Post on 08-Jun-2020
CORRECT USE OF
DISTRICT HEAT
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Correctuseofdistrictheat
©FinnishEnergyIndustries
ISBN978-952-5615-12-8
Illustration/LayoutJanneInkeroinen
PrintingLibrisOy,Helsinki
Reprinted2007
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CONTENTS
Districtheatisneat CorrectuseofdistrictheatsavesheatandmoneyHeatmeasurement Meterreadings Cooling Monitoryourenergyconsumption Heatindex
Heatingdegree-dayPressureanddifferentialpressureofthedistrictheatingnetworkStrainer Customerequipment Heatexchangers Balancingtheheatingnetwork Controldevicesfortheheatingnetwork Room-specific controlFloorheatingcontrolSettingofthecontrolcurve Impactofthecontrolcurveselectiononroomtemperature Checklist Servicewatercontroldevices Detectingaleakintheheatexchanger Pumps PressureoftheheatingnetworkandoperationofthemembraneexpansionvesselSafetydevices Temperatureandpressuremeters Instructionsforusersofdistrictheatingequipment Replacingthecustomer’sdistrictheatingequipment Iftheheatingdoesnotwork
DISTRICT HEAT IS NEAT
Districtheatingisanaturalformofheatingindensely-builtareas.Itkeepstheenvironmentcleanandimproveslivingcomfort.Districtheatingalsoconservesenergyandtheen-vironment to a significant extent. The greatest savings come fromcombinedproductionofdistrictheatandelectricity.Thissavesone-thirdoffuelcomparedwithseparateproductionofelectricityandheat.Italsocombatsclimatechange.DistrictheatinghasalsoreceivedrecognitionontheEUlevelforitsenergy efficiency.
District heating is reliable and flexible. The heat is pro-ducedintheeconomicallymostadvantageousmanner,
takingenvironmentalimpactsintoaccount.Districtheatingfuelsarenaturalgas,coal,peat,oil,wood
andotherrenewableenergysourcessuchasbiogas.Districtheatingalsoutilisestheleft-
overheatfromindustrialprocesses.
DistrictheatingisthemostpopularformofheatinginFinland.Itiscom-moninalmostalltownsandpopula-tioncentres.About2.5millionFinnsliveinhomesheatedbydistrictheat.Districtheatingaccountsforalmost50%ofthetotalheatingmarket.Almost95%ofapartmentbuildingsandabouthalfofterracedhouses,aswellasthebulkofpublicandcom-mercialbuildings,areconnectedtothedistrictheatingnetwork.Inthelargesttowns,themarketshareismorethan90%.
Districtheatisproducedincombinedheatandpower(CHP)plantsorinheatingplants.Customersreceiveheatthroughthehotwatercirculatinginthedistrictheatingnetwork.
Thetemperatureofdistrictheatingwatervariesbetween65and115ºC,dependingontheweather.Thetem-peratureisatitslowestinsummerwhenheatisonlyneededforhotserv-icewater.Thetemperatureofwaterreturningfromcustomerstothepro-ductionplantsrangesbetween25and50ºC.
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Ventilation36%
Roof6%An example of the distribution of energy consumption in a residential house. The consumption distribution is house-specific.
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CORRECT USE OF DISTRICT HEAT SAVES HEAT AND MONEY
Itispossibletosaveenergyinahousewithdistrictheatingwithoutgreatinvestments.Withcorrectandwell-adviseduseofheatingequipment,energyissavedwithouthavingtocompromiseovertherequirementsofhealthyliving.Whentheequipmentisingoodcondi-tion,theroomtemperatureremainscomfort-ableandstableandthereisalwaysenoughhotservicewaterofthecorrecttemperature.
Itisrecommendedthatroomtemperaturesareadjustedaccordingtotheuseoftherooms.
Recommended indoor temperatures:
• home and office 20-22ºC•shops,workshopsandindustrial premises18ºC•heatedstorerooms12ºC•garages5ºC
Energy saving tips
•Makesurethatroomtemperaturesareatanappropriatelevel• Air the rooms quickly and efficiently•Makesurethatwindowsanddoorsare sufficiently tight•Avoidunnecessaryuseofwater•Monitoryourenergyandwaterconsumption
HEAT MEASUREMENT
Thethermalenergyconsumedinthebuildingismeasured.Thecomponentsoftheheatmeterarea flow sensor, temperature sensors and a calcula-tor. The flow sensor measures the volume of circul- atingdistrictheatingwater.Thetemperaturesen-sorsconstantlymeasurethetemperaturesofwatergoingintoandcomingoutofthebuilding.Thecalculatorcalculatesthethermalenergyconsumed.Consumptionisshowninmegawatt-hours(MWh).Theheatsupplierownsthemeteringequipment.
