Same flue for Oil and Coal Boilers????

wannabwarm wrote:Reading all your input has been a great learning exp for me. While we are on the subject is there any problem with having two coal fired units with 6" flues connected to the same 8" SS chimney?

Legally, I'm not sure, physically, the math says that 8" is not twice the area of two 6"....almost, but not. It's about 15% shy of being double the area. Two 6's would be 56.5 sq inches vrs 50 sq inches for one 8". Maybe you could get away with it, maybe you'd asphyxiate yourself.

Freddy wrote:

wannabwarm wrote: asphyxiate yourself.

Hey Feddy, watch you language !!!!

Other than the 'code' issue and insurance coverage in a loss, there is one issue not discussed so far.

Every year on the forum we have some folks with draft problems.. expecially with hand fired stoves/boilers/furnaces that rely on the chimney draft to pull air through the fire. The boilers or furnaces that have fan-forced combustion air don't have this problem.. We often have people stuggling to get a fire to burn well because of poor draft, draft leaks in the stove, hand dampers set wrong, or other ' draft stealers'.

So if you have two appliances hooked to a common chimney,, you need to assess how much 'leakage' of draft [chimney vacuum] there will be through the unused appliance. If there is an automatic damper on the unused appliance blocking it's flue, then this will not be an issue.

A tall 8x8 inside chimney that can pull .05" + draft will do fine But an accurate measurement of the draft with a fire going is going to be needed..

Greg L

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