Overcurrent protection #8 NM

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electrotanman

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Can I install a 50 amp breaker on an 8/3 NM cable ? Changing out a piece of equipment with a draw of 45 amps. Or do I have to upgrade the cable ?
 
infinity

infinity

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Location
New Jersey
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Journeyman Electrician
DavidA said:
While I agree the cable should probably be replaced, I'm wondering why you can't use the 75 degree table in this situation.
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Take a look here:

334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The 90?C (194?F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.
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jute

jute

Senior Member
Location
SO CAL
#8-3 with #10 ground FNMC

#8-3 with #10 ground FNMC

I'm in Calif and in the process of hooking up an above ground spa. It's being inspected and the AHJ told me that I should use #8-3 with #10 ground FNMC connected to a 50/50 2 pole breaker. I was told this is ok as long as it's under a 50' run??? Am I ok with this set-up??? Thanks JB
 
jmsbrush

jmsbrush

Senior Member
Location
Central Florida
jute said:
I'm in Calif and in the process of hooking up an above ground spa. It's being inspected and the AHJ told me that I should use #8-3 with #10 ground FNMC connected to a 50/50 2 pole breaker. I was told this is ok as long as it's under a 50' run??? Am I ok with this set-up??? Thanks JB
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I disagree with AHJ, 50' doesn't have much Voltage drop and even if it did, 8/3 Romex is still only good for 40Amps as mentioned earlier. I believe you can use SE cable
 
charlie

charlie

Senior Member
Location
Indianapolis
jmsbrush said:
I believe you can use SE cable
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You can use SE cable; however, SE cable is required by 338.10(B)(4)(a) to comply with the installation requirements of Part II of Article 334. 334.80 (which is in Part II) requires the ampacity to be at the 60? C level so the 8 AWG SE cable is still only good for 40 amperes where used inside. :)
 
C3PO

C3PO

Senior Member
Location
Tennessee
fisherelectric said:
"only good for 40 amperes where used inside. " Why "inside"?
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See Charlie's post or look at 338.10(B)(4)(a) which directs you to Part II of Art 334, especially look at 334.80
 
F

fisherelectric

Senior Member
Location
Northern Va
This must be another change in the '08 Code. Although Va just adopted the
'05 code in April of this year, with adoption of the '08 not even on the horizon I see I'm going to have to get an '08 code book just to keep up with the discussions here.
 
E

electrotanman

Member
Thanks

Thanks

The equipment is a tanning bed with a 45 amp draw. The name plate had no breaker requirements. But after reading article 334.80 I decided to have the wire upgraded.

Thanks for all your help and input.
 
B

benaround

Senior Member
Location
Arizona
jute said:
I'm in Calif and in the process of hooking up an above ground spa. It's being inspected and the AHJ told me that I should use #8-3 with #10 ground FNMC connected to a 50/50 2 pole breaker. I was told this is ok as long as it's under a 50' run??? Am I ok with this set-up??? Thanks JB
Click to expand...

This says FNMC, 3-#8's and 1-#10 grd., you could use the 75deg column.

Should say ENT, is ENT good for 75deg??
 
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