6/3 romex used to feed a 70amp pool sub panel outside?

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Bashacses

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Location
New Hampshire
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Electrical
Can you use 6/3 romex to feed a 70 amp pool sub panel outside . Pool company ran 6/3 romex indoors then changed over to #6 Thhn outside in the conduit to the outside panel.
Question is
I thought you had to use the 60c column rule in 310.15.B because any breaker 125 amp or less must use the 60 rating per UL lug listing.
So a #6 would only be aloud up to 55 amps not 70 amps.
 
Where does it say ANY breaker under 125A (100A) must use the 60 degree temperature rating only? If the terminations are rated higher, then the higher rating of the wire matching the terminations can be used 110.14(C)(1)(a)(3) and EXHIBIT 110.5. Almost all modern breakers and equipment are dual rated at 60 and 75 degree C (verify) which allows wire rated at 75 degrees C to be used. In this case 65A is allowed, so next size up of 70A OCP is fine. You cannot exceed 65A of load however regardless.
 
infinity said:
NM cable cannot be used at its 75° C ampacity so you're stuck with 55 amps @ 60° C. Next size up (if applicable) is 60 amp maximum OCPD.
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Understood and noted 334.80, it was just stated that any breaker under 125A must use the 60C rating which is not the always the case.
 
ronmath said:
Understood and noted 334.80, it was just stated that any breaker under 125A must use the 60C rating which is not the always the case.
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Agreed, that was incorrectly quoted in the OP. In almost all cases if you're not using NM cable you can use the 75° C ampacity even when 100 amps or less and #1 or smaller. {110.14(C)(1)}
 
NM cable is NOT listed for use in WET locations, period, end of story. So once it goes outdoors you have to transition to something like UF, USE or individual conductors in conduit. Sounds like they opted for the latter. But even #6 individual THHN conductors in conduit is not good for 70A, so that was a mistake (or the "70A panel" statement is not correct and the actual load or MCA is 60A).

The #6 NM on the INSIDE is still only rated for 55A, so if the load or MCA is 60A or more, this smells of a DIY or Handyman project where someone used the 90C column, not knowing the rules.
 
retirede said:
He said it terminated in a 70A subpanel. No mention of calculated load or upstream OCPD.
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OK, but I've never seen a sub-panel rated for 70A. 60A and 100A are were the common sizes. But now that I had to look, I discovered that they are selling 70A rated panels. So my bad on criticizing it I guess.
 
Bashacses said:
Can you use 6/3 romex to feed a 70 amp pool sub panel outside . Pool company ran 6/3 romex indoors then changed over to #6 Thhn outside in the conduit to the outside panel.
Question is
I thought you had to use the 60c column rule in 310.15.B because any breaker 125 amp or less must use the 60 rating per UL lug listing.
So a #6 would only be aloud up to 55 amps not 70 amps.
Click to expand...
If they even have a clue as to how, have the pool company do a load Calc if less than 60 have them change it to a 2 pole 60.
What is your connection to this?
 
qcroanoke said:
If they even have a clue as to how, have the pool company do a load Calc if less than 60 have them change it to a 2 pole 60.
What is your connection to this?
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I’m a Master Electrician in after the pool company to install a hot tub. This was inspected by the local inspector and signed off.
I brought it to the inspectors attention that the pool company should have run a #4 wire size for the 70 amp feed to the sub panel from the ocpd. This is a neighbor’s house and I wouldn’t touch it unless the pool company fixed or replaced it.
I was wondering how many Electricians would say you could put up 75 amps on the number #6 based upon the 90 column in 310.15.B table
UL Listing on 125 amp or less breakers you should be using the 60 column cable rating.
 
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Bashacses said:
1)I was wondering how many Electricians would say you could put up 75 amps on the number #6 based upon the 90 column in 310.15.B table
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Bashacses said:
2)UL Listing on 125 amp or less breakers you should be using the 60 column cable rating.
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1) You cannot use the 90° C ampacity since the terminals on each end are only rated for 75° C max.

2) Can you provide documentation for this?
 
Bashacses said:
I’m a Master Electrician in after the pool company to install a hot tub. This was inspected by the local inspector and signed off.
I brought it to the inspectors attention that the pool company should have run a #4 wire size for the 70 amp feed to the sub panel from the ocpd. This is a neighbor’s house and I wouldn’t touch it unless the pool company fixed or replaced it.
I was wondering how many Electricians would say you could put up 75 amps on the number #6 based upon the 90 column in 310.15.B table
UL Listing on 125 amp or less breakers you should be using the 60 column cable rating.
Click to expand...
No, that’s only if everything in the system wire,lug,ect are not dual listed for 60/75.
Unless you’re dealing with something really old nothing new I have seen is soly listed at 60 degrees.
 
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