Wood Furnace Ducting Clearance and 6" SS flex liner install

[glenn1179]

This is my first post, but I have been lurking for a while gathering information to see if I would like to put a used smoke dragon furnace in the basement of my first home. I am looking to find a used furnace and connect to the existing ducting for my NG furnace. I have a 7x11 clay lined brick chimney that goes up the center of the house. I will put a liner in there. A 6" will be a tight fit, and using the insulation wrap will be impossible unless I get it ovalized and I am still not sure if that will work. Ovalized liners are pricey. Has anyone gotten the round liner and tried to ovalize it themselves? I heard about the pour down liners. Can a chimney balloon be used with that to stop it from filling all the way down to my old clean out. If I decide to pull the liner later, is that an option with the pour down?

The concern I have with ducting clearances is that the manuals I have read for different furnaces give different clearance requirements. Most agree on 18" the first 3 feet, 6" for 3-6 feet. Then they vary between 0 and 1" after 6 feet. All of my existing ducting is tight against combustibles. I figured I could get around the first 6 feet requirements by taking a round about path to get to the NG furnace plenum. Is the 1" of clearance beyond the 6 feet something that can be played with? I was looking at a few Yukon Jacks and WoodChucks, but they require a 1" clearance. The DAKA furnaces do not.

I have about 1300 ft1.5 story home with a full basement that has 1" foam on the block walls. It was built in the 40's and has good southern exposure once the leaves fall off the maples in the front yard. I am not considering a stove on the main floor at this time because I haven't found a way to make it work with the current floor plan and I am trying to get this done on a tight budget. (Ideally do the whole thing for under $2000.)

Thanks,
Glenn

 

[ikessky]

I've heard of people ovalizing the liner themselves, but have never tried it personally. If you are thinking about removing the liner later, you could use perlite or vermiculite as insulation. The dry mix won't set like Thermix or similar pourable insulation.

Not sure what to say about the clearances. Maybe a local HVAC guy could answer your question?

I've had good luck with my Daka. Just make sure you use dry, seasoned wood to make sure your not filling the liner with creasote.

Finally, where in Northcentral WI are you from?

 

[laynes69]

You will run yourself out of the home with a woodfurnace, especially if its a tight home. If your current liner isn't in bad shape, you may look into a 5.5" liner. With it being an interior chimney, you wouldn't have to insulate. Most newer furnaces require 6" for the first 6' then 1" after. The older furnaces like the yukon require 18". Adding spacers and sheetmetal will bring down the clearances some. Good luck on whatever you choose.

 

[glenn1179]

ikessky, I am in the Rapids area, but get up to Wausau frequently. You? Know of any good local HVAC guys you'd recommend?

laynes69 - I am working on tightening the home up. I don't think it is too bad right now, but an energy assessment is on the list of things to do. Do I have any other options to burn wood other then a furnace in the basement? My stairwell goes into the attached garage and from what I have read, using the stairwell is basically your only hope to get heat up to the main floor from a stove in the basement. Getting a stove on the main floor would probably put this out of budget for this year if I need to bust a wall to install a thimble and build a hearth in addition to getting the war department to ok a stove in the kitchen on the main floor. My current liner passed an eyeball check by the chimney sweep other then the clay tiles stopped about a foot above the thimble I wanted to use. His suggestion was to bust out the clay liner to make clearance for a 6" liner. He hadn't ever ovalized a liner and didn't know if could be done to the extreme needed to allow for clearance in this chimney. (That reminds me he said he was going to follow up with me and never did.) Now that I think about it, I would probably need a 5.5" liner to even get down the chimney because of the mortar and stagger in the clay tiles. I bet I couldn't even wrap the 5.5" with 1/4" insulation and get it down without tearing it. If my existing tiles are ok, would an uninsulated 5.5" liner be up to code? The 1" ducting clearance requirement after 6' is the requirement I am concerned about. This means I would have to redo the ducting in the entire house because all of mine is tight against combustibles.

 

[ikessky]

I'm still about 1 - 1.5 hours north of you! North of Medford yet.

What layne was talking about is that the furnaces you had mentioned would be putting out too many BTUs and you would end up with an 80+ degree house in a hurry. Trust me, I know. I installed my Daka before I really even did a BTU needed calculation. My current natural gas furnace is only like 65,000 BTUs. After looking into all of this, I realized that I should have gone with a Mini-Caddy or a Yukon BJ-90. Both of these units also have a secondary burn system which will keep your liner cleaner and your burn times longer. The problem is they are both over your $2000 limit. However, from what I can tell, wood furnaces are kind of a "you get what you pay for" deal.

