# How do I run furnace fan without heat



## RISurfer20 (Nov 9, 2007)

I have a forced hot air gas furnace. I am trying to find a way to distribute the heat generated from my wood stove. If I could just run the furnace fan to circulate the air in the house I think this would help to distribute the wood stove heat. Does anyone know how to just run the furnace fan without generating heat from the furnace? Do I need to install a seperate fan switch? Any help would be appreciated. Thanks.


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## snowtime (Nov 9, 2007)

I have a wood electric forced air system in the basement and it always has had a rocker switch for summer running without heat. Check yours out maybe theres a switch you just havent seen.


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## begreen (Nov 9, 2007)

Yes you do need a fan switch. Usually there is one on the thermostat marked "fan" or "fan only".

FWIW, this often doesn't work because the heat loss through the ductwork is too high. How well insulated is the ductwork on this furnace? Does the ductwork travel through and unheated or cold space? If yes, there may be a net loss when the electricity cost is counted in.


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## RISurfer20 (Nov 9, 2007)

BeGreen,

The ductwork travels through my finished basement where it is warm. All the ductwork is insulated and is not located in the attic. I just would like to receive return air where my wood stove is hoping it would spread heat throughout the house. My house is a cape so is heated easily the forced air. I think having the wood stove pumping some heat out and then turning on the fan of the furnace would help distribute the heat.

I have a programable thermostat. So there should be a way to place the wires for fan only mode? Thanks for the info.


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## Metal (Nov 9, 2007)

What brand/model of programmable thermostat do you have?  I would be very surprised if it did not already have this function or a switch on the bottom for fan only.


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## RISurfer20 (Nov 9, 2007)

I have a ritetemp. I'll have to check to see if it will work.


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## begreen (Nov 10, 2007)

It won't hurt to try it, but running a 1/2 hp motor constantly will use several KW per day. 

The programmable RiteTemp should have a Fan switch on the bottom side labeled FAN On <-> Auto. In the "On" mode it runs continuously, in the "Auto" mode it comes on when the furnace is running and up to temperature.


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## log-on (Nov 10, 2007)

Dang, theres a little bug stuck behind my monitors glass, Metal- very cool GIF
There might also be a switch on the furnace but thats correct , running  a AC motors starts to burn un renewable energy wood heat is better passive. Use your chain saw and cut a hole in the floor.


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## EddyKilowatt (Nov 10, 2007)

I spent an hour in my crawl space a few weeks ago trying to get my blower to run solo, but gave up.  My furnace is old (60s or 70s) and uses just a two-wire thermostat loop.  The same signal runs both the gas valve (directly) and the blower (thru a time delay relay), mixed in with a couple of double-pole safety over/undertemperature switches.   Given the safety implications, I decided I wasn't eager enough to risk mucking with the burner/blower interlocks... I could rewire things, but couldn't guarantee that in ten years some wire wouldn't come loose or get chewed through, and cause the blower not to run while the burner was on.    I don't trust combustion appliances that are two feet under my living room floor.

I should replace that old battleship with a modern gas burner one of these days, anyway...

Eddy


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## RISurfer20 (Nov 10, 2007)

Checked it out. I have a two wire RH and W system so I guess I cannot control the fan seperately.


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## RonB (Nov 10, 2007)

Hi Surfer,  don't give up yet.  It is possible to do.  You may need to run a 3-4 wire strand of new thermostat wire or even get help from a friend locally to help you wire it up--but I think it is worthwhile.  I use my fan to help average out room temps all the time.  I even use the fan only switch at other times of the year.  Others seem to be nay sayers about benefits and costs and supposed fan failure.  My experience is exactly contrary to their negative points.   Heat/AC experts often recommend running the fan continuously for comfort/uniformity and most of us know the most stress occurs on a motor when it first starts--not in continuous run (and you will be manually kicking it on far fewer times than the furnace would if it was running)  Cost for running my fan is negligible.  In my situation, I am able to better able to heat the back bedrooms by running the fan.  I have even considered getting an updated programmable thermostat that you can set to automatically cycle the fan on X minutes every hour.


