outlet on when thermostat on

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Hi,
Looking for a cheap but reliable solution.
I want a fan to turn on when my thermostat is on. Is there a gizmo that would do that for me. My fan is line voltage.
Many thanks in advance,
Sam
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Sam Takoy wrote:

Yes, there are several different ways you could get that to work, but I don't have enough information to suggest any in particular.
The best solution will be found by consulting with your electrician.
Jon
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On 11/29/2010 3:43 PM, Jon Danniken wrote:

Hi Jon,
Thanks a lot.
Please suggest one if you can. For example, something that would turn on an outlet when the thermostat turns on.
Thanks again
Sam
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Sam Takoy wrote:

Sam, to my knowledge there is no product sold for this purpose. To accomplish what you are trying to do would entail knowing information about what kind of heating you have (which I don't have), in addition to knowing how it is wired, and then modifying your existing electrical wiring in a manner which is safe and follows code.
This would be a custom job, which unless you are knowledgeable about electricity, would entail consulting with an electrician.
Jon
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Jon Danniken wrote:

Actually, there are such products sold. There are HVAC relay modules available to control AC loads from the usual 24V thermostat signals. There are also some current sensing products sold that can switch on an outlet when a particular AC load is on (like a furnace), though they are most commonly use to turn on dust collectors when starionary woodworking tools are turned on.
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What you want is a relay, where the 12 volt line from your thermostat closes a switch to allow 120 v house current to flow. I would guess that such things are available at your local electrical supply store, although I've never used one myself.
Paul
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How do you know that he has a 12 volt line from his thermostat?
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wrote:

How do you know that he has a 12 volt line from his thermostat?
He wouldn't, It would likely be 24 volt, unless it's electric heat
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A "line thermostat" would handle switching the receptacle all by itself.
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On Mon, 29 Nov 2010 13:18:33 -0800 (PST), DerbyDad03

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On Nov 29, 10:25pm, snipped-for-privacy@snyder.on.ca wrote:

I know that...I was asking Paul how he knew to recommend a relay "for the 12 volt line from the OP's thermostat".
Since the OP never supplied that information, the best any of us can offer is what I offered earlier:
"The input, or coil voltage, should match the voltage on the thermostat wires."
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The "gizmo" is typically called a "relay".
The input, or coil voltage, should match the voltage on the thermostat wires. When power is applied, the coil would close a set of contacts that are rated for your line voltage.
Something like this is typically used as a fan control:
http://www.emersonclimate.com/Documents/White-Rodgers/catalog_06_pages/Cat_06_pg0114.pdf
However, using something like that to control an outlet might not be code-compliant.
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P.S. I am *not* suggesting that you run out and buy the device I supplied the link to.
I am simply responding to: "I want a fan to turn on when my thermostat is on. Is there a gizmo that would do that for me?"
I have replaced such relays on my furnace to control the furnace blower, but I certainly wouldn't wire an outlet off of one of those. I can't imagine that such an installation would be code-complant.
To accomplish your goal, I totally agree with everything Jon has said: Call a professional.
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On Mon, 29 Nov 2010 13:01:26 -0800 (PST), DerbyDad03

It would not likely be up to code to install it in a wall box, but if it's in an electrical box (or any other metal box) that plugs into an outlet and allows the fan to be plugged into this metal box, it should be fine.
Just get a metal box, a cord wit hplug on the end, and install a thermostat transformer, relay whose input matches this transformer, and put an AC outlet in the same box to plug fan into. Then run a thermostat wire to this box. Just use a separate thernostat, not the one for your furnace.
I could design this in minutes, the wiring is pretty simple.
Google up a wiring diagram for a thermostat, then add a relay where the furnace would normally connect. The output of the relay supplies the positive voltage to the fan, the neutral is common.
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Depending upon the type of heating system you have, this may not be a big deal. For example, in a typical hydronic heating system the low voltage thermostat, via a switching relay, turns on a 120 volt pump. If you have such a system, you can just parallel a line from the pump to your outlet. Of course it also depends upon what this outlet will be powering as there are limits determined by the capacity of the controls involved.
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That was my thought "red-neck" it and wire into the 120 line that runs the furnace when teh relay kicks on. Seriously doubt it would be code compliant.
Harry K
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That was my thought "red-neck" it and wire into the 120 line that runs the furnace when teh relay kicks on. Seriously doubt it would be code compliant.
Harry K
No need to "red neck" it. There is no reason that the relay that powers the pump on a hydronic system, couldn't feed an outlet, or install another switching relay that is indirectly controlled by the same thermostat
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Sam Takoy wrote:

If the thermostat is the cause, consider monitoring the effect. For example. I wanted to monitor the on-time of my furnace. Instead of wiring into the furnace (cause), I put a wind vane on a microswitch at one of the output registers (effect) and used that. NO wires, no safety issues, no code issues, no furnace warranty issues and best of all, no denizens at alt.home.repair giving me grief about it.
Another option is a parallel process. Use a second thermostat to control your fan.
A LOT depends on what you're trying to accomplish.
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re: "If the thermostat is the cause, consider monitoring the effect.
The cause of what? Monitoring the effect of what?
Wild guess here:
The OP wants to plug a fan into an outlet to help circulate/move the air that the furnace puts out.
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DerbyDad03 wrote:

We don't know 'cause the objective was not stated. In my case, the thermostat was the cause, air movement out of the register was the effect. For my purposes, either would have worked. Sensing the air flow was WAY simpler and safer.
Called logical inference. If you see brake lights ahead, you can be pretty sure that the driver is pressing on the brake...at least sure enough that you'd take action to avoid running into her.

You're welcome to guess, but that doesn't shed much light on the actual problem being solved.
In my case, the furnace runs so infrequently that a fan to prevent stratification has significant effect on "comfort".

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