Homeowner’s Guide to Geothermal Heat Pump...
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Rev1.1 Ground Energy Support LLC www.groundenergy.com 1| Page Homeowner’s Guide to Geothermal Heat Pump Systems Introduction This guide is written to offer helpful information for homeowners considering installing a geothermal (often called ground‐source) heat pump system to heat and cool their home. In writing this guide, we have tried to synthesize information from a number of sources and provide useful information to assist individuals as they go through the often complex process of considering geothermal, requesting bids, selecting a contractor, having a system installed, and insuring proper performance. While we have attempted to write to the general North American audience, the content is likely biased towards our own experience which is concentrated in the eastern and mostly northeastern US. The Guide is motivated largely by a recent discussion on LinkedIn GeoExchange forum initiated by Tamar Fox, a homeowner in Minnesota. In an effort to troubleshoot her own system, Ms. Fox has become quite engaged in the industry discussion groups and after years of troubleshooting, posed the question “What is the best way to select a GSHP designer/installer?” The discussion topic elicited over 140 comments from many of the leading experts in the field, clearly indicating that it is an important question without a simple answer. One common element in the advice given is the importance of an educated homeowner. This guide is intended to provide an additional resource that will help educate homeowners on geothermal heat pump systems to facilitate a productive dialogue between homeowners and installers. Our goal is to be informative rather than prescriptive, and we encourage homeowners to consult other valuable resources that may be more pertinent to their geographic location or specific situation. How Geothermal Heating/Cooling Systems Work This Guide will refer to geothermal heating/cooling systems as Geo Systems. Geo systems extract solar energy from the shallow subsurface using a ground heat exchanger (commonly called a ground loop), and concentrate this energy to heat a home. In the cooling season, geo systems reject heat from the home to the ground via the ground loop. Geo systems can be an excellent choice to heat and cool a home because they offer the potential for long‐term low and stable heating and cooling costs, offer unparalleled comfort and reliability, and can dramatically reduce a homeowner’s carbon footprint. The reasons
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Transcript of Homeowner’s Guide to Geothermal Heat Pump...
Rev1.1 GroundEnergySupportLLCwww.groundenergy.com 1|P a g e
Homeowner’sGuidetoGeothermalHeatPumpSystems
IntroductionThisguideiswrittentoofferhelpfulinformationforhomeownersconsideringinstallingageothermal(oftencalledground‐source)heatpumpsystemtoheatandcooltheirhome.Inwritingthisguide,wehavetriedtosynthesizeinformationfromanumberofsourcesandprovideusefulinformationtoassistindividualsastheygothroughtheoftencomplexprocessofconsideringgeothermal,requestingbids,selectingacontractor,havingasysteminstalled,andinsuringproperperformance.WhilewehaveattemptedtowritetothegeneralNorthAmericanaudience,thecontentislikelybiasedtowardsourownexperiencewhichisconcentratedintheeasternandmostlynortheasternUS.
TheGuideismotivatedlargelybyarecentdiscussiononLinkedInGeoExchangeforuminitiatedbyTamarFox,ahomeownerinMinnesota.Inanefforttotroubleshootherownsystem,Ms.Foxhasbecomequiteengagedintheindustrydiscussiongroupsandafteryearsoftroubleshooting,posedthequestion“WhatisthebestwaytoselectaGSHPdesigner/installer?”Thediscussiontopicelicitedover140commentsfrommanyoftheleadingexpertsinthefield,clearlyindicatingthatitisanimportantquestionwithoutasimpleanswer.Onecommonelementintheadvicegivenistheimportanceofaneducatedhomeowner.Thisguideisintendedtoprovideanadditionalresourcethatwillhelpeducatehomeownersongeothermalheatpumpsystemstofacilitateaproductivedialoguebetweenhomeownersandinstallers.Ourgoalistobeinformativeratherthanprescriptive,andweencouragehomeownerstoconsultothervaluableresourcesthatmaybemorepertinenttotheirgeographiclocationorspecificsituation.
HowGeothermalHeating/CoolingSystemsWorkThisGuidewillrefertogeothermalheating/coolingsystemsasGeoSystems.Geosystemsextractsolarenergyfromtheshallowsubsurfaceusingagroundheatexchanger(commonlycalledagroundloop),andconcentratethisenergytoheatahome.Inthecoolingseason,geosystemsrejectheatfromthehometothegroundviathegroundloop.
Geosystemscanbeanexcellentchoicetoheatandcoolahomebecausetheyofferthepotentialforlong‐termlowandstableheatingandcoolingcosts,offerunparalleledcomfortandreliability,andcandramaticallyreduceahomeowner’scarbonfootprint.Thereasons
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thatgeosystemsarerelativelyrareintheU.S.arethreefold:1)mostAmericansdon’tunderstand,orarenotawareof,geosystemsasaviableoption;2)likesolarpanelsandother“greenenergy”technologies,geosystemscanhaverelativelyhighupfrontcostsbutavailablefederaltaxcreditscansignificantlyoffsettheseupfrontcosts;and3)geosystemsarebestsuitedtowell‐insulatedhomeswithatightbuildingenvelope.
Thereareseveralimportantdistinctionsbetweenageosystemandatraditionalfossil‐fuelbasedsystem.Thefollowingtablesdescribethesebasicdifferencesincoolingandheatingmode.
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Ageosystemconsistsoffourindividualcomponents:1)thegroundloop;2)theheatpump;3)thedistributionsystem;and4)systemcontrols.Understandinghowthesecomponentsfunctionwillhelptoselectthetypeofsystemyouwantandthebestinstallerforthejob.
