Looking at add-on wood furnaces

[blsnelling]

So you want to get a good eight hours of sleep.You are going a furnace with a firebox that will hold roughly 120 pounds of wood to achieve an all night burn.

What would it be at 20°? We see very little 0° weather here. Most of it's in the 20s and 30s.

 

[laynes69]

With the looks of your picture, the basement is partially insulated. You will get plenty of radiant heat from your ductwork and the furnace to heat the basement.

 

[laynes69]

Eric, I have a 3.5 cubic foot firebox that holds around 50 pounds of wood. I can get 8 hour burns without any issues. When its mild out, 10-12 hours isn't an issue. Thats the difference between the old and the new. Most woodfurnaces are around 6 to 7+ cubic feet.

 

[blsnelling]

With the looks of your picture, the basement is partially insulated. You will get plenty of radiant heat from your ductwork and the furnace to heat the basement.

That's a work in progress. I've made it about 75% of the way around the basement. I then intend to stud out the outer wall. I have no intentions to subdivide it. I'm also hesitant to put in a ceiling, since I don't want to prevent heat from easily rising through the floor.

 

[ericjeeper]

Eric, I have a 3.5 cubic foot firebox that holds around 50 pounds of wood. I can get 8 hour burns without any issues. When its mild out, 10-12 hours isn't an issue. Thats the difference between the old and the new. Most woodfurnaces are around 6 to 7+ cubic feet.

Now at the end of 8 hours are you down to clinkers and not making enough heat to cycle the blower? Or is there still enough juice at 8 hours to allow the blower to run?

 

[laynes69]

Yes I wake up with the blower running. With the secondary heat exchanger, it extracts more heat from the unit. I didn't think it was possible because my old furnace took a heaping load up to the baffle with double the wood and after 8 hours I had few coals to start the fire. I was suprised how well it did when I first woke up. The best thing about the furnace is it burns clean all through the night, so theres no worry for creasote buildup. Secondary combustion really extracts all the btus from the wood. Plus thats with the thermostat having the damper open in the mornings. If it had forced draft, the thing would be cold in the morning. Natural draft is much better than forced with the furnace.

 

[ericjeeper]

Yes I wake up with the blower running. With the secondary heat exchanger, it extracts more heat from the unit. I didn't think it was possible because my old furnace took a heaping load up to the baffle with double the wood and after 8 hours I had few coals to start the fire. I was suprised how well it did when I first woke up. The best thing about the furnace is it burns clean all through the night, so theres no worry for creasote buildup. Secondary combustion really extracts all the btus from the wood. Plus thats with the thermostat having the damper open in the mornings. If it had forced draft, the thing would be cold in the morning. Natural draft is much better than forced with the furnace.

your forced draft is a proven fact or an assumption? I know on my owb I use less wood with the blower than I did with a natural draft. I feel it is in part that the fire builds up faster and brings things up to temp quicker then shuts back off.

 

[CrappieKeith]

Now at the end of 8 hours are you down to clinkers and not making enough heat to cycle the blower? Or is there still enough juice at 8 hours to allow the blower to run?

Making statements like his are misleading...what size the home is will change burn times...so will many other items like how cold is it outside and how well is the home insulated.
What would be nice to know that you never hear is how many square feet of heat exchanger surface area is there?
How many lbs' of brick are there ergo thermal mass?

Stack temps do correlate in more or less heat availble in the home. The hotter the flue the less heat that goes into the home...there are only so many btus per lb. of wood.

Heck I can get 10 hours in 30 below zero and my home is at 72.
If I want I can get 20 hours, but my home will be 60.
1400 s/f

 

[laynes69]

I dropped 2+ hours from my burntimes when I used the forced draft then without it. Others with them will say the same thing. Manual draft or natural draft won't force feed the fire. I wouldn't have a fire in the morning if I had one. Especially considering my firebox size. My furnace now produces more btus an hour due to the way it burns. So I don't have a call for heat like I did before. An owb is made to shut down the fire and revive it, where my furnace won't shut down. Take 2 pieces of wood and light them. Then place a fan on one and see how long it burns with the fan on it, compared to without it. Your natural draft on the owb doesn't do well because the fire can't produce enough btus to keep the call for heat down, so it needs the assistance of the fan. So with my personal experience, I seen a difference. It would be nice to see if a study was done regarding this.

