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Exhaust vents under deck landing


montana
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The systems room containing 4 water heaters (3 provide hydronic heat for radiant floor heating, and 1 for DHW), is an exterior room off a walk-out basement. After original construction, a landing was added off a wrap-around deck, that is over the top of this systems room. So, now the 4 exhaust vents are under the deck landing. The nearest door or window is at least 16 feet away.

I know lots of standards for exhaust vent on roof, near windows, etc, but is there any concern about an exhaust vent under a deck (not immediately near a door or window)?

My first thought would be heat damage, but I know from experience that the temperature of exhaust from a 36,000 BTU water heater is nowhere near high enough to torch the deck. There is no visible indication of heat damage on the underside of the deck. I know clearance requirements for B-type vents, but is there a clearance requirement for an exhaust hood?

Puzzled Inspector

(need an icon for a home inspector scratching his head)

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I'm pretty sure the original PE wouldn't approve of that design change.

Heat may not be a problem but washing the ptw in a nice bath of moist acidic vapor may not be the best idea. Not to mention the fact that folks will be sitting right on top of these (the upside is it will take the chill off on a cool evening).

Perhaps Katen has some code to cite. If the home isn't that old, and the original engineer for that system can be found, I'd shoot them a pic and ask for a opinion.

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What Terry said, but more specifically, do you want a two-year-old playing on the deck and sucking in those flue gases? Besides which, normal clearance requirements should apply. All the instructions I've ever seen mention sidewalls, not overhead, horizontal walls, but logic suggests everything about the configuration in the photos is wrong.

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. . . Perhaps Katen has some code to cite. . . .

Katen is struggling to understand what the heck is going on.

Do I understand correctly that, before the landing was constructed, there were simply four B-vents sticking up out of the ground in front of the deck? Is the systems room in a bunker? Were the B-vents intended to be decorative?

Sorry, the old mind is reeling at this and can't quite seem to proceed until it absorbs this information.

- Jim Katen, Oregon

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. . . Perhaps Katen has some code to cite. . . .

Is the systems room in a bunker?

That's my take on it.

Small thread drift. One of the coolest places I've been back in the day was out to an ATT communication center. The only thing above ground was a bunch of air cooled Liebert glycol condensors. After going down 4 flight of stairs, into the earth, you came upon a huge steel door much like a bank vault. It was built to withstand a 1 megaton blast at ground zero. Once inside, the whole communication center was built below grade along with living quarters for the techs - with food, water and fresh air going through scrubbers. It was built in case of an attack, by the USSR, in the cold war.

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. . . Perhaps Katen has some code to cite. . . .

Is the systems room in a bunker?
That's my take on it.

Small thread drift. One of the coolest places I've been back in the day was out to an ATT communication center. The only thing above ground was a bunch of air cooled Liebert glycol condensors. After going down 4 flight of stairs, into the earth, you came upon a huge steel door much like a bank vault. It was built to withstand a 1 megaton blast at ground zero. Once inside, the whole communication was built below grade along with living quarters for the techs - with food, water and fresh air going through scrubbers. It was built in case of an attack, by the USSR, in the cold war.

Boy, that description brings back some memories,

Coincidentally, when I went through the Q course at Ft. Bragg in 1989 my team's infrastructure assignment was to figure out how to take down all of ATT's southeastern grid, including backup grids and then relatively new fiber-optic grids for a period of not less than six weeks. Those bunker nodes you're referring to figured prominently in that plan.

The teams do their research and then sit down to work out a plan. Then they have to present the plan to a visiting full bird. He liked our solution the best of all infrastructure assignments given out to the class and we got some decent kudos from the cadre for some out-of-the-box thinking.

Too bad revealing specifics would be considered a threat to national security 'cuz it would have made any of us a fortune as an action flick.

ONE TEAM - ONE FIGHT!!!

Mike

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Hi Kurt,

It isn't names and places, it's methodology. It'd be like giving a blueprint to people we don't want to have that kind of info. Fun exercise though. We train our guys to take out infrastructure and to know how to do it for specific lengths of time; then, because we couldn't exactly go to Russia and conduct research and recon on the ground there against infrastructure targets there, they cut us loose to do the recon and planning on similar targets here.

Very stimulating, very challenging exercise and a whole lot of fun. I still chuckle when I think of the ATT guy that was giving a group of "engineering students" and their professor (Me, I was about 15 years older than the next oldest of them)" a tour of one of their nodes. He suddenly paused in mid-sentence, looked around and then to me and said, "Hey, I coulda swore there were 9 of you guys when you came in here. Is anyone missing?" I just smiled and said, "Well if there was, one of us would be strapped to the hood of the Wagoneer on the way home," and we went on with the tour while #9 was unobtrusively poking around every little nook and cranny in the place.

It's always pretty cool to get paid to have fun.

ONE TEAM - ONE FIGHT!!!

Mike

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Back to the original thread, I'm not so certain that a tall chimney would have been absolutely required in any jurisdiction. As long as they were far enough away from the windows and doors, I think that it would be fine to have those vents come up out of a bunker like that.

