bigredc222

This is how I do my grounding and bonding of
multiple panel services. I know it's a good installation, but I'm not sure it covers the code for bonding to the letter. My regular inspectors always see it my way that bonding the neutral at the lug in the trough is good. I have to get this service inspected by a city inspector that's a b--l breaker. I'm wondering if he will make me run the 1/0 bond to every panel? I'm not sure how the code reads on that.

JohnJ0906

I think that I would take the #6 from the rod direct to the grounding lug in the trough, and use 1/0 from each disconnect to the lug.

What size are the disconnects, and what size total? What size service conductors?

__________________
John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.

brian john

From who's transformers utility or a seperatly derived system you have installed?

raider1

I don't understand the point in looping the #6 for the ground rod through each panel.

As John pointed out just run the #6 to the lug in the trough.

Each disconnect or panel should have a main bonding jumper.

Chris

bigredc222

It's Peco in Eastern Pa. I'm looking at the lug in the trough as the bonding point. I'm keeping the
neutral and ground separate at the disc. I know it has to have the # 6 at each panel unbroken. I wasn't sure If I also needed the bond. The neutral gets it's bond at the trough so I didn't see the point in bringing it to panel. It's done now so we'll see what the inspector says.

JohnJ0906

If you are bonding neutral to GEC in the trough, then the grounds to the disconnect would need to be sized to 250.122, I believe.

Are the disconnect fuses/breakers 200 amp or less? (#6 good to 200 amp per table 250.122)

__________________
John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.

bigredc222

The wire to the ground rod never has to be bigger that #6 for a few dollars worth of wire I should just run a properly sized ground wire to each panel and be done with it.

JohnJ0906

Is there some POCO rule that the ground rod GEC go to the disconnects?

I just think it is a lot of trouble to run that continuous the way you did when it isn't necessary, thats all.

As long as the breaker,fuses in each disconnect are 200 amps or less, I think you are legal.

__________________
John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.

bigredc222

Now I have to look it up dag nabit.

ghostwriter

Based on the drawing, I dont see the need for a ground rod, unless a local requirement, the building steel supplements the water pipe.

There is no need to bring any grounding electrode conductors into the service entrance disconnects, because the neutral is already grounded in the trough.

Just install a main bonding jumper at each service disconnect and you are done.

As drawn there will be parallel paths for neutral current, when the main bonding jumper is installed.

If the structural steel is effectively bonded together you can also install a bonding jumper from the steel to the water pipe. You would not have to bring a grounding electrode conductor all the way from the water pipe to the service entrance equipment. This may save you some time and some money.

frank

I just don't understand. Tell me if I am wrong. Your supply Company do not supply a dedicated ground/earth with a guaranteed impedance? You install ground/earth electrodes - but not always - if water pipes etc are available? How do you ensure impedance values sufficient to operate circuit breakers within specified times. And how do you protect against transient currents if a dedicated ground such as a rod becomes open circuited. I'm all mixed up. help

Frank

bigredc222

On a regular single panel service fed from a power company xformer. I am required to build the pad for their xformer with a #4 ground ring around the pad and a ground rod in the opening of the pad that the pipes enter the trans. I pull all the wire and do all the term. in the xformer. All they do is the final High volt tap at the pole or their splice box. At the panel I must bond the building steel and the water pipe to the panel and a #6 to a ground rod. The bonding wire is sized according to the service size. 250.66 There is an exception (250.66A) that says a the wire used to ground the panel to the ground rod never has to be bigger than a # 6 copper # 4 alum. You need all 3. That's in the NEC or I've been lied to by a bunch of inspectors.

raider1

I feel you have been lied to by the inspectors, unless there is a local amendment to the NEC.

250.50 requires all grounding electrodes that are persent at a building or structure to be bonded together to form the grounding electrdoe system. If you have building steel and a metallic water line that meet the requirements of 250.52(A)(1) and (A)(2) then there is no need to drive a ground rod.

Also if you have footing steel that meets the requirement of 250.52(A)(3) then you must use it as a grounding electrode.

Chris

bigredc222

bigredc222

bigredc222

Water pipe is only good if it isn't insulated from the earth. or if it changes to plastic. Biulding steel has to have like 10' of steel in contact with earth. this building meet doesn't meet that. So the water pipe and building steel needs to be bonded to the panel and ground rod

raider1

If that is the case then the ground rod must meet the 25 Ohm rule or be supplemented by an additional grounding electrode. (250.56)

Do you have an all metal water piping system?

250.104 requires a metal water piping system to be bonded to the service. If the water piping system is mostly plastic with short sections of metal it isn't a metal piping system and doesn't required bonding according to 250.104

Also is the building steel likley to become energized?

250.104(C) only requires exposed structural metal that is likely to be come energized to be bonded.

Chris

bigredc222

What I seem to run into a lot, and is the case in this building. It's block walls with bar joist roof. So that needs to be bonded. Then with the water. Inside the water is copper the drain is plastic. Outside plumbers around here use 1" black plastic pipe they roll out in the ditch, or copper that comes in big rolls already insulated. Because of that inspectors like to see ground rods.

bigredc222

OK lets see what this starts. If a building has black pipe for a sprinkler system and also black pipe for gas service. Do these get bonded also?

brian john

in a residential service the utility supplies 3-wire single phase 240/120 L1, L2 and the neutral/grounded conductor, they ground the neutral at the transformer.

Ground connections to earth have little or nothing to do with the operation of over current protection devices (OCP's), ground connections (bonding) from the service through out the facility insure proper operation of the OCP's.

Typical service, if copper is available they do earth connections to the copper water pipe, though thankfully this is going away. I say thankfully as this connection results in ground current on the water piping system. If there is plastic water pipe you are required to drive one rod and test for impedance if less than 25 ohms you are good, if higher that 25 ohms you must drive a second rod and that is it. Most electrician's drive two rods and are done with the earth ground connection.

We really do not care about the resistance to ground in residential applications as this connection is necessary for accidental utility primary to secondary faults (seldom happens?) and lightning strikes. Florida is the capital of the USA and possible the world for lightning strikes and their soil pretty much sucks for low resistance earth/ground connections. Lots of sand.

As for transients, other than lightning I do not see how a ground system would protect from line transients.