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  1. #1
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    Default Furnace Flue Pipe

    Would it be acceptable to have a smaller diameter flue pipe be installed inside a larger diameter flue pipe, they have used fire retardant caulking to seal the gaps, would this be acceptable ??

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  2. #2
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    Default Re: Furnace Flue Pipe

    No. Fire caulk is not recognized as a vent connector. You need a recognized metal transition with min. 3 equidistantly spaced screws. CAT I gas and oil no need for goops in pipe seams and joints. Must be mechanically fastened and to be able to disassemble for inspection or replacement. Condensate will pile up at the dam and rot out that joint quickly.

    Keep the fire in the fireplace.

  3. #3
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    Default Re: Furnace Flue Pipe

    You need a recognized metal transition with min. 3 equidistantly spaced screws
    Bob, look at the photos he posted, it's PVC pipe.

    Sam,
    Given the availability of PVC fittings and pipe, why did they connect a smaller diameter fitting and inject sealant into the gap? (If that's the scenario, the photo doesn't make it clear.)

    Don't take this the wrong way, but I'm surprised you didn't just call this out as it looks so bizarre.

    Dom.


  4. #4
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Sam Morris View Post
    Would it be acceptable to have a smaller diameter flue pipe be installed inside a larger diameter flue pipe, they have used fire retardant caulking to seal the gaps, would this be acceptable ??
    No. A reducer or bushing should have been used.

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  5. #5
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Gunnar Alquist View Post
    No. A reducer or bushing should have been used.
    Or have just used the correct size pipe from the furnace up to that point - the vent (pipe) coming out of the furnace cabinet looks smaller than that larger vent pipe in question ... so I'm guessing that you will find the same type of 'Git R Done' job at that lower end too.

    Jerry Peck, Construction / Litigation Consultant
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  6. #6
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Dom D'Agostino View Post
    Bob, look at the photos he posted, it's PVC pipe.

    Sam,
    Given the availability of PVC fittings and pipe, why did they connect a smaller diameter fitting and inject sealant into the gap? (If that's the scenario, the photo doesn't make it clear.)

    Don't take this the wrong way, but I'm surprised you didn't just call this out as it looks so bizarre.

    Dom.
    Well I guess I like to hear from other professionals like yourself and others on this website, I like to be as thorough as possible and by getting your input saves me some time in looking up the standards. TKS


  7. #7
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Dom D'Agostino View Post
    Bob, look at the photos he posted, it's PVC pipe.

    Sam,
    Given the availability of PVC fittings and pipe, why did they connect a smaller diameter fitting and inject sealant into the gap? (If that's the scenario, the photo doesn't make it clear.)

    Don't take this the wrong way, but I'm surprised you didn't just call this out as it looks so bizarre.

    Dom.
    LOL. Heck, I didn't notice the pics. Still a big NO. If you're gonna use PVC then use PVC fittings and solvent welding-period. Now, is PVC approved? Well, no---sorta'. Is PVC illegal? Well, uh, um, kinda'
    The ICC calls for
    approved' venting under positive vent pressure. Usually, this means 'listed', which would mean UL 1738. No PVC is listed to this std. However, in their infinite wisdom (and kissing up to appliance mfrs.) the ICC cmte looked the other way on PVC. They say look to the mfr. for venting. Really? Seriously?

    FYI, the UL Stds Technical Panel is looking into resolving this issue as we work to harmonize with the ULC Canadian stds. I was just at UL 2 weeks ago working on this. Expect PVC to be outlawed. Meanwhile, if you check with the pipe mfr., such as Charlotte Pipe, they flat out state emphatically do NOT use their pipe for combustion venting. Also, do NOT ever attempt to leak test PVC using pressurized gas.

    Keep the fire in the fireplace.

  8. #8
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Sam Morris View Post
    Well I guess I like to hear from other professionals like yourself and others on this website, I like to be as thorough as possible and by getting your input saves me some time in looking up the standards. TKS
    I get it, and I mean no disrespect.
    Don't sell yourself short, you have an attention for detail, and if it looks "wrong", trust your instincts.

    Dom.


