# wiring for fan only on electric furnace



## diyorpay (Sep 21, 2010)

If one of the wires is clearly marked 'G', that's the one that goes to the thermostat 'G' terminal.


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## thewhitemacho (Sep 25, 2010)

There are only two terminals on the furnace end. And they are already hooked up by the two wires needed to run normal furnace function. So where do i hook up the green on the furnace end?


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## diyorpay (Sep 21, 2010)

In my furnace the low voltage terminal board receiving wiring from thermostat is riveted to side of wiring box (not control board). Assume W and Y are your 2 terminals for heat. Typically other terminals are C (not used on mine) and G for fan. Total of 4. When the fan switch is thrown on thermostat only the fan goes on if the G wire is connected. Probably overrides all safety checks for ignition etc because it's just a fan. With no G terminal you won't be able to run fan only.


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## kenmac (Feb 26, 2009)

If it's an old motor .It may only be single speed. G brings in high speed which he may not have


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## newtech (Mar 21, 2009)

kenmac said:


> If it's an old motor .It may only be single speed. G brings in high speed which he may not have


 The G terminal energizes a fan relay. It doesn't have to be a multispeed motor.


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## newtech (Mar 21, 2009)

thewhitemacho said:


> I have an old wesco furnace model bru 1500 in my mobile home. It is already wired with 5 wire to the thermostat, but I only use two because it is a heat only system. Now I want to wire up the option on my thermostat to run fan only...Anyone know how to do that? thanks:thumbsup:


 Can you post a pic of where your t-stat wires are connected in the furnace?? Do you have a circuit board?


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## kenmac (Feb 26, 2009)

newtech said:


> The G terminal energizes a fan relay. It doesn't have to be a multispeed motor.


 

Yes, I know that. I should worded it a little different. His unit may not be set up to use fan only if he is heat only & is an older type furnace. He may just have a time delay relay, etc, that brings fan on since he says it's older & is heat only. I'm not saying it cant be wired to work.


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## thewhitemacho (Sep 25, 2010)

here is a picture of where the wires connect to the furnace.


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## yuri (Nov 29, 2008)

It is a basic electric furnace that has no fan relay and G and is not prewired for AC. The sequencers for the heat strips turn on the fan. No way to run the fan unless a fan relay is installed and a bunch of wiring altered by a Pro who does electric furnaces.

That furnace may not be very safe to use as one of the elements can short out soon due to age and drop to the next one and start a wiring overload and fire. I have seen plenty of roasted electric furnaces. For safety reasons I would buy a new Miller or Intertherm and it will have a G terminal etc.


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## thewhitemacho (Sep 25, 2010)

Thanks for the help, What about this option, I should be able to wire in a standard toggle switch just outside the furnace on the wall that runs the fan only right? So it would be bypassing the furnace and just engaging the fan. Just wire a switch that takes power from somewhere inside the furnace, ( im sure i could find a 110 lead in there somewhere) and just wire it up like a standard house 110 switch. am I off base here? that would work right? That is, if the fan is 110.thanks...

:thumbsup:------Tighten it till it strips,back off a 1/4 turn-------:thumbsup:


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## yuri (Nov 29, 2008)

Nope, the fan is 220 volts. Any altering and you could backfeed power to the motor or elements and damage them. Sorry.:huh:


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## thewhitemacho (Sep 25, 2010)

Right, back feed, good point, so for the sake of making it possible, you could have a switch that kills power to the fan first, then re-energizes it with another switch, a what, two pole 220v switch right?( the green ones i think), or if they make a switch that does that all in one.....Is this dangerous? lol...I know my way around wiring pretty well,ac house current that is....thanks


:thumbsup:-----tighten it till it strips,back of a 1/4 turn-----:thumbsup:


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## yuri (Nov 29, 2008)

Hard to see it from here. A green one? Homemade wiring tends to catch on fire from what I have seen and the fire marshall/ins co. don't care for it either.:no:


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## thewhitemacho (Sep 25, 2010)

True that....thanks


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## yuri (Nov 29, 2008)

Seriously, a fire in a mobile home can be very quick and deadly. Electric furnaces and their elements deteriorate with age. 20 amps per element but the main breaker/fuse is designed for the total of all the elements. Wiring burns and catches on fire when elements short out. It takes a lot before enough wiring shorts out to blow the main fuse/breaker. Not a pleasant experience. A new furnace is a better idea.


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