Reestablish neutral to ground bond

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encoreman

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Austin, TX
I have new service provided by the local electric utility at a pole near the property line. There is a 120/240 VAC meter and a fused disconnect. The neutral to ground bond is established at the fused disconnect. There is underground non-metallic conduit running from the disconnect to a shelter used to house electronic equipment. The distance between the meter and the shelter is approximately 150 feet.

Because the distance between the neutral to ground bond and the shelter is greater than 75 feet (their rule) the equipment manufacturer is requiring an isolation transformer next to the building and reestablishment of the neutral to ground bond.

When I look at the code, it allows reestablishment of the neutral to ground bond only if the service was permitted under the 2005 code (or prior). Am I missing something? Is there any way to reestablish the neutral to ground bond without an isolation transformer?

Thanks!
 
encoreman said:
I have new service provided by the local electric utility at a pole near the property line. There is a 120/240 VAC meter and a fused disconnect. The neutral to ground bond is established at the fused disconnect. There is underground non-metallic conduit running from the disconnect to a shelter used to house electronic equipment. The distance between the meter and the shelter is approximately 150 feet.

Because the distance between the neutral to ground bond and the shelter is greater than 75 feet (their rule) the equipment manufacturer is requiring an isolation transformer next to the building and reestablishment of the neutral to ground bond.

When I look at the code, it allows reestablishment of the neutral to ground bond only if the service was permitted under the 2005 code (or prior). Am I missing something? Is there any way to reestablish the neutral to ground bond without an isolation transformer?

Thanks!
Click to expand...

Sounds like a Motorola R-56 thing. Are you in Houston?
I think you could do that but you would need a delta/wye transformer IMO. There is no other way to bond neutral to ground again and be code compliant.
Wait for others to chime in.
 
No, you are not missing anything.

An SDS (the isolation transformer) is the only way to get a local N-G bond.
 
Thanks for the input.

Thanks for the input.

I'm really disappointed. I hate putting in an isolation transformer. Another thought I had was removing the disconnect on pole and leaving the meter there where the utility required it to be placed. I would then run RMC to the shelter and place a disconnect and the neutral to ground bond there.

Any problems with that?
 
qcroanoke said:
Sounds like a Motorola R-56 thing. Are you in Houston?
I think you could do that but you would need a delta/wye transformer IMO. There is no other way to bond neutral to ground again and be code compliant.
Wait for others to chime in.
Click to expand...

Yep, R-56 got another one

encoreman said:
I'm really disappointed. I hate putting in an isolation transformer. Another thought I had was removing the disconnect on pole and leaving the meter there where the utility required it to be placed. I would then run RMC to the shelter and place a disconnect and the neutral to ground bond there.

Any problems with that?
Click to expand...

Why not remove the disconnect, remove the EGC in the PVC and install a new disconnect, as you said. Is there some reason you feel the need to install new conduit?
 
You are right, this is an R56 issue.

You are right, this is an R56 issue.

Thanks for the input. Yes it is an R56 issue, but I'm in Austin not Houston. Yes Motorola requires that the neutral to ground bond be within a certain distance of the first panel where you would normally install the first panel with surge suppression. It is not accurately defined but is between 50 and 100 cable feet.

I may be able to use the conduit, but I'm changing the size of the cable going to the shelter. What I do not know is; if there are local jurisdiction issues or utility company issues that require the disconnect be at the meter.

I can check for this one instance, but I'm looking for a general answer that I can use on most of my designs. I would love to specify that the meter be where ever it has to be, and still locate the disconnect near the building. But if most or even a significant number of jurisdictions won't let me build it that way I'm going to have figure on using an isolation transformer every time. Then it will be a bonus if I don't have to use one.

Again, thanks for your thoughts.
 
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