Can 6/3 Romex support a 60amp breaker?

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  #1  
Old 09-27-07, 09:31 AM
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Can 6/3 Romex support a 60amp breaker?

I have a hottub wired up in my garage, running 40ft of 6/3 Romex on the outside of the drywall in my garage. The 6/3 Romex is hooked up to a 60amp breaker.

Somebody told me that 6/3 Romex is only rated up to 55 amps BEFORE derating factors. So they told me it's a fire hazard to have wire that is rated for less amperage hooked to a higher amperage circuit breaker.

So my questions...

1.) What is the amperage rating of 6/3 Romex?

2.) Is 6/3 Romex THHN wire? My spa calls for THHN wire. I was told that THHN wire is INSIDE Romex.

Thanks
 
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  #2  
Old 09-27-07, 10:08 AM
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6/3 is normally protected with a 60-amp breaker. Since there are no 55-amp breakers, code allows you to round up to the next larger standard size.

Is 6/3 NM-B THHN? Yes and no. We all know that it really contains THHN, but it is not labeled as such and cannot be treated as such. It follows the rules for 6/3 NM-B, not the rules for THHN.

Caveat to other readers: The rules for squale are different than the rules for most hot tubs because squale's hot tub is not outdoors.
 
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Old 09-27-07, 10:20 AM
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Originally Posted by squale View Post
40ft of 6/3 Romex on the outside of the drywall in my garage
Generally, NM-B "Romex" cable cannot be run outside of the drywall without additional protection such as conduit or a running board. It would okay, if the cable was exposed in the ceiling, but protected down the wall.
 
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Old 09-27-07, 10:39 AM
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6/3 Romex ??
That must be a joy to work with.
 
  #5  
Old 09-27-07, 10:47 AM
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I just have the 6/3 Romex (black jacket) running unprotected along the garage walls. it is zip ziped to other pvc conduit that I already have ran.
 
  #6  
Old 09-27-07, 10:52 AM
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It's a judgement call as to whether your new cable is adequately protected from physical damage. Without seeing it, I cannot tell, but my guess from what you've said so far is that it is not adequately protected as you have done it. But the conduit you tied it to may (or may not) provide some protection.
 
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Old 09-27-07, 11:02 AM
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the way I have it I am confident that it is fairly well protected. I wouldn't of left it OUT of conduit if I thought it would be damaged by something. I ran it about 4 foot high up on the wall so it should be fine. And it's zipped tied UNDER the plastic conduit so it has some protection from the top.

Code legal.. no way.. but again, I did the entire job myself and when I get money to build a nice deck outside, I will be moving the tub outside. But then again, I sorta like the tub indoors, more privacy, I have lighting setup around the tub, etc. which is nice.
 
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Old 09-27-07, 12:10 PM
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I dont know if you did this or not with all the hottubs it dont matter indoor or outdoors loacation it must have a GFCI breaker next to the hottub withen 5-10 feet away from the tub.

inside hottub codewise it may pass it ok but really it pretty much up to the local codes if they have in there.

the other thing it came up in my mind i am sure most readers will miss this part is the lighting circuit anytime near the hottub some local code required the GFCI on the lighting circuit as well this one of few area you have to check on that as well.

Merci, Marc
 
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Old 09-27-07, 12:45 PM
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Good call. I agree with Marc, any lighting over the tub should be GFCI protected and any receptacles around the tub (usually within 10') should be GFCI protected. Of course, this is a garage so the receptacles should be GFCI protected anyway.

Does the tub have GFCI protection and disconnecting means? Extra protection for the 6/3 is questionable, but GFCI protection for the tub is an absolute must have.
 
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Old 09-27-07, 08:34 PM
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oh heck yeah of course I have the 60amp GFI spa disconnect box 5 foot away from the tub. That is a must have I wouldn't do something as stupid as that!

I just hear people talking about 6/3 Romex not being suitable for a 60amp tub because it's only rated up to 55amp and the jacket on Romex retains heat that the wires put out thus it is a fire hazard. I'm running 40foot of this 6/3 Romex btw.
 
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Old 09-28-07, 04:44 AM
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Originally Posted by squale View Post
I just hear people talking about 6/3 Romex not being suitable for a 60amp tub because it's only rated up to 55amp and the jacket on Romex retains heat that the wires put out thus it is a fire hazard.
"People" are wrong.
Don't believe everything you hear.
 
