Pole Building -- Electrical Question

[woodlandfarms]

Just for my own personal edification, can someone explain to me why the 4th wire is now required? Is it in case the nuetral gets cut the ground will still be active? Is it too much juice feeding back on the Nuetral and the ground is for extra "pipeline"? We have an old well that the previous owner took out. But he converted the electrical connection to a couple of 110 plugs. But it is two hots and a ground. I know it is not the safest but trying to figure out if it is worth my while to dig up 300 feet of cable to make a change.

 

[rambler]

Thanks to all for the 4 wire explanation. Still somewhat confused but agree that the latest NEC should definitely be followed. I guess I need a newer code book! Jim

I agree it's confusing. I had the farm backbone rewired - was ovehead #8 wires installed in the 1950's. Went to 3 underground wires, a 350 foot branch, a 400 foot branch with 2 100 foot spurs, and a 100 foot branch to the house. The transformer/ meter/ main box is in the middle of the yard. They set up 200 amps to most locations, with 60 amp to each building (11 of them) along the way.

Because of ag exemption, I could do the 3 wire, ground at each building. Three of the buildings have metal water pipes connectiong; didn't matter. That was all cool in my location, my setup with the central meter pole, my farm setup.

And so on.

Pro electricians set it up & did it; county inspector came 3 months later & looked at the main panel & 3 buildings, said it all passed, & put my sticker on the main panel. Good to go.

Basically you need to follow whatever code is in the books in your county, and make your local inspector happy - they might have their own ineterpitation of the code sometimes.... Local electrical people will likely get along with the inspector real well as in my case, and things will be bried & easy. Outsiders or self-done work will take a lot closer inspection and thought to get an ok......

The 4 wire deal is a new thing. Back in the 1950's, delivering electricity was the goal. Now a days a lot of safety is more of a deal. The ground wire/ circut is there ti bleed off electricity quickly; make fuses or breakers snap _right_ away, and allow the new fangled ground fault type equipment to work. It is best to have a wire going all the way around the whole electrical system that does nothing but ground any metal off to ground. And if it is grounded in several places, it can confuse that fancy equipment & create it's own backwards loops of electricy. So - it needs to be installed correctly, and not confused with the neutral wire.

--->Paul

 

[firefighter jim]

I agree it's confusing. I had the farm backbone rewired - was ovehead #8 wires installed in the 1950's. Went to 3 underground wires, a 350 foot branch, a 400 foot branch with 2 100 foot spurs, and a 100 foot branch to the house. The transformer/ meter/ main box is in the middle of the yard. They set up 200 amps to most locations, with 60 amp to each building (11 of them) along the way.

Because of ag exemption, I could do the 3 wire, ground at each building. Three of the buildings have metal water pipes connectiong; didn't matter. That was all cool in my location, my setup with the central meter pole, my farm setup.

And so on.

Pro electricians set it up & did it; county inspector came 3 months later & looked at the main panel & 3 buildings, said it all passed, & put my sticker on the main panel. Good to go.

Basically you need to follow whatever code is in the books in your county, and make your local inspector happy - they might have their own ineterpitation of the code sometimes.... Local electrical people will likely get along with the inspector real well as in my case, and things will be bried & easy. Outsiders or self-done work will take a lot closer inspection and thought to get an ok......

The 4 wire deal is a new thing. Back in the 1950's, delivering electricity was the goal. Now a days a lot of safety is more of a deal. The ground wire/ circut is there ti bleed off electricity quickly; make fuses or breakers snap _right_ away, and allow the new fangled ground fault type equipment to work. It is best to have a wire going all the way around the whole electrical system that does nothing but ground any metal off to ground. And if it is grounded in several places, it can confuse that fancy equipment & create it's own backwards loops of electricy. So - it needs to be installed correctly, and not confused with the neutral wire.

