Woodchuck 4000 placement and chimney

[cstamm81]

I know my Woodchuck is a furnace and not a stove, but I am using it as a stand alone unit not connected to duct work, so I thought I would get better responses here. I bought this at the end of last year used. It has an auto draft blower controlled by a thermostat. I installed it and ran it the last two months of the heating season. I had quite a few draft and creosote issues requiring frequent chimney cleaning.
I have a plethora of questions so please bear with me. I have a 7" chimney liner installed into an exterior masonry chimney. There is no insulation between the liner and the chimney block, and very little room to add even a pour down insulation. Plus I just found out my liner is only rated for wood and not coal. It looks as if trying to salvage what I have may be a waste. So that leaves me installing a new 8" Class A double wall chimney. The manual for the Woodchuck asks for a 20' or greater chimney. It looks as if the online retailers want about $2600 for a through the wall all inclusive kit. Anyone know of a place to get better deals? I'm having a few installers quote it out, but I highly doubt they will be able to install for close to what I can buy and install myself.
Is it easier to run the Class A inside or outside the house? It seems outside would be a lot less work. I ask this because I had considered moving the stove closer to my basement stairs so the heat would be blown directly up the stairs, losing less in the basement.
Last, this thing is obviously designed to be used with ductwork, supplies and returns. I have an oil burner with metal ducts, but space and duct clearances will not allow me to install the Woodchuck this way. Thus I am left with a stand alone install, just dumping hot air into the basement. How can I supply return air, or makeup air in lieu of ductwork? I had seen users of other furnaces supplied outside make up air via a PVC pipe. ANy ideas or suggestions for this type opf setup are greatly appreciated. I don't have a ton of money to dump into this, but I need to do it once and do it right.

 

[Grisu]

Since it seems as you will not be able to install the Woodchuck for its intended use, why continue throwing money at an unsatisfactory solution? Chances are that even after following through with your planned modifications the Woodchuck will still not run well nor give you the heat you should be getting. For that kind of money and work you could install a freestanding stove like the Englander 30NC upstairs which should heat about 2000 sqft depending on insulation and climate. Get it right once and you will be saving money in the long run.

 

[begreen]

Agreed. This could be an exercise in futility. Before proceeding, can we start by first by posting some pictures of the existing furnace and trunk ductwork? And then of the proposed location for the Woodchuck? Without ducting you may end up burning out the motor due to lack of static pressure. And the unit will just be heating a short loop of air from the Woodchuck supply right back into its return. There has to be a better way. What about putting in a stove upstairs instead?

 

[cstamm81]

I will get some pics up here shortly. I have tried quite a few different stoves and now 2 furnaces down in the basement. I have always been able to heat my house this way, but not without a ton of wood consumption and it was always hard to get the house to a comfortable temp. I guess when I was a little younger I enjoyed experimenting with different stoves and setups. Now I just want to do it right. My house is a ranch, about 1200 square feet of living space. There is very little insulation in this place. I am getting 8" of cellulose blown in the attic in the next few weeks. My walls are cinder block from the basement up to the gable ends, which are then framed out. There is no insulation in the walls at all, save for whatever r value you get from a block wall, multiple lathed layers of old drywall and wood paneling, and now new drywall on top in some rooms. I am trying to do what I can on the insulation front, but I cannot afford to gut the perimeter walls and I cannot afford to have someone spray foam the whole place. The basement is half underground and half above ground. This is another reason it's very hard to even heat from the basement, the exposed block walls acting as heat sinks.
I do like having a heated basement, as I do work down there in a shop and I am creating a living space down there as well. I have always wanted a nice EPA stove on the living floor, to have a nice warm area to relax and the ambiance of the fire. The more I think about it, a nice EPA stove on the living floor and perhaps a used coal stoker in the basement might be a nice setup. I could probably reline and insulate in 6" the existing chimney for the stoker AND install a new 6" Class A for an EPA stove for about the same money as installing a new 8" class A for the Woodchuck.

 

[cstamm81]

Edit, my house is 1800 square feet of living space plus an equal sized basement, not 1200. Here is a crude drawing of my current oil furnace and Woodchuck furnace. Red are supply lines from the oil unit and blue are cold air returns. There is no room for a chimney to install the Woodchuck next to the oil unit. Plus, the duct clearances to combustibles are not great enough for the Woodchuck, as the oil burner requires smaller clearances. I have back-fed the duct work from the end the Woodchuck sits at (oil burner switched off at breaker). Far from ideal or meeting code but it did work. I unhooked it and just dumped heat in the basement and it also worked ok. I had thought of installing a separate duct system just for the Woodchuck, but I have little head room so as it is and it would get pricy. If there were a proper way to use it without duct work I would be interested. With a little insulation in the basement and more in the attic I am certain this could easily heat my house as is. The basement is walkout with a garage door so I bring apple crates of wood in on a pallet jack. It's a nice setup as far as wood handling and storage.
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[cstamm81]

