400 AMP SERVICE

KRG9729

Member
We are installing a separate 400 amp, 3-phase, 120-208 volt service for a residential project. The design is based on the 2014 NEC. The customer is installing a small commerical grade bakery in their basement.

We are proposing to come from the meter to a 400 amp fused service disconnect on the inside of the building. From the load side of the disconnect we would run to one 200 amp main breaker sub-panel and one 200 fused disconnect to feed an oven. The sub-panel and sub-disconnect are located on the same floor but in a separate room. My question is if the installation is code compliant if we install dual rated lugs at the main disconnect to feed the 200 amp disconnect and panel. Or is overcurrent protection for the 200 amp feeders at the main service disconnect location required.

Also, this is the second service to the same building. The original service (staying) is single phase 200 amp. Are the two services required to be bonded together? What NEC article would reference this. Thanks.
 

kwired

Electron manager
We are installing a separate 400 amp, 3-phase, 120-208 volt service for a residential project. The design is based on the 2014 NEC. The customer is installing a small commerical grade bakery in their basement.

We are proposing to come from the meter to a 400 amp fused service disconnect on the inside of the building. From the load side of the disconnect we would run to one 200 amp main breaker sub-panel and one 200 fused disconnect to feed an oven. The sub-panel and sub-disconnect are located on the same floor but in a separate room. My question is if the installation is code compliant if we install dual rated lugs at the main disconnect to feed the 200 amp disconnect and panel. Or is overcurrent protection for the 200 amp feeders at the main service disconnect location required.

Also, this is the second service to the same building. The original service (staying) is single phase 200 amp. Are the two services required to be bonded together? What NEC article would reference this. Thanks.
Both services need to tie to the grounding electrode system which ultimately will bond them together.

Unless your feeders comply with feeder tap rules in 240.21, you will need overcurrent protection at/below the conductor ampacity - or within the next size up provisions for 800 amps and below.

If your feeder were no longer then 25 feet and you complied with all the 25 foot tap rule requirements you could use a 200 amp conductor protected by a 400 amp device.
 

augie47

Moderator
Staff member
As far as the location of the downstream equipment, it will be compliant if you comply with the 240.21 tap rules. (In your case, likely the 25' rule). If not, you will need OCP that does comply with the rule.
I don't know of a requirement that specifically requires them to be be bonded together but 250.50 will require that both services be connected to the grounding electrode system so they will be bonded that way.
 
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