Forexample,thefollowingdatacanbereadfromtheheatmeter:
•thermalenergy•volumeofcirculatingdistrictheatingwater•momentarycoolingofthedistrictheatingwater•momentarytemperaturesofthesupplyandreturnwaterofthedistrictheatingwater• momentary heat effect and water flow
Windowsanddoors15%
Walls17%
Base floor 4% Servicewater22%
A drop of just one degree in room temperature means a saving of about five per cent in annual energy consumption.
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Thecalculatorcalculatesconsumptionaccordingtothefollowingformula:
Q = V ∙ ∆t ∙ 1.163
Heat consumption (kWh) = volume of circu-lating district heating water (m3) x tempera-ture difference (cooling, ºC) x specific factor of water 1.163.
1 MWh = 1,000 kWh (kilowatt-hours)
METER READINGS
Thecustomersendsmeterreadingstotheheatsupplieraccordingtoinstructions,ortheheatingcompanyreadsthemeterremotely.
COOLING
Thetemperaturedifferencebetweenthedistrictheatingwatergoingintothebuildingandthewa-tercomingoutofthebuildingiscalledthecoolingofdistrictheatingwater.Thehigherthecoolingis,thebetterthedistrictheatingequipmentofthebuildingisworking.
Thereasonsshouldbedeterminedifcoolingisunder25°Corifitdiffersconsiderablyfromvaluesrecordedearlier.Therealisedcoolingofdistrictheatingwaterisoftenalreadycalculatedonthebillorconsumptionreportsentbytheheatsupplier.
Monitor cooling on a regular basis!
MONITOR YOUR ENERGY CONSUMPTION
Districtheatingcompaniesprovidetheirclientswithfollow-upreportsonenergyconsumptionatleastonceayear.Inmanylocations,customerscanmonitortheirconsumptiondirectlyontheheatsupplier’swebsite.Theeffectoftheweatheristakenintoconsiderationwiththeheatingde-gree-dayinthecomparisonofannualconsump-tion.Thereportsusuallyincludeadjustmentfortheweather.Ifcurrentconsumptiondifferscon-siderably from the figures for previous years, it is advisabletoinspecttheadjustmentsandcondi-tionoftheequipment.
Yourheatsupplierwillprovideadditionalinforma-tiononyourenergyconsumptionandmeasure-ment.
Inform your energy or district heating com-pany if you have carried out any saving measures in your house, if you stop heating for a longer period or if there are any other changes having an effect on energy consumption.
HEAT INDEX
Theheatindexistheheatconsumptionadjusted(normalised)withtheheatingdegree-daytothenormalyearperonebuildingcubicmetreayear(kWh/m3/year).Theheatingdegree-dayhasbeendevelopedforheatcalculationsofbuildings.Withtheheatingdegree-day,itispossibletocompareindividualheatconsumptionindifferentmonthsoryearsandtocompareitwiththeconsumptionofother,correspondingbuildings.Localheatingdegree-daysarecalculatedbytheFinnishMeteorologicalInstitute.
An example of calculating the heat index:
HousingCompanyHomeSweetHome(apartmentbuilding)
• totalvolume7,000m3• normalisedenergyconsumption310MWh=310,000kWh
Heatindex:310,000kWh = 44.4 kWh/ m3
7,000m3
Normalisingisonlydirectedattheenergyusedforspaceheating;theheatingofserv-icewaterdoesnotdependontheoutdoortemperature.Energyanddistrictheatingcompaniesprovideinforma-tionaboutthecalculationoftemperatureadjustments.Theheatsupplierusuallycalculatesthenormalisedconsumptionofabuilding
andentersitontheheatingbillorconsumptionreport.
Furtherinformation:www.motiva.fi/kulutuksen-normitus(onlyinFinnish)
Inform the heat supplier immediately if you suspect that the strainer is blocked.
