How to safely bypass propane furnace central air fan.

Been reading the forums for awhile now and i'm totally immersed in CAD and wood burning.

One idea that really got me thinking is some of you have somehow been able to run just the fan on your furnace.

My living space is nice but the rest of the house could use some better distribution. I have ceiling fans in almost every room but they only do so much. I'm sure my stove could be better but i'm just starting out. I added a small cheap volgelzang in my entry way so i may be able to keep the heat on both sides of the furnace.

anyway its a dayton propane furnace. I basically have a 2 wire thermostat I'm sure it can do more but dont have anything else in the house (ac, etc.)

The thermostat clicks then the furnace ignites warms up then another exhaust fan powers up about 30seconds later the big fan kicks on warming the house.

How can I use the thermostat or even add another one to just run the big fan when wood burning and then switch back to the normal propane program when im gone?

thanks in advance its about to start snowing in montana soon. :chainsawguy:

Depending on the furnace, there will be jumper settings to change the on speeds of the furnace. A digital thermostat with a fan on setting would allow the blower to operate without the burners. There's a large issue with it though, duct loss. You may loose more heat than gain running the blower of the central furnace. Also changing blower speeds can affect the heat rise over the exchanger if it would fire. In the end, a few box fans or ceiling fans would help spread the heat, at that point if you still arent happy a wood furnace would accomplish this.

^Agree. Easiest is to probably put on a $30 thermostat that is digital and has a Fan On switch

We do this at our house by shutting off most of the vents (not all) and running the blower fan to pull some of the warm air downstairs. Eventually I'm going to put another stove down there but for the time being it works just fine at keeping the basement around 60

You'll have to wire in the fan on switch. There should be something on it in your manual. A new thermostat isn't all that expensive. I wired mine up in an hour or so.

there will be jumper settings to change the on speeds of the furnace. A digital thermostat with a fan on setting would allow the blower to operate without the burners. There's a large issue with it though, duct loss. You may loose more heat than gain running the blower of the central furnace. Also changing blower speeds can affect the heat rise over the exchanger if it would fire.

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Ok tonight i'll try to dig a bit deeper.

I have a digital thermo that im positive has a fan on setting however I don't think i have communication wires to support it so i could easily just buy another thermo and park it closer to the furnace?

When u say duct loss does that include the ducts being fully wrapped insulation and R-60 blown over them as thats whats up there (just did it last week and fell through the ceiling on my way out hehe)

now your last comment went over my head. I don't want to really change speeds of the fan just want it to come on. do you mean the sequence of how the furnace fires?
thermo signals, igniters come on, exahust fan on, finally big fan the one i'd like on comes on to distribute heat

Also i have lots of ceiling fans but they don't get it in the bedrooms very well. sometimes i even turn on the fans in the bedrooms to push cold out and allow warm in dunno if it does anything.

My stove im sure is on the small side its basically a freestanding stove that is actually a insert for a goofy old system where the open fire used fans and fancy concrete work to pressurize the house.

the insert can hold a crazy amount of wood 20"+ logs times a half wheel barrow at a time. i'll see if i can figure out pics on my smart phone.

I also played the vent game last year closing the warm ones and opening only the cold ones but ithink it made the furnace run more cause the thermo isn't zoned in everyroom just one in th emainroom so when the fire ran down the furnace would cook the bedrooms and run alot.

Interested in these OWB's but aren't they radiant heat boilers? how would you run piping under the house in a horrific crawspace with joices everywhere?

Thanks for the quick reply guys.

Craz z said:

Ok tonight i'll try to dig a bit deeper.

I have a digital thermo that im positive has a fan on setting however I don't think i have communication wires to support it so i could easily just buy another thermo and park it closer to the furnace?

When u say duct loss does that include the ducts being fully wrapped insulation and R-60 blown over them as thats whats up there (just did it last week and fell through the ceiling on my way out hehe)

now your last comment went over my head. I don't want to really change speeds of the fan just want it to come on. do you mean the sequence of how the furnace fires?
thermo signals, igniters come on, exahust fan on, finally big fan the one i'd like on comes on to distribute heat

Also i have lots of ceiling fans but they don't get it in the bedrooms very well. sometimes i even turn on the fans in the bedrooms to push cold out and allow warm in dunno if it does anything.

My stove im sure is on the small side its basically a freestanding stove that is actually a insert for a goofy old system where the open fire used fans and fancy concrete work to pressurize the house.

the insert can hold a crazy amount of wood 20"+ logs times a half wheel barrow at a time. i'll see if i can figure out pics on my smart phone.

I also played the vent game last year closing the warm ones and opening only the cold ones but ithink it made the furnace run more cause the thermo isn't zoned in everyroom just one in th emainroom so when the fire ran down the furnace would cook the bedrooms and run alot.

Interested in these OWB's but aren't they radiant heat boilers? how would you run piping under the house in a horrific crawspace with joices everywhere?

Thanks for the quick reply guys.

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You could install a switch near the furnace if you want to. It's usually just an extra wire and ground. You could use a simple light switch if you wanted to instead of another thermostat.

If you scan the manual for your furnace, we may be able to tell you which terminal to install the switch to.

I think they meant heat loss through the ducts. If you don't mind heating the basement, then it's not too big of a deal.

