Wiring Pole Barn

Does the following sound like I"m on the right path?

1: Got a 100 amp breaker for the breaker box at the house - 2 pole. Connect 2 to breaker one to the common(white wire) and one to ground bar.

2: Have a 100 amp breaker box in barn: Same as with the house, 2 at the main lugs, 1 at common and 1 at ground bar.

Do I need to ground the box at the barn? i am installing a water spicket/hydrant/hose bib at barn. If I need a ground can I just connect to that? If so how? Where?

Any other pointers?

Black and red should hook to the hot 100 amp feeds at the house panel. White to the neutral bar in that panel. Bare or green goes to the ground bar, and in that panel the ground bar will be connected to the neutral bar, probably through a grounding screw and the case.

At the barn panel, black and red go to the main breaker input terminals. White goes to the neutral bar and the neutral bar grounding screw is removed. Bare or green goes to the ground bar which is connected to the case. That provides the safety ground for the wiring in the barn. You can add a ground rod at the barn, but 3' is not sufficient to be worth any safety. It needs to reach permanently damp ground and lots of it. 8' is minimum, sometimes to get a good ground takes several rods longer than 8'.

Gerald J.

It is possible to wire with one less wire (no ground) and drive an 8' ground at the outbuilding, but not all locations support that to code. It is basically an ag exception, and even less allowed when water lines are involved because of the potential for stray voltage being carried between your buildings on the water pipes. You already have the wire with ground, so good for you.

According to voltage drop calculators (such as
Link

So, I think you will be limited to running with a 60 amp supply breaker.

--->Paul

According to that one I only have a 4.1% drop....

If I put a 60 amp breaker at the house, wouldn't I end up with 55(or some lower number) at the barn, due to losing voltage over a long run??

I was thinking 100 amp breaker at house but may end up with only 90 at the barn(still plenty for me)

I think a lot of electric motor folks do not like more than 3% voltage drop. Makes their motors work harder, & burn up a bit sooner, and you lose the 4% to heat so your electric bill is a tad higher.

I think you are ok with a 5% voltage drop as far as code goes?

So your 4+ drop is in the grey area. Ok to use & I suppose you won't really use 100 amps ever anyhow.....

Maybe. From just a simple dirt farmer.

You might want to consider the runs to the box you are drawing from, as well as how long the runs will be inside your building. If you have long runs all over on marginal wiring, your motors might not be happy.

But I guess it will be alright for you, you seem to have apretty good handle on it.

Figured the real electricians here would come in with good numbers for you. :)

--->Paul

Gerald J.

But no matter the supply breaker I will lose some due to length of run correct? So if I start with 100 I will end with 90(or so) and if I start with 60 I would only end with 55(or so).

Paul stated the wire at that distance would only support 60 amps. That has me confused. #2 will support 100 amps at a shorter distance.

I really do appreciate your help I am just confused.

Should I use a 60 amp supply breaker? Or is 100 ok.

Thanks Gerald for your input.

You will lose VOLTAGE at the far end of the run not current. Say you have 240 V at the source end (your house) and your load at the barn is drawing full 100A, you will have less than adequate voltage at the barn to run your load, considerably less than 240V. What paul means is that to have adequate voltage at the barn the most current you can flow (biggest load)is 60A. Your loads at the barn should be protected by there own breaker so the breaker at the source end only needs to protect the wire from OVERCURRENT in the case of a fault. If you already have the 100A breaker I would use that, If not, a 60A breaker would be cheaper but the #2 might not fit in it. Hope that helps...

Gerald J.

There is a concern of having different potential ground if you have it grounded at the house and also at the barn.

steveormary