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Installing gas FP in old home

I hope this is the appropriate place for this question!

I'm interested in installing a vented gas Fireplace in my home (built 1891).

While the original brick fireplace 'box' or frame is still in place, the opening/face has been plastered over and the exhaust for my nat. gas furnace (perhaps 8' diameter?) was installed in the chimney out to the roof many years back. :confused:

I hope to tear out several coats of plaster/plywood and place a gas fireplace insert in the old fireplace. Assuming I do find enough room back there for both a modern FP insert as well as the furnace exhaust, would it be safe/practical to:

1. Have a professional draw a gas supply line from the basement to a new fireplace insert AND
2. Conect the insert's exhuast to the existing furnace exhaust that leads up to the roof?

I've already rescued a great mantle piece from a home in the neighborhood and have started stripping generations of paint from it!! :eek: I'd hate to see it wasted! Plus it's bloody cold this winter!

Thanks a lot,


Re: Installing gas FP in old home

I applaud your decision to go with a vented unit, for a number of reasons I think the vent-free models are a bad idea. However, I would not have the fireplace and furnace share the same flue. In most instances, you should not have any appliances (furnace, water heater, fireplace, etc.) sharing the same flue. If you still have the installation manual for the furnace or for the fireplace, I would expect they address this exact scenario.

Re: Installing gas FP in old home
titleist wrote:

You should not have any appliances (furnace, water heater, fireplace, etc.) sharing the same flue.

Are you sure about that? Maybe it's different in different parts of the country but in my current, and three before that homes, the furnace and water heater shared the same stack. All natural gas.

Re: Installing gas FP in old home

Even though that was a common practice in the past, most codes no longer allow it.

Re: Installing gas FP in old home

kentvw....No, I am not 100% sure and I edited my post to be a little more generic since there may be some configurations that would allow sharing a stack. I haven't done an exhaustive google search on installation manuals as some might :D :D .

I think there has been some change in requirements over the years due to more attention being paid to draft requirements and CO issues. Some contributing factors may be that there is less heat going up the chimney with the more efficient units.

Like you, I had an oil furnace and lp water heater sharing a stack on the present house, built in early 60's. When I swapped out the water heater after we moved in, the installation manual was clear that it should not share a chimney. One of the main reasons in my case was the 8" flue size necessary for the furnace was too big to allow a good draft for the 4" water heater flue. The old water heater also had a 4" stack, so I am guessing it probably didn't ever have a very good draft since we rarely used the furnace (heated with a coal stove on its own stack) and I am sure the WH wasn't warming the block chimney very much. The last WH I put in also had the same single flue requirement documented. We have since replaced the old oil furnace with an lp high efficiency through the wall power vent version so I am now a 3 stack guy. :)

If you need to replace your water heater some day it may be a good idea to check the installation manuals of the possible replacements to make sure it will be OK with your shared stack.

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