Most OWB's are connected like you would a forced hot water furnace. So you'd need baseboards. There may be some with a hot air system using radiators, but I'm not sure.

Best of luck.

I think they meant heat loss through the ducts. If you don't mind heating the basement, then it's not too big of a deal.

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No basement a real nightmare of a crawlspace tho. Lost all the pipes in the house when i first got here the pipes are exposed to the elements and have to run the water 24/7 so i don't lose em in super cold -40 temps.

You could install a switch near the furnace if you want to. It's usually just an extra wire and ground. You could use a simple light switch if you wanted to instead of another thermostat.

Click to expand...

Love this idea simple and cheap and no 10 mile trips to ACE. I know this forum loves pics whats the best way to get em on here with a smart phone?

Most OWB's are connected like you would a forced hot water furnace. So you'd need baseboards. There may be some with a hot air system using radiators, but I'm not sure.

Click to expand...

Gotcha sounds super expensive and lots of plumbing to do my other house has one but adding a OWB might not go over well in a house in town.

THe house im in and remodeling is on a ranch and a ways from town its been additioned 4 times using old stuff thats a night mare to fix.

Reps all around thanks guys

I did pretty much the same thing. I added an extra furnace control and a cheap heat/cool thermostat to the oil-fired hot air furnace. The stove is in the basement, and I modified the exposed duct work so that I could pull the air off the top of the room into the return duct. The thermostat is set to cool mode so that it turns on when the temperature gets over about 80. When the fire burns down the blower goes off.

However, our old furnace is a single speed blower. It may be more complicated if you have a multi-speed blower. The way mine is set up, if the burner had kicked on it would not have mattered if the blower was already powered. If the two were trying to run the blower at a different speed it may be a problem - it should not be hard to make a lock-out so only one system can run the blower at a time, with priority to the burner. Our oil burner is no longer connected anyway.

One thing to keep in mind - the air circulated is not very warm. Our basement gets up to the mid-90's even with the blower on full time. But the air coming out in other rooms is still not that warm. Also, the blower takes about 800W, which is a fair amount of power running a lot of the time. I will probably put a different pulley on the blower to slow it down now that the burner is not connected anymore and I don't have to worry about keeping the airflow up through the heat exchanger.

Most newish furnaces have a “continuous fan” tap on the control board. If you accidently short something on the control board it can be very expensive, so… First cut the power to the furnace. Second, make sure you have cut the power to the furnace. Next, after triple-checking that power has be cut, open it up and pull the control board out. If you follow the wires from the blower motor you will probably find three wires plugged into the board, one will be plugged onto the “common” tap (usually a white or black wire), one will be plugged onto the “heat” tap (usually a red wire) which kicks the fan into low (or medium) speed when the burner fires, and one will be plugged onto the “cool” tap (usually a blue or yellow wire) and starts the blower in medium (or high, depending on the heat speed) when the central A/C starts up (if installed). If you look closely there will also be a “continuous fan” tap; you can move either the “heat” or “cool” wire over to that tap and the blower will run when ever power is present to the furnace. BUT, if the furnace is still used for heating, even backup heat, you have to have one of those wires on the “heat” tap… because, when the burner fires voltage is removed from the “continuous fan” tap and applied to the “heat” tap. Perhaps the best, and recommended way would be to leave the (red?) wire connected to the “heat” tap and run a jumper between it and the “continuous fan” tap… that way you would have the same blower speed for both.

If your currant thermostat has a “fan on” switch and your furnace control board supports it… you just simply need to run the extra wire(s) needed. If you don’t have A/C, just heat, you’ll probably only have two wires going to the thermostat… just go buy a length of 4 or 6 (as needed) conductor thermostat wire (solid core phone wire or even 8-conductor Ethernet cable will be fine, and cheaper) and use the old wire to pull the new wire up through the wall (usually a simple thing). If your control board doesn’t currently support the “fan on” switch function you may have to buy (or make) a “continuous fan kit” which is usually nothing more than the above mentioned jumper wire and a relay to open and close said jumper wire. You need the relay because the taps for the blower motor supply 120-volts AC and the thermostat taps are normally 24-volts DC.

Often the blower on a furnace will have several speeds available, up as many as 6 or 7. Usually there is some provision to change which speed the “heat” and “cool” wires will use. Commonly this is accomplished by pulling the plug out of the motor itself and moving the wires to a different position within the plug. Do you have the installation paperwork for your furnace? If not, you should be able to find it on-line.

Thanks guys

I think i figured it out. I did shut power down before messing around thank god i didn't blow the circuit board.

Looks like i got lucky and found a third wire hiding in the wall behind thermostat. I jumped R and G and the blower came on but the propane was cycling so i hooked up the third wire to G on thermo and G on ciruit board and voila can turn the blower on off whenever i want.

The weird thing is it came on once on auto/cool but never worked again after. now i can run heat program and just manually switch from auto to just on.

I surely hope my fan isn't pulling 800w or this was a waste of time. can you tell by horsepower? and is 800w at startup or continuous?

I'm getting to eager to fire up the stove was around 50 degrees but with the new R-60 in the attic the house was stuck at 70 degrees. Started a small fire anyway and got the place to 75-80 slept with the windows open all night but the fan distributed heat nicely the real test will be -40 in a few months.

Reps for all thanks

Really want to start throwing pics around how do i do it with a smart phone? log in with phone and post?