  9. #9
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Jerry Peck View Post
    Or have just used the correct size pipe from the furnace up to that point - the vent (pipe) coming out of the furnace cabinet looks smaller than that larger vent pipe in question ... so I'm guessing that you will find the same type of 'Git R Done' job at that lower end too.
    This is a pretty major problem I used to run into during my 30 years at a gas company , what you are looking at is a homeowner or handyman ran this flue from a 90% + furnace he thought the run was too long for the 2 inch outlet on the furnace and decided to run 3 inch. All is ok with the idea except whoever picked up the pipe and fittings did not get the proper reducer to get from 2 to 3 inch. In the next pic further up the run with all the rtv squirted to seal it they have mixed schedule 40 pvc with schedule 20 pvc. It all probably works alright but is poor workmanship, It is not itself a violation as long as it is exhausting the flue gasses, but I would have issued a warning tag to have a licensed plumber or HVAC tech to check it out. The flue gasses for this Goodman furnace are under 110 degrees so pvc is the most common exhaust material for 90% plus furnaces. The new cellular core PVC should never be used for exhausting flue gasses only solid PVC or ABS can be used.

    Last edited by Richard Bushong; 06-06-2019 at 11:42 AM.

  10. #10
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Sam Morris View Post
    Would it be acceptable to have a smaller diameter flue pipe be installed inside a larger diameter flue pipe, they have used fire retardant caulking to seal the gaps, would this be acceptable ??
    Concentric vent. High efficiency furnace.
    Red & Hot Blue Glue PVC Pipe Cement.
    Hope that helps.

    Last edited by ROBERT YOUNG; 06-06-2019 at 03:41 PM.
    Robert Young's Montreal Home Inspection Services Inc.
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  11. #11
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Bob Harper View Post
    LOL. Heck, I didn't notice the pics. Still a big NO. If you're gonna use PVC then use PVC fittings and solvent welding-period. Now, is PVC approved? Well, no---sorta'. Is PVC illegal? Well, uh, um, kinda'
    The ICC calls for approved' venting under positive vent pressure. Usually, this means 'listed', which would mean UL 1738. No PVC is listed to this std. However, in their infinite wisdom (and kissing up to appliance mfrs.) the ICC cmte looked the other way on PVC. They say look to the mfr. for venting. Really? Seriously?

    FYI, the UL Stds Technical Panel is looking into resolving this issue as we work to harmonize with the ULC Canadian stds. I was just at UL 2 weeks ago working on this. Expect PVC to be outlawed. Meanwhile, if you check with the pipe mfr., such as Charlotte Pipe, they flat out state emphatically do NOT use their pipe for combustion venting. Also, do NOT ever attempt to leak test PVC using pressurized gas.
    Bob,

    Oy! This makes inspecting just a little more interesting. Two questions, if you could...

    1) How do I find out what the resolution regarding PVC is? Would you be willing to update us when you hear?

    2) I sometimes see ABS. Is that acceptable? Then this begs - what materials ARE acceptable?

    Hmmm... I guess that's four questions...

    Thanks,
    G

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  12. #12
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    Default Re: Furnace Flue Pipe

    Morning, Gunner.
    Hope to find you well and in good spirits today.

    Although I am not Bob Harper, and I concur, and my thoughts are, "Everything makes inspecting interesting!," what a great industry! There is so much to learn. So many great inspectors willing to discuss and help inform each other. Never been so happy. Truly!

    As to your question, "How do I find out what the resolution regarding PVC is?" I think you are referring to the manufacturing standards. And please excuse me if I am mistaken.

    Here is what I found regarding PVC and CPVC for venting BH gas venting systems, in Canada Standards Counsel. The use of plastic venting systems on gas fired water heaters, furnaces and boilers has undergone a significant change. CSA B149.1 Natural Gas and Propane Installation Code now requires all special venting material to be certified to ULC S636 across Canada. IPEX addressed this market need with System 636, a fully certified flue gas vent system.

    (ULC-S636-08 which/that supersedes ULC-S636-95. The Standard covers the design, construction, and performance of gas venting systems intended for negative or positive pressure venting of gas-fired appliances producing flue gases having temperatures under the following: (1) Class I venting systems are suitable for gas-fired appliances producing flue gas temperatures of more than 135?C but not more then 245?C; (2) Class II venting systems are suitable for gas-fired appliances producing flue gas temperatures of 135?C or less; (3) Class II venting systems are further classified into four temperature ratings as follows: (A) Up to and including 65?C; (B) Up to and including 90?C; (C) Up to and including 110?C; and (D) Up to and including 135?C.)