TheGroundHeatExchangerorGroundLoopThegroundheatexchanger,alsocommonlycalledagroundloop,isapipeorawellthatcontainsfluidinthermalconnectionwiththeground.AClosedGroundLoopcirculatesadilutemixtureofwaterandrefrigerantthroughundergroundtubingtoextractheatfromtheground.Thefluidinthetubeabsorbsheatfromthegroundanddeliversthisheatuptotheheatpumpinthehome.Incoolingmode,heatfromthebuildingisrejectedintothefluid,whichinturntransferstheheattothegroundasitcirculatesthroughthegroundloop.Differentconfigurationsofclosedgroundloopsareshownbelow:
HorizontalSlinkyVertical Pond/LakeSlinky
OpenGroundLoopswithdrawheatdirectlyfromwaterpumpedfromagroundwaterwellorsurfacewaterbodysuchasapondorlake.Afterpassingthroughtheheatexchangerintheheatpump,groundwaterisreturnedtothesamewell(StandingColumnWell)ortoadifferentwell(ReinjectionWell).Becauseopenloopsystemsdonotuseantifreeze,itisimportantthatthewatertemperaturenotdropbelowfreezing.Oneapproachtohelpmanageenteringwatertemperature(bothinheatingandcoolingmode)istobleedsomeofthereturnwateranddischargeittoanotherlocation,drawinginmoreofthegroundwaternearthewell.
Openpondloopstakewaterfromapondorlakeandreturnitbacktothesurfacewaterbody.Anyopenloopsystemthatreturnswatertoasurfacewaterbodywilllikelyrequireapermit.Also,manystatesandlocalitieshavespecificregulationsregardingthewithdrawalandreturnofgroundwaterfromwells,andspecificpermitsmayberequired.Makesuretodiscussthispossibilitywithyourinstaller.DifferentconfigurationsofOpenLoopsystemsareshownbelow:
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Extraction/RejectionWellStandingColumnWellSurfaceWaterLoop
TheGeothermalHeatPumpAgeothermalheatpumpistheequipmentthatconcentratesthermalenergyinthecirculatingfluidintotemperaturesthatarehighenoughtoheatabuilding.Theheatpumpusesarefrigerationcycle,justlikethatusedinrefrigerators,freezersandairconditioners.Asshownbelow,lowtomoderategroundtemperaturesarecarriedintotheheatexchangerinthegroundloopfluid.Theselowtomoderatetemperaturesarepassedbyaloopofrefrigerantintheheatexchanger,causingtherefrigeranttovaporizeintoalowpressure,warmvapor.Thisvaporisthenroutedintothecompressorwhereitispressurizedintoa
highpressure,hotgas.Airorwaterflowingpastthishotrefrigerantvaporpicksupheatandthenmovesintothebuildingtoheatthebuilding.Havinggivenupsomeofitsheat,the
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nowwarmhighpressurerefrigerantgasmovesontotheexpansionvalvewhereitisallowedtorapidlyexpand,therebycoolingandreturningtoitsoriginalstate,acoldliquid.
Fromthispoint,thecyclerepeatsitself.Incoolingmode,thisentirecycleisruninreverse,withheatfromthebuildingbeingtransferredtothegroundloopfluidwhichinturnrejectstheheattotheground.
CompressorStagingThegeothermalheatpumpcontainseitherasingle,dual,orvariablespeedcompressor.Asingle‐stagecompressorproducesaconstantamountofheatingorcooling.Becausesinglestagesystemsaredesignedtomeetthemaximumload,theytendtobeoversizedduringperiodsofmoderateload,resultinginrapidcyclingoftheheatpump.Rapidcyclingreducesefficiency,createsmorewearontheheatpump,andmaynotresultinthedesiredlevelofhumidityreductionduringcoolingmode.Dualstagesystemshelptoalleviatethisproblemastheycanoperatemostofthetimeat67%offullcapacity(1ststage)andthencanincreasecompressionduringperiodsofhigherdemand(2ndstage).Dualstagesystemshavelongercyclesandprovideforimprovedefficiencyandcomfort.Whileadualstageheatpumpisasignificantimprovementoverasinglestageheatpump,oversizingadualstageheatpumpcanresultinsimilarshortcyclingandpotentialproblemswithhumiditycontrol.Whenasingleheatpumpisservingmultiplezones,similarinefficienciescanresult.Becausetheheatpumpneedstobesizedformaximumloadtoallzones,itmaybeoversized,evenin1ststage,forindividualzones.Heatpumpstagingandefficientdeliveryofheattodifferentzonesareaspectsthatcanoftenbemanagedthroughpropercontrols(discussedbelow).Someofthenewestheatpumpshavemultiplestagesthatcanhelptoalleviatethisproblem.Thevariablespeedcompressoroperatesatawiderangeofcapacitiesthatcanbebetteralignedwiththewiderangeofheating/coolingloads.Variablespeedheatpumps,whileofferinghigherefficiencies,docomewithahigherpricetag.Yourinstallercanhelpyoudecidewhichtypeofheatpumpisrightforyou.
