Bonding and grounding

[bernardmulherin1978]

OK, I have an old system that I am trying to bring up to code, let me give you some details. 800 amp 277/480 .Y.at the switch gear there is of coarse parallel feeds. Three hots and a neutral, there also is ground coming from the transformer in both pipes and going to a lug on the switch gear can. Also bonding bushings at this point and the other panels that are high voltage. I have not located a ground rod as of yet. There is a 4 /0 coming off the neutral bar and bonding the cold water pipe. I know back when this was put in you guys used the pipe for your ground. This has me throwed off just a little. There is no main bonding jumper in the switch gear. Why. Can some one please explain why its done this way. And what do I need to do to bring it up to code. With the grounds coming through with the feeder pipes, is it supposed to be separate at the switch gear. And if so this is the first point of power, before the switch gear is the transformer and meter. Why the the cold water pipe bond coming off the neutral bar. Also the transformer is stepping voltage down to 120/208 .how do I bond and ground on this past the transformer. Thanks

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[ActionDave]

I would love to help, and so would other members of the forum, but I can't tell what is going on or where you think the problem is. Maybe you could break things down into some more bite size chunks.

In general, neutrals and "grounds" get bonded together at the service disconnect, everything before that belongs to the utility. Neutrals and "grounds" for the transformer get bonded in the transformer or the first disconnect.

There is nothing wrong with a lack of green wires in the conduit. Metal conduit is an excellent equipment grounding conductor.

 

[bernardmulherin1978]

I understand, its just some what strange to me cause we don't do things this way anymore, I think that its fine and with in code after studying it. They came off the neutral bar and bonded the cold water pipe. Why did they do it that way and is that OK

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[ActionDave]

If it is the first disconnect it has to be that way by code.

 

[david]

from your description it sounds like an SDS but you need to clarify this

The equipment grounds along with the neutral coming from the transformer as well as the un-bonded neutral in the disconnect would indicated the bonding was done in the transformer that too would need verified

If the bonding is being done in the transformer the neutral bond to the metal water pipe should have come from the transformer neutral not the fist disconnect neutral

250.104 (D)

 

[bernardmulherin1978]

The bonding was done at the transformer, from the transformer they brought three hots, a neutral and a ground. It is separated in the first disconnect. If you look at the pic of the main switch at the top right is the 4/0 copper that comes off the neutral bar and bonds the cold water pipe. My question is, is it within code to come off the neutral bar at this point when the bonding was done outside at the transformer. Can you bond something like this on down the line like this instead of at the point where you bond the neutral in the first place,

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[bernardmulherin1978]

Also we have a step down transformer, for all the low volt in the building, according to 250.104d,on separately derived systems we have to bond the cold water and structural steel also.

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[lordofthisworld]

I understand, its just some what strange to me cause we don't do things this way anymore, I think that its fine and with in code after studying it. They came off the neutral bar and bonded the cold water pipe. Why did they do it that way and is that OK

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If I am looking at the picture correct, it looks like the main gear, in which, the ground going to the water main, is the electrode

 

[lordofthisworld]

The bonding was done at the transformer, from the transformer they brought three hots, a neutral and a ground. It is separated in the first disconnect. If you look at the pic of the main switch at the top right is the 4/0 copper that comes off the neutral bar and bonds the cold water pipe. My question is, is it within code to come off the neutral bar at this point when the bonding was done outside at the transformer. Can you bond something like this on down the line like this instead of at the point where you bond the neutral in the first place,

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No it’s not correct if the bonding is at the Tranny, were they using the water pipe as an electrode? If so, u would have to re-route that 4/0 to the Tranny.

 

[bernardmulherin1978]

I didn't think it was correct, but if you read in section 250.104.it almost sounds like its OK. What I have is a building that has multiple offices in it. I am going to get the power company to open the transformer up so I can make sure the bonding is done there, I didn't see a ground rod outside the trans. So if its wrong then it should have been pulled from the trans, all the way into the building, inside the pipe that the feeders are in, they didn't do that which makes me think there may be an exception somewhere. Its some what confusing me. There are also bar Joyce's inside that's not bonded either. Also the transformer stepping down to low voltage, is a separately derived system, which requires it to also be bonded and its not,

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[ActionDave]

..... I am going to get the power company to open the transformer up so I can make sure the bonding is done there, I didn't see a ground rod outside the trans. So if its wrong then it should have been pulled from the trans, all the way into the building, inside the pipe that the feeders are in, they didn't do that which makes me think there may be an exception somewhere. Its some what confusing me.

It's not an exception, it's the definition of Service Point you are looking for. Look in art. 100. If that transformer belongs to the power company then those are service conductors. There is no bonding or ground rods or any other part of the NEC required grounding electrode system the service disconnect.

 

[david]

The bonding was done at the transformer, from the transformer they brought three hots, a neutral and a ground. It is separated in the first disconnect. If you look at the pic of the main switch at the top right is the 4/0 copper that comes off the neutral bar and bonds the cold water pipe. My question is, is it within code to come off the neutral bar at this point when the bonding was done outside at the transformer. Can you bond something like this on down the line like this instead of at the point where you bond the neutral in the first place,

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If it is a utility transformer one would wounder why the extra conductors you are calling equipment grounds

also if it is a utility transformer the conductors are not feeds rather the would be service conductors

Also understand you can have the neutral bonded at the transformer and also at the disconnect location under certain conditions, you would not expect to see the 5th conductor from the transformer though