8-3 NM-B for hot tubs?

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SLC James

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I called my local supply house for a price on 6-3 NM-B (what I run @ work for a 50 A hot tub) and was told I could run 8-3 NM-B and still run 50 A OCPD. Table 310.16 says OK in the 75 deg column, and if you look @ 110.14 (C) (1) (a) (3) IMO I think he's right. Boss says no and to run 6-3. Any one elses opinion would be appreciated. BTW all of my termination points are rated 75 deg or higher.
 
SLC James said:
I called my local supply house for a price on 6-3 NM-B (what I run @ work for a 50 A hot tub) and was told I could run 8-3 NM-B and still run 50 A OCPD. Table 310.16 says OK in the 75 deg column, and if you look @ 110.14 (C) (1) (a) (3) IMO I think he's right. Boss says no and to run 6-3. Any one elses opinion would be appreciated. BTW all of my termination points are rated 75 deg or higher.
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No .no way, forget it.Pay for 6-3.But just how are you dealing with the insulated ground ?????
 
Thats a good point. in new const, I generally don't get to see what goes in. The elect supply guy said he's been selling 8-3 for 50A hot tubs for years. Since he made the remark I figured it was worth looking into. I'll stick w\the 6-3.thanks for everyones input.
 
Jim W in Tampa said:
No .no way, forget it.Pay for 6-3.But just how are you dealing with the insulated ground ?????
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Valid point depending on a couple of other questions, indoor or outdoor tub?What exactly is the romex being terminated to? Disconnect of some sort? and of what type?

Jim
New Hampshire
 
Outdoor tub, At work we terminate in a 60 A Sq D. fuseless pullout handle. But in my reading if you use a fusible disconnect rated to at least 75 deg. you can get away with the 8-3 NM-b. but as
I talk with other friends in the trade and local inspectors, I get alot of yes and no's with each wire selection.
 
you cant "get away with" anything here. regardless of the 75 deg terminations the conductor is only rated at the 60 deg table period,nm cables are only rated at the 60 degree table and your supply guy is wrong .imho
 
What do the specs require? I'm with wireman3736 here. I helped a friend with his hot tub a couple weeks ago. It required all #6 cu conductors. 2 hots, neut & grnd. No exceptions.
 
That's the first I've heard of a listing of a hot tub requiring a #6 EGC.

I'm kind of at a loss as to why they would require that.

But if it's in the listing, then a #6 is required by 110.3(B).
 
Here I go again. I installed 4 above ground hottubs this month. ALL with 8/3 NM-B. ALL permitted and inspected. ALL without a #6 ground or equipotential grid.

Connect the 8/3 to a 50 amp breaker, run it across the attic, drop it down a 1" PVC into a small panel. The panel has a 2P30 amp and a 2P20 amp GFCI breakers. Carflex over to the tub with 2 #10 ungrounded, 1 #10 grounded, 1 #10 EGC and 2 #12 ungrounded. Pick up a check and boogie!
 
Micheal forgetting about listing, labeling or EGC sizes and insulation what you describe is without a doubt in my mind a NEC violation.

8 AWG NM can not be used on a 50 amp breaker.

The maximum over current device allowed on 8 AWG NM is a 40 amp.

The fact that they have been passing does not change the fact it is a violation and you are on the hook for any issues with that indefinitely.
 
Minuteman said:
So I guess the 22 houses we wired with 8/3 on a 50 amp range circuits are wrong too?
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Yes, they are all in violation if it is NM cable.

The 60 C rating of 8 AWG copper is 40 amps.

There is a standard breaker size of 40 amps so you can not 'round up' to the next breaker size.

334.80 requires that the ampacity of NM be determined using the 60 C rating.

Now if you happen to be using 8/3 CU SE in place of NM than your 50 amp breaker is fine.

Do I think that this is a major issue?

Heck no, but none the less it is an NEC violation.
 
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