Woodchuck 2900

[jarvis]

Hi all,
I bought my first house earlier this year and am going through an extensive remodeling process. One of the upgrades was a dual heating system with a Goodman gas furnace and a Woodchuck 2900 wood furnace, both which were purchased new. I chose the Woodchuck because my parents have had a model 526 for over 25 years and have never had a problem with it. My house is about 2200 sq ft so I chose the model 2900 for its larger heating capacity, plus I liked the shaker grates and secondary heat exchanger.

Here's the issue:
My plumbing/heating contractor handled the installation and duct work and as soon as he looked at this furnace he's been all wound up about the secondary heat exchanger design. Anyone who is familiar with this model should know what it looks like. The opening for the heat exchanger pipe sits directly over the fire box, makes a 90 degree bend, then goes straight out the back of the furnace where the smoke pipe connects. He seems to think all the heat from the fire is going to funnel right out that pipe and up the chimney and has warned me several times I'm going to have fire going through and up the chimney as well. He's even shown it to several of the other contractors I have working as if it's some kind of novelty and they have jumped on the bandwagon too. Basically in their eyes this thing is going to be like a blow torch and is a chimney fire just waiting to happen. I've called the factory and talked to them and they assured me this isn't the case, but still I'm a little rattled by their taunting. Basically I'm wondering if anyone has experience with this model and can share what they know? How hot does the flue get, are they as efficient as the company claims, etc.?

One other thing...I installed all new Supervent 8" insulated pipe on the outside of the house with an insulated chase, so I should pull a good draft. The plumber handled this as well, but I'm not happy with the job he did. He set the "T" in cement, so the only way I can clean it out is by removing the pipe inside and raking the soot out through the opening in the basement wall. There isn't much room in the basement so in order to connect to the chimney I'm going to have to run two 90 degree elbows with a short section, maybe 2 feet of pipe between. Any problems with this setup? And does double wall insulated stainless pipe typically last a lifetime? I'm a little concerned with his choice of pouring cement around the T if it ever needs replacement.

 

[begreen]

Expert {def} - Ex = the unknown factor, xpert [pronunciation, spurt] = a drip under pressure.

 

[freeburn]

How long have they been selling these furnaces? And they haven't changed the design? Something must be right. . .

 

[jarvis]

I know...I said the same thing to my dad. I'd like to hear from someone who has one and their experience with it. My parents have the model 526 and are very happy with it, but it is slightly different in the design of the firebox compared to the 2900.

 

[Gooserider]

Hi all,
I bought my first house earlier this year and am going through an extensive remodeling process. One of the upgrades was a dual heating system with a Goodman gas furnace and a Woodchuck 2900 wood furnace, both which were purchased new. I chose the Woodchuck because my parents have had a model 526 for over 25 years and have never had a problem with it. My house is about 2200 sq ft so I chose the model 2900 for its larger heating capacity, plus I liked the shaker grates and secondary heat exchanger.

Here's the issue:
My plumbing/heating contractor handled the installation and duct work and as soon as he looked at this furnace he's been all wound up about the secondary heat exchanger design. Anyone who is familiar with this model should know what it looks like. The opening for the heat exchanger pipe sits directly over the fire box, makes a 90 degree bend, then goes straight out the back of the furnace where the smoke pipe connects. He seems to think all the heat from the fire is going to funnel right out that pipe and up the chimney and has warned me several times I'm going to have fire going through and up the chimney as well. He's even shown it to several of the other contractors I have working as if it's some kind of novelty and they have jumped on the bandwagon too. Basically in their eyes this thing is going to be like a blow torch and is a chimney fire just waiting to happen. I've called the factory and talked to them and they assured me this isn't the case, but still I'm a little rattled by their taunting. Basically I'm wondering if anyone has experience with this model and can share what they know? How hot does the flue get, are they as efficient as the company claims, etc.?

One other thing...I installed all new Supervent 8" insulated pipe on the outside of the house with an insulated chase, so I should pull a good draft. The plumber handled this as well, but I'm not happy with the job he did. He set the "T" in cement, so the only way I can clean it out is by removing the pipe inside and raking the soot out through the opening in the basement wall. There isn't much room in the basement so in order to connect to the chimney I'm going to have to run two 90 degree elbows with a short section, maybe 2 feet of pipe between. Any problems with this setup? And does double wall insulated stainless pipe typically last a lifetime? I'm a little concerned with his choice of pouring cement around the T if it ever needs replacement.

Not quite sure I get what you mean about the tee being set in concrete, pictures might help... I know the standard setup I've seen for outside pipes is to have a sort of shelf bracket on the side of the house that holds the tee with the side branch going through the wall (using the proper wall insulation adapter kit) and the bottom of the tee sticking out the bottom of the shelf with a plug cap on it. This allowed one to clean by removing the cap and either going up from the bottom or down from the top, and then just having the side branch to get from the stove end...

