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A guide to effective equipment servicing HVAC SYSTEM MAINTENANCE
A guide to effectiveequipment servicing
HVAC SYSTEM MAINTENANCE
Every HVAC system willhave an average usefullife – a typical lifespanafter which it is runningon borrowed time. That’swhy it makes sense toimplement an effectivemaintenance plan.
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Unenlightened companies viewmaintenance as a cost with no benefit –the maintenance workforce is simplymeasured on speed of response tobreakdowns. Excuses for failing toimplement proper maintenance abound– it’s too expensive, disruptive, complex,time-consuming, troublesome, difficult,and so on. In fact, the case for effectivemaintenance should be a no-brainerbecause its cost is absurdly lowcompared to the cost of dealing with acatastrophic HVAC equipment failure.Indeed, maintenance is the most cost-effective way to ensure reliability,safety, and energy efficiency in HVACplant and equipment.
There are many compelling reasons totake maintenance of HVAC systems incommercial buildings seriously. Quiteapart from the need to comply withhealth & safety and environmentallegislation, it makes sense to provide
comfort for building occupants to avoidcomplaints and improve productivity.
It also saves energy and thereforeoperating costs, retains the assets’ value,enhances the business’s reputation,leads to better working relationships andreduces disruption to the business.Increasing energy costs are another goodreason to employ an effectivemaintenance strategy; best practicemaintenance can deliver cost savings of10 to 40% compared with poormaintenance.
Air conditioning components consumeenormous quantities of energy; chillers,for example, are responsible for usingmore than half the energy used on somebuildings so keeping them working attheir optimum efficiency will effectivelycontribute to a company’s bottom line.Implementing a maintenance plan willalso ensure a longer a life for the ACsystem and reduce its total cost ofownership dramatically.
One of the best reasons for a properlyimplemented maintenance strategy isthat it guarantees reliability. And justabout every indicator – safety,environmental performance, morale,retention, customer service – gets betterif reliability is established as a core valueof the organisation.
Finally, the pressure on companies toreduce their emissions footprints hasbeen an incentive for them to developbest-practice maintenance strategies.
Every HVAC system will have an averageuseful life – a typical lifespan after whichit is running on borrowed time. That’swhy it makes sense to implement aneffective maintenance plan. Not only willthis extend the system’s lifespan, but itwill also boost the system’sdependability and therefore contribute topeace of mind.
MAINTENANCE POLICYGood HVAC maintenance begins with acommitment from the top of theorganisation to develop a corporatepolicy on maintenance, repair andoverhaul that is unified and clearlycommunicated. From here, an effectivemaintenance strategy can be developedwith the policies (aims) and strategies(the means for achieving the aims)sometimes combined into a singledocument.
A maintenance policy is a writtenstatement that defines the standards towhich a building and its services will bemaintained. In other words, it is a set ofactions that need to be applied duringthe life cycle of a system or piece of plantor equipment to maintain or restore it todefined operating conditions. Themaintenance policy should align with thebusiness’s sustainability objectives.
The policy will typically contain:
l A list of the maintenance goals (forexample, safety, reliability and peaceof mind).
l An outline of the maintenancestrategy (the plan that sets thedirection for annual maintenanceprogramme and contains action plansfor achieving a desired future state forthe organisation).
l Key performance indicators (KPIs) tomeasure progress in the maintenanceprogramme.
MAINTENANCE STRATEGYThe maintenance strategy can containone or a mix of the following types ofmaintenance – corrective, preventative,predictive and reliability-centred.
Corrective maintenance involvesrestoring defective equipment to aworking condition as quickly as possible.
Since it means fixing breakdowns it is,essentially, a ‘run to failure’ approach. Itis reactive and unplanned becauseremedial work is carried out as andwhen equipment fails in operation. It willnot deliver high performing HVACequipment and also is expensive in thelong term, leading to the depreciation ofasset value.
The old adage ‘prevention is better thancure’ doesn’t apply only to the health ofpeople; it is equally applicable to plantand equipment. It has been estimatedthat total building costs could be slashedby up to 50% simply by switching from areactive to a predictive maintenanceprogramme.
With the benefits of some form ofpreventive maintenance includingextended equipment life, reduced energyusage, less frequent system downtimeand decreased interruptions to buildingoperations, it makes solid business
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sense to attempt to predict the futurerather than simply react to the present.
Preventive maintenance is designed toensure the best possible operation ofequipment and avoid expensive unforeseenequipment failure or shutdowns. Unlikecorrective maintenance, plannedpreventive maintenance (PPM) findspotential problems before they causeequipment to fail.
Essentially, PPM – which includes tests,measurements, adjustments, partsreplacement and cleaning performedspecifically to preclude faults – is a two-part procedure: Ensure the plant isoperating at its highest possibleefficiency and maintain this performance.
