# grounding & bonding question



## bigredc222 (Oct 23, 2007)

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.


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## JohnJ0906 (Jan 22, 2007)

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?


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## brian john (Mar 11, 2007)

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


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## raider1 (Jan 22, 2007)

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


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## bigredc222 (Oct 23, 2007)

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.


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## JohnJ0906 (Jan 22, 2007)

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)


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## bigredc222 (Oct 23, 2007)

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.


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## JohnJ0906 (Jan 22, 2007)

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.


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## bigredc222 (Oct 23, 2007)

Now I have to look it up dag nabit.


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## ghostwriter (Nov 1, 2007)

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.


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## frank (Feb 6, 2007)

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


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## bigredc222 (Oct 23, 2007)

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.


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## raider1 (Jan 22, 2007)

bigredc222 said:


> 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.


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


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## bigredc222 (Oct 23, 2007)




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## bigredc222 (Oct 23, 2007)




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## bigredc222 (Oct 23, 2007)

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


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## raider1 (Jan 22, 2007)

bigredc222 said:


> 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


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


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## bigredc222 (Oct 23, 2007)

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.


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## bigredc222 (Oct 23, 2007)

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?


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## brian john (Mar 11, 2007)

> 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


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.


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## brian john (Mar 11, 2007)

As for Big:

If it is a metallic piping system BOND IT. Though most are bonded through the equipment connected to the system.


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## raider1 (Jan 22, 2007)

> If a building has black pipe for a sprinkler system and also black pipe for gas service. Do these get bonded also?


Does the sprinkler system have at least 10' of metal pipe in direct contact with the earth? If so the sprinkler is a metal underground water pipe and should be treated as a grounding electrode. If it doesn't meet the requirements for use as a grounding electrode then it must still be bonded in accordance with 250.104(A).

And yes a black pipe used for gas needs to be bonded in accordance with 250.104(B)

Chris


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## bigredc222 (Oct 23, 2007)

I've had 2 
occasions when I thought the gas pipe should be grounded and elec. inspector told me no. One of the times was a 60 unit apartments. the gas came in the building in plastic. It hit a manifold about 8' long that had about 20 gas taps. the inside gas line was a flexible tube constructed just like sealtight. metal inside pvc or some type plastic outside. I felt the manifold should be bonded. The inspector made me remove it. Also this was a 1600 amp service it required 3 ground rods no closer that 6' from each other. It had a sprinkler system with a 8" pipe feeding it from outside. I'm sure it met the 10' rule. The inspector wanted to see those ground rods. I just always drive a ground rod It makes the inspectors happy. the last thing you want to do is get in a pissing match with your inspector. He can make your life miserable. I had a case were I wanted to bond my water pipe close to my elec. room. It was about 60' from were the pipe entered the building. there is an exception that says this is OK as long as the entire length of water pipe to the bond point, is only accessible to qualified personal. It was going to save me 60' of 1/0. No go. I even showed the book to the inspector he read it in front of me send that what it says, but I don't care I want it bonded at the entry point. I give them what they want. I'm tired of this topic. I'm going to start a new one.


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## brian john (Mar 11, 2007)

> Also this was a 1600 amp service it required 3 ground rods no closer that 6' from each other


Why 3?


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## bigredc222 (Oct 23, 2007)

I was told it's in the code by an inspector, like over 1000 or 1200 amps needs tryatic ground. I'm sure I'm spelling that wrong. It was also in the spec. for that job. A guy told me a few months ago that all services need 2 rods now. He said it's in the 05 book. I havn't found anything about either . He is from NJ. It might be a code for them. They have sandy soil. 250.53 B addresses. the 6' spacing if more than one rod is used. Like I said inpsectors around here like ground rods. I did fine that gas pipe can't be used as a electrode that's 250.52 B. Holy cow I havn't looked in the book this much in ages. I might be remembering it wrong about the 3 rods. Maybe when I told the inspector the job specified 3 rods he said don't forget about the 6' spacing. I'm no code expert. I know how to look things up when I need to. I used to have the whole amp table memorized. Now for the less common sizes it's more guessing than knowing. Then I look it up.


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## frank (Feb 6, 2007)

Thanks Brian- but more questions.

Do your PoCo provide you with lives and neutral. They bond the neutral to the 'star point'of their transformer . You then bond within your distribution board your ground/earths to the neutral. Is that correct?

Frank


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## brian john (Mar 11, 2007)

We do not distribute to residentials with a star/wye transformer as you guys do. We use a single phase transformer centered tapped. L1 to L2 240 VAC center tapped grounded with 120 VAc to L1 or L2.

The utility bonds the neutral to ground (refereded to in the NEC as the grounded conductor) and we bond the neutral to ground in the service disconnects.


Distribution is Single Phase 3-wire (2 energized and one neutral/grounded conductor)









This can be achieved with one or two pole mounted transformers or one pad mounted transformer (on grade for underground distribution)


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## frank (Feb 6, 2007)

Brian.

We have a similar system here but it is seldom used. We call it a PEN system and the neutral.earth is taken straight back to the transformer.





The system below is the most used and utilises a system of earth electrodes (not shown) connected to the return neutral path conductor along its journey to the transformer. The Supply Co provide all the terminal connections for us to connect to. Each is separate /individual and any bonding of earth/neutral is taken care of by the company.