As for the deck over the top, though; that's just plain silly. The acidity in that exhaust gas is probably going to cause a host of problems with that wood and any metal fasteners, and the gas is liable to spread out under that deck and rise through that deck over a much broader area than it would have if the deck weren't there. It might be entirely possible to be sitting there in a deck chair and literally be surrounded by air that's heavily laden with C.O..

Someone should get the Darwin award for this one.

ONE TEAM - ONE FIGHT!!!

Mike

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Back to the original thread, I'm not so certain that a tall chimney would have been absolutely required in any jurisdiction. As long as they were far enough away from the windows and doors, I think that it would be fine to have those vents come up out of a bunker like that.

ONE TEAM - ONE FIGHT!!!

Mike

Have you been sniffin' Drano, my brother? What about kids getting burned or asphyxiated by those flues? I've never seen a B-vent terminate a couple of feet above grade (with the exception of the occasional DIY job).

And what about burying the flues? I Googled and couldn't find anything definitive, but those things aren't allowed to be installed below ground, are they? I've never seen installation instructions that describe how to install subterranean B-vents.

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Back to the original thread, I'm not so certain that a tall chimney would have been absolutely required in any jurisdiction. As long as they were far enough away from the windows and doors, I think that it would be fine to have those vents come up out of a bunker like that.

ONE TEAM - ONE FIGHT!!!

Mike

Have you been sniffin' Drano, my brother? What about kids getting burned or asphyxiated by those flues? I've never seen a B-vent terminate a couple of feet above grade (with the exception of the occasional DIY job).

And what about burying the flues? I Googled and couldn't find anything definitive, but those things aren't allowed to be installed below ground, are they? I've never seen installation instructions that describe how to install subterranean B-vents.

Oh, I suppose a kid could touch one one time and singe his finger and from that point on wouldn't hang around them. We have direct vent fireplace flues all over the place around here and I can't remember every hearing or reading about any kind being grieviously burned by one. They probably don't even get that hot; I've touched plenty of them and have never been burned.

I've seen kids playgrounds with sewer vent stacks surfacing right in the middle of them too; I can't remember ever hearing about a kid dying out on the playground because he'd inhaled sewer gases.

The burning thing aside, once that gas hits the outside air it dissipates pretty quickly. what's a kid going to do - go over to one of these throw a garbage bag around it and then stick his head in the garbage bag along with the flue and inhale deeply? I don't think so.

There are bibs around the base of each of those. Those bibs are probably integrated into whatever type of waterproofing has been applied to the top of that bunker under that gravel. Those bibs take the brunt of the weather and whatever else touches them; not the B vent.

ONE TEAM - ONE FIGHT!!!

Mike

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Back to the original thread, I'm not so certain that a tall chimney would have been absolutely required in any jurisdiction. As long as they were far enough away from the windows and doors, I think that it would be fine to have those vents come up out of a bunker like that.

ONE TEAM - ONE FIGHT!!!

Mike

Have you been sniffin' Drano, my brother? What about kids getting burned or asphyxiated by those flues? I've never seen a B-vent terminate a couple of feet above grade (with the exception of the occasional DIY job).

And what about burying the flues? I Googled and couldn't find anything definitive, but those things aren't allowed to be installed below ground, are they? I've never seen installation instructions that describe how to install subterranean B-vents.

Oh, I suppose a kid could touch one one time and singe his finger and from that point on wouldn't hang around them. We have direct vent fireplace flues all over the place around here and I can't remember every hearing or reading about any kind being grieviously burned by one. They probably don't even get that hot; I've touched plenty of them and have never been burned.

I've seen kids playgrounds with sewer vent stacks surfacing right in the middle of them too; I can't remember ever hearing about a kid dying out on the playground because he'd inhaled sewer gases.

The burning thing aside, once that gas hits the outside air it dissipates pretty quickly. what's a kid going to do - go over to one of these throw a garbage bag around it and then stick his head in the garbage bag along with the flue and inhale deeply? I don't think so.

There are bibs around the base of each of those. Those bibs are probably integrated into whatever type of waterproofing has been applied to the top of that bunker under that gravel. Those bibs take the brunt of the weather and whatever else touches them; not the B vent.

ONE TEAM - ONE FIGHT!!!

Mike

Imagine how quickly the metal will corrode when buried in soil. Also, how well will the gases draft when the flue is surrounded by frozen ground? If you have to maintain flue-pipe-termination distances from doors and windows, it only makes sense that there would be similar termination distances from pedestrians.

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Now you did it Mike. Every kid in that neighborhood will be hanging out over there making garbage bag hot air balloons over those B's, then the delinquent in the group will convince them to start huffing flue gasses[:-dev3]

Seriously, kids are doing worse things than that. It's really stupid, and I'd say so, then I'd punt it to the AHJ and let him decide if he wants to be liable for that stupidity. I bet only the bunker portion has a permit, the deck was done after the fact to hide those things and make the missus happy.

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