Preventive maintenance involves anumber of steps, including:
l Maintain a daily operating log andcompare the performance you recordwith design and start-up data. Anaccurate log offers a daily snapshot ofthe equipment’s operatingcharacteristics, making abnormalconditions easier to spot. This meansthat corrective action can be takenbefore problems get serious andexpensive. A log will also enable youto put together a history of operatingconditions that can be analysed toestablish trends.
l Check for leaks and moisture ingress.It has been estimated that 1psi of airin a condenser equates to a 3% loss inchiller efficiency. Moisture in a chillercan create acid that corrodes motorwindings and bearings and cause rustto form inside the shell.
l Treat water with appropriate chemicalsto reduce scale and corrosion andprevent biological growth.
l Finally, cleaning – HVAC equipmentperformance is dictated by its abilityto transfer heat and that starts withclean coils and fans.
PPM offers a host of solid businessbenefits. For example, it:
l Boosts reliability.
l Improves energy efficiency.
l Allows you to control costs and budgetmore accurately.
l Helps you plan more effectively.
l Prevents unscheduled and oftencostly stoppages.
l Enables large repairs to beundertaken at a convenient time,limiting disruption to operations.
Predictive maintenance means examiningthe ‘vital signs’ of the HVAC systemthrough testing, inspection and monitoring.This condition-based maintenanceapproach dictates that servicing shouldonly be performed when certain indicatorsshow signs of decreasing performance orupcoming failure.
To that end, it employs (typically non-invasive) predictive maintenance toolssuch as vibration analysis, infraredthermography, ultrasonic testing andmotor current analysis to monitor systemsand diagnose problems in advance.
Reactive maintenance is up to four timesmore expensive than one form ofpredictive maintenance – condition-basedmaintenance (CBM) – so a sharp focus onCBM can result in significant savings aswell as improvements in operations.
Importantly, CBM also involvesdetermining the condition of machinerywhile in operation. The key to a
successful condition monitoringprogramme includes knowing what tolook out for, how to interpret it and whento put this knowledge to use.
Successfully using this programmeenables the repair of problemcomponents before failure. Conditionmonitoring not only helps plantpersonnel reduce the possibility ofcatastrophic failure, but also allows themto order parts in advance, schedulemanpower, and plan other repairs duringthe downtime.
Reliability-centred maintenance (RCM)is used to systematically andscientifically determine what must bedone to ensure that a HVAC systemcontinues to do what its user wants it todo. It can be used to gather data from theresults achieved and feed this back toimprove future maintenance
It emphasises the use of predictivemaintenance techniques in addition to
traditional preventive measures.However, it focuses on the functionrather than the equipment – in otherwords, what the system does rather thanwhat it is.
In his influential book on the subject(‘Reliability-Centred Maintenance’),author John Moubray lists sevenquestions you should ask about the‘asset’ to be maintained:
l What are the functions and associatedperformance standards of the asset inits present operating context?
l In what ways does it fail to fulfil itsfunctions?
l What causes each functional failure?
l What happens when each failureoccurs?
l In what way does each failure matter?
l What can be done to predict orprevent each failure?
l What should be done if a suitableproactive task cannot be found?
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Reactive maintenance isup to four times moreexpensive than one formof predictive maintenance– so a sharp focus onCBM can result insignificant savings aswell as improvements inoperations.
RCM differs from the previous threemethods because it emphasises that theobjective should be to prevent or mitigatethe consequences of failures rather thanthe failures themselves. Theconsequences of failure will differdepending on where and how the HVACequipment is installed and operated. Aformal review of failure consequenceswill focus attention on maintenancetasks that have most effect, and divertenergy away from those that have littleor no effect.
RCM defines failure as ‘anyunsatisfactory condition’. It may be eithera loss of function (perhaps the airconditioning stops working) or a loss ofacceptable quality (for example, the airconditioning continues to operate, butfails to improve air quality).
RCM can be used to gather data from theresults achieved and feed this back toimprove future maintenance. In otherwords, it can improve systems andprocedures and not simply keep themthe same. The US-based ‘Whole BuildingDesign Guide’ has defined RCM’s fiveprimary principles as:
l Function oriented – RCM seeks topreserve system or equipmentfunction, not just operability foroperability's sake.
l System focused – RCM is moreconcerned with maintaining systemfunction than with individualcomponent function.
l Reliability centred – RCM is not overlyconcerned with simple failure rate; itseeks to know the probability offailure at specific ages.
l Design limitations – RCM’s objectiveis to maintain the reliability of theequipment design recognising thatchanges in inherent reliability are theprovince of design rather than ofmaintenance. Maintenance can, atbest, only achieve and maintain thelevel of reliability for equipment thatwas provided for by design. However,RCM recognises that maintenancefeedback can improve on the originaldesign.
l Safety, security, and economics –Safety and security must be ensuredat any cost; thereafter, cost-effectiveness becomes the criterion.