    I have been seeing PVC and CPVC for many years. Typically/usually System 636? PVC & CPVC
    The certified system for flue gas venting.

    Normally, the pipe has manufactures stamp on the pipe referencing the pipe makeup.
    OP, any identification on the pipe?
    .

    Robert Young's Montreal Home Inspection Services Inc.
    Call (514) 489-1887 or (514) 441-3732
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  13. #13
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    Cool Re: Furnace Flue Pipe

    When I was up at UL in Chicago a few weeks ago we formed a task group to harmonize the ULC Canadian stds. with the US. The issue of polymeric venting is THE single biggest hurdle for the group. It will be the toughest issue to resolve.

    The S636 std. has some shortcomings we're just not read to overlook.

    For now I just recommend using listed venting products currently available in the US. That means rigid pipe, such as AL29-4c and 444 stainless steel alloys listed to UL 1738 as well as polypropylene flex vent also listed under 1738. This std. is not really properly designed to address liners so for now it serves as a catch-all until we can get it straight. Same thing happened in 1980 when Martin Walwra introduced Ventinox flexible stainless steel chimney liners to the US. Initially, they tried listing them to UL 103HT but that didn't suite so they created UL1777 for liners. BTW, we're going to separate listings for solid fuel applications from gas and oil.

    I'll try to keep y 'all posted.

    Keep the fire in the fireplace.

  14. #14
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    Default Re: Furnace Flue Pipe

    Thank you for the posted information, Bob. Yes. Please keep the member's posted.

    Plastic venting was a trigger that propelled me further into the home inspection industry. Caring for a family member locked me into the carrier change. I could not work long hours. Our father through his kind benevolence, rescued both of us. I am a certified home inspector. No more building. Yahoo! Mother is in her 97 year of life. Never been happier. Father, You're the best! Truly.

    What were codification or standards concerns for the group?

    Last edited by ROBERT YOUNG; 06-11-2019 at 02:44 AM.
    Robert Young's Montreal Home Inspection Services Inc.
    Call (514) 489-1887 or (514) 441-3732
    Our Motto; Putting information where you need it most, "In your hands.”

  15. #15
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    Default Re: Furnace Flue Pipe

    I'll advise when there are any relevant changes and what they mean. Meanwhile, just go with what you've got.

    Keep the fire in the fireplace.

  16. #16

    Default Re: Furnace Flue Pipe

    Admittedly late to the discussion, but it looks like they transitioned to central vac piping....

    Egbert Jager
    Diamond Home Inspection
    http://www.diamondhomeinspection.ca

  17. #17
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    Default Re: Furnace Flue Pipe

    Quote Originally Posted by Bob Harper View Post
    FYI, the UL Stds Technical Panel is looking into resolving this issue as we work to harmonize with the ULC Canadian stds. I was just at UL 2 weeks ago working on this. Expect PVC to be outlawed. .
    PVC is approved in Canada, but ABS is not approved. How is the UL going to resolve this with Canadian standards? And what will they approve for condensing gas appliances. It seems obvious that PVC manufacturers don't rate their piping for use as flues because they don't have to. The manufacturers of condensing furnaces approve it and therefore take on the liability for its use and the PVC manufacturers don't have to assume added risk.

    Or is there something that I'm missing?

    If you choose not to decide, you still have made a choice.

  18. #18
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    Default Re: Furnace Flue Pipe

    Lon, polymeric CAT IV venting is THE toughest, most complex issue we have to resolve so no easy solutions. I'll let you know how it goes.

    IMC/IFGC punted and deferred to appliance mfrs. right after they said all pos. pressure venting must be listed. They need to make their minds up. Meanwhile, yes, PVC mfrs. state don't use their stuff for combustion venting. Fernco sells their couplings to water heater mfrs like Bradford White knowing what they're using it for but officially state don't use their flexible pvc couplings for combustion venting. Its all a game.

    Keep the fire in the fireplace.

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