AuxiliaryElectricHeatAgeothermalheatpumpisoftenequippedwithanelectricheatingelementthatiscommonlyreferredtoastheauxiliaryheat.Theauxiliaryheatcanservetwoseparatepurposes.First,itcanturnonasa3rdstageofatwostagesystemwhentheheatpumpatfullloadisnotsufficienttomeetingtheheatingdemand.Thisiscommoninverycoldclimateswhereitmightmakemoreeconomicsensetodesignasystemtomeet90‐95%ofthemaximumdemandanduseelectricheattomeettheremaining5‐10%.Undertheseconditions,theauxiliaryisusedincombinationwiththeheatpumpandreductionsinefficiencyaremodest.Thesecondpurposeoftheauxiliaryelectricheatistoprovideasourceofemergencyback‐upheatiftheheatpumpshutsoff.Wehavefoundthathomeownerscanbequiteunhappyifanunexpectedlyhighelectricbillistheirfirstcluethattheirheatpumpwasnotfunctioningproperly.Onesolutiontoavoidthesurpriseon
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anelectricbillistoincludesystemmonitoringthatwillalertthehomeownerwhentheauxiliaryheatisactive.
Desuperheater:HotWaterHeatingAdesuperheaterisasecondaryheatexchangerthatusesexcessheatfromtheheatpumptopreheatwaterenteringthehome’shotwatertank.Thedesuperheateronlyoperateswhentheheatpumpisactivelyheatingorcoolingthehome.Insomecases,thedesuperheatercanprovidemorethanhalfofahome’sdomestichotwater.Manyinstallersstronglyrecommendusinganintermediatestoragetank(oftenreferredtoasabuffertank)insteadofplumbingdirectlytothedomestichotwatertank(s).
CoefficientofPerformanceThetermCoefficientofPerformance(COP)isusedtodescribeboththeefficiencyofaheatpumpandtheoverallefficiencyofageothermalheatpumpsystem.ManufacturerstesttheirequipmentinthelabaccordingtoindustrystandardsandreportaCOPforarangeoflaboratoryoperatingconditions.ThesedataarecommonlyreferredtoasPerformanceData.TheCOPoftheinstalledsystemtakesintoaccounttheactualheatpumpefficiency(underactualoperatingconditions)aswellasadditionalelectricalloadssuchascirculatingpumps,distribution‐sidepumps/fans,andauxiliaryelectricheating.TheCOPoftheentiresystemmaybe,andusuallyis,differentthantheratedheatpumpCOP.
Asshowninthefiguretotheright,oncetheinstalledCOPexceedsapproximately3.5,mostofthesavingshavebeenachievedandthecostssavingsassociatedwithincreasingtheCOPfrom4to5canbeontheorderofafewdollarspermillionBTUs(MMBTU).Thereis,however,asignificantdifferenceinthecostperMMBTUbetweenaCOPof2and3.
Geosystemsshouldbeinstalledinhomesthatarewellinsulatedandhavemadeeveryreasonableefforttoreducebuildingload.Loadreductioncansignificantlyreducebuildingload,systemsize,andthereforethecostofinstallation.Onceyoubegintalkingwithprospectiveinstallers,youshouldaskyourinstallerwhatyoucanexpectintermsofactualCOPandwhatmeasurestheytaketoensureahighperformingsystem.
TheHeating/CoolingDistributionSystemThethirdcomponentofageosystemisthedistributionsystemthatisresponsibleformovingtheheatfromtheheatpumpthroughthehome.Airductinggoeswithawater‐to‐
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airgeothermalheatpump,andaradiant(usuallyfloor)systemgoeswithawater‐to‐watergeothermalheatpump.
Whetheryouchoose/haveaforcedhotairorradiantsystem,anefficientdistributionsystemisveryimportantforahighperformancegeosystem.Forradiantsystems,pipesmustbeproperlysizedhaveproperspacingandhaveagoodthermalconnectionwiththeroom.Forairdistributionsystems,ductsmustbetightlysealedandefficient.
SystemControlsAsnotedabove,optimizingtheefficiencyofageothermalheatpumprequirescarefulattentiontoproperheatpumpstagingandefficientdistributionofheatthroughoutthehome.Mostheatpumpmanufacturershavespecificthermostatsfortheirheatpumps,thoughinmanycasesitispossibletouseotherthermostatsthathaveadditionalfeatures,suchasinternetaccess.MostofthecommonWiFithermostats(e.g.Ecobee)arecompatiblewithgeothermalheatpumps,howeverbesurethatyourinstallerisfamiliarwithyourpreferredthermostatandthattheyhavebeenabletouseitsuccessfullyinotherinstallations.
IsaGeothermalHeating/CoolingSystemRightforYou?Nowthatwehavecoveredwhatageothermalheatpumpsystemis,thenextstepistodetermineifitisappropriateforyourapplication.Unlikehomesheatedwithoilandpropane,geosystemsusethermalenergyfromthegroundastheirprimary“fuel”andelectricitytoruntheheatpump.Giventhehighlyvariablepriceofoilandpropane,homesheatedwiththesefossilfuelsoftenhavehugefluctuationsintheirheatingbills.Homesheatedwithageosystembenefitfromusingrenewablethermalenergyinthegroundandtherelativelysteadycostofelectricity.
