hot tub

Status
Not open for further replies.
J

jap2525

Senior Member
(3) #8's and a #10 grn. thhn were previously piped from a 50 amp gfi breaker in emt conduit to an outside disconnect for a hot tub.The hot tub calls for 50 amp 240volt 6 guage 4 wire copper conductors to serve the hot tub.Is there any reason for the conductors including the ground to be 6 guage? or are they assuming most installations are done in romex.
 
Re: hot tub

#8 copper conductors are only good for 40 amps for this installation when you take 110.14(C)(1)(a) into consideration.

#10 EGC would normally meet the code, but 110.3(B) comes into play also.
 
Re: hot tub

I agree, No. 6 sounds like overkill, maybe they are using the 60?C ampacity, but if the instructions say 6, install 6 per 110.3(B), that way you are covered if problems arise. :cool:

[ October 11, 2004, 05:34 PM: Message edited by: electricman2 ]
 
Re: hot tub

Originally posted by physis:
I'm curious how 110.14(C)1(A) applies?
Click to expand...
Did you read it? :D

Unless marked otherwise (and most are) terminations for less than 100 amps or marked for 14 AWG through 1 AWG conductors, are rated 60 C. This means you have to use the 60 C column of 310.16 for the cable rating.
 
Re: hot tub

I'm curious how 110.14(C)1(A) applies?

If you look at the breaker you will see a termination rating of 60/75-deg c. This means when the breaker is installed with other breakers typically in a panel the termination rating is 60-deg c and while you can use a higher temp for deration of conductors the termination must be applied at the 60-deg ampacity. If the same breaker is installed in it's own enclosure the termination rating would be 75-deg c because the breaker is not effected by the surrounding breakers as in the panelboard.
 
Re: hot tub

I think this spells it out. :)

2003 UL White Book.
CIRCUIT BREAKERS (DHJR)
GENERAL
1. Circuit breaker enclosures are marked to indicate the temperature rating of all field installed conductors.

2. Circuit breakers with a current rating of 125 A or less are marked as being suitable for 60?C, 75?C only or 60/75?C rated conductors. It is acceptable to use conductors with a higher insulation rating, if the ampacity is based on the conductor temperature rating marked on the breaker.

3. Circuit breakers rated 125 A or less and marked suitable for use with 75?C rated conductors are intended for field use with 75?C rated conductors at full 75?C ampacity only when the circuit breaker is installed in a circuit breaker enclosure or individually mounted in an industrial control panel with no other component next to it, unless the end-use equipment panelboard, switchboard, service equipment, power outlet, etc.) is also marked suitable for use with conductors rated 75?C.

4. A circuit breaker with a current rating of more than 125 A is suitable for use with conductors rated 75?C.

5. Circuit breakers intended for continuous operation at 100 percent of rated current may be marked to be connected with 90?C rated wire with the size based on 75?C ampacity.
Click to expand...

[ October 11, 2004, 06:59 PM: Message edited by: iwire ]
 
Re: hot tub

Posted by Volt102

#8 copper conductors are only good for 40 amps for this installation when you take 110.14 (C)(1)(A) into consideration.
Click to expand...
The conductors are not necessarily limited to the 60c coloumn.
 
Re: hot tub

The problem is the Hot tub maker asks for 6 AWG which strongly suggests that the terms on the tub are only 60 C rated.

Beyond that we run into 110.3(B) as previously noted.
 
Re: hot tub

My answer was based on the information that was available in the thread at the time I posted my curiousity about applying 110.14(C)(1)(A). At that time Volt102's post could only have been true given an assumption that the terminals were rated 60c.
 
Re: hot tub

OOPS

My bad. The tub asks for 6 awg. Sorry Volt102. That's probably enough information to conclude at least that you'd need 6 awg.
 
Re: hot tub

to make things worse the subpanel that the hot tub is fed from has #3's thhn for line and neutral and only a #8 ground wire.In this case the groundwire to the tub would be larger than the ground wire feeding the subpanel.How much replacing needs to be done?
 
Re: hot tub

Jap look at table 250.122 and you will see that only a # 10 ground is required for a 60 amp circuit. And a 100 amp circuit only requires a #8. Grounding conductors are only for fault current and only have to carry a short circuit current for a very short time. this is very different from over load protection as an over load can last many times longer and cause damage to the conductor's insulation. If you ever noticed that any #6 NM you buy will only have a #10 bare grounding conductor in it.

[ October 12, 2004, 12:47 AM: Message edited by: hurk27 ]
 
Re: hot tub

I realize that but if we have to follow their rules for the phase conductors and neutral why don't we have to follow them for the grounding conductors?
 
Status
Not open for further replies.
Top