2 services on one building question

[KWH]

Looking at job with existing service, there is going to be a building addition

Existing service is 480 volt 3phase 4 wire 1200amp rated no main with 5 spaces in use with one spare

Fed by 2 runs of 2" pvc with (4) 3/0cu wires per conduit

These wires terminate in a above ground cabinet (splice box ) The POCO transformer feeds this box.

The building owner wants the exact same setup for addition fed thru (2) 2" spare conduits coming from same junction box.

Would this be considered one service since there is only one set of secondarys coming from xfmr and if this falls under one service I will need a main breaker on the addition to stay under the 6 handle rule also the spare in the existing gear wouldnt count against you would it.

I also know they would be limited to a 400amp main based on the 2" conduits.

 

[Smart $]

Do the 2 spare conduits run to the same location as the in-use ones?

IMO, one service. The junction box is the transition to service entrance conductors (SEC's). You can run one set of SEC's to each service equipment enclosure... but all enclosures must be "grouped" at the same location for "six handle rule" compliance.

 

[Npstewart]

If the services terminate in the same location then it is one service in my opinion and most others opinion, and building as a whole would have to comply with the 6 disconnect rule (NEC 225.33). It is common over here to come from the transformer twice to save money on purchasing higher rated equipment (ie. 1200A +).

If the services terminate in different locations then you would need permission from the AHJ and the labeling would have to comply with 230.2(E). (ie. service disconnect #1 of 2, service #2 is located on the...)

 

[Npstewart]

guess I was too slow

 

[augie47]

If I'm reading correctly, the existing service is a bit scary 1200 amp fed with (2) 3/0s per phase,,, ?????
If that's handling the load, why not just add the new 3/0s to the existing 1200 doubling its capacity to 800 amps.

 

[Npstewart]

Maybe he meant 6 runs.

 

[KWH]

I have no idea why the 1200amp rated switch gear is fed with 400amps of cable, there are no as built drawings and this was installed in the early
90's. The customer says he needs 400amps for the addition and was wanting to match what he has. The suggestion to double the ampacity with the spare pipes which is a good idea makes me think the original contractor was aware of this and installed the spares and left one space in the switch gear for future use. I think the 480 is only used for a power conditioner and everything else is stepped down to 120/208.

 

[A-1Sparky]

If I'm reading correctly, the existing service is a bit scary 1200 amp fed with (2) 3/0s per phase,,, ?????
If that's handling the load, why not just add the new 3/0s to the existing 1200 doubling its capacity to 800 amps.

And he could then use a 400 amp breaker in the "spare" location to feed the new loads (transformer/panels, etc.) and still comply with the 6 throw rule for the service.