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Thread: Indoor unit

  1. #11
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    I'm not an engineer. I am an HVAC technician. I can tell you that almost all of these (incl. 3/4 HP 120V) are on a 15A circuit breaker in the panel. The local disconnect is sometimes a cord-and-plug (NEMA 5-15P), and sometimes a 15A rocker switch.

    I guess I never saw the need to do the math to verify something that's been done a certain way for decades.

  2. #12
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    Quote Originally Posted by MAC702 View Post

    I guess I never saw the need to do the math to verify something that's been done a certain way for decades.
    Sorry if this sounds rude, but I find that philosophy akin to being a lemming or such.

    “That’s the way we have always done it” does not work for me.

    Common does not mean correct.
    "Electricity is really just organized lightning." George Carlin


    Derek

  3. #13
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    Quote Originally Posted by jumper View Post

    Same math though. HVAC loads are also usually considered continuous loads so I would multiply by 125% also, but a 20A disco still works.
    I need to double check on whether the disco actually needs to have the continuous load multiplier, I know the conductors do per 430.22.
    "Electricity is really just organized lightning." George Carlin


    Derek

  4. #14
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    Quote Originally Posted by jumper View Post
    Sorry if this sounds rude, but I find that philosophy akin to being a lemming or such.

    “That’s the way we have always done it” does not work for me.

    Common does not mean correct.
    I agree with that principle. But I literally see several hundred of these a year. I've never not seen one installed on something other than a 15A circuit.

    Obviously, a lot of people have already engineered this, including every manufacturer and local home builder.

    I'm not referring to just some local custom of "old guys."

  5. #15
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    Quote Originally Posted by MAC702 View Post
    I agree with that principle. But I literally see several hundred of these a year. I've never not seen one installed on something other than a 15A circuit.

    Obviously, a lot of people have already engineered this, including every manufacturer and local home builder.

    I'm not referring to just some local custom of "old guys."
    The question noils down to what would you do for next installation you see continue to use 15amp?

    Sent from my SM-G935U using Tapatalk

  6. #16
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    Quote Originally Posted by codequestion View Post
    The question noils down to what would you do for next installation you see continue to use 15amp?
    I'm certainly not going to tell an engineer what to design. So maybe it's best he doesn't know what I would do when I've never heard of a reason why every existing installation I see on a daily basis might be questionable. All I'm telling him is what the real world is doing.

    I'd be very interested if the math says everyone is doing it wrong, though.

  7. #17
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    Quote Originally Posted by MAC702 View Post
    I'm certainly not going to tell an engineer what to design. So maybe it's best he doesn't know what I would do when I've never heard of a reason why every existing installation I see on a daily basis might be questionable. All I'm telling him is what the real world is doing.

    I'd be very interested if the math says everyone is doing it wrong, though.
    And the AHJ is in agreement with the engineer design?

    Sent from my SM-G935U using Tapatalk

  8. #18
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    Quote Originally Posted by codequestion View Post
    And the AHJ is in agreement with the engineer design?
    I no longer deal with AHJ's except to work on equipment that has been approved for decades.

  9. #19
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    Quote Originally Posted by MAC702 View Post
    I no longer deal with AHJ's except to work on equipment that has been approved for decades.
    15 amp breakers never nuisance trip i.e when motor turn on or other conidtions?

    Sent from my SM-G935U using Tapatalk

  10. #20
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    Quote Originally Posted by codequestion View Post
    15 amp breakers never nuisance trip i.e when motor turn on or other conidtions?
    Not that I've ever seen. The only issues I've seen somewhat related to this have been when the installers used the backstab connections on the 15A switch, and the switch fails from overheating. I replace with another 15A switch, using the screws.

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