Air fans into my ductwork

[101885]

Hi guys, I'm new to this forum. I'll give you a little background info I have a 2 story house with a finished basement, I have a woodstove in the basement that is a bit undersized to heat the whole house radiantly. Before going out and buying a new stove I wanted to try to put a fan into the supply line of my ductwork that runs right overtop of where the woodstove is. I was wondering if anyone knew of a fan that I could do this with that would mount right on the bulkhead of my duct and be able to suck the heat out of the basement and disperse it throughout the house. Thanks

 

[Dune]

Although stuff like this has been done it is a bad idea. To get the most heat from the fire you would need a heat exchanger like that found in a hot air furnace. Additionaly it would be very possible to spread CO throughout your house, killing you while you sleep. If you insist upon this plan, far more effective than trying to spread slightly heated air, would be to use only the return side of the existing ductwork to bring cold air from the far rooms to the basement, thereby encouraging the warm air in the basement to replace the cold air drawn from elsewhere. this would be possible if you left doors open. Modifications to your existing sheetmetal would be minimal and you could use the existing blower.

 

[katwillny]

Welcome to the Forum Bowmaste10. There are multiple discussions on this forum that address your questions. Do a search for Head Distribution or Moving Heat and you will get many previous posts. I have a similar setup to what you are describing. What I am currently doing is that i am leaving the door open in the stove room and I placed a floor fan blowing cold air into the room where the stove is. I recently started doing this as a suggestion by Backwood Savage (Dennis) and it works great. I am noticing that the heat is rising faster to the upstairs. I also have a ceiling fan on the second floor which further helps with the heat distro.

 

[semipro]

I used a very quiet, ceiling-mounted bathroom ventilation fan to do this. Its mounted so that the outlet of the fan exits into the nearby duct work. I also installed a thermostat to turn it on and off depending upon air temps near the ceiling.

The safety concerns others have mentioned are real and there may be building codes that limit how close your fan can be to the stove.

Welcome to the forum.

 

[littlesmokey]

If you have a fire, plan on paying to rebuild, because your insurance company will deny your claim. It would be like blowing the fire throughout your house. Floor fans are much better.

 

[semipro]

If you have a fire, plan on paying to rebuild, because your insurance company will deny your claim. It would be like blowing the fire throughout your house. Floor fans are much better.

Would they deny the claim if all building codes are met? I ask this in earnest because I'd really like to know.

My fan is located at least 15' horizontally from the stove in an area where hot air collects? My understanding is that codes prohibit an air return of any type closer than 8 ft. (thought this might vary by authority).

Has anyone considered that blowing air towards a source of flame (the stove) is basically creating a blowtorch effect, very effectively feeding the fire? Oxygen is usually a limiting factor with fires. I was planning to do this very thing (blowing cool air towards the stove) on my new 1st floor install but am now thinking twice about it.

 

[littlesmokey]

If you have a fire, plan on paying to rebuild, because your insurance company will deny your claim. It would be like blowing the fire throughout your house. Floor fans are much better.

Would they deny the claim if all building codes are met? I ask this in earnest because I'd really like to know.

My fan is located at least 15' horizontally from the stove in an area where hot air collects? My understanding is that codes prohibit an air return of any type closer than 8 ft. (thought this might vary by authority).

Has anyone considered that blowing air towards a source of flame (the stove) is basically creating a blowtorch effect, very effectively feeding the fire? Oxygen is usually a limiting factor with fires. I was planning to do this very thing (blowing cool air towards the stove) on my new 1st floor install but am now thinking twice about it.

The OP said above his stove. I take that to be way too close. You will have to ask your insurance carrier, but an adjuster I spoke with from Farmers said any compromise to the air exchange is an auto deny. That includes holes cut through the floor for venting air upwards. You need to consider the need for "fire-blocking".

Building codes vary, but I think last year they addressed the issue differently. I am not sure as I don't install or consider or recommend cutting into a ducting system.

Last, the issue of using fans to move air are to place the fan in the cold corner, low and start the air moving towards the warmer stove air. I don't think anyone would place a fan to act as a fire feeder. The blowers on your stove do not push air into the fire, but circulate air around the stove. If you were to have a stove go out of control, the fan will make no difference to the demand of the stove for air, it will create it's own "blow-torch".

 

[semipro]

If you have a fire, plan on paying to rebuild, because your insurance company will deny your claim. It would be like blowing the fire throughout your house. Floor fans are much better.

