added service

[puckman]

when running a parallel service does the added run have to be done like the oringinal run?. if the first run used al wire can the added one use copper? I have a 400A service and need an added 150 amps. This is my first attempt to do a 3 phase service and would be very costly to make a mistake so any help i get i would be thankful.

[mdshunk]

Can you describe "added run" a bit more? Are you adding more conductors in an existing riser down into an existing CT can? Or are you building a complete second service right next to an existing service?

[puckman]

i am adding a conduit and wires along side the existing 400a 4 wire 240 volt service in place now that goes to a 800a ct. An air condition unit with a minimum circuit ampacity of 124amps and mocp of 150amps is needed for this unit. I will be using the same ct as the 400a service is using now. This is my first atempt doing a 3 phase service with a ct. I welcome any input anyone has. thanks for the response. The cost is very important and the owner as me to keep it down . Do you think 150 amp. will be sufficent for this added load?
If there is a different way to do this i 'm all ears.

[augie47]

if you are trying to keep the cost at a minimum, then follow the guidelines of the HVAC requirement (124 mca, 150 mocp), of course, you have no room for added future load. A 150 amp service adjacent to the existing one to the ct would be sufficient. To a great degree the added service is "stand alone" in this case and you can wire it with any approved method. Service disconnects would need to be grouped.

I have no idea how POCO is supplying these services, but since you mentioned an 800 amp ct, I would suggest you at least address the fault current situation.

[LarryFine]

Puck, if you parallel the new conductors with the existing ones by connecting them at both ends, then they must be identical: conductor size and type, insulation, conduit, length, etc.

If you connect them at the source end, pass them through the CT's, and supply an independent new panel, then they only need be suited for the new panel and load as you would any service.

[puckman]

Thanks larry , thats something i didn't know. I though you had to connect them at both ends. are you saying the wires go through the ct without connecting to it and then go to the new panel ? There is a 400a and i'm going to add just 150a. so the wiring is going to be of different sizes.

[danickstr]

is the CT used to meter/monitor the building? I don't think he meant to go through the CT cabinet, but I am not sure.

[mdshunk]

is the CT used to meter/monitor the building? I don't think he meant to go through the CT cabinet, but I am not sure.I don't see any other way, unless they're going to give him a bit of free power. This is basically a second service, the way I see it, but running through the existing CT rings for metering purposes only.

[satcom]

I don't see any other way, unless they're going to give him a bit of free power. This is basically a second service, the way I see it, but running through the existing CT rings for metering purposes only.


How is he going to run thru the existing CT unless he runs identical, conductor size, and length.

How about just running a 200A service with it's own meter next to the existing 400

I would talk with the utility, and the AHJ, before commiting to anything, if your in JCP&L area the fun has just begun.

"The cost is very important and the owner as me to keep it down"

There is your biggest problem, a customer all wrapped up in what's it gona cost, translated means, what ever your price it's going to be too much.

[danickstr]

I did mean bypass the meter by feeding through the cabinet, but not the CT, sorry for the lack of clarity.

But I didn't know you could stick two wires (dissimilar notwithstanding) through a CT, anyway.

[iwire]

How is he going to run thru the existing CT unless he runs identical, conductor size, and length..

No reason they have to be.

As I understand it the conductors will only connected at the supply and end in separate disconnects.

[mdshunk]

How is he going to run thru the existing CT unless he runs identical, conductor size, and length.Perhaps you're confused on what a CT is?

If he was beefing up the existing equipment, then he's have to run identical parallel conductors. Since he's building a totally new service, but running through the CT's for metering only, none of that parallel stuff applies, in my opinion.

[mdshunk]

But I didn't know you could stick two wires (dissimilar notwithstanding) through a CT, anyway.Oh heavens, yes. You can stick a dozen through. All kinds and sizes of CT's.

[danickstr]

i do know that you shouldn't disconnect the CT from its load while the primary is powered up, or very high voltages are created.

[LarryFine]

I will be using the same ct as the 400a service is using now.I took this to mean that you intended to use the CT's for the additional load. I recommend this if possible; see below.
]Are you saying the wires go through the ct without connecting to it and then go to the new panel?Keep in mind that the CT's are the transformers themselves, not the enclosure. I am suggesting running the new conduit to the CT cabinet and passing the new power through the existing CT's.

If they are the ring type, this is simple and there's no issue with conductor matching. Just make sure you pass the phases of the old and new lines together. This is the most economical way to go.

If the CT's are the bar type, there will be bolted connections, and the new conductors will be in parallel with the old, and must match. In this case, a separate meter may be cheaper, but the POCO may not allow it.

[satcom]

No reason they have to be.

As I understand it the conductors will only connected at the supply and end in separate disconnects.

I have installed CT's in just about every config there is, from small commercial to distribution switchgear, the problem I see, is with what the utility will accept, I believe he is in JCP&L area.
As you said, as you understand it, I am still having a hard time understanding how he intends to do it, would be nice to have a scketch board on the site.

[brian john]

The secondary of a CT should either be connected to a meter relay or shorted, most switchboard CTs installations will have a shorting block, for shorting the secondary allowing disconnecting of the secondary device.

As far as installing multiple wires in CT, this is not uncommon but can effect the accuracy, when test GFP systems we often use multiple wraps of our test leads permitting higher current, 100 amp output can become 400 amps with 4 wraps.

[satcom]

The secondary of a CT should either be connected to a meter relay or shorted, most switchboard CTs installations will have a shorting block, for shorting the secondary allowing disconnecting of the secondary device.

As far as installing multiple wires in CT, this is not uncommon but can effect the accuracy, when test GFP systems we often use multiple wraps of our test leads permitting higher current, 100 amp output can become 400 amps with 4 wraps.

Not uncommon at all, on the accuracy issue most utilities, want to review your plans, that is why it is best to check with the utility before moving ahead.

[brian john]

In our area there are several utilities one ONLY utilizes through bus CTs with line load bolted connections, the other utilities utilize either through bus or doughnut depending on the application.

[danickstr]

i wondered about that since you now have a non-centric impedance field.

[mickeyrench]

:) [B]The op appears to be in upper n.j. which is pse&g area.
He says he never did a 3 - p service and i don't think he is sure how he is
going to hook up to the cts at all. Maybe he should put in a seperate service
and be safe. Puck if I knew how I 'D put in my 2 cent. GOOD LUCK
call your inspection dept -call afriend

[quogueelectric]

i do know that you shouldn't disconnect the CT from its load while the primary is powered up, or very high voltages are created.
This is why they are shipped with shorting bars in them. The short circuit current is inherently limmited by coil resistance/reactance however the open circuit voltage can be very high with a heavy load running through the CT aka CURRENT TRANSFORMER

[bill@nkapc]

caution!!! Read art.230 Are the services the same voltage? Check ahj