DB7110U UNIVERSAL HEAT PUMP DEFROST CONTROLLER
34-00032EF—03
10
System does not
defrost completely
Observe defrost cycle Defrost starts too late. Too
much ice is built up before
starting a defrost cycle.
• Verify sensor placement and readings
are correct.
• Increase the “Enable Temperature” to
trigger a defrost sooner.
• Lower the “Defrost Cycle Time” to
trigger a defrost sooner. Note this
parameter has no effect if an outdoor
air sensor is installed as the decision
would be made based on the
temperature difference between coil
and air.
Defrost cycle ends too
soon. Not all the ice is
removed.
• Verify sensor placement and readings
are correct.
• Increase the “Termination
Temperature” to allow the coil to get
hotter before a defrost cycle is
terminated.
• Increase the “Maximum Defrost Time”
to allow a defrost cycle to run longer.
System defrosts
too much
Observe defrost cycle Defrost triggers too
frequently, even with little or
no ice buildup.
• Verify sensor placement and readings
are correct.
• Decrease the “Enable Temperature” to
force the coil to get colder before a
defrost is triggered. Increasing this
parameter too much can result in not
triggering a defrost at all. Verify coil
readings with respect to this parameter.
• Increase the “Defrost Cycle Time” to
delay triggering a defrost. Note this
parameter has no effect if an outdoor
air sensor is installed.
Defrost cycle lasts too long.
Ice is melted long before the
cycle ends.
• Verify sensor placement and readings
are correct.
• Decrease the “Termination
Temperature” to allow the defrost cycle
to end with a cooler coil temperature.
• Decrease the “Maximum Defrost Time”
to force the defrost cycle to end sooner.
No
Auxiliary/Emergen
cy Heat
Check configuration
parameters
Active W request with no
Aux heat output
• Verify warm weather aux heat lockout
isn’t active. Adjust “Aux Heat Lockout
Temperature” if necessary.
• Check wiring
• Replace control
No Aux heat output during
defrost cycle
• Check wiring
• Replace control
Table 5. Troubleshooting. (Continued)
Condition
Procedure
Control Status
Corrective Action