Runningaheatpumpisnotcarbon‐freebecauseoftheelectricityusedtooperatetheheatpump.However,inpartsofthecountrywhereelectricityisgeneratedwithemissions‐freeenergysourcessuchashydroelectric,nuclear,andwind,thenetcarbonemissionsassociatedwiththeoperationofaheatpumpareverylow.Eveninpartsofthecountrythatrelymoreheavilyoncoal‐generatedelectricity,thenetcarbonemissionsfromheatpumpsarenearlyalwaysconsiderablylessthanheating/coolingwithnaturalgas,oilorpropane.Whilegeosystemsproduceasteadystreamofcomfortableheat,ifthehomeisnotwellinsulated,thegeosystemoranyhighefficiencyheating/coolingsystemwillbeneedtobeverylargeorwillneedtooperatewellbeyonditsdesigncapacity.Themainreasonwedon’trecommendinstallingageosysteminahomethatlacksatightbuildingenvelopeisthathomeownerswilllikelyblamethegeosystemfortheirhighelectricitybillsinsteadofthesimplefactthattheirhouseispoorlyinsulated.
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Forawell‐insulatedhome,ageosystemwillcostmoretoinstallupfront,butwillpayforitselfinthelongrun,especiallyasfossilfuelcostscontinuetorise.Thehigherupfrontcostsofageosystemstemfromtheneedtoinstallagroundloop(asdiscussedabove).Justasthemosthighlyefficientoilandgasfurnacescomeatapremiumcost,themostefficientheatpumps(thosewiththehighestCOP)tendtocomeatapremiumcostaswell.However,aswillbediscussedbelow,dualstageheatpumpsdeployedinathoughtfulmannercanofferhomeownersreliablelow‐costheatingandcoolingfordecadestocome.Takealookattheflowchartbelowtoseeifageosystemisrightforyou.
Ifyouarrivedatthegreenboxandhavedecidedthatageothermalsystemisrightforyou,it’stimetostartlookingforanexperiencedandqualifiedinstallerinyourarea.
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FindingandSelectingtheRightGeoInstallerFindingtherightinstallerisessentialforageosystem.Whiletheprocessweproposeheremayseemlengthy,itisn’tthatmuchdifferentfromthestepsoneshouldundertaketoinstallatraditionalHVACsystem.Thefourstepswerecommendtofindagoodgeoinstallerisasfollows:
1. CreateyourLongListofpotentialgeoinstallersbydoingsomesimpleresearch2. AskinstallersonyourlonglistaseriesofquestionstonarrowdowntoaShortList
of3or4installers3. RequestbidsfromyourShortList–askthemasetofspecificquestions,detailed
below,whentheyconductthesitevisit4. Comparethebidsandcheckreferences.
IdentifyGeoInstallersinYourArea(YourLongList)Youwillfirstwanttoidentifypotentialinstallerswithinalargeradius(potentially50milesormore)fromyourhome.Thereareseveralresourcesthatcanhelpincreatingyour“longlist”ofgeothermalsysteminstallers:
WordofMouth GeothermalProfessionalOrganizations GeothermalHeatPumpManufacturers
WordofMouthIfyouknowsomeonelocallywhohasageothermalsystemthattheyarehappywith,byallmeansaskthemwhoinstalledtheirsystem.Thiscanbeagreatwaytogetstartedwithyoursearch.
ProfessionalOrganizationsManyprofessionalorganizations,bothnationallyandregionally,providealistofmembers.Whilethisisonegoodsource,keepinmindthattherearemanyexcellentinstallerswhoarenotmembersoftheseorganizations.Anon‐exhaustivelistincludes:
NationalOrganizations
GeothermalExchangeOrganization(GEO)http://www.geoexchange.org/GEOisaprofessionalindustrygroup.Whileinstallersonthislistareprobablygoodones,therearemanyhighqualityinstallersnotonthislist.
InternationalGroundSourceHeatPumpAssociation(IGSHPA)http://www.igshpa.okstate.edu/IGSHPAistheleadingtrainingorganizationforclosedloopgeosystemandmaintainlistsofaccreditedinstallersandcertifiedgeothermaldesigners.
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RegionalOrganizationsSomeregionsofthecountryhavetheirownregionalgeoprofessionalorganizations.Membersoftheseorganizationsarecommittedtoexcellenceandfurtheringtheirindustry,andthereforemembersoftheseorganizationsarelikelytoofferhighqualityinstallations.
CaliforniaGeothermalHeatPumpAssociation ColoradoGeoEnergyandHeatPumpAssociationCoGHPA ConnecticutGeothermalAssociation GeothermalAllianceofIllinois IowaGeothermalAssociation LongIslandGeothermalEnergyOrganizationLIGEO MinnesotaGeothermalHeatPumpOrganization MichiganGeothermalProfessionalAssociation NewEnglandGeothermalProfessionalAssociation(NEGPA) WisconsinGeothermalAssociation
Manufacturers’WebsitesMostheatpumpmanufacturersmaintainasearchabledatabaseofinstallerswhoaretrainedontheirgeothermalheatpumpsystems.TheleadingmanufacturersofresidentialgeothermalheatpumpsinNorthAmericainclude:
Climatemaster WaterFurnace ComfortAir Bosch Enertec(Hydron,GeoComfortandTetco) Geofinity Nordic(Canada) NextEnergy(Canada)
NarrowDownYourList(YourShortList)Dependingonwhereyoulive,youmaynowhavequitealonglist.Tonarrowyourlistdowntothetop3or4thatyouwillrequestbidsfrom,wesuggestyourequestthefollowinginformationfrominstallers:
WhereDidTheyGettheirTrainingandCertification?Therearemanyexcellentmethodsforaninstallertoreceivetrainingandcertification,bothonlineandintheclassroomsetting.ThemostcommonGSHPtrainingandcertificationprogramisofferedthroughtheInternationalGroundSourceHeatPumpAssociation(IGSHPA)andconsistsoftwodifferentlevels.TheCertifiedGeothermalDesigner(CGD)istrainedinsophisticatedgroundloopdesignoftenassociatedwithlargeresidentialandcommercialbuildings.ACGDleveloftrainingistypicallynotnecessaryforasinglefamilyresidentialsystem.IGSHPAalsooffersanAccreditedInstaller(AI)certificationthatis
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gearedmoretowardsthecompletedesignandinstallationofaclosed‐loopresidentialGSHPsystem.Thereiscurrentlynonationallyrecognizedtrainingprogramforopenlooporstandingcolumnwellsystems,butasexplainedbelow,somedistributorshaveextensiveexperienceinthistypeofinstallationandofferprofessionaltrainingtotheirinstallers.Amongothers,thefollowingorganizationsofferexcellenttrainingandcertificationforgeoinstallers:
IGSHPAoffersavarietyoftrainingclassesattheirOklahomaheadquarters HeatSpringLearningInstituteworkswithIGSHPAtodeliveronlinetraining GeoConnectionsIncSeveralcoauthorsoftheIGSPHAtrainingmanualshave
integratedmuchofthetechnicalmaterialinvolvedindesignintoacommonlyusedpieceofdesignsoftware‐‐LoopLink.TrainingandcertificationonthesoftwaremeansthattheindividualisfamiliarwiththesamedesignmethodsastheIGSHPAAccreditedInstaller.
