hvac unit ocpd

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jcole

Senior Member
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Lawrenceburg, Kentucky
Hello guys and gals.

Have a situation where condenser, evaporator, blower, supp. heat, and controls are all located outside in one unit for dwelling. I called hvac company when I roughed in and asked for nameplate info and he said I needed a 100A branch circuit. Now that I am back to finish, I think I might have a situation.

It has two nameplates. One for heat and one for compressor.

Compressor: Min. 16A Max 40A
Heat: Min. 52A Max 65A

It seems to me that I needed 2 circuits. But there is only one terminal block for whole unit. The branch circuit is protected by 100A breaker inside panel.
The 100A is more than both Max ratings, which is a violation.

What am I missing?

Thanks for replies.
 
jcole said:
Hello guys and gals.

Have a situation where condenser, evaporator, blower, supp. heat, and controls are all located outside in one unit for dwelling. I called hvac company when I roughed in and asked for nameplate info and he said I needed a 100A branch circuit. Now that I am back to finish, I think I might have a situation.

It has two nameplates. One for heat and one for compressor.

Compressor: Min. 16A Max 40A
Heat: Min. 52A Max 65A

It seems to me that I needed 2 circuits. But there is only one terminal block for whole unit. The branch circuit is protected by 100A breaker inside panel.
The 100A is more than both Max ratings, which is a violation.

What am I missing?

Thanks for replies.
Click to expand...

Do you mean to say that the addition of both maxes 105A is more than your CB rating? You are unlikely to have heat AND cool on at the same time, so you should be OK. I think that the internal controls are usually preventing this. The HAVAC manuafcturers are required to internally protect their devices,their individual circuits, so the only thing you are protrecting is the feeder to the unit.

Normally in their literature and on the nameplate they list the minimum amperage rating of the feeder to the unit.

No worries, mate.
 
jcole said:
It has two nameplates. One for heat and one for compressor.

Compressor: Min. 16A Max 40A
Heat: Min. 52A Max 65A

It seems to me that I needed 2 circuits. But there is only one terminal block for whole unit. The branch circuit is protected by 100A breaker inside panel.The 100A is more than both Max ratings, which is a violation.

Thanks for replies.
Click to expand...

Simple-- The uNit is a combo unit like the old Gas packs but this is a heat pump with electric heat built in.

You only need one circuit. The unit min is 16A and 52A that is 68 amps. If you multiply the heat by 125% you get 65 amps. 65 amps plus 16 amps is only 81 amps. You are well under the 100 amp breaker and circuit. You can still protect it at 100 amps.
 
Dennis Alwon said:
The unit min is 16A and 52A that is 68 amps. If you multiply the heat by 125% you get 65 amps. 65 amps plus 16 amps is only 81 amps. You are well under the 100 amp breaker and circuit. You can still protect it at 100 amps.
Click to expand...


The unit minimums already have 125% added by the manufacturer. There should be no need to add an additional 25% to the calculation.
 
infinity said:
The unit minimums already have 125% added by the manufacturer. There should be no need to add an additional 25% to the calculation.
Click to expand...

Well then he is better off then he thought. Thanks Trevor. I always forget that.
 
Thanks again for the replies.

I was thinking that it would be considered a branch circuit not a feeder.
But what does that have to do with anything. Sometimes as my wife says I think to damn much.

Thanks again.
 
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