# CT Cabinet and commercial service



## guitarboyled (Jun 22, 2009)

Pretty basic stuff

I'm trying to figure out what is a typical commercial service entrance.

To start with...

In a three phase commercial distribution is the neutral provided by the service utility... always, sometimes, never?

What's the CT cabinet for?


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## Mr Rewire (Jan 15, 2011)

Anything over 400Amps here will be CT metered.The utility provides the ?CTs and CT meter box EC provides the cabinet.


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## Bulldog1 (Oct 21, 2011)

Mr Rewire said:


> Anything over 400Amps here will be CT metered.The utility provides the ?CTs and CT meter box EC provides the cabinet.


One poco here CT's anything over 200 amps.


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## guitarboyled (Jun 22, 2009)

What's the purpose of the CT cabinet?


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## Mr Rewire (Jan 15, 2011)

guitarboyled said:


> What's the purpose of the CT cabinet?


you mount Cts in them


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## dronai (Apr 11, 2011)

guitarboyled said:


> What's the purpose of the CT cabinet?





Mr Rewire said:


> you mount Cts in them


 
:laughing:


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## brian john (Mar 11, 2007)

Here 208/120 at 400 amps and above with Dominion get a CT cabinet, and 480/277 get a CT cabinet.

If your service is grounded wye the utility has to supply the neutral.

Even if you use a ungrounded or resistance grounded (around here) the utility pulls the neutral to your CT Cabinet. IN MY EXPERIENCE.

AS noted the CT cabinet is for the Utility CT’s (Current Transformers), this is for metering purposes. In older overhead distribution the utility would mount the CT’s close to the weatherhead outside on the wall, or on the utility pole.


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## Podagrower (Mar 16, 2008)

There are a couple of POCO around here that will go as high as 600 amp 120/240 or 120/208 with a non CT service. The smaller ones, usually anything over 200 amps is CT.


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## guitarboyled (Jun 22, 2009)

Therefore...

The current transformers (not the same as transformers) reduce current for the metering instruments portion... They are not actually transforming the line/load.

Typically they bring the current down to what voltage for the metering?


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## Cletis (Aug 20, 2010)

*Mounting*

How do you plan on mounting those CT's ? Quiz...


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## jza (Oct 31, 2009)

guitarboyled said:


> What's the purpose of the CT cabinet?


That's a trade secret.


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## guitarboyled (Jun 22, 2009)

Again, if the current/power is under a certain value, the meter can be directly wired like in these illustrations? If not, power going to the meter has to be stepped down via current transformers. Makes any sense?

Sorry for not knowing... trying to get the knowledge, thanks for sharing.


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## RePhase277 (Feb 5, 2008)

Instead of the all of the load current passing through the meter, the current is measured by the meter indirectly, through the CT's.


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## dronai (Apr 11, 2011)

jza said:


> *That's a trade secret*.





guitarboyled said:


> Again, if the current/power is under a certain value, the meter can be directly wired like in these illustrations? If not, power going to the meter has to be stepped down via current transformers. Makes any sense?
> 
> Sorry for not knowing... trying to get the knowledge,* thanks for sharing.*


:thumbsup:


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## brian john (Mar 11, 2007)

Read this about 1/2 way down.

http://www.kappaelectricals.com/technical.html


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## Peerless Design (Dec 3, 2011)

*Current Transformer*

While it is not uncommon to have a remote meter as depicted in your first example, it is not the typical electrical service here in the U.S. The meters are usually included in the same cabinet with the current transformers.

Meters and sockets are only rated to carry 200 amperes. The full load passes through the meter in small services 200 amperes and under. This limitation is resolved in larger services by using current transformers. These change the current, not the voltage. The current is reduced to a fraction of the current that is passing through the feeder. This fraction will vary based on the size of the service. The meter reads the fractional current, then multiplies the value to determine actual usage.

Jim Smith, PE, LC, RCDD, CET


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## Cletis (Aug 20, 2010)

*Buy*

I found 3 in my shop. Thanks for reminding me about these. Wanna buy ?


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## BBQ (Nov 16, 2010)

Peerless Design said:


> While it is not uncommon to have a remote meter as depicted in your first example, it is not the typical electrical service here in the U.S. The meters are usually included in the same cabinet with the current transformers.


At dwelling units, normally yes.

In commercial or industrial I never see the meter with the CTs.