Pic of oil burner. Excuse the mess I have a lot of remodeling going on. WoodChuck is directly behind me when taking the pic. Shows the wall with doorway and the main trunk line.
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[cstamm81]

couple of the Woodchuck installed and the Woodchuck's lined chimney.
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[cstamm81]

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[JonOfSunderland]

I used to rent shop space in a big drafty old barn and a Woodchuck 4000 was the only heat source. Very very inefficient. Don't believe the 80% number the manual gives. I'm sure that's heat transfer efficiency alone. That thing has no secondary combustion system or even a baffle. It has the option for a cat but it literally sits right at the top of the firebox above the flames in the outlet pipe. I can't imagine it lasts too long. Coal, fine. Wood, there are much better options.

Like yours, there was no ductwork. I simply fashioned a plate to fit on top of the furnace and put some 8" 90° elbows in place so the air wasn't being blown straight up but rather to areas where I was working. The return just sucked surrounding air.

You mentioned you had draft issues. You shouldn't be having any since it is a forced draft furnace. Have you gotten the hang of how the draft blower control works? It has a feature where the draft blower will turn off automatically when the fire dies out. There is an override that must be turned on when starting a fire cold. Then once the unit is up to temp, you turn off the override. This is completely separate from the circulation blower.

 

[cstamm81]

I actually have a top box I made that has 8" 90 elbows on it as well. I agree it is not efficient, but I do like the unit. Have not tried coal in it yet but would like to, I have heard good things.
The manual states it needs ducted return air. My house and basement are so drafty I know I get some make up air. I wonder what would happen if you brought in ducted fresh air from outside? It would be pure cold outside air so probably a poor idea.
My draft issues are related to my 7" chimney liner, not the forced draft settings. Food idea though, they did take a little bit to figure out. I know there are better wood furnaces and better setups. The thing is I got this for a good price and do like it. If there is a fairly economical way to use it properly and safely I will run it for a few years.

 

[begreen]

The pictures help, I wasn't sure if this was already installed or not. The clearance for the trunk duct doesn't look that bad. What is there now at the trunk end above the Woodchuck, 4-6"? If so, I would put either a heat shield on spacers like you did for the flue or a double layer of durock NexGen cement board, over the first 4 ft of the plenum connection there. Is there a back draft damper installed in the oil furnace plenum?

 

[JonOfSunderland]

You're confusing outside combustion air with heating zone air. You never bring in outside air for circulating through a heating system. That would essentially negate insulating your house. If you're going to continue simply heating the surrounding air in your basement, there's no reason to duct return air from anywhere. Just make sure there's a filter on the return box behind the furnace. It's just like having a circulating blower on a wood stove. You're just moving air around.

 

[laynes69]

From the pics, you weren't using the heat exchanger for the flue, or the barometric damper? With the furnace having a basic firebox design, draft shouldn't be an issue. A 7" liner should be fine for a furnace like that, it's things like the flue heat exchanger or barometric damper on a shorter chimney will cause all sorts of problems.


What model is your woodchuck?

Insulation will put you in the right direction, but could make the operation of the furnace more difficult as far as temperature control and creosote accumulation due to a reduced heating demand. If the woodfurnace proves to be too much after upgrades, then consider a smaller more efficient woodfurnace, or wood stove.

 

[cstamm81]

begreen, I may be able to get the proper clearances with a heat shield, I will have to take measurements tomorrow. There is a section of the main trunk directly in the middle of the trunk length where it passes through a doorway in the wall that separates both sides of the basement. This small section is touching wood framing, the truck sits directly below the 2x6's. So there is zero clearance there, doubt it meets code. Probably cannot get hot enough to do anything that far from the oil burner and the Woodchuck though.
The issue still is that I am feeding the duct work backwards, directly across the house from the oil burner. When I hook it up this way I turn the oil burner off at the breaker. The biggest problem is little airflow out of the registers as the ducts have scoops inside of them where they meet the trunk to scavenge air from the oil burner. I still can and have heated this way with this and with an Englander add on. I do not have a backflow preventer for the oil burner. I did put in a removable block off plate to stop most of the air from entering the oil furnace. I installed it in the main trunk right off of the oil burner. The issue with this is there are two supply ducts that come from the rear of the oil burner. When I use the block off plate no heat gets to those ducts. With the block off plate out, those ducts get heat but I know I lose a lot as I am now pumping heat into the oil furnace and out the filter box.
I actually did best using the Englander and backfeeding the trunk. But, I was over firing that unit to heat the house on cold days. That's why I went with the Woodchuck when I found it, figured the extra BTU's and auto forced draft would do better. But, my flue temps rarely go above 400 with the Woodchuck, where I would routinely hit flue temps of 800 (and I hate to admit higher). This is mesured with an internal probe about 12 to 16" above the furnace collar. This also why my uninsulated chimney liner now gives me more creosote, with the Englander I was burning it so hot it was keeping it clean. With the Woodchuck and it's low flue temps, the creosote never gets burnt out.