 

[ericjeeper]

I ahree about the study. But it is like Keith says., To many factors to likely get any definite concrete results. Or at least results that would work in your basement then the next guys.
On an owb you basically want the fire to die out. Otherwise they will run away. Where as in a house worse thing could happen is the house get to warm.At least it won't boil over. LOL

 

[laynes69]

I wish I had a 1400 square foot home to heat, but ours is much bigger. Climate has everyting to do with a homes heating, plus its tightness and insulation. I live in the same state as the poster, I have more square footage and some good areas of heat loss which we need to fix. 42 windows doesn't help either being the amout of glass in the home. My furnace keeps our home warm.

 

[blsnelling]

I just made an amazing re-discovery. In the back of my mind, I thought there was a dead corner somewhere in my house. I went looking for it. It turns out that I will be able to run my chimney pipe straight up through the floor and then the roof! How's that for good luck?! It also looks like the 16' of pipe I bought today will be enough. The wood furnace will be able to set right beside the gas furnace.

I'll be able to plumb the cold air return directly into the houses cold air plenum, right before it goes into the gas furnace. I still don't understand why I can't put an insullated block off above my A coil, behind where my humidifier currently is, and plumb the hot supply air right into my existing plenum, and use the current central ac fan. If not, please help me understand why not. I have no problem having to remove it each spring.

 

[flotek]

Your natural draft on the owb doesn't do well because the fire can't produce enough btus to keep the call for heat down, so it needs the assistance of the fan. So with my personal experience, I seen a difference. It would be nice to see if a study was done regarding this.

right and also we gotta remember an OWB has a very short stack in comparison to an indoor woodstove in the home so the flue draft effect isnt there which i m assuming plays a huge part in why they need forced draft. ,kinda like a lazy campfire heating a pot of water

 

[OhioGregg]

Brad,
I am no expert or even a think I know what Im doing guy when it comes to this stuff..LOL I can tell you how ours works. The wood furnace sits next to the LPgas furnace/Central Air unit.
The cold air returns go to the gas furnace, then right after it exits the fan, goes into the warm air ductwork. There is a couple of air diverter gates, (don't know proper terms for them) that you turn when your going to use the wood furnace. They direct the air down and into the wood furnace, and exit the top of the wood furnace directly back to the warm air duct work.

This old house is approx. 1300 sq.ft. We have added new windows, doors, over the years, with some blown in isulation. There was absolutely none before. Two story, with small rooms upstairs. Only one heat vent going up there. In the basement, cellar is better word, its unfinished, with a block wall and door to the wood/coal room. On the other side is small food/can good room. The rest is crawl space.

The wood furnace giving off some radiant heat, keeps it quite nice down there. No heat vents down there at all. Im sure your house will not be a problem. I usually put 3-4 chunks of wood in right before I go to bed, usually around 11-12:00pm. Usually get up anywhere from 5-7 am. The fan will be running, the temp dropped a couple degrees, but far from being cold.

I remove some ash, rake the hot coals around, add wood, and in a few minutes its cranking out heat again. I have the gas furnace set to come on if it drops more than 5 degrees, so far it hasn't come on at all, that I know of.

When the T-Stat calls for heat and fan kicks on, the auto draft damper on the wood furnace opens and the fire is burning. When it kicks off, the damper closes down, and knocks the fire down, so to speak. The fan on mine usually will come back on and run briefly, then stop. Then come back on briefly again. Does this several times, till the heat in the wood furnace has subsided sufficianty. By the preset on-off temp setting on the fire box enclosure.

Long story short, LOL I don't see why you can't in some simple way, direct the airflow from your existing fan to pass through your new wood furnace. Theres obviously some technical issue I'm not grasping.
Seems to me a wood furnace would heat your house nicely, whether you use exisiting fan or add on blowers, either way.

Anyway, this has been an interesting thread to follow. and will continue to follow.

