I am increasing the service to an industrial machine shop building that includes HPS lighting, a small office space (875 sg ft) and warehouse space (30,000sq ft). The existing service is 400amp 277/480volts. The new service will be 1000amps 277/480volts. On the line side of the utility CT metering cabinet I plan to install 3 parrallel sets of 400MCM THHN/THWN CU conductors in 3 inch schedule 80 PVC. 310-16 shows the 400 as rated for 335amps at 75 deg rating. The majority of the load in this building is 3 wire motor loads. I am not reducing the neutral and am not including it as a current carrying conductor. (FYI)On the load side of the CT cabinet will be 2 panelboards. One will be the existing 400 amp panel that already includes a 400 amp service disconnect breaker. The second will be a new 600 amp panelboard with a 600 service disconnect breaker. With regards to the line side conductors - do you agree with my use of 400MCM?
Service entrance conductor sizing
- Thread starter jwcooke
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- Massachusetts
Re: Service entrance conductor sizing
IMO you are right on the money with 1005 amps of capacity.
IMO you are right on the money with 1005 amps of capacity.
From you description it does not sound like 'the major portion of the load consists of nonlinear loads' so you do not have to count the neutral as current-carrying conductor.
- Location
- Massachusetts
Re: Service entrance conductor sizing
One more thing, have you checked with the power company about their requirements?
Specifically hot or cold sequence metering?
A lot of the power companies in this area require cold sequence metering (Service Disconnect ahead of CTs) for 480/277 services.
In this area the job you describe would require a 1,000 amp main ahead of the CTs. Even if the existing metering had been hot sequence. Any newly installed metering must meet the present rules.
The info is probably available on the power company's web site.
I would verify this before ordering any equipment.
Bob
One more thing, have you checked with the power company about their requirements?
Specifically hot or cold sequence metering?
A lot of the power companies in this area require cold sequence metering (Service Disconnect ahead of CTs) for 480/277 services.
In this area the job you describe would require a 1,000 amp main ahead of the CTs. Even if the existing metering had been hot sequence. Any newly installed metering must meet the present rules.
The info is probably available on the power company's web site.
I would verify this before ordering any equipment.
Bob
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