Mos likely your heat pump has the cooling on by default (mfgr can't
seem to come to consensus on this). If it lacks an orange wire hookup,
the change over valve isn't in play and it will still do whatever
function is the non energized one. On my Trane PTAC that is heat, and
it works fine in the winter with a non heat pump thermostat, but it
won't cool without the orange wire energized. Clear as mud?


Peachy wrote:
I recently replace the Honeywell thermostat for my Coleman heat pump,
with a Hunter digital and after I got it installed I notice that the
package said in very small type that it was not suitable for heat
pumps. It seems to work, so I'm wondering what the difference is. Do i
need to get a different one?