Chimney Size

I am in the process of researching coal burning. I have picked up a lot of usefull info from reading the different postings. At tis point in time I think that I have settled on the purchase of the Hitzer 503 fireplace insert unit. I have one concern from reading information on cimneys, my chimney on my fire place is in excellent condition and is about 30 foot high. It is formed in a 12 inch square, do you think this will creat a draft problem as I read in the forum info that an 8" chimney is ideal.

Bob
Mohegan Lake, NY

Is the chimney on the inside of the home all the way to the roof? If so you might get away with it. If it is an exterior chimney, probably not. In either case, it would be better to match the flue size to the stoves vent size. I just helped a friend yesterday install a 6" liner in a 12x12 flue for a coal stove. It wasn't too bad except we had to cut out part of the metal damper housing to get the liner through.

Coalkirk is right on the money here.

The fire place is located inside my living room on an outside wall and he chimney runs up the outside of the house. Does metalabestos liner have to be used or is the plain 6" metal liner OK.

Thanks Bob

Bob,

Not metalbestos. It's a flexible 316ti stainless steel material. My friend bought his on the web. I think the place was called Rockwood. For a 30' length, your're looking around $500.00 or so. With the insulation kit, add another $300.00. the kit includes the top and botttom connectors.

Terry

Will stainless steel hold up better that galvanized due to the corrsive nature of coal.

Bob

Yes it will. The 316ti has titanium in it which apparently is the best for coal.

The bigger the inside measurements of the chimney the more draft you'll have, if the your measurements are 12x12x30 that will give you more draft then a 8x8x30. Also if your liner isn't in bad shape I would use what you have, the only problem you may have is too much draft but I would error on the side of risking to much save some money and invest in a good damper.

U235a4 wrote:The bigger the inside measurements of the chimney the more draft you'll have, if the your measurements are 12x12x30 that will give you more draft then a 8x8x30. Also if your liner isn't in bad shape I would use what you have, the only problem you may have is too much draft but I would error on the side of risking to much save some money and invest in a good damper.

Don't jump to conclusions. Trying to keep that big chimney warm and drafting will be a hard task when using a stove. Really hard with an outside chimney and trying to run the stove at a low setting. You would be better served with the same size flue that you have on the stove.

Gambler is right.
It's best to match the flue size of the appliance.

While a 12x12 flue can handle more volume than an 8x8 the draft will be limited by the appliance connected to it. Think if it like water pressure through a hose. If you have a small diameter hose (with a certain water pressure) then connect it to a larger one, what happens happens to the pressure coming out the end. You'll have less pressure and slower flow than you had in the smaller hose. It's the same with a chimney, the flue gases would slow down and cool once they enter the larger flue and this is not what you want.

Connecting the stove to this exterior oversize chimney would most likely draft poorly and possibly cause CO problems in the home.
Also, like Gambler said, it would take a lot of heat for this chimney to have good consistent draft.

Gambler, Rockwood
To a point your both right and both wrong but I'm not getting into a dispute over something trivial but in general a larger size flue will always have more draft then a smaller one even with out a heating appliance running and this is because it can more quickly exchange the hot air from the house to the outside. now for the case here you can safely go 3-4 times the cross sectional area on a chimey, figuring on the low side of things (3 times cross sectional area) if your appliance is asking for a 6x6 (which = 36" sq inchs of area times that by 3 and you have 108") then you can safetly go to a 10x10 chimney (which has a area of 100"). Like wise if you appliance is calling for a 8x8 (which = 64" sq inchs of area times that by 3 and you have 192") chimney you can safetly go to a 12x12 chimney (which has a area if 144"). My point which I have many but the main one is this, you can try it the way it is and it doesn't cost anything and if it works fine you saved your self some money, in the case that it wouldn't then you could always line it. I personaly use a AA260 which calls for a 8"x8"x15' and my chimney is a outside 12"x12"x30' clay lined red brick chimney, when the boiler is shut down I still pull -.02 draft and thats just exchanging house air. now I think another thing commonly over looked is make up air or combustion air.

I agree you could give it a try.
Stoves usually have a 6" round flue exit which is 28.27"
But being an outside chimney I don't think it will work well.
I am not here to argue either but to let Robert know he may be in for some poor performance from his stove and it may not meet his expectations. Also if he ends up with a drafting issue he may be up on a ladder at the end of December installing a liner.