Wood Fireplace Question

[Terence McCann]

Inspected a house that had a wood burning fireplace that has been converted to gas logs.

Also, sharing the same chimney is a forced hot air, wood burning add-on heating system (the original furnace is oil). Can the now gas fireplace, which use to be wood burning, share the same flue as the wood burning furnace?

TIA

[hausdok]

Hi,

Don't think so. According to my CodeCheck HVAC: No solid fuel and gas in same vent......IRC 2426.5.7.1 and UMC 802.4

It's a few years old so the citation numbers could have changed but I doubt that the citation has.

OT - OF!!!

M.

[Terence McCann]

Thanks Mike. What is the main reason for this rule?

[hausdok]

This is just a guess, because I don't remember anyone explaining this to me, but in my mind the building science works.

Woodburning stoves, fireplaces and appliances need a larger flue than gas-burning stoves, fireplaces and appliances. When the wood burning object isn't actually burning any wood, I should think that cold air trying to dive down that big flue could overcome the bouyancy of gas exhaust, because it's at such a low temperature, and cause the gas appliance to backdraft into the home through the woodburning appliance.

Any 'sperts out there know if I'm even close?

I gotta go. If nobody's answered with a better reason by the time I get back, I'll look it up.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

Originally posted by hausdok

This is just a guess, because I don't remember anyone explaining this to me, but in my mind the building science works.

Woodburning stoves, fireplaces and appliances need a larger flue than gas-burning stoves, fireplaces and appliances. When the wood burning object isn't actually burning any wood, I should think that cold air trying to dive down that big flue could overcome the bouyancy of gas exhaust, because it's at such a low temperature, and cause the gas appliance to backdraft into the home through the woodburning appliance. . .

That's all true. But in Terry's case, a set of gas logs in a fireplace designed for wood logs is going to be operating under those conditions anyway.

I think the rationale for the rule is that wood-burning appliances create creosote and soot that can build up and narrow the flue or block it entirely.

- Jim Katen, Oregon