Can there be TWO separately derived systems in one building?

[11bgrunt]

Existing facility has three phase 240/120V Delta secondary. Two pole mount 15kVAs and one 25kVA transformer.

Customer has increased the size of the building and added significant equipment load in the new area.

The POCO was asked to add a 480Y service to power the new loads.

The POCO said no, can’t have those two services in the same building. Then another POCO employee said yes, if a firebreak wall is added between the two services. This is an open bay work area.

I may have suggested that the POCO view is not supported by the NEC.

Can someone lead me to a rule that supports either view, to help us work with the POCO / AHJ in this unincorporated area.

 

[augie47]

Sounds as if you are asking about 2 services from POCO (as opposed to SDS). You can have two services on one building under certain circumstances one of which is each having a different characteristic such as in your case. NEC 230.2(D)

POCO's willingness to provide such and the cost depends on a number of factors determined by your POCO

 

[11bgrunt]

Sounds as if you are asking about 2 services from POCO (as opposed to SDS). You can have two services on one building under certain circumstances one of which is each having a different characteristic such as in your case. NEC 230.2(D)

POCO's willingness to provide such and the cost depends on a number of factors determined by your POCO

TWO different services from two different transformer banks.
I have always used SDS to mean;
By definition, a separately derived system is a “premises wiring system whose power is derived from a battery, a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.”

 

[petersonra]

It would probably be more cost effective for your customer to have the POCO change the service to 480 and just add a customer supplied transformer for the existing loads.

 

[Strathead]

TWO different services from two different transformer banks.
I have always used SDS to mean;
By definition, a separately derived system is a “premises wiring system whose power is derived from a battery, a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.”

And the first word is "premises" Utility feeds are services. And as was answered, yes you can.

 

[augie47]

TWO different services from two different transformer banks.
I have always used SDS to mean;
By definition, a separately derived system is a “premises wiring system whose power is derived from a battery, a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.”

Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served
Service Point. The point of connection between the facilities of the serving utility and the premises wiring

As shown, any wiring, transformers, etc. that are installed by POCO ahead of the customer wiring is SERVICE.
SDS are customer owned and wired.

 

[hillbilly1]

I’m doing something similar, upgrading to a 1600 amp 480 volt service from a 400 amp 120/240 volt delta. Could have left the old service, but customer is wanting to move the utility pole back 50’ to make room for more storage sheds. I’m re-feeding the old service with a 75 kva transformer for the 200 amp three phase panel, and using a 50 kva single phase transformer to feed the single phase panels.

 

[11bgrunt]

Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served
Service Point. The point of connection between the facilities of the serving utility and the premises wiring

As shown, any wiring, transformers, etc. that are installed by POCO ahead of the customer wiring is SERVICE.
SDS are customer owned and wired.

Thank you all for the replies and the SDS clarification. The customer will be reviewing the long term cost but having only one 480V service from the utility and using a dry type transformer to serve their 120/240 loads has been discussed.

 

[augie47]

Don't overlook the reverse possibility (240 service to SDS for 480) The best route will depend on loads plus there is an inherent problem with customer 240/120 transformers (see this thread https://forums.mikeholt.com/threads...e-and-single-phase-load.2574765/#post-2841571 )

 

[hbiss]

I have always used SDS to mean;
By definition, a separately derived system is a “premises wiring system whose power is derived from a battery, a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.”

That's certainly not what you are talking about here.

-Hal