Mitsubishi EHST20C-VM2C - Page 71

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No. Fault symptom Possible cause Explanation - Solution
9 Waterheating takes
longer.
1. Heatpumpnotworking. 1. Check heat pump – consult outdoor unit service manual.
2. Booster heater cut-out tripped. 2. Check booster heater thermostat and press reset button if safe.
Resetbuttonislocatedonthesideofboosterheater,coveredwithwhiterub-
bercap.See"4.PARTNAMESANDFUNCTIONS"tondoutitsposition.
3.
Booster heater breaker (ECB1) tripped. 3. Check the cause and reset if safe.
4. The booster heater thermal cut-out has
trippedandcannotberesetusingthemanual
reset button.
4. Check resistance across the thermal cut-out, if open then connection is bro-
kenandtheboosterheaterwillhavetobereplaced.
Contact your Mitsubishi Electric dealer.
5. Immersionheatercut-outhasbeentriggered. 5. Check immersion heater thermostat and press reset button located on im-
mersionheaterboss,ifsafe.Iftheheaterkeptrunningwithnowaterinside,
thismayhaveresultedinfailure,soreplaceitwithanewone.
6.
Immersion heater breaker (ECB2) tripped. 6. Check the cause and reset if safe.
7.
Flowrateofthesanitarycircuitmaybereduced. 7. Checkthefollowingitems
•Checkfortrappedairinwaterpump(sanitarycircuit).
•Checkifthespeedofwaterpump(sanitarycircuit)issetto2.
•Checkwaterpump(sanitarycircuit)formalfunction.(Referto"10-6.
CheckingComponentParts'Function".)
•Replaceplateheatexchanger(water-water)orscaletrap,iftherearea
blockagewhichblocksthesanitarycircuit.
10 Temperature of DHW
tankwaterdropped.
WhenDHWoperationisnotrunning,theDHW
tankemitsheatandthewatertemperaturede-
creasestoacertainlevel.IfwaterintheDHWtank
isreheatedfrequentlybecauseofasignicant
dropinwatertemperature,checkforthefollowing.
1. Waterleakageinthepipesthatconnectto
the DHW tank
1. Takethefollowingmeasures.
•RetightenthenutsholdingthepipesontotheDHWtank.
•Replacesealmaterials.
•Replacethepipes.
2. Insulationmaterialcominglooseoroff. 2. Fixinsulation.
3. 3-wayvalvefailure 3. Checkplumbing/wiringto3-wayvalve.
(i)
Manuallyoverride3-wayvalveusingthemainremotecontroller.(Referto
<Manualoperation>in"9-4.Servicemenu".)Ifthevalvedoesnotstillfunc-
tion,goto(ii)below.
(ii) Replace3-wayvalvemotor.Ifthevalvedoesnotstillfunction,goto(iii)
below.
(iii)Replace3-wayvalve.(Referto"11.DISASSEMBLYPROCEDURE".)
4. Waterpump(sanitarycircuit)speedsetting
failure
4. Water pump (sanitary circuit) MUST be set to speed 2
.
Whenitsettospeed1,hotwaterwouldbemixedwithcoldwaterdueto
circulation.
11 Hotorwarmwater
from cold tap.
Heatofhotwaterpipeistransferredtocoldwater
pipe.
Insulate/re-routepipework.
12 Waterleakage 1. Poorly sealed connectionsofwatercircuit
components
1. Tightenconnectionsasrequired.
2. Watercircuitcomponentsreachingtheendof
life
2. RefertoPARTSCATALOGforexpectedpartlifetimesandreplacethemas
necessary.
13 Heatingsystemdoes
not reach the set
temperature.
1. Prohibit, schedule timer or holiday mode se-
lected or demand control input (IN4) or smart
gridready(switch-offcommand).
1. Checksettingsandchangeasappropriate.
2. Checksettingsandchangeasappropriate. 2. Checkthebatterypowerandreplaceifat.
3. The temperature sensor is located in a room
that has a different temperature relative to
that of the rest of the house.
3. Relocate the temperature sensor to a more suitable room.
4. Heatpumpnotworking. 4. Check heat pump – consult outdoor unit service manual.
5. Booster heater cut-out tripped. 5. Check booster heater thermostat and press reset button if safe.
Resetbuttonislocatedonthesideofboosterheater,coveredwithwhiterub-
bercap.(See"4.PARTNAMESANDFUNCTIONS"forposition.)
6.
Booster heater breaker (ECB1) tripped. 6. Check the cause of the trip and reset if safe.
7. The booster heater thermal cut-out tripped
andcannotbereset using the manual reset
button.
7.
Check resistance across the thermal cut-out, if open then the connection is bro-
kenandtheboosterheaterwillhavetobereplaced.
Contact your Mitsubishi Electric dealer.
8. Incorrectlysizedheatemitter. 8. Check the heat emitter surface area is adequate
Increasesizeifnecessary.
9. 3-wayvalvefailure 9. Checkplumbing/wiringto3-wayvalve.
(i)
Manuallyoverride3-wayvalveusingthemainremotecontroller.(Referto
<Manualoperation>in"9-4.Servicemenu".)Ifthe3-wayvalvedoesnotfunc-
tion,goto(ii)below.
(ii)Replace3-wayvalve motor .Ifthe3-wayvalvecoilisreplacedbutthe
3-wayvalvedoesnotfunctiongoto(iii)below.
(iii)
Replace3-wayvalve.(Referto" 11.DISASSEMBLYPROCEDURE" .)
10. Batteryproblem(wirelesscontrolonly) 10. Checkthebatterypowerandreplaceifat.
11. Ifamixing tank isinstalled,theowratebe-
tweenthemixingtankandthecylinderunitis
lessthanthat  betweenthemixingtankand
the local system.
11. Increasetheowratebetweenthemixingtankandthecylinderunitdecrease
thatbetweenthemixingtankandthelocalsystem.
OCH570C