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ASSESSING MAINTENANCENEEDSMaintenance is usually based onpreserving the physical assets usingfailure prevention and asset care.However, such a strategy must add valueto the business process. What’s neededis a reliable way of assessing themaintenance needs of the servicesagainst the business risk of plant failingin service.
Research organisation BSRIA hasproduced a risk assessment toolkitdesigned to do just that. ‘BusinessFocused Maintenance -https://bit.ly/2uRpo1k’ enablesfacilities managers to focus theirmaintenance activities based on a logicalassessment of risk to the business, saysBSRIA.
The guide provides a cost-effective wayto assess, manage and maintainservices, and reduces the risks of systemfailure. The result: maintenance that willprotect your business without wastingmoney. The toolkit contains everythingyou need to prepare a completemaintenance programme based on therisk to your business.”
So maintenance improvement isn’t acontradiction in terms. It really isachievable. But like most things successonly comes by following considered,carefully crafted and coherent plan.
Two aspects of HVAC maintenancerequire particular attention – airhandling units (AHUs) and refrigerants.
AIR HANDLING UNITSThe AHU encourages heated or chilledair to move through ductwork so it is acritical piece of HVAC equipment.Preventing the build-up of debris in thechambers and fan blades, as well asreplacing filters, drive belts and pullies,and ensuring seals are operatingefficiently will keep it working at itsoptimum.
Condensation is another potentialproblem, but this can be negated bycovering drip trays and floors with ananti-corrosion coating.
F GAS REGULATIONFluorinated (or F) gases are man-madegases used in a range of industrialapplications including refrigeration andfire protection. The original F GasRegulation (EC) 842/2006 was laterrevised and replaced by (EU) 517/2014.The core aims of the latest regulationinclude:
l Better containment of F gases in theirapplications.
l Recovery of F gases from products andequipment reaching their end of life.
l Training and certification of technicalpeople and companies working with Fgases.
l Reporting of production, import andexport data within the EU.
l Labelling of certain products andequipment containing those gases.
But the overall aim of the F GasRegulation is to contain and reduceemissions through responsiblerefrigeration practice.
The original F Gas Regulation in 2007was designed to reduce emissions fromF gases, but it really only involved factorssuch as leak testing, monitoring andservicing of systems. Essentially, the onlyban it brought in was to say thatautomotive air conditioning would haveto move to a refrigerant with a GWP ofless than 150 for new models by 2012and for all cars from 2017.
The second F Gas Regulation, whichcame into force in 2015, was different. Itintroduced a phase-down mechanisminvolving a gradually declining cap on thetotal placement of bulk HFCs on themarket in the European Union.
F Gas Regulation 2015 set out caps andphase down schedules for the sale of Fgases. So, in 2015 there was a startingpoint volume allocated to companies thathad placed F gases on the marketbetween 2009 and 2012. They were givena proportion of the ‘quota’ of gasesallowed based on sales.
Finally, protecting physical assets suchas the HCVAC system is all very well, butremember: your most important asset isyour people and protecting them isparamount. That’s why it is critical toensure that they are can gain safe accessto any equipment that is to bemaintained. To that end, ECEX haspublished a guide to access – ‘Access AllAreas - https://bit.ly/2Ok0ijR’ –available for free here.
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For more information, call 01635 244100 or email [email protected]. Visitwww.ecex.xo.uk for our fullrange of products andservices.
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KEEP EQUIPMENT CLEAN
THE NEED FOR GOOD HOUSEKEEPINGGood housekeeping practice is part of good maintenance practice. The Carbon Trust recommends the following general advice for air conditioning systems:
l Ideally, set timers so that there isno cooling when the building isunoccupied.
l Time-control each unit in localisedcooling systems to avoid out-of-hours operation.
l Check temperature settings. Findout the temperature at which yourair conditioning switches on andyour heating system switches off.
The greater the temperature gapthe better. Check and comparetemperature settings for each unitin localised air conditioningsystems. The Carbon Trust says it is common to see one unitheating and another cooling in thesame space.
l Clean ductwork, fans and grillesregularly, and ensure furniture
doesn’t obstruct air pathways – anyblockage can increase energyconsumption and maintenance costs.
l By taking these measures, you willbe reducing the chance of an airconditioning system failure. But,equally importantly, you will behelping to cut carbon dioxideemissions from your buildings.
