This weekend I replaced my Trane Weathertron BAYSTAT240A thermostat
with a Honeywell RTH7400D. I used the same thermostat on my
conventional heat system and wanted to use it with the heatpump.
heat pump had a tan wire connected to the “T” terminal.
The instructions for the RTH7400D don’t mention anything about
a “T” terminal. But that’s what
google is for 🙂 Gosh I love the internet. Here are some helpful links for folks if you have similar problems: Trane wire
RTH400 wiring 1
RTH400 wiring 2
RTH400 wiring 3