#6 NMB

N

nizak

Senior Member
Can #6/3 NMB cable feeding a sub panel be on a 60 amp breaker?

The calculated load as installed is approximately 40 amps.

Thank you
 
nizak said:
Can #6/3 NMB cable feeding a sub panel be on a 60 amp breaker?

The calculated load as installed is approximately 40 amps.

Thank you
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While technically allowed, I wouldn't. Not a trusting sort. HO will ultimately add loads and if you are the last "electrician" on site and when it overloads the wire, you will be the one left holding the bag.
 
Fred B said:
While technically allowed, I wouldn't. Not a trusting sort. HO will ultimately add loads and if you are the last "electrician" on site and when it overloads the wire, you will be the one left holding the bag.
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I would not loose sleep over it. If this was type SE cable it could be loaded to 65 amps on a 70 amp breaker. The only real difference between NM-B and SE is the NM has a paper wrap over the conductors and the SE has a reinforced plastic wrap. Conductors and jacket are the same.

I have felt for years they should just eliminate NM cable larger than #10.
 
The 60° C rating is fictitious anyway so the cable has a real ampacity of 65 amps at 75° C.
 
ptonsparky said:
I believe someone would deliberately be trying to cause damage.
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Not really, we get a lot of handyman and DIY guys that haven't a clue. And as long as the "panel" has spaces, just keep adding loads and if the feeder breakers not big enough and keeps tripping just put in a bigger one. (Seen it done.) I get from HO a lot "Why is the main tripping? There is still spaces in the box and none of the small breakers are tripping."
100A panel only $20 more than the 60 or 75A so just put in the bigger one, is what I'll get a lot too. Now you've got at least 20 spaces, instead of the six spaces.
 
Funny I just posted this on another thread the limitations of #6 AWG NM cable in particular seems to come up at least once a week on here if not more often and a new tread started on it..
Until the 1950's #5 AWG wire was in the NEC ampacity tables, it would be a super easy code change to add 5AWG back to the table, then NM cable manufacturers could make a true 60Amp 60C cable, 5/2 - WG and 5/3 -WG.
 
Fred B said:
Not really, we get a lot of handyman and DIY guys that haven't a clue. And as long as the "panel" has spaces, just keep adding loads and if the feeder breakers not big enough and keeps tripping just put in a bigger one. (Seen it done.) I get from HO a lot "Why is the main tripping? There is still spaces in the box and none of the small breakers are tripping."
100A panel only $20 more than the 60 or 75A so just put in the bigger one, is what I'll get a lot too. Now you've got at least 20 spaces, instead of the six spaces.
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of course this might fit into the Ron White setup
 
Fred B said:
Not really, we get a lot of handyman and DIY guys that haven't a clue. And as long as the "panel" has spaces, just keep adding loads and if the feeder breakers not big enough and keeps tripping just put in a bigger one. (Seen it done.) I get from HO a lot "Why is the main tripping? There is still spaces in the box and none of the small breakers are tripping."
100A panel only $20 more than the 60 or 75A so just put in the bigger one, is what I'll get a lot too. Now you've got at least 20 spaces, instead of the six spaces.
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I've seen so many houses run on 60 amp services it doesn't particularly worry me.
 
tortuga said:
Funny I just posted this on another thread the limitations of #6 AWG NM cable in particular seems to come up at least once a week on here if not more often and a new tread started on it..
Until the 1950's #5 AWG wire was in the NEC ampacity tables, it would be a super easy code change to add 5AWG back to the table, then NM cable manufacturers could make a true 60Amp 60C cable, 5/2 - WG and 5/3 -WG.
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My only complaint would be most small lugs are rated to #4 and you know people would jamb a #5 compact stranded into a #4 lug all day long. Just waiting for another listing issue to come up.
 
letgomywago said:
My only complaint would be most small lugs are rated to #4 and you know people would jamb a #5 compact stranded into a #4 lug all day long. Just waiting for another listing issue to come up.
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Did you mean #6 lugs? Isn't #5 AWG smaller than #4?
 
letgomywago said:
My only complaint would be most small lugs are rated to #4 and you know people would jamb a #5 compact stranded into a #4 lug all day long. Just waiting for another listing issue to come up.
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ptonsparky said:
I've seen so many houses run on 60 amp services it doesn't particularly worry me.
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Just give the stranded a hair cut, they don't need all those strands anyway. Seen that done many times too. Another way, if it is your grounded, is to split the strands between 2 or 3 lugs to get your 4/0 to land.
 
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