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Old 10-07-2011, 04:08 PM   #1
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direct venting question


I'm still considering my options switching from oil to gas. My current oil setup will need a SS liner which is $1900-2100, I'd like to avoid that expense which will just lock me (financially) into oil.

My questions are:

Can a direct vent PVC exhaust be run up an old chimney? It's about 30' from basement level to fresh air. Or is there a vertical/horizontal limit to direct venting? If it matters, my chimney flue for the boiler is a straight shot up, in fact, if you pull the metal exhaust ducting off on a sunny day you can see daylight shining down... I was thinking it would be pretty fantastic to be able to run the exhaust and intake as PVC directly up the chimney and avoid any new penetrations outside the house.

In case this wouldn't work, what are the typical restrictions with direct vent placements? For example, how close to windows can the vent be? On the side of the house where the boiler is the largest gap between any two windows is only about 6-8'. Any issue with it being located near a driveway? I know it has to be a minimum distance from the ground, is that 4' now, or lower? (my last rental had one that was only ~8" off the ground (they stuck it in a piece of plywood and covered an old basement window), I was always worried about it in the fall and winter, so I'd be clearing the leaves and snow quite often)

Can a boiler and a hot water tank share a direct venting setup, or do they require separate venting and intakes?

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Old 10-07-2011, 04:48 PM   #2
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direct venting question


All of the furnace install manuals have the basic national gas code reqs regarding placement of external vent and intake openings. You can look for a site that sells Goodman and pull up a manual to check out the venting locations.

The actual length of pipes you can run depends on the actual furnace (varies by brand and size) and you have to add extra for elbows and such to get equivalent total feet. Each furnace manual specs it own reqs. For example my York 80,000 BTUH allowed up to 65 equivalent feet using 2" pipe.

I don't see why you couldn't run the pipes up an old chimney but I'll leave it for the pros here to confirm. 30 feet isn't far at all and almost any furnace should accomdate that.

Godo luck.





Quote:
Originally Posted by bubbler View Post
I'm still considering my options switching from oil to gas. My current oil setup will need a SS liner which is $1900-2100, I'd like to avoid that expense which will just lock me (financially) into oil.

My questions are:

Can a direct vent PVC exhaust be run up an old chimney? It's about 30' from basement level to fresh air. Or is there a vertical/horizontal limit to direct venting? If it matters, my chimney flue for the boiler is a straight shot up, in fact, if you pull the metal exhaust ducting off on a sunny day you can see daylight shining down... I was thinking it would be pretty fantastic to be able to run the exhaust and intake as PVC directly up the chimney and avoid any new penetrations outside the house.

In case this wouldn't work, what are the typical restrictions with direct vent placements? For example, how close to windows can the vent be? On the side of the house where the boiler is the largest gap between any two windows is only about 6-8'. Any issue with it being located near a driveway? I know it has to be a minimum distance from the ground, is that 4' now, or lower? (my last rental had one that was only ~8" off the ground (they stuck it in a piece of plywood and covered an old basement window), I was always worried about it in the fall and winter, so I'd be clearing the leaves and snow quite often)

Can a boiler and a hot water tank share a direct venting setup, or do they require separate venting and intakes?

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Old 10-07-2011, 05:10 PM   #3
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direct venting question


Yes you can run pvc pipes up through the old chimney. Appliances will not be able to share pipes though. As stated the side wall terminations are specified in the installation manual.
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Old 10-07-2011, 05:16 PM   #4
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direct venting question


You can run your vents up the old chimney, have done it many times and it is a nice way to get vents out of the way. You won't be able to share venting with your water heater however, each appliance needs to be vented seperately.
With a height of 30 feet you will have some challenges getting the venting down the chimney in one peice, so you will need someone to assist you and glue sections together as they go down the chimney, you will then have to make a support bracket for the top, which may be a metal plate with holes cut in the same diameter as the piping and hang it off couplings at the top.
As mentioned by a previous poster, you will have to check specific instructions based on make and model, but most follow a pretty similar pattern.
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