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  1. #1
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    Doing a maintenance call on a gas fired furnace

    I got into the habit of using my nanometer to make sure the gas pressure is correct on the inlet and outlet. I make sure the draft inducer is pulling well over the pressure switch. Is this not needed when doing my PM


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  2. #2
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    *Manometer

    I always check manifold (outlet) gas pressure on PMs. You'd be surprised how many gas valves are out of calibration. Inlet pressure and draft pressure isn't necessary on a PM, IMO.

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  4. #3
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    Quote Originally Posted by CircusEnvy View Post
    *Manometer

    I always check manifold (outlet) gas pressure on PMs. You'd be surprised how many gas valves are out of calibration. Inlet pressure and draft pressure isn't necessary on a PM, IMO.
    Why don’t you think the inlet is important ? And also with check the draft pressure, can’t it show signs of the motor going weak?


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  6. #4
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    I went to one last year....2.5in gas pressure...furnace started great. The shutoff valve was behind the furnace and half shut.
    I wish I had a $1.00 for every response I deleted.....

    1. "your ductwork is too small"
    2. "your system is too big"
    3. "You Need a New contractor" Your's might be okay, but if it's not ME working on your system-your contractor must be a loser-I can see it from here.

  7. #5
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    This is what I do .

    1. Check inlet&outlet gas pressure make sure there at unitnspecs.
    2. I test the vacuum pressure that the inducer motor is pulling.
    3. I test&clean flame sensors.
    4. I remove the burners and I clean them out with a vacuum.
    5. I Test all the safety’s&roll outs
    6. I do AMP draws on the inducer&blower motor to make sure there in proper range.
    7. I replace the filters

    What am I missing and or what am I over doing


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  8. #6
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    What do you do with this information? Put it on the invoice, make adjustments? What does your employer think. Personally I think it is a good idea.

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  10. #7
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    Quote Originally Posted by Craigmeednj View Post
    Why don’t you think the inlet is important ? And also with check the draft pressure, can’t it show signs of the motor going weak?


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    If there's an inlet pressure issue, you'll know because your outlet pressure can't be adjusted to spec.

    Measuring draft pressure wouldn't necessarily tell you if there's something wrong with the motor because there generally isn't any specification on what your draft pressure should be on any particular furnace. As long as it's above the threshold of the pressure switch, you have enough draft. Checking the inducer motor bearings for play and current draw (attach your meter inline with motor) will tell you more about the motor's health than anything else.

  11. #8
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    Quote Originally Posted by Craigmeednj View Post
    What am I missing and or what am I over doing
    Inspect the blower wheel, flue pipe, duct work, and evaporator coil (if accessible).
    Check temperature rise and static pressure.
    Clear the orifices with a wire.
    Clear pressure switch tubing.

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  13. #9
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    Quote Originally Posted by beshvac View Post
    I went to one last year....2.5in gas pressure...furnace started great. The shutoff valve was behind the furnace and half shut.
    I found one at about 2 IWC. Turned it up to 3.5 IWC and that's when it occurred to me that someone turned it down because this furnace was way oversized for the duct work.

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  15. #10
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    Quote Originally Posted by Craigmeednj View Post
    5. I Test all the safety’s&roll outs
    How do you test these? If by tripping them by intentionally causing a fault, DONT DO THIS
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"

    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

    Jtrammel - "I’m going to sell hvac systems derp derp derp"
    BBeerme - "every time he opens his mouth, he reminds me of a cow without the fart bag."

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  17. #11
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    Quote Originally Posted by HVAC_Marc View Post
    How do you test these? If by tripping them by intentionally causing a fault, DONT DO THIS
    I unplug one side of the switch make sure the unit acts as if it was tripped


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  18. #12
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    Quote Originally Posted by Answer-Man View Post
    What do you do with this information? Put it on the invoice, make adjustments? What does your employer think. Personally I think it is a good idea.
    When I do a PM I not all my findings on the invoice. I do it to help make myself more professional, never really cared what the employer thought of the information


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  19. #13
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    Quote Originally Posted by Craigmeednj View Post
    I unplug one side of the switch make sure the unit acts as if it was tripped


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    What you're really testing is the board response to the open circuit. Not really necessary
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"

    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

    Jtrammel - "I’m going to sell hvac systems derp derp derp"
    BBeerme - "every time he opens his mouth, he reminds me of a cow without the fart bag."

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