my attic fan switch just gave out and we are attempting to wire a new
one in. The fan has hi/low/off but there are 2 red wires, 1 blue wire
and 1 black wire coming out of the new switch. The way it is wired
now, it will go on low and high but not turn off. He is unsure about
what to do with the blue wire? how should this be wired?
For Master Flow fans...
1) black is hot
2) red goes to the low speed wire on the motor
3) blue goes to the high speed wire on the motor
the switch is just a simple SPDT switch with an additional "off"
throw, but mechanically the switch always forces you to "pass through"
"High" before getting to "Low". This is so that the fan motor always
has enough starting current to get it going at high even though the
user eventually wants it on low. So getting the wires correct is
important for the life of your motor, you dont want it always starting
in low. Dont go by colors though, test your switch with a
multimeter. Make sure that the first wire to get energized when
leaving "off" gets hooked to the "high" speed wire on the motor.
so how your switch works...
1) in "Low" the hot supplies current to the red wire
2) in "High" the hot supplies current to the blue wire
3) in "Off" the hot is disconnected
Didn't the replacement switch come with a wiring diagram? Did you
check online to see if you can find one? Without one, it would only
be a guess as to what goes where. First thing I'd try to do is
identify the incoming side of the switch. It's probably the black
wire. The fan should have 3 wires going to it, one for high, one
for low, one neutral. The neutral normally doesn't go through the
switch and is wired directly to the incoming white neutral. That
means two wires from the switch should go to the fan. With a simple
test meter you should be able to figure out which of the output leads
is high and which is low speed.
As an aside, is this an attic fan or actually a whole house fan? All
the attic fans I've seen were one speed and had a simple thermostat
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