Hello HVAC Pros,
I have been in a 3000 ft2 cape cod in western NY built in 1988 for the last 4 years. 2x6 exterior framing and thermopane casement windows. No natural gas available here, we are on a municipal electric system that buys hydro power from Niagara Falls. Elect rates are $.035 for first 1000 KWH and $ .0525 there after. The house is all electric, with 4 people here, and a large 400 gal hot tub. My usage was 5142 KWH in Jan with 1068 heating degree days. Last year was 6168 KWH in Jan with 1333 degree days. I try to keep the place at a constant 68 degrees.
The (I believe) original Trane XE 900 HP system seems to work OK until the defrost cycle when the unit blows cold air. The aux heating coils (in a Trane air handler) are not energizing during the defrost cycles. I can hear the relays click on and generate the resistance heat when I raise the thermostat's set point 3 degrees (as the jumpers are set to do) above the current indoor temp.
The outdoor coils never seem to ice up so far this heating season.
The defrost control was replaced 10 years ago, based on a service sticker on the air handler. Last week I shut down the system including the service disconnect, and looked at the defrost control board. It is an American Standard unit CNT 1924 with only 1 jumper for diagnostics. The board is smaller than the original since I see two mounting holes in the sheet metal that are not used for this replacement board.
Is the board the most likely reason for no aux heat during defrost? Should other hardware be looked at also?
When a service person comes in next week, if this board is replaced should I make sure a different defrost control is used that has more configurability in defrost settings?
When finances allow in the fall/winter 2012-13 should I look into replacing this unit? Will I gain enough in energy efficiency to have a decent payback period? We will probably be here another 5-6 years minimum.
Sorry for being so wordy, I wanted to minimize requests for more info.
Thanks in advance,