Heat Pumps and Electric Heating - Defrost Mode

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mjb
02-06-07, 10:04 AM
Why would the 2nd stage heat not activate when in the defrost mode? I know that 2nd stage comes on if the thermostat set point is raised +3 degrees. In fact I do not recall seeing 2nd stage heat activate when heat pump is running in 30 degrees or below temps. In addition, heat strips do work in emergency mode.

Robert Shaw 9420 Thermostat
1st Stage is set at 1 degree differential.
2nd Stage is set at 2 degree differential.

mjb
02-11-07, 03:29 PM
If anyone is interested, it turned out to be a faulty thermostat that was warrantied through Robert Shaw.
Ed Imeduc
02-11-07, 09:04 PM
When the unit goes into defrost its from the defrost board outside . This should cause the elements on the unit to turn on so as not to blow cold AC air into the home. Have you checked and see if just the 1st stage does come on in defrost??????