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Thread: Hvac breaker and cutoff

  1. #1
    Join Date
    May 2013
    Posts
    1,465

    Default Hvac breaker and cutoff

    General question on breakers and outside cutoff: InDies a 30 amp breaker in the box and a 60 amp cutoff outside make sense?
    I know outside cutoffs are sometimes rated higher than the breaketbox breaker ( still not sure I understand that completely), but this seems like the guy used what he had on the truck.
    Might add this unit had done pretty good for about 20 years except for a couple of fan motors, contactors, and a capacitor I have had to replace.
    Have another question or two on this residential unit, but will make other posts.

  2. #2
    Join Date
    Feb 2012
    Location
    Kent, WA
    Posts
    215

    Default

    Yes. The outside disconnects seem to be rated at 30A and 60A. The cost difference isn't that much so it makes sense to just carry the larger one. Plus, the larger one will have a beefier bus and will be a heavier duty disconnect.

    The smallest overcurrent device is what trips when an overload occurs. It doesn't matter whether it is the main panel breaker or the disconnect next to the unit. But if the smaller breaker is at the panel, then you don't need to upsize any wire. If the large breaker is at the panel, then you most likely need to use wire rated per that larger breaker until you hit the disconnect with the smaller breaker.

    I think a good solution is disconnects that are rated at 60A that have a switch only (they look like a breaker handle, but there is no overcurrent trip). These generally cost less than the breaker variant but are good for all installs up to 60A, so you need to make sure the breaker in the main panel is rated no higher than the Max Overcurrent rating on the HVAC unit.
    Mark
    Kent, WA

  3. #3
    Join Date
    May 2013
    Posts
    1,465

    Default

    Thanks for responding.
    Had a more prolong response, but I tried to edit it. This phone deleted it!
    Grrr, dang touch tone screen.

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