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fyrmnk
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Hi all,

Here's a first for me today. This was in a rural setting. Step down transformers were in a box on the side of the house with the meter attached to the top of it. This fed two main panels with no main disconnect in the basement(more than 6 throws).

I wrote it. But at least it was a NEMA 3R box and had a proper Myer's Hub for the meter conduit connection. Still interesting. I told the seller and buyer never to open it.

I also referred it out to the utility and an electrician to evaluate this and due to numerous other problems.

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Originally posted by fyrmnk

Hi all,

Here's a first for me today. This was in a rural setting. Step down transformers were in a box on the side of the house with the meter attached to the top of it. This fed two main panels with no main disconnect in the basement(more than 6 throws).

I wrote it. But at least it was a NEMA 3R box and had a proper Myer's Hub for the meter conduit connection. Still interesting. I told the seller and buyer never to open it.

I also referred it out to the utility and an electrician to evaluate this and due to numerous other problems.

What you've got there are current transformers. They produce a small amount of current in direct proportion to current flow in the service entrance wires. (Think: clamp-on amp meter.) They are not stepping down voltage to feed the service. That is, there's nothing above 240v in that box.

I see this type of meter arrangement fairly often on larger houses. Sometimes the CTs are in a box, like the one in your pictures, and sometimes they're mounted outside on the the weatherhead. In that case, they'll look like ceramic dounuts around the drip loops.

The box in your picture should have had a utiliy company seal on it. Otherwise, it looks fine to me.

- Jim Katen, Oregon

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Thanks for the clarification Jim. This was the first time I've seen this. It was a small house (about 1400 sq. ft.).

I opened it to see if they had mounted a disconnect in the box since there wasn't any inside.

So what exactly is the purpose of the current transformers? Are they just for metering?

Thanks again.

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From the OSHA website: Current transformers can be used to supply information for measuring power flows and the electrical inputs for the operation of protective relays associated with the transmission and distribution circuits or for power transformers.

This is one we should all bookmark:

http://www.osha.gov/SLTC/etools/electri ... ml#Current

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Originally posted by fyrmnk

Thanks for the clarification Jim. This was the first time I've seen this. It was a small house (about 1400 sq. ft.).

I opened it to see if they had mounted a disconnect in the box since there wasn't any inside.

So what exactly is the purpose of the current transformers? Are they just for metering?

Thanks again.

Yes. That's they're only function. It's just a different style of metering.

You might have seen it before and now known it because the CTs are usually in boxes that are sealed shut.

You were right to tell the seller and buyer to stay out. There's no overcurrent protection in there. I once had a 5 year old kid open one of these during an inspection. Fortunately, it was full of wasps and he shut it and ran away immediately. The presence of the wasps may have saved his life.

- Jim Katen, Oregon

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