Dirty equipment is disproportionatelyresponsible for HVAC equipmentfailures. Ensuring it is kept clean canbe helped by technology such as ECEXAir Intake Screens. These are longlasting, weather-resistant filter meshproducts which fix to external intakeson air handling units, chillers andcondensers. This protects coils beforeany airborne debris can clog the finsand reduce the efficiency of evaporatoror condenser coils.
ECEX Air Intake Screens pre-filteroutside air and to ‘catch’ detritus suchas dust, pollen and leaves. By movingthe airborne debris to a position in
which it can easily be removed (using asoft brush, hose or vacuum cleaner),the ECEX Air Intake Screen provides asimple, retrofit protective option foron-site equipment.
This simple cleaning regime will allowfan motors to run more efficiently,coils to remain unsoiled for longer andless frequent changes required forinternal filters. Used with air handlingunits, ECEX Air Intake Screens canincrease the life of internal filters byup to 60%, while deliveringmeasurable results in improvedenergy efficiency, reducedmaintenance time and costs.
As well as saving energy and reducingmaintenance demands, ECEX AirIntake Screens also help extend thelife of coils and ensure they continueto operate at optimal efficiency.
Furthermore, they boost energyefficiency because the fans need notwork harder to overcome the effects ofblockages. They also reducemaintenance requirements, largely forthe same reason, and they ensure thecleanest possible air enters thebuilding, improving the health, safetyand welfare of occupants.
STEPS TO BETTER MAINTENANCEBroadly maintenance improvement takes place in five steps:
l Determine where you are now withan audit.
l Decide where you want to get to.
l Plan how to get there.
l Implement the plan.
l Continuous improvement demandsthat you return to step one.
Maintenance improvement starts witha diagnostic – basically an audit ofcurrent maintenance activities –followed by a broad brush initialassessment to identify areas forimprovement, then a detailedjustification of individual projects
selecting specific methods to achieveoverall business objectives.
This last point is critical – yourmaintenance strategy can't operate inisolation. It must be firmly rooted inyour business plan.
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COIL MAINTENANCE – CLEAN, REPAIR AND PROTECTCoils contained in condensers andevaporators are placed underadditional strain in the cold wintermonths and, should they fail, abusiness could potentially be broughtto a halt. However, this can beprevented by applying effectivemaintenance and the right equipmentto prevent clogging, corrosion orleakage. There are essentially twotypes of coil:
l Condenser coils which dissipateheat absorbed from the refrigerant.
l Evaporator coils which absorb heatfrom the surrounding environmentrather than the refrigerant.
Airborne particulates such as leaves,pollen and dirt begin to layer up on thefins and tubes of condenser coils overtime. As a result, the condensing
temperature increases which makesthe compressor work harder forlonger to achieve the necessarycooling effect.
This makes the condenser coil moreexpensive to run and increases thestrain on the unit leading to anincreased risk of breakdown.
An evaporator coil can also becomeeasily clogged with airborne debris, butthe consequences are slightly different.By restricting the airflow through theunit, the pressure drop means thecooling effect of the air is also reducedso the unit has to run for longer toachieve the requisite level of cooling.
Reduced airflow not only results in theunit remaining operational for longerthan is necessary, but also means thatit has to work harder in order to
achieve the airflow required. Boththese factors place the unit undergreater risk of breakdown and moreimportantly, downtime for the endclient or tenant.
In a typical building servicesinstallation, both condenser andevaporator coils are left unfiltered.However, there are several steps youcan take to reduce the problemsassociated with clogging and, indeed,reduce it altogether.
ECEX offers a range of coil servicesincluding repair, replacement,maintenance and protection. Not onlycan the company bring equipment upto its most efficient through effectivemaintenance and cleaning, but it canalso repair localised damage orcompletely replace if required.
CHILLER MAINTENANCE IN A NUTSHELLSteps that can be taken to maximise your chillers’ efficiency include:
l Turn off unnecessary chillers orsequence your chillers to saveenergy as well as wear and tear.
l Schedule maintenance operationson a daily, weekly, monthly orannual basis and draw up achecklist that is signed each time amaintenance operation iscompleted so that everybody knowsthe state of the maintenance plan.
l Check for condenser andevaporator tube corrosion andclean. Clues to potential problemsinclude poor water quality andexcessive fouling.
l Inspect chilled water andcondenser water piping systemsannually for evidence of corrosionand erosion.
l Lubricate the compressor, pumpsand motors to comply with themanufacturer’s specifications.
l Check refrigerant condition annuallyand level and top up if necessary.Have the refrigerant analysed toensure that it has not degraded.Also, check for refrigerant leaks –excessive refrigerant loss indicatesa leak, which you need to fix as amatter of urgency.
l Check wiring for overheating andtightness of connections.
l Test the compressor motor and oilpump motor windings.
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