ECKELMANN Case Controller UA 4 E Series - Superheat Control

Firmware V3.13
21.04.2021
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5.7.7 Superheat control
Superheat control works parallel with temperature control. As required, control is made to the defined
superheatsetpoint. Superheat control works in two modes that can be toggled by a parameter (offset).
Operatingmode“StandAlone”:Withactivatedlocalpressuretransmitter(seechapterOn-off control):
Calculating differences in the temperature measured at the local pressure transmitter (suction gas
temperature,basedonthemeasuredpressurewiththeassistanceofthesetcoolanttable)andthetemperature
measuredattheevaporatoroutput(R6.x).Ifthepressuretransmitterfails,theninthefirststepanattemptis
madetoswitchtotheoperatingmode“InterconnectedOperation”.Ifthisisnotpossible,forexamplebecause
“InterconnectedOperation”isnotconfiguredorbecausethepackcontrollerdoesnotprovideanysuction
pressure,thenanattemptismadetoswitchtostandaloneoperationwithtemperaturesensors.
Operatingmode“StandAlone”:WithevaporatorinletsensorOffset=--
Difference between temperature measured at evaporator inlet (R5.x) and evaporator outlet (R6.x). If it is
notpossibletocalculatethedifference,forexamplebecauseoneofthetworequisitetemperaturesensorsdoes
notsupplyavalue,thenthesystemisswitchedtoemergencyoperation.
Operatingmode“Compressorpack”:Offset>=0K
Difference between evaporating temperature measured on compressor pack (transmitted via CAN bus) and
atevaporatoroutlet(R6.x).Anadjustableoffsetcorrectsthetemperaturet0measuredbythepackcontroller
(suctionpressureactualvalue)byanypressurelossinthesuctionlineandtheassociatedvariationsbetween
evaporatingtemperatureonthesuctionpressuresideandevaporatorside.Correcttransmissionofsuction
pressureviatheCANbusrequiresthePackNo.(menu6-1)tobesetonthecasecontroller.WhenusingaVS
3010 BS pack controller, the compressor pack parameter must also be set. If transmission of evaporating
pressurebythepackcontrollerisinterrupted,superheatisderivedfromthetemperaturedifferencebetween
R5.xandR6.x.Asasupplementaryprotectivefunctiontheexpansionvalveisfullyclosedifsuperheat
temperaturedropsbelowacriticalminimumlevel.
Reset of the I-sum
TheI-sumisresetinthecaseofthefollowingevents:Duringthedefrost,manualshutdown,setpointswitching,
emergencyoperationandforcedcooling.WhentheResetI-Sumparameter(Menu6-2-7)issettoON,the
procedure is as follows:
If the valve opening is set to 0% due to superheat dropping below the low level, the I-sum integrated over
time(NOTtheI-term)isadditionallysettozeroonthePIDcontroller.Thisisapplicabletobothsuperheat
controlandtemperaturecontrol.Distinctionalsomadebycontrolzone.
This is intended to allow the controller to re-learn an I-sum that may have become too large, thus enabling it
toadjusttochangedambientconditions.WhentheResetI-Sumparameter(Menu6-2-7)issettoOFF,the
integratedI-sumisnotchangedondropofsuperheatbelowthelowlevel.
Analysis of the pack controller superheat
IfthecasecontrollerisoperatedwithaVS3010packcontroller(version≥V3.00),thenthesuperheatstatus
isalsoanalysed.
If the superheat of the pack controller is in a non-critical range (dependent on the parameterisation of the
packcontroller),thenthecasecontrollercontinuescontrollingevenwhenthereisashortfallrelativetothe
minimumvalueofitsownsuperheat.Thecasecontrolleronlyclosesthesolenoidvalvewhenthepack
controllersuperheatisalsotoolow.