Alarm Communication - Danfoss Heat Pump Troubleshooting Manual

Troubleshooting Guide

Alarm communication

Action:
Check if the communication between the display card and relay card is broken.
Test with another TP cable or communication cable between display and control card
If the alarm remains test with another I/O card using the old cable.
Newer heat pumps with 901 921 display card (Control card) have all thinking/functions in the display.
So if the communication between the display card and the relay card drops the heat pump will stop, while older heat pumps produced
before Autumn 2008 will run as usual with the most recent setting.
Alarm com Air, DHP-A
Action:
Check if the cable between the relay card and the defrost card is properly located and is the 4-core type (this is important if the heat
pump is equipped with the online accessory)
Measure incoming voltage to the defrost card (230V)
Check that air is selected as heat source
If there is voltage to the defrost card but the card still does not function, replace the card.
The card illustrated is an I/O card 901-920
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Alarm communication
VMIFB202