PRESSURE AND DIFFERENTIAL PRESSURE OF THE DISTRICT HEATING NETWORK
Thepumpsinthedistrictheatingproductionplantordistrictheatingnetworkcirculatethedistrictheatingwaterinthecustomer’sdistrictheatingequipment.Thepressureandthedifferentialpressure in the network fluctuate constantly. They aregenerallyhigherinwinterthaninsummer.
STRAINER
The strainer filters the largest impurities of the water in the district heating network. The first sign ofablockageisthelowtemperatureofhotservicewater.Ifthestrainerisbadlyblocked,theheatsupplymayalsobeaffected.Whenthestrainerisblocked,thepressuremetersontheprimarysideofdistrictheatingshowalmostthesamereadings.
District heating supply pipe
District heating return pipe
Heat supplier’s main shut-off valves
Customer’s main shut-off valves
Flow sensor
Strainer
Calculator
Temperature sensors
District heating equipment owned by the heat supplier
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HEATING DEGREE-DAY
Heatingdegree-dayisobtainedbyaddingupthedifferencebetweenthedailyindoorandoutdoortemperaturesforeachmonth.Themostcommon-lyusedheatingdegree-dayisS17,whichiscal-culatedonthebasisofthedifferencebetweentheassumed 24-hour mean value of +17°C between theindoorandoutdoortemperature.Themonthlyheatingdegree-dayisthesumofthedailyheatingdegree-days,andcorrespondinglytheheatingdegree-dayfortheyearisthesumofmonthlyheatingdegree-days.Dayswithanaveragetemperature of more than +10°C in the spring and more than +12°C in the autumn are not takenintoaccountinthecalculationoftheheatingdegree-day.Thus,itisassumedthattheheatingofbuildingsisstoppedandstarteddailywhentheoutdoortemperatureexceedsorfallsbelowtheabove-mentionedlimits.
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HEAT EXCHANGERS
District heating water heats the water that flows throughtheheatexchangers,whichisthenusedforthebuilding’sspaceheatingsystemandforhotservicewater.Theheatexchangerskeepthewaterinthedistrictheatingnetworkandthebuilding’sheatingandhotservicewaterseparatefromeachother.Heatexchangersaredurableandtheydonotneedmuchserviceormaintenance.
Regulator
Summer shut-off
Control valve for heating
Control valve for service water
Customer’s main shut-off valves
Safety valve
Expansion vessel
Heat exchanger for heating
Heat exchanger for service water
Service water
Cold water
Pump
Heating network
Filling valve
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CUSTOMER’S DISTRICT HEATING EQUIPMENT
Theequipmentinthesubstationincludestheheatexchangersforheatingandservicewaterand,possibly,aheatexchangerforairconditioning,controldevices,pumps,expansionandsafetyequipment,thermometersandmanometers,andshut-offvalves.Customersacquiretheirdistrictheatingequipmentandtherelatedinstallationworkfromheatingcontractorsor,ascomprehen-sivedeliveries,fromenergyordistrictheatingsuppliers.Thedistrictheatingequipmentispres-sureequipment.
Thesubstationislocatedintheheatdistributionroom. A sufficient amount of space should be re-servedforthesubstationandthesupplier’sequip-mentformaintenancepurposes.Theconnectiondiagramfortheequipmentisdisplayedonthewalloftheheatdistributionroom.
The heat distribution room is used for district heating equipment only. Its door is to be kept locked. The heat supplier shall have free access to the heat distribution room.
Districtheatisverysafe.However,hotdistrictheatingwaterandhotsurfacesmustbehandledwithcare.Districtheatingwaterisnotsuitablefordrinking.
Balancingofthespaceheatingnetworkisprofessionalwork,anditpaystoletanexpertcompanytotakecareofitsplanningandimplementation.Theheatingnetworkisbalancedbyregulatingtheprecontrolvaluesoftheradiatorvalvesand,ifnecessary,possiblebalancingvalves.Thedimensioningoftheheatingpumpisalsoinspectedinconnectionwiththebalancing.
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BALANCING THE HEATING NETWORK
Thebalanceoftheheatingnetworkisthefoun-dationofwell-functioningheating.Thebasicadjustmentoftheheatingnetworkensuresthatthetemperatureineachroomremainsatthedeterminedlevel.Whenhavingcorrecttempera-tures,theneedforairingisreducedandenergyuse becomes more efficient. An unbalanced space heatingnetworkwastesthermalenergybecauseexcessivelyhotwaterwillhavetobefedintotheradiatorsofthewholebuilding.
