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I'm looking for help with a load calc for two geothermal units. First unit is 80a max 50a min
Heat strip backup is 15kva

2nd unit is 40a max 27.5a min heat strip backup is 10kva

Do you use the max breaker size for the first part? I've talked to two different inspectors and have been told two different answers.

My calc was:
80a and 40a at 100%
Back ups 62.5A x 1.25 = 78x.65 =50a per 220.82
42a x 1.25 =52.5a x .65 =34a per 220.82

Please let me know where you come up as this is listing 184a-204a for just the geo. On top of this everything else in the house.
If you need any other details let me know.

Thanks
Knauer
 

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Bababoee
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9,187 Posts
I could be wrong but I don't think the heat pump and electric heat coils work at the same time or for to long...just until the go catches up.
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My 2 cents:

First unit will not draw 80. That's just the max OCP. Same with second unit. I would size 50 and 30, plus the electric heat. They may run concurrently from time to time, but not for long periods.

If it is still an issue, you can add a control to lockout the geo unit when the electric heat is on, but the electric may run a little longer then.
 
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