2 transformers

[countryboyinar]

The reason is that the transformer in the furnace is a low va rated one. It does not have enough capacity to power the a/c controls, only the furnace. The second transformer in the a/c unit only powers the cooling side (compressor contactor and indoor blower relay)unless someone rewires the system to use only one transformer.

[Milk man]

Originally posted by countryboyinar
The reason is that the transformer in the furnace is a low va rated one. It does not have enough capacity to power the a/c controls, only the furnace. The second transformer in the a/c unit only powers the cooling side (compressor contactor and indoor blower relay)unless someone rewires the system to use only one transformer.

I've seen several in old add on AC. Remember when every house wasn't built with an AC.

Trailers can be a real *****. especially the ones with AC and a two wire thermostat.

[chadman]

Originally posted by countryboyinar
The reason is that the transformer in the furnace is a low va rated one. It does not have enough capacity to power the a/c controls, only the furnace. The second transformer in the a/c unit only powers the cooling side (compressor contactor and indoor blower relay)unless someone rewires the system to use only one transformer.

This is the correct answer, Learned the hard way once, I have rewired the indoor unit with a bigger transformer many times, I think it is cheaper then buying the kit. Not sure but I think that is the reason I have done it. If I remember right I first figured this out because I did not read the instructions and only pulled a 2 wire to the condensor,and did not want to pull a new wire. Prior proper planning prevents piss poor proformance. If they rewired the condensor the same way they took it out there should not have been any problem. Wire should have been adaquit and nothing should have had to be changed inside the furnace. Probably have it wired now so its only using the indoor transformer.If this is the case you will find out sooner or latter when the indoor transfomer fails and he can sort out this mess.