The radiators are functioning correctly when their upper parts are warm and the lower parts at almost room temperature. The radiators are warm only when the room temperature falls below the set value.
SETTING OF THE CONTROL CURVE
Thecontroldevicesofvariousmanufacturersaredifferentfromoneanother.Computer-basedregulationandcontrolsystems(DDCcontrol)are house-specific and very different. The fol-lowinginstructionsareofprincipleonly:
Thesettingofthecontrolcurveusuallytakesplaceprogrammatically,inwhichcasetheuserdeterminesthesetvaluesofthesupplywatertemperatureforvariousoutdoortemperatures.Thesupplierofthecontrolsystemprovidesde-tailedinstructionsonthesettingofthecontrolcurve.
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CONTROL DEVICES FOR THE HEATING NETWORK
Thecontroldevicesinthesubstationregulatethewater temperature in the radiator or floor heating networkaccordingtotheoutdoortemperature.
Whentheregulationsystemistunedandfunctioningcorrectly,thewatertemperatureenteringtheheatingnetworkautomaticallyremainsatthecorrectlevelthroughouttheyear.
Thecontrolcurvechosenatthecontrolcentreisspecific for each building. Unnecessary increase of thecontrolcurveshouldbeavoided.
Thefunctionsandequipmentofthecontrolcentreinclude:
•settingofthecontrolcurvefordetermining thetemperatureofthewaterenteringthe radiators or floor heating •parallelshiftofthecontrolcurve•possibilitytoreduceindoortemperature•programselectorswitch(forexample, clockcontrol,dayornightprogram,manualoperation,mechanicalcontrols)• timer for 24-hour or weekly programs•indicatorforvalvemovementdirection•alarmfunctions
ROOM-SPECIFIC CONTROL
Thethermostaticradiatorvalvepreventsexcessive heating of the room. Room-specific thermostaticvalvestakeintoaccounttheextraheatfromthesun,electricappliances,lightingandpeople.
FLOOR HEATING CONTROL
It is possible to have partial or full underfloor heating in a building. Underfloor heating always requiresaseparatecontrolsystem.Excessivelyhot water must not enter the underfloor heat-ingnetwork.Supplywatertemperaturethatistoo high may damage pipes, floor structures and coatings. A high floor surface temperature is also unhealthyandwastesenergy.Thewatertem-perature leaving the floor heating circuit must not exceed 45ºC under any circumstances. If thetemperaturerisesabovethepermittedlevel,thepumpstopsandwillonlystartagainoncethetemperaturehasfallen.
Read the instructions for the control carefully.
Shifting of thecontrol curveup or downwards
Setting of thecontrol curve
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Impact of the control curve selection on room temperature
Thesetcontrolcurveistoosteep.Theroomtemperatureistoohighincoldweather.Remedy: the control curve is adjusted to a more gently sloping position
Thesetcontrolcurveistoogentle.Theroomtemperatureistoolowinverycoldweather.Remedy: the control curve is adjusted to a steeper position
Theslopeofthecontrolcurvehasbeenselectedcorrectly,buttheroomsaretoohotwithalloutdoortemperatures.Remedy: the curve is parallel-shifted downwards. (Atemperaturechangeofapproximatelythreedegreesinthesupplywatertemperaturechangestheroomtemperaturebyaboutonedegree.)
The correct control curve has been found when the room temperature remains stable and suitable under all conditions.
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CHECK LIST
•Read the operating instructions of the control equipment carefully and follow the instructions.
• A correctly set control curve guarantees the desired room temperature in all normal weather conditions.
•The control curve is building-specific, and you may have to seek for the correct curve. The control curve selected at the installation stage is directive only.
•Write down the changes made to the set values of the control devices in different weather conditions.
•When adjusting the control values, it will take a few days before the room temperatures are normalised.
•If the building’s control centre includes extra functions, e.g optimisation, learn how to use them.
• If in doubt, ask the supplier of the control devices or the heat supplier for advice.
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TIMER
Thetimerreducestheroomtemperatureforthedesiredperiodoftime.
SERVICE WATER CONTROL DEVICES
Thetemperatureofservicewaterisadjustedbymeansofacontrolvalveonthedistrictheatingside.Thetemperatureoftheservicewateris55°C.Thetemperatureoftheservicewatermustnotbereducedforthenightwiththetimer.