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Old 09-28-07, 09:23 AM
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Originally Posted by squale View Post
I just hear people talking about 6/3 Romex not being suitable for a 60amp tub because it's only rated up to 55amp
It's not the ampacity that makes Romex (NM-B) unsuitable for use with most hot tubs, it's that NM-B cannot be used outdoors and most hot tubs are outdoors. Additionally, the ground wire in NM-B is bare, which is not allowed for many spa installations. Yours is a special case because this is a single family home and the wiring for the tub is entirely indoors. These two conditions allow for NM-B in your case.
 
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Old 09-28-07, 10:48 AM
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Just my 2 cents

NM-b works on 60 amp breaker if the operating load falls over 50 but not over 55 amps. If it falls on 56 amps you cannot use 6/3 G nm-b and a 60 amp breaker.

Roger
 
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Old 09-28-07, 11:59 AM
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well in the owners manual of my hottub, it says the MOST the hottub can pull with all motors on high, blower on, heater on, etc. is 48 amps. BUT one of the spa professionals told me that if there is a locked rotor condition on one of the pumps then this can make the amperage go higher than 48amps thus rendering the 6/3 Romex unsuitable.

plus he said that Romex tends to build more heat because of the black jacket encasing all the wires, so he said it's the heat buildup that is bad because it can catch the wire on fire.
 
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Old 09-28-07, 01:12 PM
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Originally Posted by squale View Post
the MOST the hottub can pull with all motors on high, blower on, heater on, etc. is 48 amps.
The #6/3 is fine with 48A circuit ampacity.

BUT one of the spa professionals told me that if there is a locked rotor condition on one of the pumps then this can make the amperage go higher than 48amps thus rendering the 6/3 Romex unsuitable.
All motors have a locked rotor ampacity which is typically several times the running ampacity. The electrical code, UL and various other standards account for this already with built-in thermal protection on the motor. More than a few seconds with a locked rotor would completely burn out the motor if there wasn't thermal protection.

If you had to design appliance circuits for the locked rotor ampacity you'd need a 60A circuit to the fridge and a 150A circuit to the air conditioner.

he said that Romex tends to build more heat because of the black jacket encasing all the wires
While this may or may not be true, it's irrelevant because the cable ampacities are established in the code and are not subject to speculation.

the heat buildup that is bad because it can catch the wire on fire.
It can, but far above 60A on #6 cable. The more realistic danger is that a slightly elevated wire temperature will cause the plastic to break down more quickly leading to brittle, cracking insulation. This doesn't even happen until about 75A on #6 cable which corresponds to the 90C ampacity and still would take a long time before it was an issue.
 
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Old 09-28-07, 02:06 PM
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Ben covered all points very politely.

I would have simply said your hot tub guy should refrain from giving electrical advice since it is obvious he has NO clue what he is talking about. This is FAR more dangerous than knowing nothing at all.
 
  #17  
Old 09-28-07, 04:41 PM
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what's weird is that this was a used tub, and there was already about 10 foot of cable 6 guage running through flexible conduit coming out of the tub when I picked it up. There are 2 black power cables and 1 green ground cable. One of the black power cables when I stripped the end of it was actually discolored. Instead of the copper being COPPER color, the cooper was black in color, I took my knife and scrapped at the copper wire to reveal the COPPER color. Why would that one particular cable be discolored under the insulation? did it overheat maybe? would it be dangerous to use? I don't see any other cracks or breaks in the cable.
 
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Old 09-29-07, 01:12 AM
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Originally Posted by squale View Post
what's weird is that this was a used tub, and there was already about 10 foot of cable 6 guage running through flexible conduit coming out of the tub when I picked it up. There are 2 black power cables and 1 green ground cable. One of the black power cables when I stripped the end of it was actually discolored. Instead of the copper being COPPER color, the cooper was black in color, I took my knife and scrapped at the copper wire to reveal the COPPER color. Why would that one particular cable be discolored under the insulation? did it overheat maybe? would it be dangerous to use? I don't see any other cracks or breaks in the cable.
Hmm,, excuse my pun but let get few facts stragten out for a sec..

you did see one end of the wires is discoloured that is a useall sign for loose connection at the GFCI breaker.

and over the time on hevey loaded devices the connections can get loosen up by thermal expanding and contraction.

the copper wires useally dont expand and contract very fast not like pain in the arse alum wires but the biggest thing is propely toqured that is the whole issuse there

if i were you i just replace the wires but if it is pretty new you can reused again as long the wire is marked " THHN/THWN " in the whip but if it dont have any marking i will just yank that out and get new one that marked "THHN/THWN"

after you put in new wires and tighten down you want to wiggle it a little to make sure they dont come out because some brand breaker the screw dont catch all the straids in place [ that happend once awhile but with #6 straided it should not have much issuse with that but just double check it to make sure it is snugged good ]

Merci, Marc
 
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