> Meters and sockets are only rated to carry 200 amperes.


In my area you can direct meter up to 400 amps and in some areas they direct meter up to 600 amps.

It is a big country and all the power companies are very different and each has different standard procedures. 

These Internet forums will quickly make you realize how different electrical installations are across the US.


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## cguillas (Jun 25, 2009)

Cletis said:


> I found 3 in my shop. Thanks for reminding me about these. Wanna buy ?


You write your name on your hand in case you forget it?


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## Cletis (Aug 20, 2010)

*yeah*



cguillas said:


> You write your name on your hand in case you forget it?


Yes. I have very short term memory problems, also dementia.


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## BBQ (Nov 16, 2010)

Cletis said:


> Yes. I have very short term memory problems, also dementia.


How do you remember you have dementia?


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## Cletis (Aug 20, 2010)

*?*



BBQ said:


> How do you remember you have dementia?


I'm not sure. I just know somehow. It's words I can't remember. They tell me it's dementia, but, I can't remember who told me that?


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## nolabama (Oct 3, 2007)

I always thought they put em in cabinets to keep people like me from messin with em


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## guitarboyled (Jun 22, 2009)

Just realized we are talking current (amps) transformers and not standard (voltage) transformers... My bad

Is it the actual limitation of the meter (possibly supplied by the utility company) and not a code article that dictates the maximum amps for a direct connect?

Also if the main entrance is split to multiple users who require individual meters... a CT cabinet will be required every time the current is above 200, 400 or 600 amps.

With a 200 amp limitation... would this installation make sense :


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## BBQ (Nov 16, 2010)

guitarboyled said:


> Is it the actual limitation of the meter (possibly supplied by the utility company) and not a code article that dictates the maximum amps for a direct connect?


That is correct, the NEC does not really address metering at all. 



> Also if the main entrance is split to multiple users who require individual meters... a CT cabinet will be required every time the current is above 200, 400 or 600 amps.


Yes, and that will be determined by the particular utility. You can usually go online and get all their rules as a pdf download. 



> With a 200 amp limitation... would this installation make sense :


It could.

But what you show is called 'hot sequence' metering, the meters are ahead of the disconnects. That can be fine, BUT, some power companies require 'cold sequence' metering and if that is the case there must be disconnects ahead of the meters. 

Where I am it is usually hot sequence under 250 volts to ground a cold sequence above 250 to ground.

Again this info could be found in the power companies 'service requirements' or other documents.


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## Bulldog1 (Oct 21, 2011)

Peerless Design said:


> While it is not uncommon to have a remote meter as depicted in your first example, it is not the typical electrical service here in the U.S. The meters are usually included in the same cabinet with the current transformers.
> 
> Meters and sockets are only rated to carry 200 amperes. The full load passes through the meter in small services 200 amperes and under. This limitation is resolved in larger services by using current transformers. These change the current, not the voltage. The current is reduced to a fraction of the current that is passing through the feeder. This fraction will vary based on the size of the service. The meter reads the fractional current, then multiplies the value to determine actual usage.
> 
> Jim Smith, PE, LC, RCDD, CET



As BBQ stated they direct meter over 200A in many areas of the country. In a lot of cases we can use a 400A meter can and not a CT on residential jobs.


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## Meadow (Jan 14, 2011)

The only time I will use a meter feed through for over 200amps is in a residential other than that its always cts.


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## Chris Kennedy (Nov 19, 2007)

You named your ring finger Cletis??? Do your other fingers have names?:blink:


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## Peerless Design (Dec 3, 2011)

BBQ said:


> At dwelling units, normally yes.
> 
> In commercial or industrial I never see the meter with the CTs.


Switchboards from all major manufacturers in this country include meter sockets in the same cabinet as the current transformers as standard. You can look at switchboards meter sections at GE, Eaton, Siemen, and Schneider web sites to see this. I'm certain they can build them separately if desired, but typically, the meter location has a blank on it if you use remote metering.



BBQ said:


> In my area you can direct meter up to 400 amps


I'm not saying meters larger than 200 amperes do not exist. I've installed 400 ampere services on homes without current transformers, but never on a commercial service which is what we are talking about in this thread. The utilities will not allow that in this part of the country anyway.



BBQ said:


> and in some areas they direct meter up to 600 amps.


Who manufactures a meter and socket rated for 600 amperes?



