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  1. #1
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    Default Water heater venting

    This gas fired water heater venting is negative pitched, but vents into the boiler vent pip that is wired up with an inline draft inducer. I found the system on line, but am not sure if the negative pitch is a problem. I tested the system by running hot water till it fired, and it seemed to work ok.

    In Line Draft Inducer Vertical Vent Systems for All Fuels : Chimney Fan : Tjernlund Products, Inc.

    Comments?

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  2. #2
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    Default Re: Water heater venting

    I'm confused. What controls the induced draft fan? If the fan does not operate when the water heater burner fires, then I'd say it is wrong. With a negative pitch it still may be wrong. Did you look at the manufacturer's instructions?


  3. #3
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    Default Re: Water heater venting

    You can see that the control is on the hot water heater. I found the system, per the web link on my original post. Both the hot water heater and the boiler have separate controls to the same fan. Fan cycled when hot water heater cycled.


  4. #4
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    Default Re: Water heater venting

    There is likely an interlock system so the system calls for heat the power vent starts, then hw heater fires up.

    http://www.tjernlund.com/Tjernlund_8500370.pdf

    This link from above (if its the correct model) says its good for 100' and each 90 degree elbows are equivalent to 6 feet of straight vent pipe. The exhaust likely overcomes negative slope, but doesn't make it right.

    Last edited by Raymond Wand; 04-11-2016 at 07:04 PM.

  5. #5
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    Default Re: Water heater venting

    What happens when the fan bearings seize up? Do the boiler and water heater shut down?

    It looks like a retrofit in an old basement.
    I would call for a professional upgrade. The water heater could be moved over to the exterior wall below the bathroom, for example.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  6. #6
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    Default Re: Water heater venting

    Is it just me, or do those brick columns look a bit wobbly kneed?

    Is that where this guy lived?
    "There was a crooked man, and he walked a crooked mile. He found a crooked sixpence upon a crooked stile. He bought a crooked cat, which caught a crooked mouse, And they all lived together in a little crooked house."

    Jerry Peck, Construction / Litigation Consultant
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  7. #7
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    Default Re: Water heater venting

    It appears to have a valve in the gas line that will shutoff the gas in the event the blower is not working. did you see the link? The system on the website looks identical to the one installed on the hot water heater. The fan cycled seconds before the water heater fired. This does not appear to be a hack job.


  8. #8
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    Default Re: Water heater venting

    Yup, its amazing what you can find in the links

    - Built-in Fan Proving Switch interlocks with gas valve.

    4. Interlock Relay or Timer/Relay and Fan Proving Switch with burner.



  9. #9
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    Default Re: Water heater venting

    Quote Originally Posted by Russell Melville View Post
    This gas fired water heater venting is negative pitched, but vents into the boiler vent pip that is wired up with an inline draft inducer. I found the system on line, but am not sure if the negative pitch is a problem. I tested the system by running hot water till it fired, and it seemed to work ok.

    In Line Draft Inducer Vertical Vent Systems for All Fuels : Chimney Fan : Tjernlund Products, Inc.

    Comments?
    Could you explain further, please?
    What type of venting.

    There are other components that require size to achieve a "Balanced Flue Vent System."
    A negative pitch may be required.
    What does the manufacturer say? The recommendation trump all.


    Robert Young's Montreal Home Inspection Services Inc.
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  10. #10
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    Default Re: Water heater venting

    The water heater is natural draft venting.
    IMO, suspect!

    Is the vent pipe entering a power draft setup?
    How large is the diameter of the pipe?
    B vent?
    I will return after work to see where the thread is going.
    Good luck.
    Happy safe inspecting everyone.

    Robert Young's Montreal Home Inspection Services Inc.
    Call (514) 489-1887 or (514) 441-3732
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  11. #11
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    Default Re: Water heater venting

    Quote Originally Posted by Russell Melville View Post
    ... but vents into the boiler vent pip ...
    That fan is listed for use with a 4" vent pipe, but says:
    - "If the appliance flue outlet is greater than 4'', install a tapered reducer after the draft hood, draft diverter or barometric draft control, reducing vent pipe diameter to 4''. All vent pipe from the appliance to the Power Venter may be 4''."

    Is the power assist interlocked with both the water heater and the boiler?

