- Q.
My client’s metal fireplace is supplied by a makeup
air system with a built-in circulation fan. This fan —
which plugs into an accessible outlet — is triggered by a
heat sensor in the fireplace. While effective, it’s also
very loud. To reduce the noise, I’d like to replace the
fan’s on/off switch with a variable-speed control. Is
that possible? The manufacturer doesn’t seem to offer
anything.
A.Rex Cauldwell, a master electrician in
Rocky Mount, Va., responds: Noisy single-speed fireplace
fans are common. To reduce the fan’s speed — which
can help solve the problem — I use a Dial-A-Temp control
(866/667-8454, northlineexpress .com). This device (see photo,
below) plugs into a 120-volt receptacle; the fireplace fan, in
turn, plugs into it. Rated for motor loads up to 3 amps and 300
watts, it has both an on/off switch and a variable-speed
switch. It costs about $20.
Remember that you can’t use a light dimmer on a fan
motor. Dimmers are designed for resistive devices — like
the filament of a light bulb — and operate by lowering
the voltage to the lamp. A fan motor is a capacitive and
inductive device that needs a relatively constant voltage to
keep it from overheating and burning out. A motor speed
controller like the Dial-A-Temp contains electronics designed
to create variable resistance while maintaining the constant
voltage required by the fan motor.