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Thread: Gas HWT clearances from doors, other intakes

  1. #1
    DIY Junior Member billyh's Avatar
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    Default Gas HWT clearances from doors, other intakes

    I did a search and I cannot find the answer, or if there is a specific answer.

    I live in Ontario and I would like to know the clearances for a gas hot water tank (from anything).

    If you have these, please share or point me to a link.

    Here is the backstory:

    I have an electric hot water tank and electricity prices have risen quite a bit.
    I would like to replace this with a Gas Hot Water tank.
    I have a 5'10" crawl and room along several walls to put the hot water tank.

    I will have this done by a professional (I wouldn't even try gas) but I will reduce my costs if I can have the tank in place and ready (hole drilled through concrete).

    I looked online for the regs.
    I checked the GE installation instructions and they state wall clearances and vent angles.
    I called two different contractors who didn't want to take the time to explain (unless I paid the hourly rate for them to come check) but told me to call union gas.
    Union told me to call tssa.
    Tssa told me to hire a contractor.

    I have been told that there is a 12" clearance of some sort from a valve (as the contractor impatiently spat it out and told me to hire him when I found out the regs). As well that it has to be so far from a door or another intake.

    What about a certain direction wall? If I have no choice but to vent through a well exposed wall (to the wind), will the simple vent cover protect against strong winds?

    Thanks for the help

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    There are gas WH that can vent out a sidewall, but many can't - they need a flue that rises to the roof. If you get one that can vent out a sidewall, each manufacturer has specific rules on where it can be relative to a window, door, overhang, and the ground (can't be below the normal snow level). There are several different ways a gas appliance can be vented: natural vent requires a flue up to the roof; power vent, can often vent out a sidewall, and is also used when the flue is too long (which cools the gasses off and can be problematic) and could go to the roof; and closed combustion which normally goes out a sidewall, but could also go out the roof. Closed combustion is similar to a power vent, but in addition to blowing the exhaust out, it also provides a closed supply of fresh air to the burner. This last type is often the most efficient, but also costs more to buy. Generally, the code specifies "installed per the manufacturer's instructions and national/local codes". So, while the code issues might cover a bit of it, it gets more specific once you've decided on a particular brand and model.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Plumber jimbo's Avatar
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    You will need to get the specs for your specific model, but typical might look like this: 3" front, 1" sides, 0" rear, 12" top. An even more important spec is combustion air. A closet with a door will need approx. 1 sq" per 1000 BTU free air inlet grill, in two places..high and low. As for the flue pipe, single wall needs 6" clearance in all directions from combustibles including drywall. Double wall B-vent needs 1".

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    Moderator & Master Plumber hj's Avatar
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    5'-10" may be too low for anything other than a "stubby" gas water heater, and they are hard to find.

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    DIY Junior Member billyh's Avatar
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    Quote Originally Posted by hj View Post
    5'-10" may be too low for anything other than a "stubby" gas water heater, and they are hard to find.
    It is 5'10" to the joists and then another 8" (well less than 8") to the floor above. I checked and the height of the tank is 55" + 12" clearance = 67". Since I am getting a smaller tank, it looks like it might fit, however, I heard it is also recommended to raise the tank a little bit? Thanks for your help again hj! Your time is much appreciated.

    Quote Originally Posted by jimbo View Post
    You will need to get the specs for your specific model, but typical might look like this: 3" front, 1" sides, 0" rear, 12" top. An even more important spec is combustion air. A closet with a door will need approx. 1 sq" per 1000 BTU free air inlet grill, in two places..high and low. As for the flue pipe, single wall needs 6" clearance in all directions from combustibles including drywall. Double wall B-vent needs 1".
    It will be in a crawl space that is open, so the closet clearances wont be a problem. I guess I will buy a double wall b-vent to save on some of the clearances. If I have my crawl spray foamed, and I have to have a 1" clearance around the vent pipe, is there a way to insulate with non-combustibles around the 1" around the vent? Thank you.

    Quote Originally Posted by jadnashua View Post
    There are gas WH that can vent out a sidewall, but many can't - they need a flue that rises to the roof. If you get one that can vent out a sidewall, each manufacturer has specific rules on where it can be relative to a window, door, overhang, and the ground (can't be below the normal snow level). There are several different ways a gas appliance can be vented: natural vent requires a flue up to the roof; power vent, can often vent out a sidewall, and is also used when the flue is too long (which cools the gasses off and can be problematic) and could go to the roof; and closed combustion which normally goes out a sidewall, but could also go out the roof. Closed combustion is similar to a power vent, but in addition to blowing the exhaust out, it also provides a closed supply of fresh air to the burner. This last type is often the most efficient, but also costs more to buy. Generally, the code specifies "installed per the manufacturer's instructions and national/local codes". So, while the code issues might cover a bit of it, it gets more specific once you've decided on a particular brand and model.
    Haha. Took me a few minutes... I thought you said that the tank can't be installed below normal snow level. I was trying to find a reference to that somewhere. Yes, I will make sure the vent is high enough. I couldn't find anything about windows or doors (but I posted the link to the pdf below if you have time).

    I am just thinking of buying a GE from Home Depot and getting someone with a ticket to install it. However, if this is a bad choice looking at cost vs. savings, I am all ears for a better recommendation. From what I've seen, the payoff on tankless heaters, and some of the problems, does not make them worth my while. I would consider a more efficient one though. Thanks for taking the time to type all of that out!


    http://products.geappliances.com/Mar...GAS%20FVIR.pdf
    I don't expect anyone to look at it but I didn't see any mention about where the vent can be located in relation to other things outside.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Per the manual, you need to check out this document, or talk to the local inspector or a licensed HVAC or plumber...
    "Consult the Vent Tables in
    Appendix G of the latest version of the
    National Fuel Gas Code (ANSI booklet
    Z223.1 or NFPA booklet 54.)"

    An atmospheric vent appliance must vent high, typically, like through the roof. You'd need a different WH with a different combustion system to vent it out the sidewall.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Moderator & Master Plumber hj's Avatar
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    The distance from the bottom of the joists to the floor above is usually irrelevent unless you can run the vent parallel to the joists ALL the way, which is seldom possible.

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    Plumber jimbo's Avatar
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    The only insulation which qualifies as non-combustible in this context is CEMENT! Fibreglas, etc, are NOT considered non-combustible. Around here, you will not find the direct vent (horizontal venting) water heater in HD. It is a totally different model, which they do not stock. "regular" water heaters must vent vertical, and extend above the roof.

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