WaterEnergyDistributorsisaNewEnglanddistributorthatoffersclassroomandhands‐ontraininginallaspectsofgeoinstallations,andarewellknownfortheirexpertiseinstandingcolumnwellopenloopinstallations.
PhoenixEnergySupplyinupstateNewYorkoffersIGSHPAtraining LitchfieldGeothermaloffersIGSHPAtrainingseminarsaroundthecountry AshevilleGeothermaloffersIGSHPAtraininginNorthCarolina TheEnergyEfficiencyBusinessCoalition(EEBC)offersIGSHPAtraininginColorado TheGeothermalTrainingInstituteinMinnesotaoffersawidevarietyofonlineand
classroomIGSHPAtrainingseminars.
Ifyouexpectyouwillbeusingaverticalgroundloop,alsochecktoseeifthedrillerthatyourinstalleruseshasindividualsonstaffwhohavereceivedtheIGSHPAVerticalLoopInstaller(VI)training.ItisveryimportanttokeepinmindthatIGSHPAaccreditationrepresentsaleveloftrainingbutdoesnotinsureproperinstallationorahighlyefficientgeosystem.
Otherprofessionalcredentialsthatarecommoninthegeothermalindustryinclude:ProfessionalEngineer,ProfessionalGeologist,Architect,andLicensedDriller.Whilethesecredentialsmayaddtoone’squalificationstheyareusuallynotsufficienttodesignahighperformanceGSHPsystemwithoutspecifictrainingandexperienceinGSHPtechnology.
HowMuchExperiencedotheyhavewithGeoSystems?Asktheinstallerabouttheirexperienceinstallinggeothermalheatingcoolingsystems.Askthemquestionsregarding:
Howmanyyearshavetheybeendoinggeoinstalls? Howmanysystemshavetheyinstalled? Istheirexperienceinresidentialorcommercial?
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Ifyouarebuildinganewhome,makesuretheyhaveexperiencewithnewinstallations.Likewise,ifyouarereplacinganexistingheating/coolingsystemwithgeo,confirmthattheyhaveplentyofexperiencewithgeoretrofits.
HowdotheySizetheGeoSystem?SizinganyHVACsystemisveryimportanttoachieveoptimalperformance.TheResidentialEnergyServicesNetwork(RESNET)usesthisanalogy:
“Youwouldn’tbuyan18‐wheelerjusttodrivearoundtown,right?Thatvehiclewouldn’tmatchthetaskathand,andwouldcostyoualotmoremoneytooperate.Thesamegoesforheatingandcoolingequipment.Ifyoursystemislargerthannecessary,itmeansthatyouarepayingtooperatelargerfansandlargercompressors.Thegoalistobuyonethatissized“justright.”Thiscanbeequatedtohighwaymileageinavehicle.Ifitrunssteadily,withoutstoppingandstarting,it’smoreaffordabletooperate….TheManualJ[ofabuilding]isthenameforaspecificprotocolusedtodeterminehowmuchheating/coolingahomeneedstostaycoolanddryinthesummerandwarminthewinter.Thisloadcalculationprocesswasdevelopedbyengineersintheheatingandairconditioningindustryandhasbeenusedfordecadestoaccuratelysizeheatingandair‐conditioningequipment.”
Forageosystem,propersizingisadditionallyimportantasthesystemsizewilldeterminethesizeofthegroundloop,whichisyourinvestmentenablingyoutoutilizeyourownenergyfromtheground.
AllgeosystemsshouldbeproperlysizedbyusingeitherACCAManualJorASHRAEmethods,alsocommonlyreferredtoasloadanalysis.Eithertheinstallershoulddothecalculationthemselvesortheyshouldhiresomeoneelsetodoit.Besuretogetthenameandcredentialsoftheindividualdoingtheanalysis.Largerhomesthathavemorethanafewheatpumpsandhavehigherheating/coolingdemandstendtobedesignedbyanarchitectandmayutilizeanengineertodesignthegeothermalHVACsystem.Inthatcase,theengineerwillperformtheloadcalculationsandmostlikelyuseeitherASHRAEorACCAManualJmethods.Eithertypeofhouse,largeorsmall,itisveryimportantforthehomeownertodemandthattheloadsaredoneusingASHRAEorACCAManualJmethodsbyindividualswithtrainingandexperienceingeosystems.Forgeosystems,calculationsshouldtendtobeaggressivewithfew‘safetyfactors’.
