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  1. #1
    Join Date
    Oct 2008
    Location
    Northern NY, (Qc, Vt, NY Border)
    Posts
    7

    New System and Noise problem fixed

    I recently installed a York PM9 gas-fired system in my house. CFM / BTU was closely matched to the existing Friedrick Oil-fired unit that it replaced. As the new is gas fired, it had the 2" vent and 2" combustion air connections. The vent went outside and the intake was left inside.

    The system worked almost flawless. Once the blower kicked up to high speed, a distinct rumble could be heard. It was at such a low pitch that it resonated throughout the entire house. I would check the system for level, good. Check the plenums for vibration, nothing. I was at a loss. Then other day, I was getting the wood stove ready when I listened to the combustion air intake. It was quite loud, then the system began to rumble at high speed. I put my hand partially over the air intake and the rumble went away!

    I ended up putting a 2" x 1-1/4" reducer in the inlet and now the system runs at high speed with no rumble at all. And the combustion flame appears to be happier as well (was blue with slight orange/red), now almost all blue).

    I am thinking that the design of the system included a design of so many feet of 2" combustion air pipe (assuming that the majority of systems would draw air from the outside). Since I am drawing from the inside, the system does not see that static, so I had to create it.

    Now all is well.

  2. #2
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,802
    Most likely all will not be well later. Call the installer and have him check the vent system over. In your area of the country, once you get down into the low teens or single digits, the intake will give you problems.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  3. #3
    Join Date
    Oct 2008
    Location
    Northern NY, (Qc, Vt, NY Border)
    Posts
    7

    Explain it to me.

    System works fine now with daily temps in the 20's-30's, night temps single to teens.

    System combustion air is pulling from the basement, discharging outside

  4. #4
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,802
    Defeats the purpose and benefits of a two pipe system and also explains the burners resonating. Your installer cheaped out.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  5. #5
    Join Date
    Feb 2003
    Location
    pittsburgh,pa
    Posts
    727
    sounds like a good future service call. the temporary fix now may lead to trouble later

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,775
    I doubt you have been at high fire yet with that mod.
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    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Oct 2008
    Location
    Northern NY, (Qc, Vt, NY Border)
    Posts
    7

    High Fire and Intake Air

    So, at what temp rise would I expect to see a "High Fire" on the furnace? Lastly, the combustion air intake pulling room air comes straight from the IOM. Granted, it also has provisions for piping the intake to the outside.

    So, let's say it is a zero degree day. I have the Tstat set at 70. Is it better for the furnace to pull 65 deg air from the basement for combustion, or zero degree air from the outside?

    Just curious.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,775
    Depends on the humidity of the basement air.
    High humidity, and it could freeze up around the PVC termination.
    Tends to help keep the basement dryer from pulling i n that cold 0° outdoor air into teh basement.

    No one set temp, for it to go to high fire. But it should only happen when its close to outdoor design temp, unless its sized wrong.

    Has it gone into extended run yet. (when it continues to run the burner, even though the stat isn't calling anymore)???
    That only happens when it has reached or exceeded 54% of its modulation.
    And that will be varied by both outdoor temp, and stat CPH setting.
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  9. #9
    Join Date
    Oct 2008
    Location
    Northern NY, (Qc, Vt, NY Border)
    Posts
    7
    The basement has a dehumidifier that is set to just a tad dryer than normal.

    Regarding the extended run, I have not yet encountered that as yet. Typically it shuts down w/in 5 minutes of reaching setpoint.

  10. #10
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,802
    Would you think that burning 0* air would be better or drawing 0* air into your conditioned environment would be better. It's the whole nothing can exist in a vacumm statement. Anything that leaves a space (in this case exhausted combustion air) MUST be replaced by a like volume (outside infiltration air). Not to mention all of the airborn contaminates drawn into the combustion process that can wreak havoc on you equipment.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


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