Remote CT cabinet

[hhsting]

I have remote CT cabinet outside building walls. The service disco is inside the building electrical room right opposite to the walls the CT cabinet.

Engineer tells me neutral is pass thru CT cabinet and he would be providing supply side bonding jumper from service disconnect to bond the remote CT cabinet.


Cannot the remote CT cabinet be bonded thru neutral per NEC 2014 Article 250.80, 250.92 or it has to be bonded thru supply side bonding jumper?

 

[texie]

Yes, you could bond the neutral to the CT cabinet.

 

[hhsting]

Ok I get that but the engineer is saying neutral is passing thru remote CT cabinet and he is not going to bond CT cabinet via neutral instead provide supply side bonding jumper from service disco to remote CT is that normal practice?

 

[texie]

Ok I get that but the engineer is saying neutral is passing thru remote CT cabinet and he is not going to bond CT cabinet via neutral instead provide supply side bonding jumper from service disco to remote CT is that normal practice?

If they pass the neutral thru unbroken how are they going to connect the metering leads?

 

[hhsting]

If they pass the neutral thru unbroken how are they going to connect the metering leads?

Not an expert never left my desk to go see actual CT cabinet. Any electric utility experts here explain it? I dont know and am not sure but I guess they have round current transformer that go around the cable it self without breaking. Dont current transformer leads go to the meter then so how can one have phase and neutral conductor leads?

 

[texie]

With CT metering you have the CTs and also PT connections to the phases and neutral.

 

[Hv&Lv]

1

 

[Hv&Lv]

Ok, it loaded twice..
We have donut CTs. We don’t use PTs to lower the voltage. We meter at 277/480.
the bond at the CT cabinet goes in with our neutral connection.
this particular one didn’t have it, so we took a picture and requested it be bonded.
the electrician said the bond is in there... I told him to get me some wire the correct size and we would make it up in our connectors.

 

[texie]

Ok, it loaded twice..
We have donut CTs. We don’t use PTs to lower the voltage. We meter at 277/480.
the bond at the CT cabinet goes in with our neutral connection.
this particular one didn’t have it, so we took a picture and requested it be bonded.
the electrician said the bond is in there... I told him to get me some wire the correct size and we would make it up in our connectors.

I'm with you. I was just trying to get the OP to understand that there needs to be a potential connection to the neutral.

 

[Hv&Lv]

I'm with you. I was just trying to get the OP to understand that there needs to be a potential connection to the neutral.

I understand, I was just making a point regarding them.
with the meters today being 120/480, there’s no need for the extra equipment...


BUT...

Many utilities though still use PTs to get the voltage in the meter base below 130. Many won’t allow 277 in a base for safety. They allow untrained contractors to change meters.

this means the utility he is on possibly may have 2.5 PTs in the CT cabinet.

 

[hhsting]

I'm with you. I was just trying to get the OP to understand that there needs to be a potential connection to the neutral.

Potential transformer in cabinet? No way if its 480V or greater voltage rated meter what is the use of PT in CT cabinet?

 

[electrofelon]

I think the layout varies depending if you use an actual purpose made CT cabinet or do it "home brew". Every utility CT cabinet I have seen has CT mounting bases and a neutral terminal block. The CTs bolt on. Or you could make one with a box and donut type CT's. I have had PV designers home brew it (for their metering purposes not utility) often because it ends up being cheaper, but they loose all the savings in the increased labor, especially when they don't provide you with split core CT's :slaphead::rant:

 

[Hv&Lv]

Potential transformer in cabinet? No way if its 480V or greater voltage rated meter what is the use of PT in CT cabinet?

read my post...
that will tell you why

 

[tom baker]

Our poco - Puget Sound Energy - has very specific rules and detailed drawings on CT metering, and require pre approval on CT jobs. PSE does a great job of coordinating poco requirements with the NEC.
Have you checked with your poco?

 

[david]

Engineer tells me neutral is pass thru CT cabinet and he would be providing supply side bonding jumper from service disconnect to bond the remote CT cabinet.

It is not uncommon for an engineer to address objectionable current in this way, another way is to specify PVC between the CT cabinet and service disconnect

 

[electrofelon]

It is not uncommon for an engineer to address objectionable current in this way, another way is to specify PVC between the CT cabinet and service disconnect

I think that is an excellent point. Often people talk about objectionable current being "unavoidable" at the service, but using a SSBJ or a nonmetallic raceway will eliminate it and the wording is in the NEC for an inspector to require one of those two things if she wants.