well, let me start by saying that overall, you really do not want a
power ventilator. We had one at our cottage in ontario on lake huron
(really hot attic). We had friends who also had one, and it "froze"
(Motor burnt up). After hearing their story (house caught fire) we
installed a manual motor control with a heater coil, so if the motor
took excessive power, it would just trip the switch. We came home to
the cottage one day, and my 14 year old noticed the switch was "off".
He went into the attic and discovered the motor totally frozen, and
there was no real cause for the freeze up. The motor was new, and the
unit itself was only a year old. Anyway, they are a real pain in the
a** and I would not reccomend buying one.