ECKELMANN Case Controller UA 4 E Series - Discharge Gas Defrosting (Hot Gas Defrosting)

Firmware V3.13
21.04.2021
73/466
•
•
•
•
5.8.3 Discharge gas defrosting (hot gas defrosting)
Discharge gas defrosting involves feeding discharge gas into the evaporator and can be performed with
eitherhotorcoldgas.Thedischargegasissuppliedfromapointupstreamofthecondenser(hotgas
defrosting)orfromthereceiverdownstreamofthecondenser(coldgasdefrosting).
Notes on discharge gas defrosting (controller type UA 131 E, UR 141 TE)
These notes apply to two-pipe discharge gas defrosting. The defrost relays are used to control special
solenoidvalvesspecificfordischargegasdefrosting.Indischargegasdefrostingallowanceismadeforthe
specificpropertiesofthedischargegas:
Demand defrost counter ignored on initiation of defrosting
No internal initiation of defrosting
No interruption of defrosting in occurrence of temperature alarm
Discharge gas defrosting requires the system to include a pack controller. Case/coldroom controllers
involvedindischargegasdefrostingmustbeassignedtoapackcontrollerthroughthePackNo.parameter.
WithVS3010BSpackcontrollers,theRefrigerationPackparametermustalsobesetonthecase/coldroom
controller.
Activating discharge gas defrosting with UA 131 E:
InordertoactivatethedischargegasfunctionoftheUA131E,theparameterHGoperation(DischargeGas
Mode, menu 6-3) must be set ON on the controller.
Activating discharge gas defrosting with UR 141 TE:
Discharge gas defrosting can be performed at any time with the UR 141 TE and does not need any further
parameterstobeset.
Termination of discharge gas defrosting with UA 131 E:
Defrosting is terminated by the defrost termination temperature sensors and can be carried out immediately. In
contrast to the UA 131 DD (see UA 300/UA 400), there is no time delay before the start of defrosting.
Termination of discharge gas defrosting with UR 141 TE:
Defrosting is terminated by the defrost termination temperature sensors without delay. If an internal defrost
timerissetoncontrollertypessuitablefordischargegasdefrosting,itwillbechangedautomaticallytoexternal
defrostingbythepackcontrollerthefirsttimedischargegasdefrostingisinitiated.Thispreventsthecase
controllerfromautomaticallyinitiatingdefrosting.
ATTENTION
Compressor damage! Danger due to liquid refrigerant on the suction side of the compressor!
Discharge gas defrosting as described herein is D2D two-pipe discharge defrosting, which can be
performed only with hot gas.

ATTENTION
Compressor damage! Danger due to liquid refrigerant on the suction side of the compressor! At
first start with the UA 131 E, defrosting is initiated directly after starting. If the system is not interlocked
by appropriate pack controller control leads for initiation of discharge gas defrosting, it is then possible
for liquid refrigerant to enter the suction line for example. Therefore, in applications with discharge gas
defrosting, always make sure that manual defrosting is disabled when the controller starts and the
defrost timer is set to external defrosting. Alternatively or additionally, operation of the positioners
specific to discharge gas can be interlocked by the pack controller by means of suitable control leads.

Discharge gas defrosting cannot be used together with the master-slave function. With discharge gas
defrosting the operation must be terminated when the CAN bus defrost command ends, whereas with
master-slave defrosting the operation always continues until the safe defrost time expires. Alarm will be
generated by the controller if such a combination is set.