As to the flue setup, remember that every 90 reduces your effective flue height by about 5', and with what you are describing you'd have three 90's -two inside, and one outside at the tee. It would be better if you can do two 45's and a pipe length if you can... However if you have to do the 90's it should work, just not as well.

Gooserider

 

[jarvis]

Thanks. With the chimney, I had an old masonry chimney that we tore down, leaving the concrete footing which was below ground level and hollow inside. My basement walls only extend above the ground about 2', which didn't leave enough room for a shelf bracket with an 8" insulated pipe so the plumbing contractor set the T inside the old footing from the brick chimney and poured concrete around it.

Due to the location of the duct work in the basement, there really wasn't much choice as to where I could set the wood furnace. The only way I could have made a 45 fit would be to move the furnace to the center of the basement, which would be a pain to walk around plus require more duct work to connect everything. I'd rather not have two 90 degree bends inside, but I don't have a lot of choice. I'll try to take some pictures this afternoon.

 

[jarvis]

Ok, I took some pictures. As you can see there's really no other place I could have run the chimney because of window location, electrical service, and the roof from the addition. There was an old brick chimney in the same place which was torn down and replaced with 8" Supervent stainless insulated pipe surrounded by an insulated chase.

This is the concrete footing from the old brick chimney. The sides are about 3" thick and it was hollow inside, extending about 1 1/2' underground. The basement walls aren't high enough above the ground to go through the wall with a 8" double wall pipe and shelf bracket, so he set the T inside the concrete footing and ran a 1' section of pipe through the wall, then filled the footing with concrete. I'm not especially happy with that method, but I'm pretty much stuck with it now.

Inside, the Woodchuck connected to the Goodman gas furnace. Again, because of the location of the existing duct work there really wasn't any other place I could set it.

This shows the space between the furnace and chimney connection. There's really no way I can make a 45 degree elbow work, so I'll have to use two 90s.

And this is a shot of the inside of the wood furnace, the opening to the flue which sets directly over the fire. This is what set my plumber off, claiming all the heat will go up the chimney, I'll have fire going into the chimney pipe, etc.

Hope that helps make things a little easier so you have a better idea of the setup I'm working with.

 

[laynes69]

Theres no baffle below the secondary chamber opening? I guess if not thats where your draft settings will help keep everything inside the furnace. Do they recommend a Barometric damper for the draft? You would think there would at least be a baffle. I noticed your ductwork looks close to the joists above, and why not connect the furnace into the return? Or run returns for the furnace to aid in circulation.

 

[Gooserider]

Yes, I can see how you are pretty much constrained by other aspects of your setup, it does look like you did a good job overall... The only thing you might do on the connector pipe, and I don't know just how much help it would really be is to try and smooth out the bends as much as possible - for instance two 45's in a row is supposed to offer less flow restriction than a 90 - not sure if it would really help all that much.

Everything else looks pretty good.

Gooserider

 

[jarvis]

Theres no baffle below the secondary chamber opening? I guess if not thats where your draft settings will help keep everything inside the furnace. Do they recommend a Barometric damper for the draft? You would think there would at least be a baffle. I noticed your ductwork looks close to the joists above, and why not connect the furnace into the return? Or run returns for the furnace to aid in circulation.

No, there is no baffle. I admit I was a little surprised to see the way it was built too, but my heating contractor is the one who got all bent out of shape over it. I called the company and talked to a rep, he said it's still a controlled burn and there won't be flames shooting up into the chimney as the contractor seems to think. I had to order this furnace from the dealer so I wasn't able to actually see it until I picked it up. I just figured they've been building these things for around 30 years now so they must know what they are doing, although I do admit it looks like an odd design. I'm still hoping to hear from someone who has one to see how it works for them and how well they like it.
The company doesn't really say much about using an automatic damper. I bought a manual one to put in the pipe between the elbows and a magnetic flue thermometer came with the furnace, so I'll have to see how it works and adjust the draft accordingly. The cold air return is plumbed into the left side of the gas furnace. I suppose we could build a plenum and connect into that so it draws into the wood furnace too, but that would add a lot more clutter to it. I'll see how it works this winter, if anything I might hook up a fresh air inlet so it doesn't dry out the air so much.

 

[laynes69]

I hear they are well built, but its a poor design. It would have to be burned hot to keep the flue clean. Doing so will cause higher wood consumption if the unit doesn't incorporate heated secondary air into the firebox. Are you going to buy a Catalytic Combustor for the furnace? That would help, but not sure now long the combustor would last without a bypass. I'm sure someone who owns one of these furnaces can chime in on their operations.

