Danfoss AK-CC 550 - Advanced Defrost Features

AK-CC550 Manual RS8EN502 © Danfoss 02-2010 7
Coordinated defrost
There are two ways in which coordinated defrost can be arranged.
Eitherwithwireconnectionsbetweenthecontrollersorviadata
communication
Wireconnections
ThedigitalinputDI2isconnectedbetweenthecurrentcontrollers.
Whenonecontrollerstartsadefrostalltheothercontrollerswill
followsuitandlikewisestartadefrost.Afterthedefrosttheindi-
vidualcontrollerswillmoveintowaitingposition.Whenallarein
waitingpositiontherewillbeachange-overtorefrigeration.
Coordinationviadatacommunication
Herethesystemunithandlesthecoordination.
The controllers are gathered in defrosting groups and the system
unit ensures that defrosting is started in the group according to a
weeklyschedule.
Whenacontrollerhascompleteddefrosting,itsendsamessage
tothesystemunitandthengoesintoawaitingposition.When
everycontrollerinthegroupisinawaitingposition,refrigeration
isagainpermittedinalltheindividualcontrollers.
System manager
Defrost on demand
1Basedonrefrigerationtime
Whentheaggregaterefrigerationtimehaspassedaxedtime,
a defrost will be started.
2Adaptivedefrostingbasedonmonitoringofevaporatorper-
formance
This function is based on a registration of the air flow through
theevaporator.ByusingtheAKVvalveasmassowmeterforthe
refrigerant flow it is possible to compare the energy input on the
refrigerant side with the energy output on the air side. Via this
comparisontheairowthroughtheevaporatorcanbedeter-
minedandhencealsotheamountofice/frostbuild-uponthe
evaporatorsurface.Iftheice/frostbuild-upreducesthecapac-
ityoftheevaporatorthefunctionwillcarryoutanadditional
defrost.
Enterintheweeklydefrostschedulethenumberofdefrosts
correspondingtothebasicload.Iftheloadoftheevaporatoris
increased beyond this, defrost on demand will add the required
additional defrosts.
The function requires the following connections:
-ExpansionvalvetypeAKV
-TemperaturesignalfrombothS3andS4
-TemperaturesignalfromthecondensingpressurePcwhichisto
bedistributedviathenetworkfromthesystemmanager.
NOTE.TheS3andS4sensorsmustbeplacedintheairow/chan-
nelimmediatelybefore/aftertheevaporator.
Min. time between defrosts
There is a 2 hours minimum time between defrosts.
Thisavoidsthatplanneddefrostsinaccordancewiththeweekly
schedule are carried out immediately after a defrost on demand
has been carried out. The time applies from when a defrost on
demand has been completed to when a planned defrost is again
permitted. The defrost on demand will not start defrosting with a
shorterintervalthanthe2hourseither.
Reset
Iftheadaptivedefrostfunctionregistersproblemswiththe
defrost, it will show an error message and the function will no
longercarryoutextradefrosts.Inthiseventamanualresetofthe
functionviad22shouldbecarriedout.
Whentheresetfunctionisactivateditwillstartadefrostsothat
thesubsequenttuningwilltakeplaceonanevaporatorwithno
ice/frostbuild-up.
Note
Thefunction"Adaptivedefrost”shouldonlybeactivatedwhenthe
evaporatorrunsundernormaloperationalconditions.
Melting function
Thisfunctionwillstoptheairowintheevaporatorfrombeingre-
duced by frost created by uninterrupted operation for a long time.
Thefunctionisactivatedifthethermostattemperaturehas
remained in the range between -5°C and +10°C for a longer
periodthanthesetmeltinginterval.Therefrigerationwillthenbe
stopped during the set melting period. The frost will be melted
sothattheairowandhencetheevaporator’scapacitywillbe
greatlyimproved.
Real-time clock
Thecontrollerhasabuilt-inreal-timeclockwhichcanbeusedto
startdefrosts.Thisclockhasapowerreserveoffourhours.
Ifthecontrollerisequippedwithdatacommunication,theclock
will automatically be updated from the system unit.
Max. 10