New member wood furnace backdraft damper install

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01_Sentea2.0

New Member
Sep 7, 2021
14
WV
I need to get a backdraft damper put in my plenum for my wood furnace so it won't backfeed in my gas furnace. The problem I'm having is there's little to no room and the plenum is taped. Anyone have any recommendations to get one put in. I'm hoping to get something that's a gravity damper so it's automatic in case I need to run the gas furnace when the fire dies out when I'm not home.
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stoveliker

Minister of Fire
Nov 17, 2019
1,483
Eastern Long Island NY
I don't think it is legal to have a solid wood appliance share a flue with any other appliance .....
 

moresnow

Minister of Fire
Jan 13, 2015
1,780
Iowa
I don't think it is legal to have a solid wood appliance share a flue with any other appliance .....
Believe the OP is referring to the forced air plenum/apparatus. Not the exhausting components by appearance?
@brenndatomu may have some words of wisdom on this topic.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
6,389
NE Ohio
Believe the OP is referring to the forced air plenum/apparatus. Not the exhausting components by appearance?
@brenndatomu may have some words of wisdom on this topic.
Correct.

Boy, that's a tough one there OP...that install doesn't allow the room to do much of anything that I can tell, at least by these pics.
The only thing that I can think of would be to install one in the return air duct of the gas furnace that closes whenever its off...use a "power open/spring closed" damper motor (I like Belimo) and power it from the gas furnace blower. This is similar to what I had to do on my own setup...except its in the return leg of the Kuuma furnace, and its "spring open/power closed" (most Belimo's can be switched either way) and powered up by the oil furnace blower running.
 

01_Sentea2.0

New Member
Sep 7, 2021
14
WV
Correct.

Boy, that's a tough one there OP...that install doesn't allow the room to do much of anything that I can tell, at least by these pics.
The only thing that I can think of would be to install one in the return air duct of the gas furnace that closes whenever its off...use a "power open/spring closed" damper motor (I like Belimo) and power it from the gas furnace blower. This is similar to what I had to do on my own setup...except its in the return leg of the Kuuma furnace, and its "spring open/power closed" (most Belimo's can be switched either way) and powered up by the oil furnace blower running.
If I get a damper like you're saying and put it in my return air of my lp gas. Won't the air entering the top of the plenum from the wood furnace go down in any way? Im worried about my ac coil. Should I put some sort of baffle to direct the air upwards?
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,389
NE Ohio
If I get a damper like you're saying and put it in my return air of my lp gas. Won't the air entering the top of the plenum from the wood furnace go down in any way? Im worried about my ac coil. Should I put some sort of baffle to direct the air upwards?
No, the damper is blocking its path to go anywhere other than where you want it to go, up into the house through the supply ducts
With the damper closed the furnace becomes a "dead end" so to speak, as far as air flow goes...so with the airflow, goes the heat...I mean the AC coil and tray may get warm, but no warmer than they get when the gas furnace runs...
 

01_Sentea2.0

New Member
Sep 7, 2021
14
WV
No, the damper is blocking its path to go anywhere other than where you want it to go, up into the house through the supply ducts
With the damper closed the furnace becomes a "dead end" so to speak, as far as air flow goes...so with the airflow, goes the heat...I mean the AC coil and tray may get warm, but no warmer than they get when the gas furnace runs...
Okay that's great to know. If I was wanting to use my existing return for my wood furnace the power open/ spring closed damper would not work right? That would allow the damper to spring open when the wood furnace was drawing air. How do I wire a damper for the blower? The thermostat wires on the furnace. They make a 24v or a 110v and I have no idea on which one is best. I need to get a better damper for my hesr duct. I just have a manual one in there right now. Can you hook up multiple ones to your gas furnace and which powered one would I need to get on that one?
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,389
NE Ohio
If I was wanting to use my existing return for my wood furnace the power open/ spring closed damper would not work right?
You'd have to tie the wood furnace in ahead of the damper.
As far as wiring and voltage...you'd have to sit down and figure out what works best...tie into a blower to get 120v, or tie into an accessory tap on the gas furnace control board...might need to use some relays to make it all work too...if you aren't good with electrical you may want to get an electrician or a HVAC guy in to help with all this...
 
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01_Sentea2.0

New Member
Sep 7, 2021
14
WV
You'd have to tie the wood furnace in ahead of the damper.
If doing this, that don't sound like that would work with the power open/ spring closed damper because the damper would only be open when the gas furnace would be running. It would suck heat back through the furnace because the damper would be shut. Do you mean ahead on the return to the house vent or ahead being towards the furnace?
 
