reply to ropeguru
Re: Thermostat Install Help Cap W2 and put W1 under the "E/Aux" terminal. The Trane manual shows it connected to an outdoor temperature switch which jumps W1 to W2 should the outside temperature drop too low.
On the old 'stat, when "Emergency" mode is selected, the compressor does not run at all, and a single heat strip is uses unless the outside temperature is too low (in which case both are used). When "Aux" is triggered ("normal" heating mode but the inside temp drops too far below the setpoint) the compressor and one set of heat strips run. Should the outside temperature be too low or the system is in defrost mode, "Aux" also turns on both sets of heat strips.
Capping W2 and using W1 under E/Aux uses 1 heat strip when "Aux" is triggered normally, and both strips when "Aux" is triggered and either the outside temperature is too low or the system is in defrost mode.
ON my system, and I forgot to mention it, there is no outdoor thermostat that I know of. Inside the air handler there is w1, w2, and w3 in which w2 and w3 are tied together.
I saw the section you are referring to about ODT-A and ODT-B which as far as I know I don't have either one. THey refer to an external unit for the ODT and I do not have that. I will do some more research on that and see what I can come up with.
The ODT is most likely built into the outside unit. If you follow the wires and both W1 and W2 go to the defrost board, then it's somewhere in there.
Thanks... I am guessing that the ODT-A is internal to the outside unit and that ODT-B would be the external unit in a waterproof enclosure they were talking about.