best practice examples of reduced power consumption in building services and refrigeration by...
TRANSCRIPT
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]
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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.
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www.bigfootsystems.com.au
the complete solution
Pro Pipe Supplies Pty Ltd, 13-15 Main Street, Beverly, SA5009t: +61 8 8268 8633 [email protected]
eColI br I u M • MArCH 2011 32
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
eColI br I u M • MArCH 2011 34
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:
eColI br I u M • MArCH 2011 36
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
Australian Institute of Refrigeration, Air Conditioning and Heating
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
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA18
APPLICATION MANUAL
NOISE CONTROL
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA02
APPLICATION MANUAL
FANS
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA13
APPLICATION MANUAL
HUMID TROPICAL AIR CONDITIONG
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA20
APPLICATION MANUAL
DUCT WORK FOR AIR CONDITIONING
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA03
APPLICATION MANUAL
AMMONIA REFRIGERATION
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA21
APPLICATION MANUAL
HVAC&R AN INTRODUCTION
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA08
APPLICATION MANUAL
AIR FILTERS
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA15
APPLICATION MANUAL
WATER SYSTEM BALANCING
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA24
APPLICATION MANUAL
AIR CONDITIONING LOAD ESTIMATION
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA09
APPLICATION MANUAL
AIR CONDITIONING WATER PIPING
Australian Institute of Refrigeration, Air Conditioning and Heating
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
DA16
APPLICATION MANUAL
INDOOR AIR QUALITY
Australian Institute of Refrigeration, Air Conditioning and Heating
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
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
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
DA
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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
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
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
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
DA18
APPLICATION MANUAL
NOISE CONTROL
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
DA02
APPLICATION MANUAL
FANS
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
DA13
APPLICATION MANUAL
HUMID TROPICAL AIR CONDITIONG
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
DA20
APPLICATION MANUAL
DUCT WORK FOR AIR CONDITIONING
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
DA03
APPLICATION MANUAL
AIR FILTERS
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
DA15
APPLICATION MANUAL
AMMONIA REFRIGERATION
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
DA21
APPLICATION MANUAL
HVAC&R AN INTRODUCTION
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
DA08
APPLICATION MANUAL
AIR CONDITIONING WATER PIPING
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
DA16
APPLICATION MANUAL
WATER SYSTEM BALANCING
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
DA24
APPLICATION MANUAL
AIR CONDITIONING LOAD ESTIMATION
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
DA09
APPLICATION MANUAL
COOLING TOWERS
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
DA17
APPLICATION MANUAL
INDOOR AIR QUALITY
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
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
IntakeFront
Q = 1/2
APPLICATION MANUAL
COOLING TOWERS
Australian Institute of Refrigeration, Air Conditioning
and Heating
THE AUSTRALIAN INSTITUTE OF REFRIGER ATION, AIR CONDITIONING AND HEATINGDA
17
— C
OO
LIN
G T
OW
ER
S —
AP
PL
ICA
TIO
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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
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA01
APPLICATION MANUAL
STEAM AND CONDENSATE
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
NOISE CONTROL
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA02
APPLICATION MANUAL
FANS
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA13
APPLICATION MANUAL
HUMID TROPICAL AIR CONDITIONG
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA20
APPLICATION MANUAL
DUCT WORK FOR AIR CONDITIONING
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA03
APPLICATION MANUAL
AIR FILTERS
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA15
APPLICATION MANUAL
AMMONIA REFRIGERATION
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA21
APPLICATION MANUAL
HVAC&R AN INTRODUCTION
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA08
APPLICATION MANUAL
AIR CONDITIONING WATER PIPING
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA16
APPLICATION MANUAL
WATER SYSTEM BALANCING
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA24
APPLICATION MANUAL
AIR CONDITIONING LOAD ESTIMATION
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA09
APPLICATION MANUAL
WATER TREATMENT
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
DA18
APPLICATION MANUAL
INDOOR AIR QUALITY
Australian Institute of Refrigeration, Air Conditioning
and Heating
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
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
16
HVAC HYGIENEAIRAH BEST PRACTICE GUIDELINES
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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
AIRAH BEST PRACTICE GUIDELINES
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13
HVAC HYGIENE
AIRAH BEST PRACTICE GUIDELINES
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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
PRACTICE
GUIDELINES