I called a couple heating contractors who said this was OK, but I’d like to get some more opinions. The deck was added to the back of a house that has a high efficiency Trane furnace that exhausts through 4″ PVC pipe. The exhaust is now directed under the deck. The deck is 15’x35′ with Timbertech decking and railing and has solid wood skirting around the sides. With the 1/8″ gaps between all the deck and skirt boards, I estimate there is 12-14 square feet of exhaust area, and about 1500 square feet of volume under the deck (3-4 feet off the ground).
Is this OK? I’m worried both about the proper furnace operation and any possible damage to the decking, fasteners, etc from the acid in the exhaust fumes.
The option is to extend the furnace pipe across th 15 foot width and exhaust it into the open air as before.
Replies
I know in Canada you can not sidewall vent oil or gas appliances under a deck, porch/veranda, etc.
Actually, you can.
8.14.8(h)(i) the veranda,porch, or deck is fully open a minimum of two sides beneath the floor; and (ii) the distance between the top of the vent termination and the the underside of the veranda, porch, or deck is greater than 1 ft.
Rich:
Which code is that from?
From the CSA International developed standard for oil heat appliances, section 4.3.2.2 (i) states: A vent shall not terminate underneath a veranda, porch or deck.
In post #5, you say you doubt it can be vented under these items. I'm a bit confused.
Sorry, B149.1-05 Gas and Propane. I avoid oil.
The OP said the bottom of the deck had a solid skirt.
Thanks!! Learned something new.
Funny though how one standard (B149-gas) in Canada allows the venting and another (B139- oil) does not allow this venting arrangement!!
Even if that provision is met, I would be reluctant to do it.I've seen plenty of gas appliance installations which "meet code" but don't perform properly.
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Sojourners: Christians for Justice and Peace
I don't have any of the trane 90+ installation instructions handy.
There was supposed to be a copy left on or near your furnace, and you could check the specs for venting.
As a carbon monoxide and combustion analyst, and home inspector, I think it is a bad idea, mainly because it is unanticipated by the manufacturer, but also because of some small degree of potentially really big safety risks.
First: many 90+ installation instructions have restrictions on terminating the flue near "inside corners" as well as restrictions on proximity to windows and doors.
The inside corner concern is unusual wind patterns and pressure zones. It doesn't seem likely that would be a problem with your set up, but can that be ruled out?
Also, if the furnace goes bad, it can pump out huge amounts of carbon monoxide. Although it is unlikely you'll be running the furnace when people are out on the deck, that can't be ruled out either. Could someone sitting above the flue get poisoning from CO being emitted below it?
Doesn't seem likely, but dead is dead.
Second: there is a potential concern with debris building up under the deck over time: is the air intake also there?
And, if the air intake is there, the anticipated air movement and flue gas movement might not occur, and the air intake might end up sucking in flue gas with 9% +/- oxygen content instead of 20.9%, turning the furnace into an extremely effective CO device.
Classic risk analysis:
The likelihood of the risk(s) occurring is low.
The cost of the consequences could be extremely high.
The cost of avoiding the risk is pretty low.
I say change the exhaust location.
Trouble for the deck?
The flue gases themselves are about 110 - 130 degrees F, and much of the condensate has already formed and will flow back down the flue (expected) or drip from the discharge.
And, I believe, the condensate isn't all that acidic. That conclusion is based on collecting the condensate from my 90+ last winter for a couple of days (about 5 gal a day in really cold weather with the 100,000btu furnace running maybe 75% of the time -- don't ask why <G>.)
Out of curiosity, I tossed some baking soda into the condensate, thinking it would foam nicely. (Remember the baking soda and vinegar volcanoes we made in grade school?)
Not a bubble!
I'm not saying it isn't acidic, nor that it doesn't need to be treated with respect, but it isn't exactly hydrochloric acid in your eyes, either!
I don't know the code for your area, but I doubt you can. Call your local gas inspector.
"Is this OK?" The short and best answer is NO. There is a host reasons and code sections to be cited, and many if not all have been cover well by others. Find another way to vent your furnace, and remember the contractors that said this was OK. It is not and neither are they.
Extend the 4" pipe to the outside of the deck and don't forget slope for condensate...BTDT in North Carolina a few yrs ago, it was kosher with the County inspecter.
An Ipe deck with frost on it was a neat sight, above the pipe, no frost. Spheramid Enterprises Architectural Woodworks
"We adore chaos, because we love to restore order"
Mauriets Chavailier Escher
Yeah, even if the code allowed it, I wouldn't do it. We have very little gas/propane in Nova Scotia so I don't hear all the stories those folks in gas only areas would. I'm willing to bet there are some difficulties with this arrangement that just haven't hit the codes yet.
