does this sound right to you?

[RonnieD]

hi all.....new to this forum and seeking input from the many experienced posters.

I am looking into a job where a customer has a facility feed by a 600 amp 208/120 service. The incoming feeds hit a mdp with a 600 amp main. The customer has contracted with the power company to remove the existing transformser and replace with a new one to increase the service size from 600 to 1200 amps. The customer plans to add a second 600 amp mdp with a 600 amp main. They would be bringing 4 4inch conduits into the ct can with 4 sets of 350 mcm conductors. Two sets of the 350 would feed the existing mdp and two sets would feed the second and new mdp. Is this ok in your opinion?
Can a main disconnect for the 1200 amp service be omitted because shutting down the service could be accomplished with only two throws? Thanks in advance for any input.

 

[Jraef]

Depends on a couple of factors, i.e. location and accessibility of the MDPs and their main CBs, length of cables etc., but it sounds as though it would fall under the "6 hand rule". NEC 230.71

 

[wireman71]

I have a quick question not related to the thread issue. Do most people bring in their service entrance conductors into the CT can? I've seen it done where the conductors come out of the POCO transformer right into service and the CT can sits next to it and is fed by #10 or #12 from the transformer. Guess the "donuts" are being put on in the transformer. Seems like this is the easiest method. I'm curious why you would bring your service conductors into the CT can?

 

[iwire]

Can a main disconnect for the 1200 amp service be omitted because shutting down the service could be accomplished with only two throws? Thanks in advance for any input.

Assuming the power company is OK with hot sequence metering of this service the NEC will allow it as long as the issues Jraef mentioned are satisfied.

The disconnects must be 'grouped' what that means is really up to the local inspector / AHJ.

The service disconnects must be 'located nearest the point of entrance' and again that distance is really up to the local inspector / AHJ.

 

[iwire]

Do most people bring in their service entrance conductors into the CT can? I've seen it done where the conductors come out of the POCO transformer right into service and the CT can sits next to it and is fed by #10 or #12 from the transformer. Guess the "donuts" are being put on in the transformer. Seems like this is the easiest method. I'm curious why you would bring your service conductors into the CT can?

The service conductors have to run through the CTs someplace.

I think you may be calling the meter pan (where the #10 or #12 run to) a CT can.

With large services typically you need a large CT can or a CT section in the service gear unless the power company is willing to do it at their transformer.

As far as electrical contractors are concerned having the CTs in the transformer enclosure and the meter itself on or next to the transformer is the best route to go. Almost no labor for the EC.

However not all power companies will do that.

From their prospective having the metering at the transformer is a major hassle if the transformer dies and needs quick replacement. Usually that would need an entire other crew from the POCO to relocate the metering.

 

[kingpb]

Utilities usually have standard drawing details for each type of service entrance. The questions raised are valid, however final set-up and installation will need to meet the utility standards if it falls into their jurisdiction. If not, then the Code dictates, assuming by in from the AHJ.

 

[RonnieD]

ct cans

ct cans

In this case the CT can is roughly 20ft from the t-former pad. The POCO seems fiie with this set up. The ct can will have to be changed to be 48x48x11 for the 1200 amp service and 2 more 4 inch pipes will need to be added from the ct to the pad.