BBQ said:


> It is a big country and all the power companies are very different and each has different standard procedures.
> 
> These Internet forums will quickly make you realize how different electrical installations are across the US.


Yes, I forget that not all utilities follow EUSERC standards. It makes it a little difficult to come up with a typical service when there is no nationwide standard.

Jim Smith, PE, LC, RCDD, CET


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## frenchelectrican (Mar 15, 2007)

Peerless.,

There are couple manufacter do make 600 amp meter socket I know Milbank and L-G ( Landis & Gry ) so let me post the photo of this 











Just be aware not all POCO will approve this type I know in Wisconsin there is only 3 POCO's will approve this but the rest will not { the other one will say ok on 208Y120 but not on 480Y277 }

This meter socket I posted that is L&G verison and it is rated for 480 amp contionus and 600 interment rating so that is a 480 class { that what I always say it } 

And with my notes that my POCO ( WPS ) will only approve K-7 can types on triphase supply the K-4 is too small for triphase in that class due there is not much room to bend the conductors on triphase but single phase that is not a issue it can be either K-4 or K-7 cans 

However this direct bolt metering for this size is slowing dropping out to CT's for safety reason and with my POCO they rather have cold sequince with 480 class on 480Y277 system on K-7 cans 

As far for the meter itself there are few of them around that will work that class the last 480 A class meter I did see was G-E meter.

But there is a major gotcha the AIC rating is very lousy only 10/22 KA.

Merci,
Marc


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## BBQ (Nov 16, 2010)

Peerless Design said:


> Switchboards from all major manufacturers in this country include meter sockets in the same cabinet as the current transformers as standard. You can look at switchboards meter sections at GE, Eaton, Siemen, and Schneider web sites to see this. I'm certain they can build them separately if desired, but typically, the meter location has a blank on it if you use remote metering.


Those are switchboards with CTs, not 'CT cabinets'. And yes we install many of them.





> I've installed 400 ampere services on homes without current transformers, but never on a commercial service which is what we are talking about in this thread.


That is fine, but what I am pointing out is you have not seen it all. (Neither have I  )

We do in fact use plug in meters for non-dwelling units up to 400 amps. Other times we may use CTs.




> Who manufactures a meter and socket rated for 600 amperes?


Many, it is called a class 480 meter and they are rated 480 amps continuous and 600 amps non-continuous. 

https://www.google.com/search?q=Cla....,cf.osb&fp=c88a66347476f89e&biw=1440&bih=756



> Yes, I forget that not all utilities follow EUSERC standards. It makes it a little difficult to come up with a typical service when there is no nationwide standard.


I had never heard of that group, I had to look it up, it seems CA based.


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## frenchelectrican (Mar 15, 2007)

BBQ said:


> I had never heard of that group, I had to look it up, it seems CA based.


 
BBQ .,

It is started in Southen California area so let me post the link in case other readers want to know more details.

http://www.euserc.com/

Merci,
Marc


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## joethemechanic (Sep 21, 2011)

Cletis said:


> Yes. I have very short term memory problems, also dementia.



Damn, I need to write my name on a woman, and take a picture

Should be a contest. 

Just remember, family members don't count.


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## Peerless Design (Dec 3, 2011)

frenchelectrican said:


> Peerless.,
> 
> There are couple manufacter do make 600 amp meter socket I know Milbank and L-G ( Landis & Gry ) so let me post the photo of this


Wow! I've never seen one of these out here. Milbank isn't very big out here, but I looked at their website before posting. They said their meters only go up to 320/400 amperes. Landis & Gyr isn't big out here either. I didn't think to look there.

I noticed it isn't actually a meter socket though. It appears to be a bolt-on meter base as you mentioned.

Nice to know about even if we can't use it out West.

Thanks.

Jim Smith, PE, LC, RCDD, CET


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## Peerless Design (Dec 3, 2011)

BBQ said:


> Many, it is called a class 480 meter and they are rated 480 amps continuous and 600 amps non-continuous.
> 
> https://www.google.com/search?q=Cla....,cf.osb&fp=c88a66347476f89e&biw=1440&bih=756


I think we're saying the same thing, just different terminology.

Thanks for the information.


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## Hairbone (Feb 16, 2011)

meadow said:


> The only time I will use a meter feed through for over 200amps is in a residential other than that its always cts.


Intersting, in my area the electric company always requests a load sheet and makes the determination of a 320amp socket or cts based on the load.


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