House to pole barn, about 230 ft. 100 amp to barn, #2 alum AWG. Direct buried currently.
Do I need to have ground from house to barn? The both have their own ground rods.
2 hots, 1 common, and a ground at the moment. 1 of the hots is only putting out about 50 volt. I know the problem is under ground.
I need to trench and put in conduit with new cable.
For a TEMPORARY fix to get the barn working could I just switch the ground cable to to replace the bad hot one?


Edit to add:Is EMT plastic conduit the thing to use?

are you going under a driveway ? gravel?

Disclaimer: This advise is worth half of what you pay for it!
Rigid Polyvinyl Chloride Conduit id what you need, known as PVC. Get schedule 80. 1 1/4" conduit.
Don't use the existing underground ground wire as a replacement for the burned up one. Likely the rest of the conductors are in almost as bad a shape as the "bad" one.
If you do so, you have no grounding at the barn. This is a very bad thing in a system that already is questionable.
Would it work in the short term? Perhaps.
Is it dangerous? definitely.
Do it right.
I have seen too many "tempory" fixes become permenant because "problem solved, next project"
Good luck

Yes to the driveway, not used daily but does have propane truck across it 4/5 times a year. Other then that my pickup is the biggest thing on it.

I'll follow up in a bit. The short answer is unless you have power company add second service you DO NOT ground at the subpanel. All electrical equipment is bonded to the electrical service from which it comes from, you never create multiple ground paths (house grounding + building grounding). The existing wiring is also too small.

Edit - this reply contained wrong information it's a separate structure and needs ground rods. Completely screwed that up.

Here's a picture of correct set up. This one uses direct burial cable, works the same with conduit.

This message has been edited. Last edited by: Skins2881,

your no 2 wire is way to small and that's why you are getting a voltage drop, you always need a ground. I would be running a 4/0 4/0 2/0 and a 4 for ground. expensive yes.

Here's what you need to do:

Direct burial wire is OK to use. I would not use it but it is up to code and if you live somewhere there is not a lot of rock it is OK.

As far as ground rods/grounding. It used to be allowed to run three wires (two hots and neutral) to an out building and drive ground rods. It no longer is because it turns the building into part of the grounding for the house. You need to run four wires and rewire how the panel is set up at the garage by adding a ground bar attached to the metal enclosure of the panel, then isolating the grounds from the neutrals.

Wiring sizing used to be OK per 315.15(b)(7) (feeder table). They changed the wording of the code to say that this only OK if it serves the entire premise's load, which it will not even though it is a feeder. You now need to use 315.16 (b)(16) which used to be 310.16 which treats the sub-panel like it's a branch circuit.

Per that chart you would need a #1Al or #3Cu before taking into account voltage drop. To account for voltage drop I would use #1Cu or 1/0Cu (boarder line if allowing for 3% voltage drop and a huge price difference). If you go with aluminum then 2/0Al. Run the wire in 1.5" PVC schedule 80 for Cu or Al, but 2" may make it easier to pull for that distance if you go Al.

Use the above size wiring for the two hots and neutral. If you use Cu use a #6 for the ground, #4 for Al. If you do choose to do direct burial than make sure to remove the rock from the trench backfill dirt before backfilling.

Burial depth for either should be 18" to the top of the wire or conduit, so approx. 20" deep.

Conductor Ampacity

VD calculator Use 80A for VD calc as you will should not be using more than 80% of the service rating anyways.

I've found grounding questions to be among the most difficult in terms of NEC. A lot of the rules are counter intuitive.

As an example, a lot of ham operators ground their stations using their own ground rods at their ham stations, and sometimes at the antenna. Apparently if done wrong, this is against NEC. Who would have thought.

quote:

Originally posted by radioman:
I've found grounding questions to be among the most difficult in terms of NEC. A lot of the rules are counter intuitive.

As an example, a lot of ham operators ground their stations using their own ground rods at their ham stations, and sometimes at the antenna. Apparently if done wrong, this is against NEC. Who would have thought.

See above. The RG-6 used from the antenna to the house is a better conductor often than the ground rod, so a overcurrent/surge at the house will go to the antenna through coax, especially true if the antenna is closer to the transformer than the house grounding. Also the opposite is true. The house grounding is a better path for lightning to go to ground so a lightening strike will travel through Coax towards house possibly and melt coax and isolators along the way.

You should run a #6 ground to the house and attach to the houses grounding electrode conductor. Usually the easiest place is at the ground rod using an intersystem bonding terminal. Or directly to the houses neutral point connection.

Google antenna struck by lightening. Often times it melts the coax and fries anything connected to that coax (unsure of HAM equipment names or cost, but I assume the radios are not cheap). Also Google side flashes, scary stuff if comms wiring is not properly bonded.

For HAM or other radio stuff I would contact an electrician specializing in that because I am unsure the effects of properly bonding would have of radio signals. *Added* I don't see anything wrong with ground rod at antenna as long as its bonded with #6 going to house GEC. Again consult electrician electrician with experience grounding/bonding antennas.

