Are too many registers closed?
not close off more than 20 % of the registers because this can
high resistance and unnecessary heat build up in the furnace.
to close some registers to save on energy costs if rooms are
unused...but do not exceed 20%. So if you have 10 rooms, you
be closing a maximum of 2 registers.
The furnace will get to hot and shut down on a limit over load. You
will have to turn off the power
to set the furnace.