Author Topic: ducting wood heat??  (Read 4361 times)

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A6D9

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ducting wood heat??
« on: June 02, 2008, 03:11:38 AM »
I just bought an older mini home.


has all new windows.


has an electric forced air furnace...EWWWWW


we are planning to install a woodstove in the front of the minihome and keeping the electric forced air for back up only.


my idea is...since we have a duct right next to where the stove will be for the forced air.  can i just put a fan on it and suck the heat from the woodstove and hopfully that duct will help bring some heat to the bedrooms in the back of the minihome?


the way the living room will be set up is we will have a couch in front of the duct...i can put some flexi duct and a fan behind the couch.  leave all the doors open to allow cold air to circulae back around


does anyone see anythign wrong with this idea?

« Last Edit: June 02, 2008, 03:11:38 AM by (unknown) »

bob g

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Re: ducting wood heat??
« Reply #1 on: June 01, 2008, 11:11:55 PM »
you mentioned sucking the heat off the wood stove, so i would like to draw a distinction if i may


while removeing the heat from the wood stove into the ductwork is an ok idea, how it is done makes all the difference in the world on whether it is safe or not safe.


for instance, if you put the fan on the down stream side so that it pulls a negative pressure around the wood stove firebox you run the risk of pulling carbon monoxide into the ducts and distributing that through the living area, something you don't want under any conditions.


however if you put the fan before or upstream to the wood stove you will put a positive pressure in the system which will tend to force air into the wood stove keeping the carbon monoxide inside the firebox and up the flue where it belongs.


hopefully that makes sense :)


think this project through very well, and you will get a good and safe result


bob g

« Last Edit: June 01, 2008, 11:11:55 PM by bob g »
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ghurd

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Re: ducting wood heat??
« Reply #2 on: June 01, 2008, 11:47:11 PM »
I don't see it as that complex.

"have a duct right next to where the stove will be for the forced air"

"can i just put a fan on it"


Meaning, can you put a fan on the existing duct near the stove, to blow air into a duct?

Why not?  Seems fine to me.


"put some flexi duct on it" is the problem.

One end ON the duct and the other end in free air near the stove?  OK, I think.

One end ON the stove?  No.  Not good.


It doesn't take much air flow to move the heat one direction, if the cold has an easy return path ("leave all the doors open to allow cold air to circulae back around").


Depending on the duct work, it could be easier to do it backwards.  Suck the cool air from the other rooms out of the duct near the stove.  No flexi duct. Maybe more efficient.

G-

« Last Edit: June 01, 2008, 11:47:11 PM by ghurd »
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A6D9

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Re: ducting wood heat??
« Reply #3 on: June 02, 2008, 04:51:32 AM »
thank you...yes  the fan and flexi duct was meant to be not on stove.  and as for negative pressure....I'll be sure to watch out for that.


thank you all for th great ideas  :)


i think this might work.

« Last Edit: June 02, 2008, 04:51:32 AM by A6D9 »

RogerAS

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Re: ducting wood heat??
« Reply #4 on: June 02, 2008, 10:48:24 AM »
A6D9,


I heat my home with just such a system.


I posted about it in detail here.

http://www.fieldlines.com/story/2006/10/12/1352/1405


Here is a drawing of how it works.


Any questions?

« Last Edit: June 02, 2008, 10:48:24 AM by RogerAS »

thirteen

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Re: ducting wood heat??
« Reply #5 on: June 02, 2008, 07:22:49 PM »
I may have missed it but could you use the fan on your electric heater to circulate the air. Alot of furnaces have it so you can use just the fan to move cool air. You might look into it.
« Last Edit: June 02, 2008, 07:22:49 PM by thirteen »
MntMnROY 13

A6D9

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Re: ducting wood heat??
« Reply #6 on: June 02, 2008, 07:45:14 PM »
i thought about that..but then it would blow the air to the stove


my idea was to take the heat and blow it in the out of the furnace and hope it will go in the other outs thruout the home

« Last Edit: June 02, 2008, 07:45:14 PM by A6D9 »

nothing to lose

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Re: ducting wood heat??
« Reply #7 on: June 02, 2008, 08:09:01 PM »
It really depends what you have and how it is setup.

As was already mentioned you don't want to suck a vacume on the wood burner that would cause carbon monoxide to enter the home!


Really though if you have a good setup you can do anything you want within reason.

