditions.

Often, extreme conditions result from inadequate or deficient operation and maintenance practices. Therefore, a simple but effective strategy for minimising energy cost involves attention to operation and maintenance procedures.

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Blower

Cooledair

Cooling coils Temperaturesensing bulbs Indoor air

Outdoor air

Hot air

Expansion valve

Condenser coils

Fan

Fan axle

Compressor

OUTDOORS

Figure 1: Typical air conditioning unit


These include:

5.1.1 Minimise the temperature difference• Cleanheatexchangesurfaces.

• Checkandreset–ifpossible,evaporatingandcondensingtemperatures.

• Avoidnon-condensableitemsintherefrigerant.

5.1.2 Reduce the cooling load• Insulatethecooledspaceandrefrigeration/chilledwaterlines.

• Reducewarmairinfiltrationtothecooledspace(especiallymoistair).

• Minimiseexcessenergyconsumptionloadswhichaddtothecoolingrequirement,such as open kettles in the kitchen.

5.1.3 Optimise cooling towers• Performchemicaltreatmentteststodetermineifsolidconcentrationsare

being maintained at an acceptable level.

• Keepthetowercleantominimisebothairandwaterpressuredrop.

• Cleanintakestrainer.

• Checkfansbylisteningforanyunusualnoiseorvibration.Inspectthecondition of the V-belt and align the fan and motor as necessary.

5.1.4 Adjust control set pointsProper control maintenance is essential in operating air conditioning systems optimally. Situations may prevail where the existing controls are not appropriate or are not capable of controlling the systems properly. The symptom of this may be as simple as a thermostat that fails to effectively control comfort levels in an occupied space.

5.1.5 Raise evaporator temperature (suction pressure)The amount of power demanded by an air conditioning compressor is determined by the difference between the evaporator and condenser temperature (or pressure). Therefore, if the system requiring cooling can tolerate a small increase in temperature at the evaporator, an opportunity to reduce compressor power may exist. In order to determine if such a change is possible, and will not damage the compressor, one should consult an air conditioning expert. Since compressors are finely tuned systems, caution should always be exercised when considering adjustments to operating conditions.

5.1.6 Lower condensing temperature (discharge pressure)The amount of power demanded by an air conditioning compressor is determined by the difference between the evaporator and condenser temperature (or pressure). Therefore, if the compressor can tolerate a small reduction in temperature at the condenser, an opportunity to reduce compressor power may exist. In order to determine if such a change is possible and will not damage the compressor, one should consult an air conditioning expert. Since compressors are finely tuned systems, caution should always be exercised when considering adjustments to operating conditions.

5.1.7 Clean heat exchange surfaces If the heat exchanging surfaces of the evaporator or air handling unit (AHU) in an air conditioningsystemofanysizeisnotclean,theevaporator/AHUisforcedtooperate at a lower temperature than necessary, increasing compressor power. In smaller systems, air, dust and other contaminants accumulate, while in large liquid systems regular maintenance is required to avoid excessive fouling of exchange surfaces.

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5.1.8 Provide cooler air to the condensers

Cooler air may allow the compressors to operate more efficiently.

• Rooftopcoolingunitscontainingcompressorsandcondensersgenerallydrawairfromclosetotherooftop.Coolerairmaybeavailable–ascloseas1.2to1.5metreshighofftheroof.

• Condenserunitsruncoolerwheninstalledonthesouthernsideofabuilding.• Avoiddirectsunlighttoshineoncondenserunitsanytimeduringtheday.• Ensuresufficientnaturalcrossventilationoverthecondenserunittoremoveanyhotairefficiently.• Avoidinstallingcondenserinclosedconfinedroomswherehotairmightaccumulate.Provideenoughvents

for hot air to escape or install whirley birds to remove hot air efficiently. 5.1.9 Regular maintenance and monitoring

• Usethesightglasstospotproblems–bubblesindicateproblems.

• Checklubricantsfrequently–thiswillalsoprolongthecompressorlife.

• Logtheoperatingparameterssuchasmotorcurrentstospotabnormalities.

5.1.10 Specific to refrigeration, the following maintenance procedures are recommended:

• Listenforunusualcompressoroperationsuchascontinuousrunningorfrequentstoppingandstarting,either of which may indicate inefficient operation. Determine the cause and, if necessary rectify the problem.

• Inspectinstrumentationfrequentlytoensurethattheoperatingoilpressureandtemperaturecomplywiththemanufacturer’s specifications.

• Inspectthetensionandalignmentofallbeltsandadjustasnecessary.• Lubricatethemotorbearingsandallmovingpartsaccordingtothemanufacturer’srecommendations.• Inspecttheinsulationonsuctionandliquidlines.• Inspectallheatexchangersurfacesandcleanasnecessary.• Inspectcompressorjointsandpipingconnectionsforleaksandrepairasnecessary.

6. General opportunities for energy efficiency which apply across all HVAC systems

With commonalities in the air handling equipment such as ducting and intakes, electrical components such as fans, pumps, compressors and piping systems, there are a number of maintenance areas that are applicable to all HVAC systems. These include:

6.1 Air handling systems

Simple maintenance procedures include:

• Inspectingductworkforairleakage.Sealallleaksbytapingorcaulking.• Inspectductworkinsulationandrepairorreplaceasnecessary.• Inspectdamperbladesandlinkages.Cleantheoilandadjusttheseonaregularbasis.• Inspectmixingdampersforproperoperation.• Cleanorreplaceairfiltersonaregularbasis.• Inspectairheating,cooling,anddehumidificationcoilsforcleanliness.• Inspectforleakagearoundcoilsoroutofthecasingandsealallleaks.• Inspectallroomairoutletsandinlets(diffusers,registers,andgrilles).Theseshouldbekeptcleanandfreeofalldirt

and obstructions.