HowdotheySizetheGroundLoop?Acriticallyimportantpartofthedesignisdeterminingthepropersizeofthegroundloop.Thismaybethesinglemostexpensivecomponentofthegeosystemandpropersizingwillbeessentialtoinsureproperperformance.Thegroundloopshouldbesizedbasedonanunderstandingoftheload(determinedabove),thethermalpropertiesofthegroundmaterials,andmaterialsusedinthegroundloopconstruction.
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Forlargerprojects,atestwellwilloftenbedrilledtoallowforanonsitethermalconductivitytest.Forresidentialsystemsthisistypicallynotpractical,bothlogisticallyandfinancially.Instead,thedesignerwillberelyingonestimatesofthermalpropertiesbasedonrocktype,obtainedthroughobservations,geologicmaps,andexperienceinthearea.
WhatBrandofHeatPumpdotheyRecommend?Manyinstallerscarryasingleheatpumpbrand,whileothersofferavarietyofbrands.Asktheinstallerwhytheypreferthisbrandofheatpump,andaskthemwhatfeaturesoftheseheatpumpswillbefavorableforyourapplication.MakesurethattheheatpumptheyarerecommendingislistedintheAHRIdatabase.
HowdotheyHandleAvailableTaxCredits/Rebates?The US federal government offers a tax credit of 30% of total installation cost of a geothermal heat pump system, both for new construction and for retrofits. The system must be put into service by December 31, 2016. Several state governments, local governments and electric utilities also offer financial incentives around the installation of geothermal heating systems. The Database of State Incentives for Renewables and Efficiency (DSIRE) provides a comprehensive listing by state of financial incentives. Ask the potential installers how these credits/rebates will be handled. Be sure that you understand how these benefits are incorporated into their bid, particularly for new construction.
WilltheyMonitortheGeoSystem’sPerformance?Optimalperformancefromageosystemisachievedwhentheheatpumpequipmentisproperlysizedforthebuilding,thegroundloopisproperlysizedandinstalledfortheheatpumpequipment,andtheheating/coolingisdistributedefficientlythroughthebuilding(loadside).Ifoneormoreofthesesystemcomponentsisoutofbalanceitcanresultinothercomponentsoperatinglessefficiently.Agoodmonitoringsystemwilltellyouifallthesesystemsareoperatinginbalance,andmoreover,willalertyouandtheinstallerifthesystemisoutofbalanceandneedsanadjustment.Inshort,amonitoringsystemcanalertyoutoapotentialproblembeforeyouaresurprisedbyeitheraverylargeelectricbill(ifyoursystemfaultsoutandgoestoauxiliaryelectricheat)orworse,thesystemstopsworkingaltogetherandleavesyouwithoutheatorairconditioning.Askyourpotentialinstallerswhattypeofmonitoringandverificationsystemtheyplanonusingtokeeptrackoftheperformanceofyourgeosystem.Iftheinstallerdoesnotintendtouseamonitoringsystem,makesureyouaskwhyandhowtheyintendtokeeptrackofyoursystem’sperformance.
DoTheyOfferaMaintenance/ServiceContract?Geosystemsgenerallyrequireonlylimitedmaintenance.Becauseopenloopsystemsfeedgroundwaterorsurfacewaterdirectlythroughtheheatexchangerintheheatpump,thegroundwaterfilterontheenteringwaterlinewillneedtobechangedperiodically.Who
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willberesponsibleforthat?Andhowoftenwillthatneedtobedone?Inthecaseofclosedloopsystems,theantifreezeshouldbecheckedonanannualbasisand,ifnecessary,charged.Also,allforcedhotairheatingsystemsneedperiodicairfilterchanges.Again,findoutwhowilldothatandhowoftenshoulditbedone?Iftheinstalleroffersaservicecontract,whatisthatcostforthatcontractandwhatisincluded?
RequestBidsfromyourShortListInstallers:TheSiteVisitOnceyouhavenarroweddownyourlist,goaheadandrequestbidsforinstallingageosystematyourhome.Installerswillvisityourhometopreparetheirbid.Thisisyouropportunitytohaveexpertsevaluateyourspecificsituationandprovideyouwithrecommendationsonwhetherageothermalheatpumpisappropriateforyourhome,givenspecificinformationaboutHVACdistribution,buildingload,andsitegeology.
Werecommendyouaskthemtodiscussthesetopicswithyouduringtheirsitevisit.Whileyoucanexpectmanyinstallerstodiscusstheseissueswithyouingeneralterms,manyspecificsofthedesignmaynotbeshownonthebid.Inmanymarkets,thedesignistheinstaller’scompetitiveadvantagethattheyhavehonedoveryearsofexperienceinconditionsspecifictoyourgeographiclocation.Theeffectivenessoftheirdesignswillbeevidencedthroughtalkingtotheirreferences,performancedatafromtheirotherinstallations,andaserviceagreementthatshowstheywillstandbehindtheirwork.
Also,beawarethatduringthesitevisit,youshouldn’texpectinstallerstoprovideconcreteanswerstoallthesequestions,butratherbeabletodiscussthemintelligentlywithyou.Installerswilldeterminetheanswerstothesequestionsduringtheirdesignprocess.
