Moving Disconnect Away From Meter

[encoreman]

I work on the electrical design for the small building you see at the base of a tower used for radio frequency communications. It is important to protect these "shelters" as we call them from electrical surges, many times caused by lightning. These shelters are often served by a meter and a disconnect mounted on a utility company owned power pole. When the neutral to ground bond is a long distance from the first electrical panel (let's say in excess of 100 feet) we are required (by specifications in the contract) to install an isolation transformer so we can re-establish the neutral to ground bond nearer to the first panel. My study of the code (250.24) tells me I must establish the neutral to ground bond at the first disconnect or before.

I would like to mount the meter on the utility company pole and mount the first disconnect on the side of the shelter running the wires through schedule 80 PVC pipe.

I am told that frequently there are local codes requiring a disconnect at the meter on the utility company pole. What experience to others on the forum have? Will this design fail permitting frequently?

Thanks for your help!

Jack

 

[zbang]

You may need a service disconnect at the pole, which would have the main bonding jumper, but with a transformer at the shelter, you're creating a Separately Derived System (SDS) there, so you need to follow those rules. It's possible that you may not even need to run a neutral/groundED conductor to the shelter at all if everything is connected to the load side of the transformer.

So, bond the neutral at the service but don't take it to the shelter. Derive a new neutral there and follow the SDS rules. Don't forget about required disconnects. If you search these forums, esp the one for grounding/bonding, you'll find a fair bit about comm huts, antenna grounding systems, and related parts.

I'm sure smarter folks than I will comment, too.

 

[encoreman]

Trying to avoid the cost of a transformer

Trying to avoid the cost of a transformer

Correct. That is what we are doing now. I'm trying to avoid the cost of a transformer by moving the bonding jumper to the shelter without a transformer.

You may need a service disconnect at the pole, which would have the main bonding jumper, but with a transformer at the shelter, you're creating a Separately Derived System (SDS) there, so you need to follow those rules. It's possible that you may not even need to run a neutral/groundED conductor to the shelter at all if everything is connected to the load side of the transformer.

 

[Sierrasparky]

i guess you will be moving the meter also.
Most POCO will allow this to be at the first building.

 

[encoreman]

Trying to avoid the cost of a transformer

Trying to avoid the cost of a transformer

Correct. That is what we are doing now. I'm trying to avoid the cost of a transformer by moving the bonding jumper to the shelter without a transformer.

You may need a service disconnect at the pole, which would have the main bonding jumper, but with a transformer at the shelter, you're creating a Separately Derived System (SDS) there, so you need to follow those rules. It's possible that you may not even need to run a neutral/groundED conductor to the shelter at all if everything is connected to the load side of the transformer.

 

[Sierrasparky]

ok so why are you repeating yourself?

 

[WIMaster]

I work on the electrical design for the small building you see at the base of a tower used for radio frequency communications. It is important to protect these "shelters" as we call them from electrical surges, many times caused by lightning. These shelters are often served by a meter and a disconnect mounted on a utility company owned power pole. When the neutral to ground bond is a long distance from the first electrical panel (let's say in excess of 100 feet) we are required (by specifications in the contract) to install an isolation transformer so we can re-establish the neutral to ground bond nearer to the first panel. My study of the code (250.24) tells me I must establish the neutral to ground bond at the first disconnect or before.

I would like to mount the meter on the utility company pole and mount the first disconnect on the side of the shelter running the wires through schedule 80 PVC pipe.

I am told that frequently there are local codes requiring a disconnect at the meter on the utility company pole. What experience to others on the forum have? Will this design fail permitting frequently?

Thanks for your help!

Jack

This design would pass in the jurisdictions I usually work in if the disconnect contains OCPDs. You will have to check with your poco and local AHJs.
Some local ordinance are stricter than others.

 

[robbietan]

... I would like to mount the meter on the utility company pole and mount the first disconnect on the side of the shelter running the wires through schedule 80 PVC pipe.

I am told that frequently there are local codes requiring a disconnect at the meter on the utility company pole. What experience to others on the forum have? Will this design fail permitting frequently?

Thanks for your help!

Jack

Our utility requires a disconnect at the meter if the main disconnect is more than 50 feet away from the meter. Something about the safety of the lines. 50 feet is the measure that "you can see the disconnect while standing beside the meter"