    If so, how is its efficiency affected by the unused opening sucking in air and not drawing all air from the active appliance?

    Hopefully Bob H will see this thread and comment - it just 'does not look right' and defies logic of fan assisting both appliances with the same vent, and the vent (at least near the fan) looks to be installed with the fittings backward.

    Jerry Peck, Construction / Litigation Consultant
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  12. #12
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    Default Re: Water heater venting

    The diagram shows that both boiler and water heater can be both hooked up to power vent.


  13. #13
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    Default Re: Water heater venting

    Also says: (bold is theirs)
    - "Determine maximum pipe length from type of equipment being vented and GPAK Model. Column A pipe runs over 30 linear feet should use Type B vent. Column B & C pipe runs over 15 linear feet should use Type B vent."

    And that looks longer allowed for non-Type B (some of the vent in the photo is Type B, some is single wall), and the information also states that the reduction to 4" be made at the appliance, not at the fan.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  14. #14
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    Default Re: Water heater venting

    Quote Originally Posted by Jerry Peck View Post
    Is it just me, or do those brick columns look a bit wobbly kneed?
    Look like typical rough column masonry to me.

    Robert Young's Montreal Home Inspection Services Inc.
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  15. #15
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    Default Re: Water heater venting

    It was all single wall vent pipe. There was a separate controller for each appliance. I have to go back to get the radon test, so let me know what other pics you would like.


  16. #16
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    Cool Re: Water heater venting

    The gas codes do not have provision in them for aftermarket accessories such as this Tjernlund device. It is a "power venter" and not an 'inline draft inducer", which is another critter made by this company.

    Aside from the improper sediment trap on the gas piping, improper pitch on the gas vent connectors, lack of proper support of the vent connectors and excessive horizontal run, let's look at a few issues.

    This WH has a draft hood. That means it can still vent out into the room instead of being sucked up the chimney (Oh, that's right--we don't have a chimney: we have a wall mounted Suck-O-Matic). In the event of failure of this device, it could easily spill into the room (CAZ). Therefore, we are solely relying upon the vacuum switch attached to the blower as a proving switch. These things fail all the time. They are never set up using a manometer. It is interlocked to the gas control. This is another aftermarket device that can fail. It is not all tested and listed as a system. Therefore, the AHJ must sign off.

    OK, so, what's the big deal with these wall suckers? In a natural draft system, you have the physical forces of nature generating negative vent pressure, which is wholly unreliable. So, we bring in a powerful fan to suck out the fumes and not give it a choice, right? That's actually a good thing........in part. Who set the draft pressure with a manometer? Who performed combustion analysis on the appliance to ensure it is operating properly? Other than the pressure switch, are there any other safeties on the market (since we're already into unlisted aftermarket devices)? Since this abortion is common vented, when one appliance fires, it would suck heat out of the other, thus lowering efficiency. It would have to set priority to the DHW so they both did not fire concurrently.

    Here's what I would recommend: pull all the vent connectors and closely inspect for corrosion-replace as needed. Remove the draft hood and replace with a bullhead tee with a double acting barometric damper with a spill switch wired to the gas control (see Field Controls). With all the vent connector reinstalled with seams above 5-7 O'Clock orientation, min. 3 equidistantly spaced screws per joint with a min. overlap of 1". Support every four feet and in two axes at any offsets. Perform combustion analysis with the unit firing and adjust per certification training (see National Comfort Institute). Regulate draft at wall sucker using a rheostat to control fan speed rather than integral damper. Set so max. draft -0.04 inches water column. Set double acting baro. damper to -0.06 wci Then, get the AHJ to sign off on it all. BTW, how are you going to set the draft for one and it work for both? Also, there should be a post-purge cycle for about 4-5 minutes to dry that pipe out after each cycle. That will cool the house down thus lowering efficiency.

    Or, do the right thing: replace this water heater with a listed power vented model and be done with it. :-)

    Last edited by Bob Harper; 04-18-2016 at 09:48 AM.
    Keep the fire in the fireplace.

  17. #17
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    Default Re: Water heater venting

    Thanks very much Bob!


  18. #18
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    Default Re: Water heater venting

    Thank you, Bob.

    Robert Young's Montreal Home Inspection Services Inc.
    Call (514) 489-1887 or (514) 441-3732
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