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## RISurfer20 (Nov 10, 2007)

RonB,
Thats exactly what I want to do. Run the fan a couple of minutes every other hour or so to distribute the heat. I think it will really help my little cape. I'll have to call my heating company. Thanks for the info.


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## JimWalshin845 (Nov 10, 2007)

RISurfer20 said:
			
		

> RonB,
> Thats exactly what I want to do. Run the fan a couple of minutes every other hour or so to distribute the heat. I think it will really help my little cape. I'll have to call my heating company. Thanks for the info.



I have a possible alternative that you might like.

Instead of running the 3 wire from your existing thermostat, install a new thermostat near your stove.  Set the wires on the *AC* side of the new thermostat for ON at temperature RISE.  This way the fan will kick on automatically when the temp reaches your preset and shut off when the temp lowers to the differential you have set, just like you are using an air conditioner during the summer.

This way you never have to touch it and the rest of the house should benefit 24/7 when burning the stove.

You should be able to pick up a new thermostat for about $25 and the wire is cheap.

Jim


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## WarmGuy (Nov 10, 2007)

Hey guys, my advice: forget about it.

I put my kill-a-watt on my furnace and determined that the fan takes 500 watts.  So run it for 10 hours a day, and you're talking $20+ per month.  Run it continuously and it would cost me $63.72 per month (.5 KW * 24 hr *30 days * $.177/KWh).

But it doesn't matter, 'cause it just doesn't work that well.  Put your hand up to the register and you'll just feel cool air being pumped around at high cost.  You're mostly just heating up a hundred feet of ducting.  The moving air will make you cooler.


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## JimWalshin845 (Nov 10, 2007)

WarmGuy said:
			
		

> Hey guys, my advice: forget about it.
> 
> But it doesn't matter, 'cause it just doesn't work that well.  Put your hand up to the register and you'll just feel cool air being pumped around at high cost.  You're mostly just heating up a hundred feet of ducting.  The moving air will make you cooler.



I think in Surfer's case here, since the duct work is all in 'finished' areas, that heating even the duct work will help dissipate the heat throughout his home and with the fan cycling on and off using my relatively inexpensive solution it may be worth the try.


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## RISurfer20 (Nov 10, 2007)

I have a two wire system. I need to dig deep and find the G wire in the fan control center so I can run the wire to the thermostat. Good advice Jim. I may consider placing one near the stove.

WarmGuy. I just intend on runnng the fan a couple of minutes every other hour. Certain areas in my house can get up to 80 plus degrees while other areas are below 70. I just want a way to spread the heat around and cool off some of the areas.


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## JimWalshin845 (Nov 10, 2007)

RISurfer20 said:
			
		

> I have a two wire system. I need to dig deep and find the G wire in the fan control center so I can run the wire to the thermostat. Good advice Jim. I may consider placing one near the stove.



Sometimes the electrician buries the other stands of the wire in the wall behind the thermostat.  So if your home was built after the '60s there usually are more than 2 wires.

On most fan limit controls, (that is the doo-hickey that controls the ON/OFF switch for the fan) there is a wire insert hole that is labeled 'FAN'.  Look for that first before you go wild.


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## laynes69 (Nov 10, 2007)

The only way that our home heats with wood is through the ducting and through the lp furnace. My woodfurnace is tied in series with my lp furnace. When my wood furnace gets 145 degrees, the limit on the wood furnace tells the circuit board on the lp furnace to kick in its fan. Then it runs until it gets down to 85 degrees. In winter time, our furnace fan runs non stop all winter long. I don't notice more than maybe a 10.00 increase a month. On most thermostats there is a jumper wire that you can keep in place to allow for the fan to turned on without heat. But for our woodfurnace to kick in the lp furnace, its 2 wires. The nice thing with our setup, is the Lp Furnace has a built in relay. If the LP furnace kicks in heat, the blower on the furnace will shut off for a sec, then it will kick back on. Its a slick setup and very efficient with heathing. I could see it cooling the air too much running through the ductwork. I would try ceiling fans, or a couple box fans.


