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We’re considering adding a gas “woodstove” in our living room, to replace the existing, old and ineffective “central” heating. We’ve got a woodstove in one corner of the house which does more to heat the house in an hour than the central heating does in a day, and we love the radiant heat. Can’t afford my ultimate wish, which is radiant floor.
Anyhow, the best stoves we’ve found are direct vent, and the best location is about six feet horizontally and twenty feet vertically (half in the living room, half in an unoccupied, unheated closet) from the roof jack through which the “central” heating exhausts. I have two questions/concerns:
1. That distance seems like a long run for a direct vent heater. As I understand the principle, combustion air runs down the outer pipe, cooling the exhaust gasses in the inner pipe. Will I lose draft in a 20-foot vertical run?
2. In addition, the O.D. of the direct vent pipe is greater than the existing Type B vent pipe, so I’d need a bigger roof jack, which means tearing off roof, not an easy move in a California winter (yeah, so it doesn’t snow here, but boy can it rain!).
So I’m wondering: can I safely make the transition from direct vent pipe to Type B vent pipe up in the attic, with a suitable mouse screen over the combustion air pipe? This would both save me from having to put in a bigger roof jack and maintain temp of the exhaust gasses, to maintain draft. At least that seems like the theory.
Help! This is an area in which I know only a little theory, and what I know is over-balanced by a lot of ignorance.
Replies
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Bill,
In my experience, most direct vent heaters vent out thorough the wall rather than through the ceiling, and have limits as to how long the vent can be. Twenty feet seems a might long. The type I have installed are limited to around 11 horizontal feet, and, if I remember correctly, about 8 vertical feet. My suggestion is to get hold of the specs on the exact appliance you plan on using, then adhere to them. If it's a listed heater, the code approved installation is whatever the mfg'r recommends.
Tom Laing
*Bill - I don't know offhand what the length limits are on direct vent stoves, it probably varies from stove to stove. However, I can say with almost complete confidence that direcvt vent pipe and B-vent are not compatible. If you take a look at a piece of B-vent and direct vent pipe side by side you will see what I'm talking about.