This message has been edited. Last edited by: Skins2881,

Not an electrician and wouldn't presume to guess at wire sizes. Will just say two things based on experience here at the ranch:

1) Go oversize on your conduit. Dunno what the price difference between 1.5" schedule 40 conduit (no need to use sch80 for conduit below grade, though it is great above grade and for high pressure H2O) and 2" sch40 conduit, but the difference it will make in pulling the wire is well worth it.

2) While you have the trench open, throw another conduit in it. Throw two or three extras in if you are going to pave, put concrete, or build something over the top of you trench. I can't tell you how many times I was thrilled I had a spare conduit or how many times I wish I had put in more. I have *never* thought, "Gee, I wish I hadn't put that extra conduit in."

A couple other thoughts on pulling wire: 1) Clear Glide is your friend. 2) Putting it together with all the bells pointing the same direction and pulling the wire so you are always crossing into the bell at each junction doesn't hurt either.

Good luck!

^^^ Good advice. You never know when you may want to add internet or TV to the building. A 3/4" run would be nice to have if you want.

40 is OK for direct burial, but if subject to physical damage go with 80. Technically where it leaves the ground is subject to physical damage, but we always use 40. Your AHJ may vary on it's uses.

quote:

Originally posted by slosig:
Not an electrician and wouldn't presume to guess at wire sizes. Will just say two things based on experience here at the ranch:

1) Go oversize on your conduit. Dunno what the price difference between 1.5" schedule 40 conduit (no need to use sch80 for conduit below grade, though it is great above grade and for high pressure H2O) and 2" sch40 conduit, but the difference it will make in pulling the wire is well worth it.

2) While you have the trench open, throw another conduit in it. Throw two or three extras in if you are going to pave, put concrete, or build something over the top of you trench. I can't tell you how many times I was thrilled I had a spare conduit or how many times I wish I had put in more. I have *never* thought, "Gee, I wish I hadn't put that extra conduit in."

A couple other thoughts on pulling wire: 1) Clear Glide is your friend. 2) Putting it together with all the bells pointing the same direction and pulling the wire so you are always crossing into the bell at each junction doesn't hurt either.

Good luck!

Include a new pull string each time you pull in metal only

Thank you gentlemen for your wisdom.
The bad leg has been disconnected. I have some lights & plugs to use.
I will be getting a backhoe in to trench for conduit/cable.
Wire alone will probably $600 or more.
I should have put conduit in the first time.
Sigh.

Ever read a thread and realize how ignorant you are about a subject?

Well, that just happened to me.

quote:

Originally posted by chongosuerte:
Ever read a thread and realize how ignorant you are about a subject?

Well, that just happened to me.

Apparently a Master Electrician can be ignorant too. See above. Mixed up separate building with non-separately derived systems grounding and bonding requuments. Told OP not to use ground rods incorrectly.

Need to go put on dunce cap now.

Skins:

Your first post now reads:
Edit - this reply contained wrong information it's a separate structure and needs ground rods. Completely screwed that up.

Your second post reads:
As far as ground rods/grounding. It used to be allowed to run three wires (two hots and neutral) to an out building and drive ground rods. It no longer is because it turns the building into part of the grounding for the house. You need to run four wires and rewire how the panel is set up at the garage by adding a ground bar attached to the metal enclosure of the panel, then isolating the grounds from the neutrals.

The two posts contradict each other?

If you have a sub panel, it should have 4 wires with an isolated ground.

In this situation when you add a second ground rod for the out building the neutral in the second building does not need to be bonded to ground. Doing so would create a parallel neutral path to ground.

quote:

Originally posted by Excam_Man:
Skins:

Your first post now reads:
Edit - this reply contained wrong information it's a separate structure and needs ground rods. Completely screwed that up.

Your second post reads:
As far as ground rods/grounding. It used to be allowed to run three wires (two hots and neutral) to an out building and drive ground rods. It no longer is because it turns the building into part of the grounding for the house. You need to run four wires and rewire how the panel is set up at the garage by adding a ground bar attached to the metal enclosure of the panel, then isolating the grounds from the neutrals.

The two posts contradict each other?

If you have a sub panel, it should have 4 wires with an isolated ground.

It makes sense to me. Maybe I'm not saying it correctly.

You need two hots, a ground, and a neutral. The neutral and ground are not bonded in the subpanel (bond screw removed), and a ground bar is added, but you do still drive ground rods. Previously you were allowed to run two hots and a neutral, and drive ground rods. This is no longer allowed.

quote:

Originally posted by Skins2881:

You need two hots, a ground, and a neutral. The neutral and ground are not bonded in the subpanel (bond screw removed), and a ground bar is added, but you do still drive ground rods. Previously you were allowed to run two hots and a neutral, and drive ground rods. This is no longer allowed.

Would you happen to know the part of the NEC which covers the requirements of the additional ground rod at the sub-panel?

250.32(A) per google. Let me go grab my code book real quick.