How to tell what breaker size to use?


Old 03-10-16, 02:00 PM
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How to tell what breaker size to use?

I have a GOODMAN central AC unit. I just noticed that at the air handler unit the breakers are 30A but at the panel it is connected to 50A breakers.

It's been this way since I bought the place 2 years ago but I never noticed it until now.

The inside handler is GOODMAN MODEL ARUF182416AA SERIAL 0608054985
The outside compressor is GOODMAN MODEL CKL24-1K SERIAL 0407618877

Shouldn't it be a double pole 30A breakers at the panel instead of 50A?

I don't know if the unit is equipped with any heat strips. I understand if it does it may increase the demand? How can one tell? I am in Miami and never turned the heat on once.

I have attached a few pictures that may be useful but I am not sure.

Inside unit.

Outside unit.

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Old 03-10-16, 02:32 PM
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I wouldn't worry about the 50 amp breaker, you have the 30 amp breaker on the furnace which is the right size.

Last edited by skaggsje; 03-10-16 at 02:36 PM. Reason: correction
Old 03-10-16, 03:30 PM
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What got me concerned is when I was looking at my electric panel I saw two #10 conductors connected to a set of double pole 50A breakers. I was scratching my head why would #10 and not #6. I didn't even know what device it goes to until I traced it in the attic and it leads to the air handler and it's 30A breakers there.

So do I have a problem?
Old 03-10-16, 04:57 PM
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Moved to electrical because the question is more electrical than A/C.
Old 03-10-16, 05:48 PM
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The important data is right on the dataplate. It will tell you the minimum circuit ampacity that determines the wire size. The next is the maximum overcurrent protection which determines the breaker size.

Motors and compressors use different sizing rules than regular circuits.
Old 03-10-16, 07:38 PM
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HKR05C is the heater strip kit (5 kw) for the air handler and on that sticker it states 30 for MOP so it should be a 30 in the panel as well.
Old 03-11-16, 06:45 PM
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It looks to me like you have a 15KW 2-circuit electric furnace, but with only the 5 KW circuit (circuit #2) is connected. Typically a furnace like this would have a 60 amp circuit (circuit #1) and a 30 amp circuit. The breaker in the panel should be changed to 30 amps since it only has #10 wire connected to it. Other than that it looks fine for your needs. It will perform just fine as it is, but the #10 wire is overprotected.
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