 

[cstamm81]

JonOfSunderland, agreed I did confuse return air with combustion air. There is always a filter on the return box. In your opinion, there is nothing wrong with running a furnace like this? Simply dumping the hot air in the basement and using the same air for the return box? The manual for the furnace states it needs a certain amount of static pressure in the supply ducts and for a cold air return to be hooked up. But I agree with what your saying, I'm just using it like a stand alone wood stove with a blower, my blower just happens to have a huge CFM rating.

 

[begreen]

You only need good clearance for the first 4-6 feet depending on the furnace, not the full trunk duct. After that the heat starts dissipating rapidly. Review the installation manual. For your air flow issue maybe try pulling the oil furnace filter and putting a block-off in it's place. Put a big warning sign on the furnace switch to remove this block-off if you do this.

In the meantime I would have an energy analysis done on the house. It sounds like there are some major heat loss situations here. How many sq ft total are being heated? What is the Englander stove model and where is it located?

 

[cstamm81]

laynes69, good eye. No, that damper and the heat exchanger was from my early stove installs, messing around with configurations. Those items are for sale and were never on the Woodchuck install. I have the model 4000, the biggest one they make. Rated to do 3600 square feet. Here is the manual if anyone is interested: (broken link removed to http://www.meyermfg.com/library_manuals/WOODCHUCK__3__8-07-12.pdf)
The guy i bought the Woodchuck from was very knowledgable and particular. He told me he had spoken to Meyer Mfg about using the 4000 with a 7" chimney. He was supposedly told it is fine as long as you can get proper draft. It drafts pretty well with a freshly cleaned chimney, but once the topf of the liner and cap get a little buildup I get smoke out the loading door. I had considered adding another feew feet of chimney, not sure if I could even adapt from 7" liner to 7" double wall class A.
My creosote is almost all in the last foot of the chimney and the cap. I believe the cap is a POS, and a more open cap would help. Also from my reading today on here, it appears I could take Roxul insulation, break it up, and stuff it down next to the liner to get some insulation in there. This might help a good deal if I can keep the last few feet of liner warmer. I cannot fit in wrap insulation, very little clearance between liner and inside of block. There is no clay liner, just regular chimney block with about a, 8" hole forming the masonry chimney. I'm also hesitant to do a pour down insulation, as who knows when I will need to replace the liner.
And even if I do all of this, should I be able to get it insured? An 8" furnace feeding into a 7" liner? Then the fact that I'm either back feeding my duct work, or just using it as a stand alone wood stove. I feel confident I have the proper precautions in place to prevent from burning my house down, but I don't know if I can ever make this install up to code.

 

[cstamm81]

begreen, the manual has this for clearances, and it's confusing. The plenum has to be 20 x 23" and no less than 18" high with an 18" or more clearance to ceiling. But, it then says for the model 4000, there only needs to be 4" from top of plenum to ceiling. Then, it has a NFPA recommended clearances picture. It shows 18" from duct to ceiling for first 3', 6" for the next 3', then 1" for the remaining. It definitely contradicts itself with the 4" from top of plenum then 18" from top of duct.
Is there anyway to get a cheap or free energy analysis that you know of? I am certain I have major heat loss going on here. Given the setup of the house, there really is only so much I can do as tackling the walls would be a gigantic project and tons of $$$. The Englander is gone, I had it installed in the same place as the Woodchuck is now. I have 1800 sq ft upstairs. There is no insulation in the ceiling of the basement. So, if using the ducts I am heating a poorly insulated 1800. If dumping in the basement I am at 3600.

 

[begreen]

If the first 6 ft is shielded their needs are satisfied. 18" seems a bit over the top. Yukon suggests 12" I think.

There definitely seems like major heat loss going on. What is the Englander model you are referring to and where is it located?

 

[cstamm81]

I will measure the existing clearances from duct to ceiling tomorrow. I forget what the ratio is when you use a shield, is it the same as when using a shield for flue pipe? I HAD an Englander 28-3500 add on furnace, I sold it when I bought the Woodchuck. I wouldnt mind one of the NC30's on the main living floor. In fact, if I can find an affordable, safe and insurable way to keep the Woodchuck going in the basement, I may put the saved funds towards a setup on the main floor. I could easily (minus going through the block wall) install 6" class A myself, and it's decently cheaper than 8". Would be a short chimney too. If I could find a stove with the right rear and side clearances, I might not even need wall protection, just a hearth pad.

 

[begreen]

I would invest in an energy audit. It should be well worth it. Then invest in sealing up the leaks they find. That may have the quickest payback.