--->Paul

Paul and any other person in the know, I did NOT bond the neutral in the subpanel of my outbuilding that I fed with the 3 wire system a couple years ago. Should I leave it that way? I'm hearing conflicting stories (to bond or not to bond subpanels with 3 wire supplies). I've been going through my NEC book (1993 edition) and I can't seem to find the answer. Thanks in advance, Jim

 

[mlitt12345]

Paul and any other person in the know, I did NOT bond the neutral in the subpanel of my outbuilding that I fed with the 3 wire system a couple years ago. Should I leave it that way? I'm hearing conflicting stories (to bond or not to bond subpanels with 3 wire supplies). I've been going through my NEC book (1993 edition) and I can't seem to find the answer. Thanks in advance, Jim

I'm curious to the answer of this as well.....my polebarn sub panel is a 3 wire set up also and I just looked at it and the electrician that installed it bonded the neutral and grounds and it has a earth ground rod also. Is mine right or wrong?

 

[kennyd]

I'm running two hundred and fifty feet of service, 100 amp, to a barn. I'm using 1/0 for the hots and a 6 gauge for the neutral. For four hundred feet I think I would want to talk to the electric company about seperate service with the barn having its own meter.

Usually the Neutral is only de-rated one size-#6 for your Neutral sounds to small to me...It's OK for the ground.

 

[ray66v]

Usually the Neutral is only de-rated one size-#6 for your Neutral sounds to small to me...It's OK for the ground.

You can use a smaller ground wire on a sub panel. But, I have never heard of an undersized neutral. Since 1/2 the current flows on the neutral wire, I don't see how you can de-rate it.

As I have said, my understanding has been you do bond the neutral, and ground, on a 3 wire sub panel. I always have used the unbonded 4 wire method, so I have never been through an inspection any other way.

 

[Inspector507]

Paul and any other person in the know, I did NOT bond the neutral in the subpanel of my outbuilding that I fed with the 3 wire system a couple years ago. Should I leave it that way? I'm hearing conflicting stories (to bond or not to bond subpanels with 3 wire supplies). I've been going through my NEC book (1993 edition) and I can't seem to find the answer. Thanks in advance, Jim

Jim, if you have an existing 3 wire feed to a separate building, yes bond the neutral to the cabinet and make sure there is a ground rod installed. It's the best you can do at this point.
The NEC was changed because the old arrangement was causing current to be carried on the neutral conductor in a fault to ground situation. The ground rod does not make a "ground". It is just a method of bleeding off transient voltage, such as lightning. The earth is a poor conductor for a fault to ground to return to it's supply and will not be a low impedance path back to to the supply. The neutral conductor then must try to be that low impedance path.

 

[SPIKER]

the outbuilding (since it is separate bld) should have a ground rod installed. the panel bond/ground should be tied to the new/2nd bld's ground rod. It should not be tied to the Neutral in the Sub panel that is in the 2nd bld.

Inspector57 is an Ohio inspector if I'm not mistaken, I have not been in the house hold buis in a good while... Moved into industrial side years back and have sense moved to mobile equipment design...

I have a copy of 2008NEC but have not specifically checked on this issue, I know it was confusing on the 2005NEC when many of the 3 vs 4 wire changes started piling up.

Mark

 

[Inspector507]

the outbuilding (since it is separate bld) should have a ground rod installed. the panel bond/ground should be tied to the new/2nd bld's ground rod. It should not be tied to the Neutral in the Sub panel that is in the 2nd bld.

Mark, when a 3 wire feed was permitted to a 2nd building, a connection from the neutral to the ground was required. He does not have a ground coming from the main panel.

 

[dcyrilc]

It is perfectly acceptable here in Ohio! Tell me why it wouldn't be.

Not legal anywhere in the United States. NEC code violation. Also, that setup DOES NOT provide short circuit protection.

Even previous versions of the NEC required neutral and ground to be bonded together in a three wire system or seperated in a four wire system.

For safety, the grounding system MUST be bonded to the neutral, and is only bonded in one location. With a three wire system to the subpanel, if the neutral and ground are not bonded together, you have no overload or short circuit protection at the remote location. Code violation, unsafe, etc, etc...

With a four wire system to the subpanel, the neutral and ground must be isolated from each other. If they are connected together at the remote location with a four wire system, 1/2 of the return current to the main panel will be on the ground wire. Code violation, unsafe, etc, etc...

Any other questions?