Feeder Service To Sub Panel?

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Rollbar

Member
Location
Fla
I have a standard house panel (200 amp w/room left in the panel)(house built three months ago) and I want to feed a sub panel 100 feet away.

Outdoor weather proof sub panel mounted on a 8' stub pole will feed:

1. 5th wheel camper (micro, small stove etc)(more for after storm use or when friends come over for the weekend)
2. Fresh water well for camper 1 1/2 HP 240V (about 8 amps)
3. GFI receptacle under sub panel for a power cord if needed

Breakers to be installed in the sub panel to feed camper etc.
1. 1 each 50amp 220 feed
2. 2 each 20 amp 110 feed
3. 1 each 30 amp 220 feed
4. 1 each 20 amp 220 feed

I would like to use a 100 breaker to feed the sub panel & use #4 copper as the feeder. So I would use #4-4-4-6 (hot, hot, neu, ground). If I have to use #2 I can, no problem.

Below is what I'm confused on. Here I see a 100amp breaker & #4 but I really don't like that configuration, if it's ok then I'll use it.


The issue here is the difference between NEC tables 310.15(B)(6) and 310.16. The former allows a 100A breaker on #4 copper when used as a feeder, and the latter allows a 90A breaker. There is some interpretation controversy whether 310.15(b)(6) applies to subpanels as well as main panels; however I believe that 310.15(b)(6) clearly applies to main and subpanel feeders.

What do U think?

Thanks,
 
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stickboy1375

Senior Member
Location
Litchfield, CT
IMO, if the feeder you are running does not start at the main disconnect and end at the lighting and appliance branch-circuit panelboard, then you cannot use table 310.15(B)(6)
 

480sparky

Senior Member
Location
Iowegia
What you are feeding is not a dwelling, so T310.15(B)(6) cannot be used. Along with the Table, there is an Article310.15(B)(6).
 

iwire

Moderator
Staff member
Location
Massachusetts
stickboy1375 said:
if the feeder you are running does not start at the main disconnect and end at the lighting and appliance branch-circuit panelboard, then you cannot use table 310.15(B)(6)

Stick, nice job summing it up with very few words. :cool: :)
 

Rollbar

Member
Location
Fla
Hum, ok thanks, I'll check it out. Yes, U R right, I'm not feeding a dwelling.

P.S. Thanks for the clarification everyone.
 

kbsparky

Senior Member
Location
Delmarva, USA
So use #3 hots, #4 neutral, and a #8 ground instead. Use type THWN wires installed in 1?" PVC conduit, and you will have a Code compliant installation :smile:

We install these types of circuits all the time.
 

Rollbar

Member
Location
Fla
kbsparky said:
So use #3 hots, #4 neutral, and a #8 ground instead. Use type THWN wires installed in 1?" PVC conduit, and you will have a Code compliant installation :smile:

We install these types of circuits all the time.

What breaker size should U use then?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Rollbar said:
What breaker size should U use then?

#3 copper is good for 100 amp. You can use the wire you mentioned and just put a 90 amp breaker on it if the calculated load is less than 85 amps.
 

Rollbar

Member
Location
Fla
I was thinking of a 90 breaker w/the #4 but really didn't think about going w/#3 but I can, I didn't purchase the wire yet. I just finished the 1 1/4" PVC/subpanel install from the main panel out to the stub pole. Now I just have to work on the 1" PVC to the camper/well pump.

Thanks,

P.S. Here is a revised breaker install list, some things changed so I should be OK.

1ea. 220 50amp breaker=feed camper. Camper will run A/C & micro. Stove is LP gas.
1ea. 220 30amp breaker=feed camper
1ea. 220 20amp breaker=feed well pump @ 7.6 amps
1ea. 110 20amp breaker=feed receptical @ pump.
 
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