Groundloop:Asktheinstallerwhattypeofgroundlooptheyrecommend.Besuretheyinspectyourpropertyandidentifypotentiallocationsforthedrilling/excavationequipment,notingoverheadpowerlines,septicsystems,andotherpotentiallimitations.
HeatPumpEquipment:Whattypeofheatpumpequipmentwilltheyberecommending?IstheheatpumpAHRICertified?
HeatDistributionSystem:Willtheyberecommendingforcedhotairorradiantheatforyourhome?Discusswiththemtheprosandconsofeach.Ifthisisaretrofit,whatchangeswillneedtobemadetoyourhometoaccommodatethegeosystem?
PumpingPenalty:Asktheinstallerforanestimateofthepumppenalty(i.e.roughlyhowmuchelectricityisexpectedtoberequiredtocirculatethefluidsthroughtheloop).
BalancePoints:Whataretheoutsideairtemperatureswhentheheatingandairconditioningshouldcomeon?Atwhatoutsideairtemperature,shouldtheauxiliarybegintosupplementheatpump(s),ifapplicable?
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PeakLoads:Whatarethedesigntemperaturesformaximumheatingandcoolingloads,(e.g.5⁰Fforheatingand90⁰Fforcooling).
MinimumandMaximumEnteringWaterTemperatures:Enteringwatertemperatureisalargedeterminingfactorintheefficiencyoftheheatpump(similartothe‘octanerating’ofgasolineinyourcar).Heatpumpscanoperatedowntoverycoldwatertemperatures(25⁰F)butlooseefficiencyundertheseconditions.Asktheinstallertodiscusswhathe/sheexpectstoseeasminimumandmaximumenteringwatertemperatureduringpeakload.
BuildingImprovements:Whatimprovementsmightbemadetotightenupthebuildingenvelopetohelptoreducesystemsizeandcostofinstallation?Ifyou(thehomeowner)agreetomakingspecificchanges,andtheybasetheirdesignonthosechanges,thenitwillbeyourresponsibilitytomaketheagreeduponchanges.
ChooseanInstallerAgroundloopisaninvestmentthatenablestheuseofarenewableenergysourcetoheatandcoolyourhome.Ifproperlysizedandproperlyconstructed,itcanbeasignificantassettoyourhome.
Ifallthebidsproposedthesamedesignandthesameequipment,evaluatingthebidswouldbesimple:comparepricesandreferences,andthechoicewouldbeobvious.However,thiswilllikelyNOTbethecase.Intermsofequipment,differentcontractorsmayfavordifferentheatpumpbrands,withdifferentfeaturesandprices.Oneinstallermightrecommendawater‐to‐airsystemwhileanotherencouragesyoutogowithwater‐to‐water.Youmighthavedifferentrecommendationsforthegroundloop;onecontractormayadvocateastandingcolumnwellduetoitslowerupfrontdrillingcostswhileanothermayadvocateaclosedloopdesignduetoitslowerpumpingpenaltyandfewermaintenancerequirements.Someinstallerswillrecommendalongergroundloop(deeperboreholesforverticaldesigns,longertrenchesforhorizontaldesigns)tomaintainhigherefficiencyduringpeakload.Othersmaysuggestinstallingashorterlooplengthwiththeoccasionaluseofsupplementalelectricheat(auxiliaryheat)duringpeakload,therebyreducinginstallationcostsbutincreasingoperatingcosts.Insomeareas,itissimplyatrade‐offbetweeninitialinstallationcostsandannualoperatingcosts.However,thistradeoffmaybelessclearwhenthebuildingloadisdominantlyheatingorcooling.Ashortergroundloopmayexperiencethermaldegradationovertime(coolingoffinaheatingdominatedclimateorwarmingupinacoolingdominatedclimate).Intheend,theremaybemanydifferentdesignoptions.However,providedthattheyareallproperlydesignedbyexperiencedgeothermalprofessionals,theyshouldallworkasdesignedanddelivertheexpectedbenefits.Thefinaldecisionwillcomedowntopersonalpreference,cost,andrapportwithinstaller.
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Toassistyouinevaluatingthebidsandmakingyourfinaldecision,youshouldreviewthebidscarefullyanddiscussthefollowingdetailswithyourinstaller:
Detailspecificationsofsystemcomponents:Asnotedabove,thebidsshouldbeadetailedaspossible(withouttheinstallergivingawaytheactualspecificsoftheirdesign).Ataminimum,thebidshouldincludeequipmentnames,modelnumbers,thetypeandlengthofgroundlooptobeinstalled(standingcolumnwell,verticalclosedloop,horizontalclosedloop)andpumpsizes.
Anestimateofthepumpingpenalty:Aftertheheatpump,thenextlargestpowerconsumerofthegeosystemisthepumprequiredtocirculatetheloopfluid.Bearinmind,thesmallerthepiping/tubing,themoreelectricitythatwillberequiredtomovethefluid(higherpumppenalty).Whilesmallerdiametertubingwillbelessexpensive,itmayendupcostingyoumoreinelectricitycostsinthelongrun.Thepumpingpenalty(inkilowatts)shouldbelessthan25%ofheatpumppowerconsumptionlistedintheAHRIPerformanceDatatable.
ManualJ:ThebidshouldspecifythataManualJanalysiswillbeconducted.IfthecontractordoesnotcomputetheManualJthemselves,theyshouldprovidethenameoftheindividualwhoperformedtheanalysis.