 

[jarvis]

No, I hadn't planned on buying the catalyst. Meyer rates the model 2900 at 78% efficiency and 150,000 btu compared to the smaller model 526 which is rated at 65% efficiency and 120,000 btu. One of the selling points for me on the 2900 was the higher efficiency and secondary heat exchanger, but after seeing how it was designed I'm a bit disappointed. I hope it works because I've invested a lot of money into this setup.

 

[laynes69]

Makes me wonder where they get their numbers from. 78% theres no way. Not much of a secondary heat exchanger.Did it qualify for the tax credit? Maybe that 78% was with the catalyst. Keep us updated. Good luck.

 

[jarvis]

I'm not sure how they got that rating. My theory with the secondary heat exchanger is since heat tends to radiate upward, they are trying to radiate more heat up into the furnace plenum as the smoke and hot gases pass through the flue pipe. Whether or not it was designed with this in mind or if it actually works, I don't know. I'd still like to hear from someone who owns one...I'm starting to have doubts myself. I never asked about the tax credit since I'm already getting the full amount back through my windows.

 

[ccwhite]

Hi Jarvis,
I received your email. After reading your post and viewing your photos I understand what your asking. I love my Woodchuck. Don't worry about the contractor hassling you about the heat exchanger, It works fine. It is just a way to get the smoke out. The old potbelly stoves just had a hole that the smoke pipe hooked up to. The 526 setup while it has the slider it is still a setup where the smoke exits the firebox in almost the exact same spot and then travels across the top of the box to the stovepipe at the rear. The 2900 design does this with a pipe rather than the box as this allows the moving air to get all the way around the pipe to reclaim more escaping heat than it does on the 526 only hitting 3 sides of the box on top of the firebox. (I hope that all makes sense) If there were any extra risk of chimney fire from this setup I would have surely had one last winter. My chimney was almost completely obstructed and I was just getting used to the new furnace. I know I put some serious heat through that stovepipe a couple times getting used to how to fire and draft it. I swept my chimney now and it is clean as a whistle so I'm sure my few troubles I had last winter will now be gone. My house is the same approximate size as yours and you definitely picked the right furnace. I run my Goodman heat pump til the nights start staying in the 30s then the Woodchuck comes online. I have electric coil backup in the Goodman air handler and they only ever ran for 5 minutes during the install to make sure everything worked. Also I use NO smoke damper at all. If you read your owners manual they don't recommend it. The furnace is designed to control the draft, that is control the air flow not the smoke flow. I don't believe you're supposed to use those old stovepipe dampers on these modern furnaces.

You should have gotten a thermometer with your Woodchuck. It is to give you a temp reading on the stovepipe on the back of the furnace. It has a magnet and a hole in the center. Just stick it as close the the furnace outlet as you can where it still convenient to read and put a screw through the hole and into the stovepipe.

As far as the chimney goes. I would always try to steer you towards a new masonry chimney but I understand you gotta work with what you have. That being said. The stovepipe connecting the furnace to the chimney will not be that big of a deal to disconnect. During the off season every year just take your stovepipe off and reach in there (I believe your saying it is only about a foot to where it goes vertical) and clean it out with your shop-vac. And i wouldn't fret about the 2 - 90 degree bends in that little run of pipe. The furnace I had before the Woodchuck had 3 - 90s and about 9 feet of stovepipe inside. I was so happy when we set up the Woodchuck and only had 2 - 45s and about 2 or 3 feet of pipe. That Jackass that installed your chimney should have left it open to the old clean-out door. I just noticed the door in the pictures.

I have one question for you. I don't see any duct dampers. How are you keeping the air from one unit from flowing backwards through the other? To make my question clearer. I use a manual duct damper I put in the plenum just above the Woodchuck. This keeps the A/C from just blowing down through the Woodchuck and back to the return air duct. I take the damper out for the heating season (when the woodchuck is used) and put in for the warm weather. I have an automatic damper on the air handler to likewise keep the hot air from the Woodchuck from blowing down across the heat pump "A" coil and back through the return air duct.

Sorry if I got more long winded than you were looking for. Let me know if I wasn't clear enough on anything. Good luck with your Woodchuck. I'm sure you'll love as much as I love mine.

 

[jarvis]

Thanks for your response, it pretty much answered all my questions. I haven't installed any of the pipe inside yet, I'll just leave the damper out and see how it works first. I do have the magnet that came with it and plan on using that. Do you use the catalytic combuster?

There is an automatic duct damper located inside the plenum between the two furnaces. It's simply a door that flips either direction depending on which furnace is running. It's a pretty simple setup, my parents have something similar with their wood/gas combo and it works well. I don't know how much wood I'll be burning this winter, I've been so busy the past year working on the house that I haven't been able to get anything cut so it had time to season. I might buy a few cords of seasoned wood for the really cold nights (it's not unusual to see -20 here) and hopefully get some cut this winter to burn next year.

