Air Handler aux fan

Keniki

I have a Goodman Air Handler in my attic. I would like to add an additional small circulating fan through a wall so that it comes on when the air handler comes on. This is to facilitate circulation when a bedroom door is close.
The blower has 3 #12 wires going to a printed circuit board that all appear to have voltage to them. Another wire(16 ga) goes from the capacitor to power also.
How do I hook up the aux blower. This is a small fan motor about 1/64 hp.

Keniki

OK so no body seems to know how to hook up this fan. Suppose I put a 24 volt relay in the thermostat circuit and have that cut on the 120v to the aux fan. Can I do that?

chris75

I personally would use a relay...

Keniki

Thanks for the input. Can I get away with one relay or do I need one in the cooling circuit and one in the heating circuit?
Keniki

chris75

Check your tstat, sometimes, G terminal is energized during a call for heat and cool.

thumbkins

Do you have an air handler with a heating and cooling coil or a horizontal furnace with a slant coil?

Check your thermostat for the terminals R-W-G-Y and sometimes C.

The thing to do would be to put a 24 volt relay powered by the W and common terminal for the heat mode and a relay powered by the G and common mode for the cooling and manual fan operation.Of course the relay would operate the 110 V. for your aux. fan.

Thermostat designations are
R- 24 V. power
W- heat
G- manual fan control/cooling fan operation
Y- compressor for cooling
C- 24V. common

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biggles

1/64th on the HP you might want to consider running the 120V hot leg thru a duct mounted air pressure switch.with this you make the supply air proofing the switch,and the fan runs heating or cooling.the switch can be mounted on the unit supply duct just up from the add on fan location,and makes it easier to break the fan power.

thumbkins

That would be easier than adding relays. Air pressure switch or a sail switch would work. Also there might be a terminal on the board for an electronic air cleaner or eac. That would energize whenever the unit calls the fan to run.

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micromind

The fan motor is 3 speed, each #12 is a different speed. One of them is actually hot, with current flowing through it. The other two appear to be hot because they're back-fed through the motor.

If you can be sure that the fan only operates on one speed, you'll have 120 from that speed to neutral. Be careful though, some units operate the fan on different speeds for heating and cooling.

As stated above, alot of these control boards have terminations for an electronic air filter, some of them hot up one of the terminals, sometimes it's a relay contact that you run power to, and the load out of.

Rob

Keniki

OK, I have found the wire from the G terminal on the tstat that has 24v when the fan is running in manual/heat/cool. I have also located a 24-110 v relay that takes 530mw to energize the contacts. Will the tstat provide enough power to work that relay?
The switch in the duct sounds like a good idea, but where do I find one. What is it called? I have checked air/duct/sail switches in the MCS catalog and washed out.
I cannot figure out why, if all the #12 wires have voltage to them, that the main blower is not running all the time.
I appreciate all the help with this project.

micromind

The G terminal on the t-stat wiring will easily operate the relay coil. Since the control voltage is 24AC, polarity on the relay coil doesn't matter.

Rob

thumbkins

sounds like you have a single speed fan if you get 24V at the G terminal in heat and cool.Usually the heat runs on low speed and cooling runs on higher speed cause cool air is heavier and harder to move. If you have a control supply house or a heating and cooling supply house they should have a sail switch. Might even try Grainger.

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Keniki

I hooked up the relay with a fuse yesterday and it worked fine.
Thank y'all so much for all the help. I really apperciate it.
Keniki