Would they deny the claim if all building codes are met? I ask this in earnest because I'd really like to know.

My fan is located at least 15' horizontally from the stove in an area where hot air collects? My understanding is that codes prohibit an air return of any type closer than 8 ft. (thought this might vary by authority).

Has anyone considered that blowing air towards a source of flame (the stove) is basically creating a blowtorch effect, very effectively feeding the fire? Oxygen is usually a limiting factor with fires. I was planning to do this very thing (blowing cool air towards the stove) on my new 1st floor install but am now thinking twice about it.

The OP said above his stove. I take that to be way too close. You will have to ask your insurance carrier, but an adjuster I spoke with from Farmers said any compromise to the air exchange is an auto deny. That includes holes cut through the floor for venting air upwards. You need to consider the need for "fire-blocking".

Building codes vary, but I think last year they addressed the issue differently. I am not sure as I don't install or consider or recommend cutting into a ducting system.

Last, the issue of using fans to move air are to place the fan in the cold corner, low and start the air moving towards the warmer stove air. I don't think anyone would place a fan to act as a fire feeder. The blowers on your stove do not push air into the fire, but circulate air around the stove. If you were to have a stove go out of control, the fan will make no difference to the demand of the stove for air, it will create it's own "blow-torch".

Thanks for the info. I thought you were referring specifically to my install not the OPs. My mistake. I'm going to check with my insurance company and maybe local fire officials though to make sure on policies and codes.

I think there are vents that you can buy that will close automatically if temps get too high. I believe they are spring loaded with a low melting point metal link that holds them open. I need to look into those.

With respect to the blow torch effect, I remain unconvinced that having fans blowing cool air into the stove room wouldn't effectively be feeding the fire. The type of fire we're talking about, one outside the stove that spreads to floors above floors by vents would also be fed by fresh, oxygen rich air being blown to it from other rooms as many advocate here. I guess its somewhat analogous to having a power vented flue versus having a powered outdoor air supply on your stove.

 

[OpenWater]

If you insist upon this plan, far more effective than trying to spread slightly heated air, would be to use only the return side of the existing ductwork to bring cold air from the far rooms to the basement, thereby encouraging the warm air in the basement to replace the cold air drawn from elsewhere. this would be possible if you left doors open. Modifications to your existing sheetmetal would be minimal and you could use the existing blower.

Interesting idea. Do you mean putting a vent in the basement return duct? If so, would this be upstream or downstream of the furnace? I'm assuming we're talking about moving air with the furnace blower, which is separate from the blower on the stove.

CB

 

[Dune]

If you insist upon this plan, far more effective than trying to spread slightly heated air, would be to use only the return side of the existing ductwork to bring cold air from the far rooms to the basement, thereby encouraging the warm air in the basement to replace the cold air drawn from elsewhere. this would be possible if you left doors open. Modifications to your existing sheetmetal would be minimal and you could use the existing blower.

Interesting idea. Do you mean putting a vent in the basement return duct? If so, would this be upstream or downstream of the furnace? I'm assuming we're talking about moving air with the furnace blower, which is separate from the blower on the stove.

CB

Yeah, you would still use the blower. You would have to be able divert after the blower into the basement. Two flappers, one that opens into the basement and one that blocks off the supply plenum. Open doors throughout the house would complete the circuit. The opening into the basement would have to be downstream of the blower or there would be no effect.

 

[OpenWater]

If you insist upon this plan, far more effective than trying to spread slightly heated air, would be to use only the return side of the existing ductwork to bring cold air from the far rooms to the basement, thereby encouraging the warm air in the basement to replace the cold air drawn from elsewhere. this would be possible if you left doors open. Modifications to your existing sheetmetal would be minimal and you could use the existing blower.

Interesting idea. Do you mean putting a vent in the basement return duct? If so, would this be upstream or downstream of the furnace? I'm assuming we're talking about moving air with the furnace blower, which is separate from the blower on the stove.

CB

Yeah, you would still use the blower. You would have to be able divert after the blower into the basement. Two flappers, one that opens into the basement and one that blocks off the supply plenum. Open doors throughout the house would complete the circuit. The opening into the basement would have to be downstream of the blower or there would be no effect.

Ahhhh! By flapper, you mean a vent with a cover that basically raises when the blower is on (essentially a one way valve). What / where is the supply plenum? I know what HVAC stands for, but that is about it!!

Thanks,

Chris

 

[Dune]

Yeah. Maybe someone who knows what I am saying and has sketchup or whatever can jump in here with a little sketch.