Incorrectlydimensionedorpoorlyfunctioningcontroldevicesforservicewatermaycause,forexample, fluctuation in the service water tem-perature.Thereasonforthefaultmustalwaysbeestablishedandrepaired.
DETECTING A LEAK IN THE HEAT EXCHANGER
Theheatexchangerforheatingmayhaveanin-ternalleakifthesafetyvalveintheheatingnet-work is leaking. A filling valve that has been left openmayalsobethereasonfortheleak.
It is more difficult to detect an internal leak in the heatexchangerforservicewater.Theconditionofheatexchangersforservicewaterthatareover10yearsofageshouldbecheckedaboutonceayear.Aleakintheheatexchangerforservicewa-tercanbedetectedasanincreaseinwaterandenergy consumption and fluctuations in the servicewatertemperature.
Manyenergyanddistrictheatingcompaniesaddacolouringagentinthedistrictheatingwater,whichhelpstodetectaleak.Thereisaleakintheheatexchangerifthehotservicewaterhasagreenishcolour.
Contact your heat supplier immediately if you suspect a leak in the heat exchanger.
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Fillingvalve
PUMPS
Theheatingpumpcirculatesthewaterinthebuilding’sspaceheatingnetwork.
Thecirculatingpumpforservicewaterkeepsthetemperatureoftheentireservicewaternetworkatthecorrectandeventemperature,whichpre-ventsunnecessaryhotwaterconsumption.Theservicewaterpumpiskeptrunningatalltimes.
Read carefully the operating and main-tenance instructions for the pumps.
PRESSURE OF THE HEATING NETWORK AND OPERATION OF THE MEMBRANE EXPANSION VESSEL
Thepressureinthespaceheatingnetworkin-creaseswhenthetemperaturerises.Duringthecoldperiod,thepressureishigherthaninspringorautumn.
Theexpansionequipmentkeepsthewaterinallradiatorsandthepressureeven.Themostcom-monmodelofexpansionvesselisthemembraneexpansionvessellocatedintheheatdistributionroom.Thewaterexpandsasitbecomeshotter,and water flows into the membrane expansionvessel.Whencooling,thevolumeofwaterdiminishes and water flows out of the membrane expansionvesselintothespaceheatingnetwork.
Thesizeandinitialpressureofthepressureves-selisdimensionedsothatthereisnoneedtoaddwatertotheclosedspaceheatingnetworkequippedwithamembraneexpansionvessel.Thepressure vessel is faulty or the filling valve is leak-ingifthepressureofthespaceheatingnetworkrisesconstantlyandwaterisleakingthroughthesafetyvalve.
Itisnotnecessarytoaddwatertothespaceheatingnetworkiftheradiatorsarebledandtherearenoleaksinthenetwork.Thereasonforanyconstantneedtoaddwatermustalwaysbeestab-lished.
Waterisaddedtothespaceheatingnetworkthrough the filling valves.
SAFETY DEVICES
Thesafetyvalveofthespaceheatingnetworkprotectstheradiatorsandtheexpansionvesseleven if the filling valve is left open or there is an internalleakintheheatexchanger,inwhichcasethepressureofthedistrictheatingwaterwillhaveaneffectonthespaceheatingnetwork.Insuchacase,thesafetyvalveopensandleakswater.
Thesafetyvalveintheservicewaternetworkpreventsapressureincreaseofover1.0MPa(10bar).
TEMPERATURE AND PRESSURE METERS
Thecustomer’sdistrictheatingequipmenthaspressureandtemperaturemetersforcheckingthattheequipmentisfunctioningcorrectly.Thepressuremetersindicatethepressuresoftheheatingandwatersystemnetwork.Thepressuremetersfordistrictheatingindicatethepressureandthedifferenceinavailablepressure.
Thethermometersindicatetheservicewatertemperatureandthesupplyandreturnwatertemperatureofthespaceheatingnetwork.Whenthespaceheatingnetworkisinbalance,there-turntemperatureisclearlylowerthanthesupplytemperature.Therearealsothermometersinthedistrictheatingsupplyandreturnpipe.Thediffe-renceintheirreadingsisthemomentarycoolingtemperatureinthedistrictheatingwater.
Thereisathermometerwithanalarmintheservicewater.Itraisesthealarmifthetempera-turerisesabove65ºC.Checkthecontrolvalveand find out the reason for the alarm.
