"dean" wrote in message
oups.com...
Its a TRANE heat pump, not sure if that also means the fan is also
TRANE.

What makes the fan speed up or slow down when on fan-only mode?

I can not see the unit from here. Trane makes 30 or so models of vfd's.

The Trane VFD I had included 4 programs that were changed by dip switches on
the control board.
I suggest you read your manual for YOUR UNIT completely. Then ask some
questions.