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#51920 05/16/05 01:56 PM
Joined: Mar 2005
Posts: 24
Hello, Im bidding a job for a print shop. They have an existing 225 amp single phase panel that pulls 190 amps when they have everything going. They want to hook up 180 amps worth of 3 phase printing equipment. I know how to do everything for the job EXCEPT how to meter the two panels. I called the supply house and asked for a 400 amp 3 phase meter base and they said all they make is a 320 amp meter base. They went on to say that I could hook up my 2 panels to this meter base but if the current goes over 320 amps then the meter will not record the watts properlly. So my question is do I need to use a current transformer? I think thats what they are called. Could someone who deals with these types of service installations please give me some help? Thanks.

#51921 05/16/05 02:42 PM
Joined: Dec 2004
Posts: 1,064
I am missing something out of your post, I think.
Do they have a single phase service now?
Are you planning on putting in a 3 phase service?

Around me, a 400a 3 phase service utilizes "ct's".

I have never seen a 3 phase 400 amp meter.


#51922 05/16/05 05:03 PM
Joined: Mar 2005
Posts: 24
Yes you are correct. They only have single phase and want to add a 3 phase panel. So I will need to use a current transformer? Should most electrical supply houses sell these. I asked the supply house I use if thats what I needed and if they sold CT's and they acted as if I was the only electrical contractor to ever ask for meter equipment for a 400 amp service. They said the highest meter they sell is a 320 amp, 3 phase.

[This message has been edited by AdamsAtoms (edited 05-16-2005).]

#51923 05/16/05 06:19 PM
Joined: Jan 2003
Posts: 4,391
A 320 meter base is rated 320 amps continuous or 400 amp max. This is no different from a standard 400 amp panel.

A 320 sockets is the right item to use for a 400 amp service as long as your local power company does not want CTs.

In my area we use plug in meters for services 400 amps and below.

Bob Badger
Construction & Maintenance Electrician
#51924 05/16/05 06:35 PM
Joined: Apr 2001
Posts: 507
Call the utility co. and ask them what they want.

#51925 05/16/05 07:30 PM
Joined: Mar 2005
Posts: 212
Around here a 400A 3PH service would require CT metering. The service conductors from the POCO's transformer enter a CT can, typically a 36366 NEMA3R can with CT mounting studs, the CT's, which are provided by the POCO slip over the conductors and they pass through the can and into the service. A 1" conduit goes from the can to a meter base and the wiring in that conduit is done by the POCO.
The real question that seems unclear in your reply to Dnkldorf is whether everyone is clear that the POCO will have to supply 3PH service to this building. I guess that should be obvious, but sometimes.....

#51926 05/16/05 09:39 PM
Joined: Mar 2005
Posts: 24
Hello Greg, after reading your post several questions came to mind. Im aware now that I need to use a 400 amp CT. I will have 2 panels. 1-225A-sinlge phase and 1-200A-3 phase. 1) Will I need to run my service wires comming off of the load side of the CT into a gutter below my 2 interior panels and feed them from there or do most CT's have provisions for feeding 2 panles? 2) I was going to parallel 2 sets of 3/0 for the line side of the service, are CT's capable of metering paralleled conductors, do they put 1 CT around both conductors? thanks.

#51927 05/16/05 11:15 PM
Joined: Feb 2003
Posts: 687

Don't take this the wrong way but I have a feeling your in over your head. Maybe you would be better off subing out the service to another EC. Or bid out the job with service work to be done by others and only bid the inside job.


#51928 05/16/05 11:46 PM
Joined: Mar 2005
Posts: 53
as in with any service you need to do what the power co. in you local wants, called there standards, get ahold of them. have you done any services at all yet? I would think anywhere, any load over 225 amps would have ct's

#51929 05/16/05 11:54 PM
Joined: Mar 2005
Posts: 24
I will just call the power company tommorow and talk to them in more detail. I talked with another master friend of mine who told me what all I need to do. Thanks for the help.

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