Min. Cir Ampacity 30.9

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Buck Parrish

Buck Parrish

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NC & IN
With all the talk about the 60 degree coloum in 310.16. I am second guessing my self. Is #10 Romex okay on a 240 v Geothermal Heat Pump? The breaker will be 50 amps, the minimum circuit ampacity is 30.9.
Is romex #10-2 WG okay?
 
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Cavie

Cavie

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Buck Parrish said:
With all the talk about the 60 degree coloum in 310.16. I am second guessing my self. Is #10 Romex okay on a 240 v Geothermal Heat Pump? The breaker will be 50 amps, the minimum circuit ampacity is 30.9.
Is romex #10-2 WG okay?
Click to expand...

It's early in the morning and I haven't had my 2nd cup coffee but I do believe Min ckt amps of 30.9 is .9 OVER 30 amps yes? We ain't playing horshoes here.
 
Buck Parrish

Buck Parrish

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NC & IN
310.16 the 75 degree column says it's good for 35. ;) I am just making sure #10 is okay on a 50 amp breaker. The name plate's minimum circuit ampacity is 30.9.
 
Dennis Alwon

Dennis Alwon

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It would probably be fine functionally but it is not to code. I can't believe they are making these units with amperages just over what our wires are capable of. Same is true with some heat strips coming in at 56 amps instead of 55. It changes the wire size fr us resi guys.
 
Buck Parrish

Buck Parrish

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Location
NC & IN
Dennis Alwon said:
It would probably be fine functionally but it is not to code. I can't believe they are making these units with amperages just over what our wires are capable of. Same is true with some heat strips coming in at 56 amps instead of 55. It changes the wire size fr us resi guys.
Click to expand...

Are you saying I have to use the 60 degree column? This is a geothermal heatpump.

I just noticed my thread topic say's 10.9 mca It should read 30.9. I think you all get it. May be one of the moderators can change it, Thanks, though I don't think any are on line right now.
 
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infinity

infinity

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Buck Parrish said:
Are you saying I have to use the 60 degree column? This is a geothermal heatpump.

I just noticed my thread topic say's 10.9 mca It should read 30.9. I think you all get it. May be one of the moderators can change it, Thanks, though I don't think any are on line right now.
Click to expand...


OK fixed as requested. :cool:
 
Dennis Alwon

Dennis Alwon

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Buck Parrish said:
Are you saying I have to use the 60 degree column? This is a geothermal heatpump.

I just noticed my thread topic say's 10.9 mca It should read 30.9. I think you all get it. May be one of the moderators can change it, Thanks, though I don't think any are on line right now.
Click to expand...

If you are you NM cable you must use the 60C column
 
Cavie

Cavie

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Cavie said:
#14,12,and 10 rx are restricted the the 65 degree coloum.
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I guess I should have stated all RX.

I wish they would put that disclaimer at the bottom of the table so everyone would see it, but NOOO... that's the the way the NEC does things.
 
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augie47

augie47

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Tennessee
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State Electrical Inspector (Retired)
Buck Parrish said:
Okay thanks, I always thought the 75 degree column was okay for condensing units.
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Don't forget, NM can't be used on any portion of the outsided wiring to the condensing unit also. That was an overlooked practice here for years,
 
Buck Parrish

Buck Parrish

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Location
NC & IN
augie47 said:
Don't forget, NM can't be used on any portion of the outsided wiring to the condensing unit also. That was an overlooked practice here for years,
Click to expand...

Yeah, I got that. They did not enforce it in my main jurisdiction either for a long time.
This condenser is inside. It uses the ground water (closed loop system) to convert freon to heat and cool. It's not blowing air.
 
N

nakulak

Senior Member
you guys are really messing with my head this morning.

correct me if I am wrong (please), but I thought he could only use this wire for the given application (article 440) under 2 conditions:
1) 60 degree column works (it doesn't, he needs next size #8)
2) per 440 (or 430 per 440.7), the unit is marked and says on the label "max size breaker 50A" (he didn't say this but I am guessing everyone assumed it ?)

am I correct here or am I missing something ?
 
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