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05-30-2018, 08:08 AM #1
Garage Unit Heater - Trap In B Vent
Is this vent installation allowed? I can't find anything in the installation instructions that would specifically prohibit it, other than having to drill a hole in the trap to allow for condensate drainage.
http://i303.photobucket.com/albums/n...s/IMG_6643.jpg
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05-30-2018, 08:36 AM #2
Re: Garage Unit Heater - Trap In B Vent
Clarify which direction is "up" for the photo.
It could be wrong for various reasons, depending on which way is "up".
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05-30-2018, 09:13 AM #3
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05-30-2018, 01:01 PM #4
Re: Garage Unit Heater - Trap In B Vent
Last time I looked at a B vent install guide, horizontal runs need 1/4 inch rise/ foot of run.
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05-30-2018, 01:28 PM #5
Re: Garage Unit Heater - Trap In B Vent
Was the installer a plumber????? In addition to Dom's answer I also thought it had to have a minimum 12" vertical connector before the horizontal (1/4" per foot) run.
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05-30-2018, 02:15 PM #6
Re: Garage Unit Heater - Trap In B Vent
A Type B gas vent should never, never, never, never go "down", and should, as the others have said, never be less than 1/4" per foot UP horizontal slope (which precludes "down").
I see why they did it:
- lack of planning (any planning)
- lack of PROPER planning (if one plans, one should an properly)
- not understanding gravity flow of heated air (heated air rises)
- that connector (bottom of Type B vent section?) projects down so far - and / or - the unit is so high ... there was not sufficient space to make a turn up.
- is it possible that furnace is not designed for B vent?
Looking up the MII (manufacturer's installation instructions) would answer all questions about that install.
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05-30-2018, 02:23 PM #7
Re: Garage Unit Heater - Trap In B Vent
Sorry for the lack of information, but I was in a hurry earlier when I posted. I should mention that this is a unit heater in a garage with a power combustion exhaust fan, not gravity flow. The manufactures installations instructions specifically say that downward slope toward the exhaust end it is an OK installation on a horizontal run, Or that condensation drain can be installed at the low point of the exhaust vent. But I have never seen a trap created an exhaust vent like this before? I do have reason to believe that it was installed by a licensed HVAC contractor.
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05-30-2018, 02:56 PM #8
Re: Garage Unit Heater - Trap In B Vent
MII: http://www.littlegreenhouse.com/reso...-GG-Manual.pdf
Starting on page 20 & 21
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05-30-2018, 05:29 PM #9
Re: Garage Unit Heater - Trap In B Vent
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05-30-2018, 05:37 PM #10
Re: Garage Unit Heater - Trap In B Vent
I did look through pages 16 and 17. If I am not mistaken we are dealing with category III, on pages 20 & 21. Figure 13A is what had me wondering if the vent can be installed downward, potentially with a condensate drain? Don't get me wrong, I do not like this installation which is the reason I brought it up. I am just trying to nail down specifically how it is not allowed.
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05-30-2018, 05:48 PM #11
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05-30-2018, 07:17 PM #12
Re: Garage Unit Heater - Trap In B Vent
Andy, not allowed based on the vent connector needs a 1/4" rise per foot, I would have them raise the B-Vent as high as they can, install a B-Vent "T" cap the bottom and install the vent connector in the side of the "T" that will give the vent connector a small rise. The single wall vent connector still needs a 6" clearance to combustibles so if that is not possible they can install a piece of sheet metal above the vent connector with a 1" air gap and that should work or lower the unit heater!
They could eliminate the single wall vent connector and install all B-Vent in to the side of the "T", the B-Vent has a 1" clearance to combustibles.
Last edited by Dan Hagman; 05-30-2018 at 07:22 PM. Reason: Additional information
Dan Hagman ACI
ProSite Home Inspections
Des Moines, Iowa
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05-30-2018, 09:00 PM #13
Re: Garage Unit Heater - Trap In B Vent
Thanks guys. I was confident it was wrong, but wanted to be able to intelligently explain why.
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05-31-2018, 11:43 AM #14
Re: Garage Unit Heater - Trap In B Vent
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05-31-2018, 12:22 PM #15
Re: Garage Unit Heater - Trap In B Vent
My answer is NO! It is an inducer to remove any combustible gasses from around the heat exchanger prior to lighting the furnace.
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