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-   -   Wiring ventilation fan in garage/workshop: Can I use a 3-way switch like this? (http://www.diychatroom.com/f18/wiring-ventilation-fan-garage-workshop-can-i-use-3-way-switch-like-27335/)

thegonagle 09-25-2008 07:03 AM

Wiring ventilation fan in garage/workshop: Can I use a 3-way switch like this?
 
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Hi all. I've been reading here for awhile, and learning a lot, but today, I have my first question.

I'm replacing an old, decrepit, dangerously wired gable-mounted exhaust fan that a previous homeowner installed (badly) in my garage.

The new fan I bought, which was designed for attic ventilation, came with a simple 120V electromechanical thermostat. I would like to use this thermostat for automatic operation, but since it would be mounted near the fan, way up out of the way, it will be inconvenient to adjust. Therefore, I'd also like to install a "manual override" switch for when I'm in there working on stuff.

As illustrated below, I've devised a way to use a three-way switch to accomplish this. While I'm confident it will work fine, I'm just wondering if this is an allowable use for a single 3-way switch.

(As you can see, I've also added a main switch, a pilot light for safety, and a speed control.)

Does anybody see any problems? (If so how would you take care of this?)

Thanks!

joed 09-25-2008 08:10 AM

You don't need a three way switch. You could use a regular switch wired across the thermostat(in parallel). That way either the stat or the switch can turn on the fan. Take the black wire you have on the traveller screw and connect it with the black power wire you have on the common screw.

If you want the 3way it will work as you have drawn it.

thegonagle 09-25-2008 03:12 PM

Thanks.

I figured I could use a single-pole, but I didn't want the on-off markings. The lack of on-off markings is the reason I chose the three-way. I'll label the switch with a label maker as well, but I mostly want a non-confusing setup for whomever might try to use the fan in the future. (Friends, neighbors, future homeowners--you never know.)

Winchester 09-25-2008 09:04 PM

Forgive me, but I've never seen a pilot light used in this way before. But according to your schematic, it would appear as though it is wired in parallel. Shouldn't it be wired in series if it's acting like a switch?

theatretch85 09-25-2008 09:16 PM

Quote:

Originally Posted by Winchester (Post 161302)
Forgive me, but I've never seen a pilot light used in this way before. But according to your schematic, it would appear as though it is wired in parallel. Shouldn't it be wired in series if it's acting like a switch?

The "pilot light" in his diagram would light up when the fan has power, whether its set to be "always on" or controlled by the thermostat. Most "pilot lights" light up when the circuit is off to illuminate the switch to be easily found in the dark.

thegonagle 09-25-2008 09:50 PM

Please forgive the poor terminology.

Yes, I intend for the light to light up when the circuit has power, as a warning that the fan could turn on automatically, and so that I won't forget to turn it off.

I guess a better term would be power light, or indicator light.

Well, I'm off to do the final wiring.

joed 09-25-2008 10:18 PM

Pilot light is the proper term for this. The others a lighted switches not pilot lights. You can actually by switches that have pilot lights.


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