Thanks for the input-- it didn't sit well with me either but I thought maybe I was just being paranoid. I'll find the manual for the furnace (or get one from the web) and see if the 15 ft extension radically exceeds any spec on the furnace exhaust.
I'll also check with my local inspector as one of you suggested.
The deck is almost 4ft off the ground, with an access door through the skirting so adding this pipe isn't a big deal.
Thanks again.
Rather than extend 15' under the deck, which could substan=yially increase the condenstaion flowing back to the furnace, consider re-routing it.
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Sojourners: Christians for Justice and Peace
now you are thinking.
check with your bldg (heating) inspector) he is right in your area, none of the posters are.
>>check with your bldg (heating) inspector) he is right in your area, none of the posters are.Always a good point, but not necessarily the determinative one.Code compliance doesn't ensure proper performance.For example: I've never seen an AHJ not approve a standard or medium efficiency furnace flue installation which follows the GAMA venting charts.But those very charts specify that they won't always work, and that proper performance is the responsibility of the person designing the system.In my area there is only one heating contractor I know of who verifies the draft is within the appropriate parameters on new installations.
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Sojourners: Christians for Justice and Peace
you say..." code compliance doesn't ensure proper performance"
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but, CODE compliance will ALWAYS be granted APPROVAL.
and can you name ONE code that causes any improper performance? It would be very interesting to see what kind of a code requirement that is featured in a widely used Bldg Manual that doesn't ensure at LEAST some kind of an minimum "proper performance."
Edited 10/27/2005 12:49 pm ET by Hubedube
In our jurisdiction, where the code intent is for "structural sufficiency and public health and safety", many foundations built to code end up having nuisance water entry through normal shrinkage cracks. One upscale house (in a golf course community) that I'm still involved with in litigation had seven foundation leaks in its first winter!!!
The code here keeps the foundation crack sealers in business by giving them their next customers.The home warranty programs only cover basement water leakage for the first year (so you better hope). I'd like to see the code require waterproof foundations rather than only structurally sufficient ones.
i agree with you somewhat, but in a lot of these cases the workmanship has not been put into place (faulty)the way the code was intended.
afterall, inspectors are only human too.
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>>you say..." code compliance doesn't ensure proper performance"----------------------------------------------------------------->>but, CODE compliance will ALWAYS be granted APPROVAL.Great, a piece of paper that the rules have been followed, not that the system or component actually performs as intended.>>and can you name ONE code that causes any improper performance? Causes improper performance? Nope, but that's not the issue>>It would be very interesting to see what kind of a code requirement that is featured in a widely used Bldg Manual that doesn't ensure at LEAST some kind of an minimum "proper performance."I gave an example of one area of "code compliance" that does not _ensure_ even minimal "proper performance."In my area, at least, and I believe this is fairly common nation wide, the AHJ will be satisfied with gas appliance venting which follows the GAMA venting tables.The GAMA venting tables are computer generated and based on certain formulas and programmingHere's what those venting tables have to say about how reliable they are:Venting table disclaimer:
QUOTE
LEGAL NOTICE: This information is, in part, a result of research performed by Battelle under the sponsorship of the Gas Research Institute (GRI). Neither GRI, members of GRI, nor any person acting on behalf of either: a.) Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of this information, or that the use of any apparatus, method, or procedures disclosed may not infringe privately owned rights;
or
b.) Assumes any liability with respect to the use of, or for any damages resulting from the any apparatus, method, or procedures disclosed
END QUOTEAnd, more importantly:The software that was used to generate the venting tables says:QUOTE
"The user should realize that no safety factors have been included in the VENT - II calculation routines for vent capacities. The results will be reasonably accurate for new, well defined vent configurations under transient-cycling or steady - state conditions. However, the field performance of vent systems can be adversely affected by installation peculiarities, outside wind conditions, house tightness, leaky vents, other exhausting appliance, partial blockage of vent pipe, or other conditions. There fore, appliance vent designer should use good engineering judgment in making allowances for the various perturbations which may occur in the field.
END QUOTEI haven't kept statistics, but I would guess that 5% - 10% of the gas appliances I test meet code for venting but don't actually vent properly.
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Sojourners: Christians for Justice and Peace
A byproduct of combustion is water (vapor). It seems to me water always wins, good building materials just delay that. I'd avoid the potential for problem and reroute it.