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## JimWalshin845 (Nov 10, 2007)

laynes69 said:
			
		

> On most thermostats there is a jumper wire that you can keep in place to allow for the fan to turned on without heat. But for our woodfurnace to kick in the lp furnace, its 2 wires. The nice thing with our setup, is the Lp Furnace has a built in relay.



The problem here is for those working with stoves is that you cant' have a thermostat on 'Heat' and use it at the same time with the AC control for temperature rise.  

Reminds me back in the late 70's when I replaced my forced hot air oil furnace with a combo unit (damn if I can remember the name of it) that burned wood or coal and had a separate chamber that burned oil.  Also, the home was a small 'Cape Codder' like Surf's.

The down side of the unit I had was going down the basement to refuel.  It did take larger logs up to 3' if I can recall.  

Heating with propane must be a last resort over oil, why did you go in that direction may I ask?

Just curious,
Jim & Kathy


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## laynes69 (Nov 11, 2007)

Im not getting what you are saying about heat and temp rise with ac. We leave our LP furnace set for 68 degrees. 90% of the winter we won't use any LP because of our woodfurnace. We have a LP dryer, LP stove and a 90% efficient Furnace. When dad purchased this home from my grandmother, it had 2 oil furnaces, one for down and up. He had the LP furnace installed so it would free up the chimney and allow usage for the woodfurnace. Been this way for 20 years. Now I have the home, and I redid the connections between the furnace and the woodfurnace. With both having a thermostat in the living room if I choose to use the forced draft of the Wood furnace. Last year I reducted the whole home for even heat distribution.


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## JimWalshin845 (Nov 11, 2007)

laynes69 said:
			
		

> Im not getting what you are saying about heat and temp rise with ac.



Every home modern thermostat has 3 positions, OFF/HEAT/AC.

The HEAT position works on temperature lowering to turn the switch ON.  The AC side uses a rise in temperature to turn the switch ON.  So in Surfer's case, we can use the AC side to turn on a switch that will activate his fan unit on his FHA system.  So that is what is meant as per Temperature Rise activation... sounds totally reversed but it will work efficiently and I think George Foreman said it the best ......"Set it and Forget it".

Sounds like your grandfather had a great efficient way to solve the one flue problem in your home too.  Most cool... or should I say.... A Great HOT idea!!


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## thechimneysweep (Nov 11, 2007)

My house is a two-story with loft.  It is built on a slab, so the forced air ducting is in the ceiling of the bottom floor; in other words, the entire duct system is totally enclosed within the house.  The air return intake is adjacent to the furnace on the bottom floor.  My woodstove is upstairs on the main floor.  I'm a smoker, and there's an electronic air filter in the system, so I run the furnace blower all year round, 24/7.  Been doing that for 15 years now, same blower.  In the Summertime, the duct system helps circulate cool air from downstairs around the rest of the house (we don't have AC).  In Winter, it circulates the heated air from our convection-style woodstove.  I know the consensus on the forum is that a forced air ducting system won't distribute the heat from a woodstove effectively, but in my case, it does.  A couple years ago, we had a power outage, and without the blower going, the downstairs temperature plummeted eight degrees in twelve hours.


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## laynes69 (Nov 11, 2007)

I have 2 thermostats, one is for the wood furnaces forced draft. If the temp drops below a set temp, then the blower feeds the firebox and the limit kicks the lp furnace's blower on. The other thermostat for the LP Furnace has AC/Heat- Blower Auto/ON.
In order for me to use the blower option, there is a jumper inside the thermostat to kick on the blower if I just want the blower. Now the blower on the LP is also controlled my the limit on the wood furnace. If he is running a wood stove, and wants to just kick on his blower of his furnace, then a Digital thermostat with the fan control should work for him. If he has his thermostat set for 65 and the house is 80 in a room, then he could manually turn on his blower through the thermostat to see if anything improves. They say it really can help even a homes comfort. But I know the 2 thermostats I have are digital and have heat/ac blower on/auto


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## swestall (Nov 11, 2007)

There are low enery consumption fans out there and they can be thermostatically controlled. Modern heat pumps and A/C systems use these. It might be worth you while to have one installed into your duct work independent of the furnace. It will do its job and won't interfere with the furnace if installed correctly.


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