Electrical wire help Please???

Tech141

Going to run some wire approx. 120 feet from a breaker box to my 30-foot apartment on wheels (camping trailer). The load on the wire will be 30-amps. After a little research, I believe that I will need to run #6-2 UF wire, due to the length of run/voltage drop over the run.

Can anyone in the know verify this as correct? If wrong, what should I use?

As always, Thank you for considering my question.

Have an Outstanding night!

Tech141

It most certainly does. Thank You.

BikerBob

I think that Forge's chart agrees with the National Electric Code table 310

http://www.necconnect.org/tools/nec-table310/


And that you should use number 8 given your run length. Number 6 (assuming you are using copper, is closer to 75 amps.

The key is voltage drop under load on long runs. You may be ok with 8 but 6 won't hurt except for the initial price. It always sucks to say I wish I'd have gone bigger once it's in the ground!

ChrisInTempe

Another useful chart:
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/wirega.html#c2

#6 copper wire will drop about 1.14 volts per current carrying wire at 30 amps over 120 feet. #8 is about 2.26 volts. This is voltage lost to run motors, light the lights, etc. Neither are enough to worry about unless you are starting with a lower than standard voltage already. In any case the more copper put in now is less you need worry about later.

Next is the ground rod. I'd imagine so long a run, you would want to place a ground rod for the camper itself. Such as if you will have a post for your electrical box, add a ground rod there. I do not know if this is to code, but I have seen it done this way.

Tailgunner1954

CIT
Code for a sub-panel calls for both a neutral and a ground wire to be run back to the main. IOW just a ground rod, at the sub, is NOT good enough.
The reason is that there can/will be some difference between the ground voltage at different points in the earth.

Note that above a certain conductor size, you are allowed to run a smaller size ground wire IE: with his 3 conductor run of #8, or #6, he may be able to run a #10 ground wire back to the main (it just needs to be large enough to trip out the main in case of a short)

babun

tail1954 got it correct.
Run the #8's.
Here is what you need, {alas,Underground feed wire is not my favorite thing, pvc conduit and THHN conductors are better [xx(]}

http://www.globalindustrial.com/p/electrical/wire-cable/wire/uf-b-underground-feeder-cable-8-2-awg?infoParam.campaignId=C5E&gclid=CKD94amV68YCFZU2aQodaDUA2g

ChrisInTempe

quote:Originally posted by Tailgunner1954
CIT
Code for a sub-panel calls for both a neutral and a ground wire to be run back to the main. IOW just a ground rod, at the sub, is NOT good enough.
The reason is that there can/will be some difference between the ground voltage at different points in the earth.

Note that above a certain conductor size, you are allowed to run a smaller size ground wire IE: with his 3 conductor run of #8, or #6, he may be able to run a #10 ground wire back to the main (it just needs to be large enough to trip out the main in case of a short)


Good info.

I did mean in addition to, not in place of.