6.2 Fans and pumps

Simple maintenance procedures include:• Checkthealignmentofthemotor,fanorpump.Alignandtightenasnecessary.

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Energy consumption

Savings lost without control maintenance and monitoring*Efficient

devices and installation Optimisation

of usage

Monitoring and maintenance

Sustained level of efficient energy use with control, ongoing monitoring and maintenance programme

Sustained level of efficient energy use without control, ongoing monitoring and maintenance programme

100%90%

70%

50%

0%

Intelligent

management of

energy end use:Efficent end use devices + automation and control system + monitoring, measurement and maintenance.

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• Lubricatemotoranddrivebearingsonaregularbasis.• Checkforovervoltageorlowvoltageconditiononmotors.• Checkforexcessivenoiseandvibration.Determinecauseandcorrect

as necessary.• Keepfanbladesclean.• Inspectdrivebelts.Adjustorreplaceasnecessarytoensureproper

operation. Proper tensioning of belts is critical.• Inspectinletanddischargescreensonfans.Theyshouldbekept

free of dirt and debris at all times.

6.3 Hot and chilled water piping

Simple maintenance procedures include:• Inspectallpipingforleakageatjoints.Repairasnecessary.• Inspectstrainersandcleanregularly.• Inspectventsandremoveallclogs.Cloggedventsretardefficientairelimination

and reduce efficiency of the system.• Inspectinsulationofhotandchilledwaterpipesandrepairorreplace

as necessary.• Checkflowmeasurementinstrumentationforaccuracyandadjust,repair,

or replace as necessary.

Effective maintenance programmes support the goals of strategic conservation, in that waste is reduced whenever the equipment is operative. Because HVAC equipment is used mostly during daytime hours, the benefits of effective maintenance are most pronounced during on-peak hours.

Various computer programmes are available to facilitate simple but comprehensive maintenance scheduling. Depending on the needs of a specific facility, some of these can provide weekly schedules along with specific ‘how-to’ instructions. More complex systems rely on monitoring devices to report service requirements as a result of excessive noise or vibration.

By targeting HVAC systems as a component of an overall energy management strategy, smart companies can ensure the continued comfort and safety of their workers without experiencing dramatic increases in energy costs.

Figure 2: Sustaining energy savings


7. Energy Efficiency Checklist Good housekeeping and regular maintenance of heating, ventilation and air conditioning systems makes perfect energy sense, saving breakdowns and money. Shown below is a summary of relatively simple actions that you can take to use electricity efficiently:

Checklist for the most important energy efficient options:

Check Date

1Where boilers are used check for scale deposits, electrical contacts, heater elements and control instrumentation.

2For compressors for cooling regularly listen for unusual sounds or vibrations and check for signs of wear.

3 Regularly lubricate fan bearings and clean fan components.

4 Regularly replace loaded air filters, replace leaky dampers and use economiser controls.

5 Insulate thermal surfaces such as coolant and hot water pipe work.

6 Inspect ductwork for air leaks.

7Optimise the performance of fans and pumps (see separate Eskom Energy Efficiency brochures on fans and pumps).

8For cooling equipment, ensure heat exchanger surfaces are clean and reset evaporation and condensation temperature particularly under extreme operating conditions.

9 Take full advantage of various control and heat recovery devices on the ventilation system.

10 Ensure electrical equipment is working at the rated voltage.

11Establish and follow a regular maintenance programme, ensure staff are trained accordingly and take advantage of a computer programme to facilitate maintenance scheduling.

12When fitting new equipment ensure that your supplier conducts a proper needs analysis, replaces oversized motors, new units are sized at optimum efficiency; and that your ventilation system is properly balanced by an experienced specialist.

13 Reduce HVAC operating hours to reduce electrical, heating and cooling requirements.

14 Eliminate HVAC usage in vestibules and unoccupied space.

15Minimize direct cooling of unoccupied areas by turning off fan coil units and unit heaters and by closing the vent or supply air diffuser.

16 Adjust thermostat settings for a change in seasons.

17 Reduce fan speeds and adjust belt drives.

18Check the combustion efficiency by measuring carbon dioxide and oxygen concentrations and the temperature of stack gases; make any necessary adjustments.

19 Close outdoor air dampers.

20Install heat recovery ventilators that exchange between 50 and 70 percent of the energy between the incoming fresh air and the outgoing return (conditioned) air.

21Be sure to switch off air conditioners when leaving the office after a day’s work or install timers to switch air conditioners off to prevent them from running over night or over weekends.

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8. Support and advice

Advice on the many techniques and technologies that are available for the purpose of saving energy can be obtained from independent technical consultants or Eskom’s energy advisory service. Interested persons can call the Eskom Contact Centre on 08600 Eskom (08600 37566) and arrange foran Eskom Energy Advisor in their area to contact them, or visit the website on www.eskom.co.za/dsm

9. References

1. Energy Efficiency in Industrial HVAC Systems–2003

2. http://en.wikipedia.org/wiki/File:Panna.jpg

3. http://en.wikipedia.org/wiki/File:Air_handling_unit.JPG


Issued by Eskom Demand Side Management Mach 2010

Issued by Eskom Demand Side Management August 2010

Eskom Holdings Limited Reg No 2002/015527/06

ESK

D12

4537

/E


In the heat of the moment - Eskom Home€¦ · In the heat of the moment Optimise heating,...

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