For instance, if your woodburners intake is on the front and exhaust on the rear, you could build a box around it that does not effect intake or exhaust, then blow or suck air through that box as you want. This assumes you have a solid wood burner, not one built in pieces like those cheap cast iron stoves. In this case your "box" would be around the top, bottom, sides, the stove front and rear exposed outside the box. Ok for a solid steel burner.


If the wood burner is in a large room that gets hot and you just circulate that hot air elsewhere you can do it either way, blow or suck. Again make sure your not going to make a vacume on the wood burner though.


Best is to seal the burner with a duct to draw in air from outside and preheat that air using the flue exhaust. This way the wood burning fumes are basically sealed from the house, provided you have a well sealed door for loading the wood, or load wood from outside the house.

I saw a neat setup where the hot burner case was in the house, the loading door, flue,  and intake were outside the house. This was a fancy large burner that only needed loaded once a day and temps rarely fell below 5F in that area. It was a rock or brick wall so no risk of fire though!!


If done right you can even build a box in the duct work itself dending on your home and burner. In this case the normal furnace should work as normal, heat's and blows the air around the house as needed. The cold air return feeds to the box at the wood burner, if a fire is burning then hot air is fed to the furnace and less normal heating is needed.  If no wood fire then the normal furnace works as normal.


So many things can be done depending what you have and want to do with it. ALWAYS make certain no fumes from inside the wood burner can enter the air going to the house!!!

« Last Edit: June 02, 2008, 08:09:01 PM by nothing to lose »

RogerAS

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Re: ducting wood heat??
« Reply #8 on: June 03, 2008, 03:15:31 PM »
A6D9,


Did you not even read my response?


Look carefully at the drawing I provided and reread the link to my efforts. There is NO SMOKE in the house. There is NO MESS in the house. I use natural convection 90% of the time and force cool air into the box surrounding the stove when it's real cold with a microwave blower fan (1/20th HP).


This isn't rocket science.


ANY good tight stove can be used in this way.


You can use your current fan to pull air through the hotbox.


All you need is a little extra duct work and a place to put the concrete pad.


mmmmm?

« Last Edit: June 03, 2008, 03:15:31 PM by RogerAS »

Live6766

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Re: ducting wood heat??
« Reply #9 on: June 03, 2008, 07:56:47 PM »
 

I also heat my house with the wood stove in the basement and a return duct just above the stove about 7' above the stove. I then run my variable speed fan on the furnace at a whisper.


 This in turn pulls air off the ceiling and back thought thr furance along with all the other returns throughout the house

 Good Luck

 

« Last Edit: June 03, 2008, 07:56:47 PM by Live6766 »

A6D9

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Re: ducting wood heat??
« Reply #10 on: June 04, 2008, 10:17:11 AM »
I did read your post, please don't be offended but this home is only a temp home and I can't really afford all the work involved with your set up.  I would love to do it that way.


I'm just looking at spending 100-200 for a stove and then doing the rest myself.  I allready have the selkert chimney, and will need to get some sheetmetal for a floor/ceiling/wall shield.


our plan is to live in this home for 2 years max and build up the hill on the back of the property.


once we build our plan is to do what nothing to lose suggested have the door to a back "woodroom" and the actual stove go thru the wall )be brick or non flamable) and the body of the stove be in the living space.


i really enjoy the heat of the stove beign in the room...radiant heat when restign or relaxing for en evening.


the convection heat is only good for my pipes to not freeze and for sleeping at night.


i never meant to insult you Roger...please don;t be offended I see the advanatge to your way.  but cannot justify it at the moment.  besides who wants to go outside in -30 celsius weather to put wood in the stove?  

« Last Edit: June 04, 2008, 10:17:11 AM by A6D9 »

RogerAS

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Re: ducting wood heat??
« Reply #11 on: June 04, 2008, 05:52:28 PM »
A6D9,


I am not offended. It's all sool.


I just think you should know, aside from the little pad, it took me all of one day to build the system. I already had the stove part but I figure I have $150 in materials including ducts. So a long weekend and this could be you. I have to really throttle back the stove as the natural convection really creeps up on you. Only when it's really really cold do I force air.


I said the same thing as you and it took me three years to get out of the RV/trialer.


Good luck, and hope your rows to hoe were easier than some of mine have been.

« Last Edit: June 04, 2008, 05:52:28 PM by RogerAS »