My sister has the following: a TRANE XL 80, model #TUD080R936A1, an
upflow, gas-fire, 2-stage fan assisted combust. There are 5 wires.
The thermostat is also a TRANE - no model number that I could find but
it's the old kind (not digital, notprogramable, etc). She wants to
install a 7 day programmable thermostat--can it be done and what model
is a good one. Thanks.