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Thread: AC Blown Fuses at outdoor disconnect

  1. #16

    Default

    Important factors for your application are:

    1) The wires feeding the condensing unit should be no smaller than 10awg copper.

    2) The fuses should be no larger than 45A.

    3) The Breaker feeding the circuit should be a 40 or 45A HACR type.

    Changing to 60A fuses would be a incorrect and a safety problem.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  2. #17
    DIY Junior Member Maniac's Avatar
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    Default Huh?

    Guess I'm confused.
    The minimum circuit amps. is 49.0 and the max fuse amps is 60.0
    The margin seems to be 'tween the 2. Where would 60 amps be a safety issue?
    The AC is working fine now and hasn't blown anymore. So it seems to me that the solution has been found. Am I missing something?

    Thanks!

  3. #18
    Homeowner Thatguy's Avatar
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    Default

    Quote Originally Posted by Maniac View Post
    minimum circuit amps. is 49.0 and the max fuse amps is 60.0
    Where would 60 amps be a safety issue?
    The AC is working fine now
    So it seems to me that the solution has been found
    Probably it hasn't.
    Just check that 60A doesn't exceed the ampacity of the cable that connects your unit to the supply. The cable insulation temperature rise above ambient at 60A will be 1.5x that of 49A so its life may be shortened.
    The high current draw may also indicate an impending failure which may call for prompt action, not so much for personnel/property safety as heading off ruining your costly compressor.

    A clamp-on ammeter will pay for itself the first time you use it troubleshoot something successfully. Having one for general house/auto use is not a bad idea, but get one that can do AC and DC.

    Amps is what makes things go; volts is just to force the unwilling amps into places they wouldn't normally go.
    Last edited by Thatguy; 09-13-2009 at 11:57 AM.

  4. #19
    Electrician ActionDave's Avatar
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    Default

    Quote Originally Posted by Maniac View Post
    Guess I'm confused.
    The minimum circuit amps. is 49.0 and the max fuse amps is 60.0
    The margin seems to be 'tween the 2. Where would 60 amps be a safety issue?
    The AC is working fine now and hasn't blown anymore. So it seems to me that the solution has been found. Am I missing something?

    Thanks!
    Most likley you're fine. I think your post is being confused with the OP.
    MCA=size of wire.
    Max Overcurrent=size of fuse or breaker.
    What guage wire is feeding your compressor?

  5. #20
    DIY Junior Member Maniac's Avatar
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    Default

    Thanks Action Dave!
    I recently was told that there usually are only 1 of 2 fuses on outside AC:

    35amp or 60amp.

    Is that true?

  6. #21
    Electrician ActionDave's Avatar
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    Default

    No .

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