 

[ccwhite]

I think you'll be very happy with it. I love being able to just set the thermostat and it will run itself til it needs more wood. I do not use the catalytic combuster. I can't see that thing doing any good.

I would love to see a picture of how the duct damper to see how it works. My system works nicely but I can't help thinking that there has to be a simpler way. Yours sounds like it may be what I was trying to find but couldn't when I put mine in.

 

[lexybird]

im sure it works okay but it also surprises me theres no baffle seems very bizzare and i dont understand how they can reconcile this as efficient ? ,youd surely be sending alot of heat right out to the chimney without even having its secondary gases burned off first.
seems in alot of ways thats howan old barrel stove is - a 6 inch hole directly over the fire for flames to rush up through

 

[jarvis]

I would love to see a picture of how the duct damper to see how it works. My system works nicely but I can’t help thinking that there has to be a simpler way. Yours sounds like it may be what I was trying to find but couldn’t when I put mine in.

I wish I could take a picture of it, but it's inside the plenum so I can't see it myself without taking everything apart. Basically all it amounts to is a door that flops back and forth depending on which furnace is running. If the wood furnace kicks in, the air flow flips the door open so it can blow into the plenum of the gas furnace since the duct work is connected to that one. The door stays in this position as long as the gas furnace doesn't run, it doesn't have to open every time the wood furnace kicks in. Once the gas furnace turns on, the air flow catches the back side of the door and blows it shut again, closing off the air flow to the wood furnace. Picture it like this: When the wood furnace is running, the door would be in this position and if the gas furnace starts up, it blows it back this way / Hope that makes sense. The plumber who did the duct work made it himself, I would imagine anyone in the plumbing and heating business should be able to do something similar.

 

[laynes69]

I made one thats just like that for a few dollars. Works exactly as I planned. Its pre weighted and opens at the center like a butterfly. When the woodfurnace kicks on, the damper opens up it blocks the central furnaces plenum. When the woodfurnace isn't running and the central furnace kicks on, it closes the damper stopping the air from backfeeding into the furnace. When they both run, both sides open up. Works like a charm. Forgot to add I then positioned the fan limit below the damper. That way when the central furnace runs, it doesn't trip the wood furnaces blower. Mines a parallel install side by side.

 

[ccwhite]

So Jarvis did ya fire that thing up yet??

 

[jarvis]

No, not yet. I'm not in the house at the moment, still finishing up the drywall...then I need to get the floors, electrical and plumbing finished up. It's been a major project, I basically gutted the whole inside and rebuilt everything. I do have the gas furnace running so I can have some heat for the joint compound and paint...but I just turn that up for a few hours while I'm working inside. It'll probably be a little while yet before I'm settled in and able to test fire the wood burner.

 

[ccwhite]

Please keep us posted.

 

[jarvis]

It's finally going!
I went through a long mess of delays with contractors, trying to get everything done with the house and was finally able to move in two weeks ago. Because things kept getting pushed back I wasn't able to cut any wood this fall so I bought two cords of seasoned wood and brought it home today. I fired it up around 5:00 this afternoon and after about 1 1/2 hours it finally started to sustain a hot enough bed of coals to keep a good strong fire going. My flue temperature ranges from 275-350 degrees with the pipe damper wide open. I do see flames being drawn up into the heat exchanger a little, but I notice it more when I open the door which lets more air into the firebox and causes the fire to flare up more. So, I don't think the flames are normally going up into the pipe even with the forced air draft blower running...it seems to only happen when I open the door and give it extra air.

So far it's heating well. It took awhile to get the fire hot enough for the blower to stay running for more than a few seconds at a time. I started out at 59 degrees three hours ago and I'm sitting here comfortably in a T-shirt now. The only annoying thing is every time I open the door, the rope gasket falls out of place and I have to use a stick to poke it back in the groove. I'm hoping after a few heat cycles it will eventually set itself in place. I also had to play an exhausting game of smoke alarm tag. The new stove pipe going to the chimney gave off quite a bit of smoke until the coating got burned off. This of course was pulled into the blower and blown into every room of the house. My house has the alarms wired together in a network, so when one goes off, they all go off. Try pushing the hush button on one and within a few seconds a different one goes off and sets the whole system off again. I finally shut them all off until the haze cleared.

 

[Gooserider]

If the gasket doesn't want to stay seated, you could try putting a little bit of high temp silicone caulk in the groove before you put the gasket in. Then put a strip of aluminum foil over the gasket and close the door to make sure everything seats properly while the gasket goop dries. The tin foil will act as a "release" to keep any ooze out from gluing the door shut.

Gooserider