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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


thatgeosystemsarerelativelyrareintheU.S.arethreefold:1)mostAmericansdon’tunderstand,orarenotawareof,geosystemsasaviableoption;2)likesolarpanelsandother“greenenergy”technologies,geosystemscanhaverelativelyhighupfrontcostsbutavailablefederaltaxcreditscansignificantlyoffsettheseupfrontcosts;and3)geosystemsarebestsuitedtowell‐insulatedhomeswithatightbuildingenvelope.

Thereareseveralimportantdistinctionsbetweenageosystemandatraditionalfossil‐fuelbasedsystem.Thefollowingtablesdescribethesebasicdifferencesincoolingandheatingmode.


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:


Extraction/RejectionWellStandingColumnWellSurfaceWaterLoop

TheGeothermalHeatPumpAgeothermalheatpumpistheequipmentthatconcentratesthermalenergyinthecirculatingfluidintotemperaturesthatarehighenoughtoheatabuilding.Theheatpumpusesarefrigerationcycle,justlikethatusedinrefrigerators,freezersandairconditioners.Asshownbelow,lowtomoderategroundtemperaturesarecarriedintotheheatexchangerinthegroundloopfluid.Theselowtomoderatetemperaturesarepassedbyaloopofrefrigerantintheheatexchanger,causingtherefrigeranttovaporizeintoalowpressure,warmvapor.Thisvaporisthenroutedintothecompressorwhereitispressurizedintoa

highpressure,hotgas.Airorwaterflowingpastthishotrefrigerantvaporpicksupheatandthenmovesintothebuildingtoheatthebuilding.Havinggivenupsomeofitsheat,the


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


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‐


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.


Forawell‐insulatedhome,ageosystemwillcostmoretoinstallupfront,butwillpayforitselfinthelongrun,especiallyasfossilfuelcostscontinuetorise.Thehigherupfrontcostsofageosystemstemfromtheneedtoinstallagroundloop(asdiscussedabove).Justasthemosthighlyefficientoilandgasfurnacescomeatapremiumcost,themostefficientheatpumps(thosewiththehighestCOP)tendtocomeatapremiumcostaswell.However,aswillbediscussedbelow,dualstageheatpumpsdeployedinathoughtfulmannercanofferhomeownersreliablelow‐costheatingandcoolingfordecadestocome.Takealookattheflowchartbelowtoseeifageosystemisrightforyou.

Ifyouarrivedatthegreenboxandhavedecidedthatageothermalsystemisrightforyou,it’stimetostartlookingforanexperiencedandqualifiedinstallerinyourarea.


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.


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


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?


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.


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


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?


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.


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.


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


integratemonitoringintomaintenancecontractssothatifproblemsdoarise,theinstallercanaccessthedataandgetaheadstartidentifyingtheproblembeforetheyleavetheshop.

Whensufficientdatapointsarecollected,BTUsproducedandkWhconsumedcanbetrackedandprovideabasisforcomputingcostandcarbonsavings,usinglocalfuelcostsandcarbonintensities.

ConclusionAgeosystemcanbeanexcellentchoiceforhomeownerslookingtoinstallaheatingandcoolingsystemthatwillofferthenstablelowheatingandcoolingcosts,unparalleledcomfort,andoftensignificantlyreducetheircarbonfootprint.Wehopeyoufindthisinformationhelpfulandpleasesendquestionsandcommentsto:[email protected]