Remember
• to keep the heat distribution room tidy
• to monitor the functioning of the equip-ment in accordance with the operating instructions
• to learn to use the control devices, pumps, expansion and safety equipment and other technical devices in the
correct manner
• to keep the shut-off valves of the pres-sure meters closed. (They are opened when the pressure is checked)
• to supply the readings of the heat meter in accordance with the heat
supplier’s instructions, when necessary
• to monitor your heat consumption and cooling
• to ensure that any faults are repaired or to report them further
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Thetemperaturelevelsfortheheatingnetworkare specific for each building. In conventional ra-diatorheating,thesupplywatertemperatureisamaximumof70ºC.Inoldbuildings,thewatertemperatureneedinthecoldestperiodsmaybeupto80ºC.
In underfloor heating systems, the supply water temperaturemustnotrisetoohigh.Plasticpipesare normally used in floor heating. The tempera-ture of water flowing in the pipes must be below 45ºC.
Temperature below –15ºC
•Cancelthenight-timetemperaturedroporensurethattheautomaticfunctionstakecareofitautomatically•Ensurethatthereisnodangeroffreezingintheradiatorsoftheventilationdevices
Summer
•Ensurethatthecontrolvalveisclosedandre-mainsclosedor,ifnecessary,closethesum-mershut-off•Iftheheatingpumpsarestopped,startthemuponaweeklybasis
Spring and autumn
•Ensurecorrectcontrolvalues•Selectsuitablenighttemperatureswiththe timerandparallelshift•Checktheclocksinthecontroldevicewhenswitchingbetweenwintertimeandsummertime•Checkthepressureofthespaceheatingnet-workwhentheheatingperiodstarts•Checkthetemperatureofthehotservicewater
INSTRUCTIONS FOR USERS OFDISTRICT HEATING EQUIPMENT
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REPLACING THE CUSTOMER’S DISTRICT HEATING EQUIPMENT
Theconditionandfunctioningofcustomerequip-mentmustbeinspectedonaregularbasis.Afullsurveyisrecommendedfortheequipmentafter15yearsofserviceatthelatest.Conditioninspec-tionsandsurveysarecarriedoutbytheinspec-torsofenergyanddistrictheatingcompanies,heatcontractors,equipmentmanufacturersandheatingandventilationdesigners.Thefunctioningoftheequipmentandanypossiblereplacementneedsareestablishedinthesurveyofthedistrictheatingequipment.
Theextentofreplacementisalwaysassessedseparatelyineachcase.Newequipmentisdimen-sionedtoequaltherealheatingneedofthebuild-ing,whichsavesacquisitioncosts.Thecontractedwater flow/heat capacity is also checked at the sametime.
Always contact your heat supplier before replacing any equipment.
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ADD MORE WATER TO THENETWORK AND CHECKPOSSIBLE FAULTS
STOP THE VENTILATIONEQUIPMENT, IF NECESSARY
SWITCH THE HEATING TOMANUAL OPERATIONIF THE FAULT REMAINS
ASK THE HEAT SUPPLIERTO CLEAN IT
STOP THE VENTILATIONEQUIPMENT
THERE MAY BE A LEAKIN THE SYSTEM OR A FAULTIN THE PRESSURE VESSEL
IS THE NETWORK PRESSURECORRECT (A SUFFICIENTAMOUNT OF WATER)?
THERE MAY BE A FAULTIN THE SWITCHES OR FUSES
ARE THE PUMPS WORKING?ARE THE SHUT-OFF VALVESIN THE CORRECT POSITION?
THE SETTINGS OF THE CONTROL DEVICES MAY BE INCORRECT
ARE THE CONTROLDEVICES WORKING?
BLOCKED STRAINERPRESSURE DIFFERENCEIN THE CIRCULATION OFDISTRICT HEATING WATER
DISRUPTION IN THE HEAT SUPPLIER’S HEATDELIVERS
MALFUNCTION ?
IF NECESSARY, CONTACT AN EXPERT
MEASURES
below60 kPa
below65°C
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65-120°C
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FAULT IN THE HEAT SUPPLIER’S EQUIPMENT
CUSTOMERS OWN EQUIPMENT
IF THE HEATING DOES NOT WORK
SUPPLY WATER TEMPERATUREOF THE CIRCULAITING DISTRICT HEATING WATER