Drilling/ExcavatingContractor:Detailedinformationregardingthedrilling/excavatingcontractorshouldbemadeavailabletothecustomer.Manyofthesecontractorshaveextensiveexperiencewithgeosystems,andyouwillwanttomakesureyourgeoinstallerisworkingwithoneofthesedrillers.Contactthedriller/excavatorandaskthemforalistofreferencesaswell.Forclosedloopsystems,besuretheyspecifythatthewellwillbegroutedfollowingIGSPHPAguidelines.
Electrician:Thebidshouldspecifythenameoftheelectricianthatwillworkonthejob;theelectricianshouldbewellversedinwiringgeothermalequipment.Besureyouareawareofanyupgradesthatmayberequiredtoyourelectricalservice.
PTPorts:Besureyourinstallerincludesinthedesignspecialportstomeasurethetemperatureandpressureofthegroundloop.ThesearecommonlycalledP/TportsorPete’sPlugs.
TaxCredits:WhilegeothermalcontractorshouldbeabletoconfirmtheeligibilityoftheequipmentbeinginstalledfortheFederalTaxCredits,thedetailsinobtainingthetaxcreditsareuptothehomeownerandtheirpersonalaccountant.
References:Requestalistofreferences,contactthem,andaskthemabouttheirexperiencebothworkingwiththecontractoraswellastheirexperiencewiththegeosystem.Didtheyhaveapositiveexperiencewiththeinstallationprocess?Didtheinstallationstaywithintheproposedbudget?Ifnot,whynot?Hasthegeosystemoperatedaspromised(comfortandreliability)?Whatmethodshavetheyusedtoverifysystemoperation?
Maintenance/Service:Detailsaboutfutureservicingofthegeothermalsystemshouldbespecified.
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Warranty:Thecontractorshouldbeabletoprovidewarrantyinformationattherequestofthecustomer.Canthecontractorinsurethatthesystemoperatestowithin10%ofmanufacturerPerformanceData?Whilethishelpstoinsurethattheheatpumpequipmentisoperatingwithinitsspecifications,andanyadjustmentorequipmentmalfunctionwillbecovered,itdoesnotnecessarilyequatetoensuringthattheentiresystemisoperatingwithin10%oftheheatpumpCOP.Understandthedifferencebetweenequipmentwarrantyandwarrantyofsystemdesign.
Selectionofthewinningbidwillultimatelycomedowntoyourconfidencethattheinstallerhasthepropertrainingandexperienceandhasprovidedadetaileddesignthatwilldeliverthefinancialandenvironmentalbenefitsyoudesire.Theirdesignshouldtakeintoaccountthespecificcharacteristicsofyourhomeandthegroundconditionsinwhichtheloopwillbeinstalled.Thethoroughnessofthedesignprocessshouldbeclearthroughtheirexplanationstoyouofthetopicsdiscussedabove.Referencesandindependentmonitoringofexistinginstallationsarewaysinwhichtheycandemonstratethattheirspecificdesignsperformaspromised.
SelectaMethodforMonitoringYourNewGeoSystemMuchofthediscussionthusfarhasfocusedonhowtoidentifytheoptimaldesignfromthebestinstallersanddesigners.Yourinvestmentinageosystemwillenableyoutoutilizetherenewablethermalenergyofyourproperty,willpaydividendsforyearstocome,andwillincreasethepropertyvalueofyourhome.However,eventhebestdesignsinstalledbywelltrainedandexperiencedpersonnelcanexperiencemechanicalproblemsthatrequiremaintenanceandrepair.Ifyouweretospend$50,000onahighperformanceautomobile,youprobablywouldnotassumethatitwouldjustruntroublefreeforthenextdecade,butyouwouldbeinterestedinhavingadashboardwithgaugesanddiagnosticssothatminorissuescouldbequicklyidentifiedandfixedbeforetheybecamebiggerproblems.
Untilrecently,themostcommonwaytomonitortheperformanceofageosystemwastopaycloseattentiontoelectricbills.Unfortunately,thisapproachhasproventobeineffectiveinidentifyingandcorrectingproblemsbeforetheycostyousignificantamountofmoney(asevidencedbyhighelectricbill).Inaddition,itisoftenverydifficulttotroubleshootthecauseoftheproblembecausethereisnorecordofwhenitoccurredorunderwhatconditions.
Today,web‐basedmonitoringthathasbecomestandardonmanysolarPVsystemsisnowalsoavailableforgeothermalheatpumpsystems.Web‐basedmonitoringallowsthehomeownertoseehowasystemisperforminginrealtime,receiveemailalertswhenoperatingconditionsexceedprescribedlimits,andcompareactualoperatingconditionswithsystemdesignparameters.Homeownersandinstallerscanworktotogetherto
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integratemonitoringintomaintenancecontractssothatifproblemsdoarise,theinstallercanaccessthedataandgetaheadstartidentifyingtheproblembeforetheyleavetheshop.
Whensufficientdatapointsarecollected,BTUsproducedandkWhconsumedcanbetrackedandprovideabasisforcomputingcostandcarbonsavings,usinglocalfuelcostsandcarbonintensities.
ConclusionAgeosystemcanbeanexcellentchoiceforhomeownerslookingtoinstallaheatingandcoolingsystemthatwillofferthenstablelowheatingandcoolingcosts,unparalleledcomfort,andoftensignificantlyreducetheircarbonfootprint.Wehopeyoufindthisinformationhelpfulandpleasesendquestionsandcommentsto:[email protected]
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