11 posts / 0 new
Last post
jbowlin2
Electrical Sub-Panel Wiring

Hello, I am installing a 100 amp sub-panel in my 48x30 morton building. I have only installed and buried 1" schedule 40 pvc from the house. I was planning on installing #4 thhn wire to supply this until I read in the code book that #4 can only be used for the main feeder panel, so now I have to go up to #3 wire. I am also using #8 wire for the ground to a grounding rod. Three #3 wires will fit in the conduit and to code, but it will be hard to pull. My question is can you down size the size of the neutral, or does it have to be the same size?

Re: Electrical Sub-Panel Wiring

Yoour missing a little info there op. What size sub panel? I assume 100 amp since you wanted to use #4 Alot of this will depend on where you are and what revision of the code is enforced. Here in jersey were still working off of 99 so so you wouldnt put a ground rod at the sub panel instead there would be 4 conductors from the main 2 hot / nuetral / and equipment ground (or gec depending on your interpritation of the definition) I hate to say call a pro on a diy site but... perhaps you could take your time and get a little more info before you start. definately submit a drawing and wait for aproval before you start.

Ernie_Fergler
Re: Electrical Sub-Panel Wiring
jbowlin2 wrote:

Hello, I am installing a 100 amp sub-panel in my 48x30 morton building. I have only installed and buried 1" schedule 40 pvc from the house. I was planning on installing #4 thhn wire to supply this until I read in the code book that #4 can only be used for the main feeder panel, so now I have to go up to #3 wire. I am also using #8 wire for the ground to a grounding rod. Three #3 wires will fit in the conduit and to code, but it will be hard to pull. My question is can you down size the size of the neutral, or does it have to be the same size?

The upgrading of the PVC to a larger diameter comes to mind.
And the price would difference would not brake the bank either.
Please check about using THHN cable. As it is listed for "Dry & damp locations".
In these parts underground means a wet location, so you my have to switch to say, THWN listed as a wet location, in the NEC table 310.13

jbowlin2
Re: Electrical Sub-Panel Wiring

I realize that a larger size pvc would be a better way to go, however, I originally was old going to put a 60 amp service in until my father-in-law told me he wanted to run his 30 amp motorhome, a 240 welder and an air compressor off this panel. This does not leave me much power left, so I wanted to up size the panel to 100amps. Also I have already buried the 1" conduit and I don't want to go through with digging it back up and renting a ditch witch again.:(

jbowlin2
Re: Electrical Sub-Panel Wiring

I will however look at thwn wire, instead of thhn. Thanks

NEC
Re: Electrical Sub-Panel Wiring
jbowlin2 wrote:

I realize that a larger size pvc would be a better way to go, however, I originally was old going to put a 60 amp service in until my father-in-law told me he wanted to run his 30 amp motorhome, a 240 welder and an air compressor off this panel. This does not leave me much power left, so I wanted to up size the panel to 100amps. Also I have already buried the 1" conduit and I don't want to go through with digging it back up and renting a ditch witch again.:(

Looks to me like FIL needs to bend over and cough up some bucks.

JLMCDANIEL
Re: Electrical Sub-Panel Wiring

The first thing to ask is are you going to be running everything at the same time? Just because the motor home uses a 30 amp plug in doesn't mean it will be using 30 amps.
Jack

Re: Electrical Sub-Panel Wiring
Ernie_Fergler wrote:

Please check about using THHN cable. As it is listed for "Dry & damp locations".
In these parts underground means a wet location, so you my have to switch to say, THWN listed as a wet location, in the NEC table 310.13

good catch

its hard to make a solid determination without more specific info on the welder and air compressor, but 60 amps is probably more then enough. If your unsure post the name plate data from each and we'll figure it out.

Ernie_Fergler
Re: Electrical Sub-Panel Wiring
NEC wrote:

Looks to me like FIL needs to bend over and cough up some bucks.

Or head over to the house with a pick & spade shovel.:D

Ernie_Fergler
Re: Electrical Sub-Panel Wiring
Lloyd wrote:

good catch

its hard to make a solid determination without more specific info on the welder and air compressor, but 60 amps is probably more then enough. If your unsure post the name plate data from each and we'll figure it out.

I agree. Chances are both will not be in use at the same time, unless the father in law is around....:o

jbowlin2
Re: Electrical Sub-Panel Wiring

Good point, I have to do a little bit more research and I will update on amp draw.:)

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.