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Old 12-09-2014, 04:47 PM   #1
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Whats the. Max size on a complete heat pump you can go on a double 100 amp breaker inside an 2 60 amps on outside breaker ..

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Old 12-09-2014, 05:36 PM   #2
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3 ton with 15KW of aux strip heat.
5 ton with 10 KW of aux strip heat.

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Old 12-11-2014, 02:00 PM   #3
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Originally Posted by beenthere View Post
3 ton with 15KW of aux strip heat.
5 ton with 10 KW of aux strip heat.
I am not exactly sure about the original question.

I have a 3 ton 18 seer heat pump with 15 kw of auxiliary heat. This was recently installed to replaced a 1970s electric furnace which also happened to be 15 kw.

The compressor unit of the heat pump is on a 10 gauge 240 volt circuit with a 30 amp breaker. This outside unit draws between 6 and 9 amps depending on if the compressor is on low stage or high stage. In my opinion the 30 amp circuit is overkill for this but I do not know what the current draw is at start up of the compressor. Note that all ampreages reported are measured at the main panel using an ampmeter.

The air handler/aux heat is on a 60 amp 6 gauge 240 volt and a separate 50 amp 6 gauge 240 volt circuit. The 60 amp circuit is connected to the 60 amp circuit breaker in the air handler which has 10 kw of aux heat on it.

The 50 amp circuit is connected to the 30 amp circuit breaker in the air handler which has the 5 kw aux heat on it.

The 10 kw heating element and blower motor draw just over 40 amps at 240 volts. The 5 kw heating element draws just under 20 amps at 240 volts.

The load that this heat pump will draw can be as low as 6 amps (+ blower motor draw) to as high as 69 amps with everything running.

You are allowed by code to have 80% of the current draw on a given circuit so that would be 80 amps on a 100 amp circuit.

69 amps is pretty close to 80 amps so 3 tom + 15 kw aux heat sounds reasonable.
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Old 12-11-2014, 05:25 PM   #4
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Quote:
Originally Posted by fljoslin View Post
I am not exactly sure about the original question.

I have a 3 ton 18 seer heat pump with 15 kw of auxiliary heat. This was recently installed to replaced a 1970s electric furnace which also happened to be 15 kw.

The compressor unit of the heat pump is on a 10 gauge 240 volt circuit with a 30 amp breaker. This outside unit draws between 6 and 9 amps depending on if the compressor is on low stage or high stage. In my opinion the 30 amp circuit is overkill for this but I do not know what the current draw is at start up of the compressor. Note that all ampreages reported are measured at the main panel using an ampmeter.

The air handler/aux heat is on a 60 amp 6 gauge 240 volt and a separate 50 amp 6 gauge 240 volt circuit. The 60 amp circuit is connected to the 60 amp circuit breaker in the air handler which has 10 kw of aux heat on it.

The 50 amp circuit is connected to the 30 amp circuit breaker in the air handler which has the 5 kw aux heat on it.

The 10 kw heating element and blower motor draw just over 40 amps at 240 volts. The 5 kw heating element draws just under 20 amps at 240 volts.

The load that this heat pump will draw can be as low as 6 amps (+ blower motor draw) to as high as 69 amps with everything running.

You are allowed by code to have 80% of the current draw on a given circuit so that would be 80 amps on a 100 amp circuit.

69 amps is pretty close to 80 amps so 3 tom + 15 kw aux heat sounds reasonable.
Now check your compressors amp draw when it goes to defrost.
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Old 12-12-2014, 08:53 PM   #5
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Thanks for the detailed info. It actually is a 2 sets of the 60 amp fuses (4 fuses) for the outside box and I was also looking to change those out to breakers instead..
From what you have said via circuits ,and my readings on draw for unit , I should be able to convert to a 3ton from the 2 &1/2 ton i have, with no issues but if you know of any factors that may be a issue let me know ,also will have 10kw heat..
Thanks again!
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Old 12-12-2014, 09:19 PM   #6
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Originally Posted by hidden1 View Post
Thanks for the detailed info. It actually is a 2 sets of the 60 amp fuses (4 fuses) for the outside box and I was also looking to change those out to breakers instead..
From what you have said via circuits ,and my readings on draw for unit , I should be able to convert to a 3ton from the 2 &1/2 ton i have, with no issues but if you know of any factors that may be a issue let me know ,also will have 10kw heat..
Thanks again!
Whatever unit that you install will have the minimum conductor and maximum breaker size listed on the plate. Why do you want to change over to a breaker? You really don't even need fuses, just an unfused disconnect outside will work.
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Old 12-12-2014, 11:34 PM   #7
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Many other complete systems similar to this one ive had have had them both in the box to switch off/on individually -Heat/AC.
I knew which one it was if tripped .

Thanks for the info beenthere..

Here is a pic of the set of both sets of the old ones 2 sets of 60s(not 1)

Last edited by hidden1; 12-12-2014 at 11:58 PM.
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Old 12-13-2014, 12:03 AM   #8
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here is the pic of fuses
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Old 12-13-2014, 04:44 AM   #9
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Ahh...you must have a package unit with everything in one box. Fuses are more reliable in an outdoor environment but either one is acceptable, your choice.

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