outside air for furnace?

[George]

We're considering the possibility of using outside air for combustion in our gas furnace. I'd appreciate links to information about this, thoughts about feasibility, and (particularly) how large a duct is needed for a given BTU rating.

(Background, FWIM: furnace is in the cellar. I don't know the BTUs, but I can probably get a ballpark estimate. We have a high radon level, and pretty dense soil under the not-very-thick floor. I've read that suction from the furnace may contribute to radon infiltration. I do _not_ expect this to fix the radon problem by itself, just that it might be part of a solution. We're just thinking of ideas right now.)

TIA, George

[hallerb]

Size intake should roughly equal output size.

so how old is the furnace?

[Tony Hwang]

Hmmm, Considering? It's code here. Outside air is for cumbustion.

[hallerb]

I want a interior french drain to fix a intermittent basement water problem. our area has high radon levels. I have been thinking of draning the french drain to near the street by gravity to give the radon gas a place to go. add a couple air inlets so air can flow a little and ventilate the drain area.

you certinally dont want to suck a vacuum in your home and should also look at your hot water tank and sealing all cracks and crevices.

[George]

Hard to say. It was there in '90, when we bought the house. It's got a Bryant "Quietline" sticker on it. (No nameplate, that I can find.) My guess is it's from the 70's, based mostly on the color quality in the stickers and the absence of 'energy conservation' information.

Inferring from the blower size and the chart on the blower cover, I'd guess it's 125K BTU.

G

[The Reverend Natural Light]

I've been meaning to ask the same question.

My 150,000BTU Chrysler Airtemp oil burner draws air either from an open window (making it cold in the basement) or from the french drain / sump pit (along with enough radon to make me glow in the dark). House has all new windows and doors so it's sealed up better than when it was built. There's no fresh air intake.

I was thinking about plumbing a 4 - 6" duct from outside into the cold air return. Anyone have any thoughts on that? It would be a bonus if it met today's code to save time/money when I have to have the 38 year old monstrosity replaced.

-rev

George wrote:

[CJT]

I don't think the cold air return is where the furnace combustion should be getting its air.

It would be a bonus if

[m Ransley]

Your present furnaces air intake will reduce radon, going to outside air will increase it since the basement air wont be circulated out as much. But retrofitting it makes little sence anyway and might just make your basement colder.

[---MIKE---]

I installed a duct for my furnace 15 years ago. There is a casement window near the furnace. I fitted a piece of plywood with a metal dryer hose flange and just ran the hose down to where the furnace draws in the air. During cold weather I can feel some cold air coming in while the furnace is running.

---MIKE---

[Mark]

thats not what he said...read it again ...

YES I did this, added a small duct from OUTSIDE to the cold air return.

When the furnace blower is on, it pulls some cold fresh air from OUTSIDIDE into the system and this has the effect of slightly pressurizing the house which will reduce radon and drafts. Sure, it also adds some cold air to the system so the furnace may have to work a little harder, but I think it is a good trade-off to get some fresh air. Also when the blower is on and the house is a little pressurized, there are less drafts comming in so in some way it actually helps keep the living space warmer. It also supplies air for the dreyer and whatever else is consuming air.

I look at it this way,...... some cold outside air MUST come in from outside to supply the various combustion and dreyer etc, and other losses that are sending air out. I may as well select where I want this cold air to come into my home, and what better place for it to come in than to feed it directly into the cold air return where it is heated before it gets to you...

Just install a small dreyer vent kit and hook it to the cold air return duct near the furnace...

Try it, you'll like it...

Mark

[Al Moran]

High radon level, are you a f****ng moron or what? Radon is a scam, pure and simple you idiot. I really hope you pay someone to fix your "problem" and they stick it to you hard. Fucking imbecile.

[roger61611]

I too am skeptical of the radon deal, but if people generally think it's a problem then it's a problem. IOW if 99% of people thought rooms painted blue caused cancer, there would be no rooms painted blue.

I've never heard of drawing in outside air, into a furnace. Why would one want to heat ultracold air in the winter ?

If you do have Radon, heating it wouldn't compound the problem. Fix the radon so you can sell your house if you ever want to.

[hallerb]

radon indeed causes cancer espically in smokers who are risk anyway.... but it increases that risk like 10 times more, smoking and high radon is a bad combo...

of course its only a risk in living spaces....

cant sell home with high radon........

bringing in outside air for combustion is common today for new furnaces, outside cold air is more dense so it burns better and less likely to be contaminated with household chemicals like bleach which can cause heat exchanger rusting...

lastly by not pulling a vacuum......... air out chimney must be replaced as its used for combustion. the vacuum pulls in radon and outside cold air thruout home.

better to pull in air directly to heat exchanger NOT air return.........

[George]

Well, great then: what size duct is needed for a given BTU rating?

G

[George]

Just to be sure I understand: you're not feeding the combustion air directly from the outside - you're bringing outside air into the cold return, to (more or less) replenish the interior air, and the combustion air feed itself is unchanged?

G