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brenndatomu

Minister of Fire
Aug 21, 2013
6,389
NE Ohio
Would I also have to put a damper in the return for the wood furnace?
You might...you could try it and see and if its an issue you could put a simple gravity damper in the supply pipe of the Englander, but, I don't care for that setup because it blocks gravity airflow if the power goes out while you have a fire in the wood furnace....so in my opinion the better option would be to put a "power closed/spring open" (opposite of the other one) on the return air of the wood furnace. (you might need to install a box over the blower to do this easily...and then that would allow you to tap the return air of the Englander into the main return too...which will make it more efficient too, since the return air will be warmer (not off the cold basement floor)
 

01_Sentea2.0

New Member
Sep 7, 2021
14
WV
You might...you could try it and see and if its an issue you could put a simple gravity damper in the supply pipe of the Englander, but, I don't care for that setup because it blocks gravity airflow if the power goes out while you have a fire in the wood furnace....so in my opinion the better option would be to put a "power closed/spring open" (opposite of the other one) on the return air of the wood furnace. (you might need to install a box over the blower to do this easily...and then that would allow you to tap the return air of the Englander into the main return too...which will make it more efficient too, since the return air will be warmer (not off the cold basement floor)
I'm looking at getting a us stove filter box that most people use for these kind of furnaces to intertwine everything together. I will just install a damper you're talking about in the return. I want everything to be automatic in case we are not home if the fire dies out. So realistic I need 3 motor dampers for this parallel setup. 1 power open/spring closed for gas furnace, 1 power closed/ spring open for return of wood furnace and 1 power closed/spring open for supply. Do I have this correct? Wired up all to the blower or accessory board.
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,389
NE Ohio
1 power closed/ spring open for return of wood furnace and 1 power closed/spring open for supply. Do I have this correct? Wired up all to the blower or accessory board.
You would only need 1 of these...
 

Firefighter44

Member
Aug 1, 2018
8
Cascade wisconsin
My recommendation is to put a manual round duct damper in the heat duct coming off the wood stove. You would have to open it for the wood burning season. But in my past experiences, I’m never gone long enough to unexpectedly have the gas furnace kick on. If you know that you won’t be able to fill the stove for 24 hours (the estimated time it takes to cool the house down enough to run the gas furnace) then just close the damper and run the gas furnace.
I thought I too would need full automated system but sometimes a simple on/off valve is more practical.
 

01_Sentea2.0

New Member
Sep 7, 2021
14
WV
So I build a plenum box attached right above the ac coil on the right side of the gas furnace connected by a 8" pipe. It's directly centered to get air in both portions of the dividers. I have an issue where I'm getting little air coming from all vents. I just have a filter box attached to a furnace along with another box to attached to the return. I have a 10" hole cut to tie in the return to the existing gas return. Is the reason being I don't have return hooked up yet on why I'm not getting enough return air?
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,389
NE Ohio
My guess is that its just such a much smaller blower on the wood furnace as compared to the gas furnace...moves much less air, but, it will run pretty much all the time though too...not on for a little bit and then off like the gas furnace does...so its basically the tortoise and the hare story here...and the tortoise wins, remember? You have to try it and see for sure, but likely the only thing you may need to do is to clamp down some of the registers closer to the furnace so that the rooms further away can get some heat too...its a trial and error thing because every house is different when it comes to heating and cooling them...
 

01_Sentea2.0

New Member
Sep 7, 2021
14
WV
My guess is that its just such a much smaller blower on the wood furnace as compared to the gas furnace...moves much less air, but, it will run pretty much all the time though too...not on for a little bit and then off like the gas furnace does...so its basically the tortoise and the hare story here...and the tortoise wins, remember? You have to try it and see for sure, but likely the only thing you may need to do is to clamp down some of the registers closer to the furnace so that the rooms further away can get some heat too...its a trial and error thing because every house is different when it comes to heating and cooling them...
The wood furnace has a 850cfm blower. I didn't really except much coming from a much bigger blower on the gas furnace. Do you mean shut off the registers on the vents. I have 3 that really don't need heated anyway. Can a person somehow add another blower beside the englanfer 28-3500 blower to get a little more cfm?
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,389
NE Ohio
The wood furnace has a 850cfm blower. I didn't really except much coming from a much bigger blower on the gas furnace. Do you mean shut off the registers on the vents. I have 3 that really don't need heated anyway. Can a person somehow add another blower beside the englanfer 28-3500 blower to get a little more cfm?
Yes, shut or nearly shut the registers that are closer and/or don't need as much heat...forced the limited air/heat on down the duct where you want it.
I would not add a blower to it...it will just cool the firebox too much and will cause it to kick on/off...A LOT! The end result will probably be less heat to the house...the longer you can keep that blower running, the better. Try it the way it is, you will be surprised the result...it won't blast the house from 60* to 75* in half and hour or anything, but keep it running all day, like most people do in the winter, it will keep the house warm.
I had a Kuuma VF200 a few years back that had that same 850 CFM blower and single 8" duct pipe on it...I was skeptical at first, but low and behold, it heated the house!
 

01_Sentea2.0

New Member
Sep 7, 2021
14
WV
Yes, shut or nearly shut the registers that are closer and/or don't need as much heat...forced the limited air/heat on down the duct where you want it.
I would not add a blower to it...it will just cool the firebox too much and will cause it to kick on/off...A LOT! The end result will probably be less heat to the house...the longer you can keep that blower running, the better. Try it the way it is, you will be surprised the result...it won't blast the house from 60* to 75* in half and hour or anything, but keep it running all day, like most people do in the winter, it will keep the house warm.
I had a Kuuma VF200 a few years back that had that same 850 CFM blower and single 8" duct pipe on it...I was skeptical at first, but low and behold, it heated the house!
Good deal! If it heats my house that's all that matters.