I mentioned 'residual currents in an earlier post. By this I meant to ask what USA safeguards there were against fault currents from an adjacent property entering the system of another. Here this is taken care of by 'separation of systems' or distance location of grounds/earths

This system below is used for construction sites and often found in locations where the supply is fed via overhead cables and no ground is taken along with them ie. Farms etc







Frank


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## brian john (Mar 11, 2007)

There is no protection from fault currents from adjacent properties entering an it's neighbor.

Common issue is with water line common copper in a neighborhood and common transformer. We have Circulating neutral current all over the place.


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## gilbequick (Oct 6, 2007)

brian john said:


> We do not distribute to residentials with a star/wye transformer as you guys do. We use a single phase transformer centered tapped. L1 to L2 240 VAC center tapped grounded with 120 VAc to L1 or L2.
> 
> The utility bonds the neutral to ground (refereded to in the NEC as the grounded conductor) and we bond the neutral to ground in the service disconnects.
> 
> ...


This is something I've never fully understood. I know here in the US residential services are 220v single phase. I know that they are not "2 phase panels". How does this work? Can someone explain this?


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## bigredc222 (Oct 23, 2007)

frank said:


> Thanks Brian- but more questions.
> 
> Do your PoCo provide you with lives and neutral. They bond the neutral to the 'star point'of their transformer . You then bond within your distribution board your ground/earths to the neutral. Is that correct?
> 
> Frank


 Yes that's how they do 
commercial / industrial transformers. It's Delta on the high side Y on low side. They used to have delta/delta and there was a high leg. We still run into that once in a while in old factories. You have to be careful every third leg is 170-190 to ground. I burned a few thing up as an apprentice.


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## brian john (Mar 11, 2007)

Actually the "HIGH LEG" is 208 VAC to ground. Assuming the actual Transformer output is properly ratioed.

From our friends at Wikipedia (cause basically I am too lazy)

A *high leg delta* (also known as wild-leg or red-leg delta) is a type of transformer winding connection sometimes found in older electrical installations. A transformer wound in this fashion will have four wires coming out of the secondary: the three phases, plus a neutral that is used to center-tap one of the windings. The voltages between the three phases are the same in magnitude, however the voltage magnitudes between a particular phase and the neutral vary. The phase-to-neutral voltage of two of the phases will be half of the phase-to-phase voltage. The remaining phase-to-neutral voltage will be √3 times half the phase-to-phase voltage. Typically, the transformer is designed such that the 'B' phase is the 'high' leg. According to Article 110.15 of the 2005 National Electrical Code, panelboards connected to this type of transformer must explicitly identify the high leg, preferably by coloring it orange.



Consider the low voltage side of a 480/240 V high leg delta connected transformer, where the 'B' phase is the 'high' leg. The line to line voltages are all the same:
_V__a__b_ = _V__b__c_ = _V__a__c_ = 240_V_
Because the winding between the 'A' and 'C' phases is center-tapped, the line-to-neutral voltages for these phases are as follows:
_V__a__n_ = _V__c__n_ = 120_V_
But the phase-neutral voltage for the 'B' phase is different:








This can be proven by writing a KVL equation starting from the grounded neutral:










Another explantion 

*Three-Phase, Four-Wire, Delta-Connected Transformers *


A three-phase, four-wire, delta-connected secondary is a little different. The illustration below shows a delta-connected secondary with 240 Volts phase-to-phase. The midpoint of one phase winding is grounded to provide 120 Volts between phase A and neutral, and 120 Volts between phase C and neutral. The voltage is 208 Volts between phase B and neutral. This is referred to as the high leg. The high leg can be calculated by multiplying the phase A to neutral voltage times 1.732 (120 x 1.732 = 208). 







Single-pole breakers should not be connected to the high leg. NEC Article 215-8 requires that the high leg bus bar or conductor be permanently marked with a finish that is orange in color. This will help prevent electricians from connecting 120-Volt single phase loads to the 208-Volt high leg. Four-wire, delta-connected transformers should always be wired so that the B phase is the high leg. Not all panelboards are suitable for use on a high leg system.


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## bigredc222 (Oct 23, 2007)

It must have been a 110/220 trans. that would put the high leg about what I remember it. I wish I was smart enough to try out some of those equations.


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## Magnettica (Jan 23, 2007)

gilbequick said:


> This is something I've never fully understood. I know here in the US residential services are 220v single phase. I know that they are not "2 phase panels". How does this work? Can someone explain this?


Simple, really. 

Half of the 240 volt coil is phase A, 120 volts to common, the other half is phase B, 120 volts to common.

The common is the tap in the center of the coil.


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## Absolutetruthz (Feb 25, 2008)

bigredc222 said:


> 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?


 
250.104(B) Gas piping does NOT have to be bonded if it has an equipment ground for the device.


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## JohnJ0906 (Jan 22, 2007)

Absolutetruthz said:


> 250.104(B) Gas piping does NOT have to be bonded if it has an equipment ground for the device.


Check with your AHJ on this. Some areas are requiring a separate bond for CSST gas piping, per manufacturers instructions.

Lipstick on a sow, IMHO.


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