CrappieKeith is a member here that works for Yukon-Eagle. He is a wealth of knowledge and a really nice guy on top of it all. From what I hear, their furnaces are built like tanks. The Mini-Caddy is really appealing to me because of the glass viewing window though. I think I would like to see my second burn in action if my stove was cabable of it.

 

[glenn1179]

I was just through there last weekend when I went up to Spooner.

I thought the Daka was in the same BTU range roughly as the BJ 90? I haven't found much smaller units (used) that are add on furnaces and not just stoves.

I have spoken to Keith a couple of times already as a couple of the used units I have looked at have been Yukons. I guess I can ask him about the ducting issue and if a 5.5 liner would be acceptable in my situation.

 

[ikessky]

The Daka is rated at like 40K - 105K, while the BJ-90 is rated at 50K-90K. I'm guessing you can get the Daka in the 40K range, but that is if you are burning soft wood and at that point, you'll be loading every 2 hours!

I'm certainly not trying to sway you one way or the other with the furnace. I've had good luck with my Daka and I'm going into my third year. Being a little oversized for my house, I have to let the fire go out more often than I'd like, but I guess that's the price you pay sometimes.

 

[laynes69]

With your square footage, almost any woodfurnace will be way too much. If its grossly oversized, you may find yourself either letting it burn out, or slowing down the fire to keep the house comfortable. I personally wouldn't get the Bj90 only because when there isn't a call for heat, the units not made to burn cleanly. On the other hand a EPA unit will burn much cleaner and give you more for your amount of wood. The mini caddy from what I have read has a average btu rating of about 41,500 btus an hour. That would be more than plenty, with a max output of around 64,000 btus an hour. I know from our Caddy when the call for heat is met and the damper closes, the unit burns cleanly eliminating creosote. The only issue would be the budget, but I would look into that or a EPA Certified stove. Having an insulated basement may make that more of a possibility, maybe check in the stove room and see what they say. I wouldn't say so much about the mini caddy, but with us having its big brother its a good furnace. Getting something that is sized properly and is EPA certified will make things much easier. Of course its easy to spend others money and when your working on a budget its understandable. A furnace that I think is of better quality than the daka thats budget friendly is the englander that is sold at home depot and other stores. Seems like a good bang for the buck. As for the 5.5" liner, Our furnace has an input rating of 140,000 btus and our 5.5" liner handles it fine.

 

[glenn1179]

Thanks for the responses. I have done a little leg work on my own and wanted to post back with what I found for future searchers. I emailed Keith at Yukon-Eagle and he stated the 1" duct clearance requirement is only necessary until the ducting makes a 90 degree turn. I looked at the NFPA code (since Keith said that is what they use) and confirmed what he said was true. (Future searchers beware that there are variances in the code for different qualifications of appliances so look up the specs for your specific style of device.) I would never have guessed this based upon the manuals I read. This makes overcoming the duct clearance issue as simple as running the duct for at least 6' with the 6" clearance and making sure there is a 90 degree turn in it after the 6' and before it connects into my existing ducting that is tight against combustibles.

The next challenge is that to properly line my existing chimney will essentially eat-up all of my $2000 budget. The quote below doesn't even include the insulation wrap that I will need to make it up to UL specs. (I am not sure my existing chimney is up to class A chimney specs, so insulation is required for the flex liner with wood burning appliances in that case.)

Rectangle Flexible Chimney Liner Kit
316Ti Stainless Steel - Custom Order
Liner: 35 ft. of 4x8.06 liner at $36/ft. ($1,260.00)
Top Plate: Rectangle Terra Cotta TP 8x13 ($134.99)
RainCap: Yes ($139.99)
Connector: Rectangle T ($214.99)
Snout Dia: 6"
Rectangle to Rectangle Connector: Yes ($104.99)

Anyone have suggestions on how to cut the cost? Otherwise, this project will be on hold until I get funds, which of course will be harder to do since I will be paying a fuel bill to heat the house for the next 5 months. Life is a series of catch-22's. Perhaps I will have to price putting a stove on the main floor a little closer since it will drop the liner costs.