I have an older Carrier split system heat pump. It was hooked up to an analog White Rodgers thermostat and I upgraded it to a Trane Taystat 540 Thermostat. After everything was hooked up I tested the fan and the heat pump which all worked well. When I forced the Em. Heat the entire system went dead. I reinstalled the analog Thermostat to test and the fan won't run, no heat, no noise, nothing.

I didn't hear a pop nor smell any electric burning in the furnace closet. When I removed the panel holding the transformer, heat coils, etc. I noticed that one of the heat coils is severed. I tested the transformer and got 52v on the output (double what it should be?). Is it possible that the heat coil being severed when I turned on the Em. Heat caused the entire system to go dead? I ordered a new set of coils and transformer. I know the heat coils need to be replaced now, but am I barking up the wrong tree thinking this was caused by the transformer?

I would check that unit from stem to stern on the electric end. It is very difficult to tell from here exactly what caused the problem but if one of the heat elements went to ground that can and does cause problems. The transformer should only be 24 volts or there abouts unless someone put in a 110 volt transformer instead of a 220 volt transformer. If it was putting our 50+ volts other items in the circuit could be damaged also.

I will begin the stem to stern check on the unit tonight. If one of the elements went to ground can I anticipate damage to the outdoor unit? I can handle all the testing on the indoor unit but I am lost when it comes to compressors, etc.

Usually the damage will be to the inside unit only.

You have to be careful with anything that says Trane on it. For some reason they choose to be universally different from any other manufacturer and this can lead to compatibility issues. One of my clients has 2 Trane RTU's that use this funky DC variable resistance stat.

It appears that my installation of the Trane thermostat fried the transformer and my stupidity apparently fried the elements (I removed the top screws from the panel holding the elements allowing them to droop after I fried the transformer and it looks like one of the elements shorted onto a lip for another panel below when I turned the unit on for my initial testing of the transformer). Luckily it looks like everything else is okay. I don't know why the Trane thermostat (or my wiring) fried the transformer but I have ordered a Honeywell Thermostat, new transformer, and new elements and I am armed with my more thorough knowledge of the system wiring for this next go around.

Let us know how it all works out.

Okay, so all the parts are in. After a snafu with the wrong transformer being shipped I went to hook everything up. Connected power to new heater elements, transformer, and fan. Connected the transformer common to C terminal on my thermostat. Connected 24v output at R terminal on thermostat. After that I find two wires, orange and violet that are not connected. I assume they are the wires for the fan relay and heat sequencer. (The note on the wiring diagram said "Relay 1, 22 VDC Coil, Rectifier). I hook violet to W2 and Orange to G on the thermostat. I turn the unit on and fan comes on even with system set to off and fan at auto. When I try to turn on the them. Heat the lights come on to indicate them heat on the thermostat but the elements do not heat up. I am assuming this has something to do with how I hooked up Violet and Orange but I don't know how else to work this out. On my thermostat W2 and E are jumped.

I am using a White-Rodgers Type 1F58-910 Thermostat, A white-rodgers 90-T60C3 transformer, a new Carrier KFCEH 8KW heating element.

I have from heating element to fan: Yellow to 2, Black to C, Blue to 1.
From element to transformer input: Yellow to 240V(orange), Black to COM(black).
From Transformer to thermostat: Com(Blue) to C, 24V to R
From Heating element to thermostat: Violet to W2, Orange to G

Heating Element Literature:
http://www.xpedio.carrier.com/idc/gr...ag-fceh-10.pdf

Transformer:
Electrical > Transformers > Transformers > Transformer,24v Output : Grainger Industrial Supply

Thermostat:
Honeywell Focus 5000
TH5220D1003