Electrical wiring to new pole barn question

[Food Scientist]

I'm in the planning stages of building a new pole barn and have an electrical question. I'm planning on running new service from the existing drop from the transformer to the barn and don't know if I need a ground wire the entire length of the cable or if a ground wire from the main disconnect in the barn to a grounding rod buried in the earth is sufficient. My thought is that the purpose of the ground wire in the cable is to basically carry current in the case of a fault back to the existing ground rod at the utility pole.

Here are more details:

Plan to run 200 amp service with a distance of about 250 feet
The two options I am looking at are an aluminum 3 wire URD (direct burial cable) with no ground wire or an aluminum 3 wire SER (service entrance cable, also direct burial) with a bare ground wire. Cost difference between the two is about 500 bucks.

For 500 bucks do I really need a ground wire if I can install a grounding rod at the barn that is connected to the main disconnect?

 

[CarbonSteel]

On the drops that I have done like this, it is 3 wires from the transformer (or utility demarc) with a ground rod at the 200AMP panel location such that the ground is "local" at the 200AMP panel. Codes vary, though, so it may not be the same practice at your locale.

 

[rfeir]

No ground wire from the pole. Two ground rods 5 feet apart with adequate cu wire run directly to ground bar in new 200 amp box. Again, check local codes.

 

[Food Scientist]

Thank you both. My township uses the Michigan Electrical Code which is based on the NEC, and yes I will use 2 grounding rods buried 10' in the ground spaced apart. These townships are not very forthright with info making it difficult to know how to proceed.

Thanks again.

 

[eljefino]

So will the barn have its own electric meter? Will you be on the hook for a minimum fee if you don't use a certain amount of power?

The code as I understand it is that each out building needs its own ground, is not grounded to the main house, and the main house will have the PoCo neutral grounded at one spot, there.

On the assumption that your barn has a meter, it may count as a "main".

You could ask the PoCo what they expect. Their end of the meter doesn't have to meet NEC, just internal criteria!

 

[Linctex]

Will you be pouring any concrete?

If so, you can use an Ufer ground

https://en.wikipedia.org/wiki/Ufer_ground

 

[exranger06]

Originally Posted by SVTCobra
I'm in the planning stages of building a new pole barn and have an electrical question. I'm planning on running new service from the existing drop from the transformer to the barn and don't know if I need a ground wire the entire length of the cable or if a ground wire from the main disconnect in the barn to a grounding rod buried in the earth is sufficient. My thought is that the purpose of the ground wire in the cable is to basically carry current in the case of a fault back to the existing ground rod at the utility pole.

Here are more details:

Plan to run 200 amp service with a distance of about 250 feet
The two options I am looking at are an aluminum 3 wire URD (direct burial cable) with no ground wire or an aluminum 3 wire SER (service entrance cable, also direct burial) with a bare ground wire. Cost difference between the two is about 500 bucks.

For 500 bucks do I really need a ground wire if I can install a grounding rod at the barn that is connected to the main disconnect?

SER is NOT permitted to be underground!
If it's going directly to the transformer, then no, there's no ground wire. It's the same as wiring a service for a house.

 

[The_Eric]

I can't offer any help directly to your question, but will offer this - if your ground is even the least bit rocky then skip the direct burial wire. I've had 2 sets of direct burial wires get a fault in them going to my garage, losing a leg each time. It's not happening again as I'm putting it in conduit this time around.

 

[Food Scientist]

To answer everyone's questions:

The current setup to the house is a drop from the utility pole on the west side of the house, then buried wire to the north side of the house where the meter is located and is only 100 amp service. I'm planning to build to the southeast of the house so the plan was for the electrical company to move the meter to the utility pole, do a split and keep the current wire to my house and lay the new wire to the barn.

So I won't have a new meter installed.

I will be pouring concrete only on part of the barn.

Thanks for the clarification on the SER cable, I did read today it was for transformer to meter wire. Not sure how I got confused.

I was planning to lay 2" electrical PVC conduit, there are quite a few rocks and my thought was if I ever have a problem conduit at least allows me to pull the wire out.

 

[exranger06]

If you move the meter to the pole, you may or may not need a disconnect right there at the pole. You might need basically a box that just has a 100 amp breaker that feeds the house panel, and a 200 amp breaker that feeds the barn. If you do install one of these, then that disconnect is basically considered to be your "main" breaker panel, and the panels in the house and the barn are considered to be subpanels.

Now, subpanels require a 4-wire feed (ground wire separate from neutral). You need separate neutral bars and ground bars inside the panel - the ground bar is to be bonded to the enclosure, and the neutral shall NOT be bonded.

So my point is, if you do have a disconnect on the pole, you would need to dig up the existing wire going to the house, replace it with a 4-wire cable, add a ground bar kit to the house panel and relocate all of the ground wires to it, and make sure the neutral bar is not bonded to the panel. And of course, to answer your original question, the wire going to the barn will indeed need to be a 4-wire cable as well. That is, if this to be inspected and up to the latest code.