Good luck with this adventure!!

Gregg,

 

[OhioGregg]

The burning of wood does not lend itself to having the air closed off as a method of controlling heat output. What you get is a smoldering, inefficient polluting burn. The more advanced wood heating systems burn at a constant rate and achieve high efficiency and low emissions. The heat is directed to a heat storage system to be called upon later when the heated space has demand. OWB's usually function the same way......by shutting down the air...hence their rep for high emissions. Users of indoor wood stove can also burn inefficiently if they try but the modern indoor wood stoves only allow the air input to be shut down so far.

Whole house furnaces have been exempt from EPA regs for some time but one day that is going to come to an end. Had they had to meet the emission standards for indoor stoves most would have been taken off of the market by now.

TreeCo, I won't argue with anything you had to say. Was just trying to explain in laymans terms, the way the OLD furnace I have works.
Or, at least as I percieve it to work. And, work well it does. Don't know if the EPA loves it or not. The one we have, must have been installed in the 70's.
I'm sure the newer high end models of now days are much better.


Gregg,

 

[OhioGregg]

Hey Gregg I quoted your post but I was really talking about wood heaters in general. I didn't mean to sound like I was picking on you....sorry about that, it was just a general rant on the subject.

No Problem at all TreeCo.

Was just trying to give Brad a little idea and perspective on way some furnaces are set up and run. I would love to have a NEW one, but as long as the old girl still puts out, will be keeping her!

Did have to replace the damper motor on it this winter, That is an expensive item...was like $300+ yikes!!.


Gregg,

 

[blsnelling]

I just made an amazing re-discovery. In the back of my mind, I thought there was a dead corner somewhere in my house. I went looking for it. It turns out that I will be able to run my chimney pipe straight up through the floor and then the roof! How's that for good luck?! It also looks like the 16' of pipe I bought today will be enough. The wood furnace will be able to set right beside the gas furnace.

I'll be able to plumb the cold air return directly into the houses cold air plenum, right before it goes into the gas furnace. I still don't understand why I can't put an insullated block off above my A coil, behind where my humidifier currently is, and plumb the hot supply air right into my existing plenum, and use the current central ac fan. If not, please help me understand why not. I have no problem having to remove it each spring.

Now that I'm going to be able to go straight up, I've got some more learning today. What bears the weight of the chimney, since there's no bracket bolted to the wall for it to set on? Does it just rest on top of the stove?

 

[CrappieKeith]

Now that I'm going to be able to go straight up, I've got some more learning today. What bears the weight of the chimney, since there's no bracket bolted to the wall for it to set on? Does it just rest on top of the stove?

Selkirk makes a support heat shield that can hang like 40 feet of pipe.

 

[blsnelling]

Selkirk makes a support heat shield that can hang like 40 feet of pipe.

Got a link?

 

[Streblerm]

Got a link?

I've been meaning to post this for days, but yahoo won't find the selkirk website, I had to go through Google. The payment must be late.

Anyway, Lowe's had the best price. I don't love buying stuff there, but they were half of what I could get the chimney pipe for from anyone else. The "supervent" from Selkirk is only sold through lowe's and it isn't compatible with other brands, or even other chimney pipe from selkirk. This means you need to buy all the pipe from one location.

The kit at lowe's should have everything you need, minus the actual pipe, to support 50' of pipe, connect to stovepipe, chimney cap, flashing, tee, 90 (for wall app) and thimble, I believe. There is one that is for through the ceiling and one for through the wall. the wall is a little more$$

It doesn't matter if it is double or triple wall as long as it is rated
UL-103 HT I prefer double wall since it takes up less space.

You can use whatever stovepipe you want in the house. Any stovepipe will hook into the supervent chimney. Keep in mind that single wall needs 16" clearance to combustibles. The stuff that lowe's has seems chincy. I spent a few extra bucks and ordered double wall stovepipe from lowe's. They can order anything that supervent makes.

Check the "view documents" sections for literature, catalog, and planning guide. The "venting" section has all the stovepipe.

http://www.selkirkcorp.com/supervent/product.aspx?id=220