50 Amp Feed to Heatpump

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Old 12-06-14, 03:25 PM
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50 Amp Feed to Heatpump

I am reinstalling a heat pump. The heat pump has three field connections, red and black 240 vac and a green ground wire. The feed breaker is 50 amps.
It will connect to a sub panel that is fed from a 200 amp main.
I plan to run a 6 awg red and black from the breaker in the subpanel to a 60 amp non fused safety disconnect. The red and black will then run to the heat pump.
Question 1:
Do I run a green from the subpanel ground bus to the disconnect? I assume the neutral bar is separate in the subpanel and I will not use it.
Question2:
Can I use 10 awg for the green ground wire? I am using 6 awg for the red and black. I do have some white 8 awg but I think I need to use some green tape on it to identify it as a ground.
 
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Old 12-06-14, 03:30 PM
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What are the minimum circuit ampacity needed? It will differ from the maximum breaker size. You can find this on the data plate on the unit.
 
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Old 12-06-14, 04:13 PM
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The minimum ampacity is listed at 40 amps. The maximum breaker size is 60 amps.
 
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Old 12-06-14, 04:18 PM
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You only need #8, but can run the #6 if you want.
 
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Old 12-06-14, 05:57 PM
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Can I use 10 awg for the green ground wire?
#10 is fine for the ground. What is the tonnage of that heat pump? I am guessing it's a big one and perhaps as big as 5 to 7 1/2 tons (probably closer to 7 1/2). I haven't seen a 5 ton unit with a 40 amp MCA in over 30 years.
 
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Old 12-06-14, 06:07 PM
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It is 8 1/3 ton, 100,000 BTUs.
 
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Old 12-06-14, 06:12 PM
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I knew it must be a big one.
 
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