Need advice on 400A service

[cfrisella]

Upgrading a service from 200A - 400A as part of a restaurant remodel. Commercial location (Mall). The meter base room is 300' from the store. The plans call for a new 400A service, which would then feed an existing 200A panel. As a cost savings measure we are considering splitting the 400A into two 200A runs. They would run out of a single meter base, through a 400A disconnect and in the same 4" conduit from the meter room into the restaurant space. Once in the space the 4" conduit would end in a gutter and two 2.5" runs would head out. One to feed the existing panel and one to feed the new panel. Is this a violation of tap rules or is this safe and acceptable?

[ March 03, 2003, 12:22 PM: Message edited by: cfrisella ]

 

[iwire]

Re: Need advice on 400A service



[ March 03, 2003, 07:42 PM: Message edited by: iwire ]

 

[russ]

Re: Need advice on 400A service

It reads like you plan to connect two sets of 200amp wire from the CT that is protected by a 400amp over current device, to two seprate 200amp panels. Does'nt sound right to me. You would need two 200amp disconects in the meter room

 

[BAHTAH]

Re: Need advice on 400A service

Like Russ mentioned, your post reads like you are protecting two 200amp feeders with a single 400amp overcurrent device. You should be able to have two 200amp service disconnects. If you combine both feeders in a single conduit you will have to derate their ampacity assuming this to be a 3ph4w system. Another option would be to run parallel 4/0 (depending on voltage drop) and then use the tap rules to split the 400amp feeder into two 200amp feeders, using gutter and fusible disconnects closer to the sub panels. 4/0 THHN-CU is rated 260amps x .80=208amps with the deration for number of current carrying conductors. You should not have to count the neutral as current carrying for this type of load. The disconnects have lugs rated for 75-deg c and your load will not exceed the 75-deg c rating or most likely not even the 60-deg c rating of the 4/0. If you install power distribution blocks in the gutter at the end of the 400amp feeder you can terminate the parallel 4/0 for each phase in a single block and make your tap to the 200amp fusible disconnect with a single 3/0. That would cut your circular mill area of copper from 500kcm min per phase and neutral, to 423,200kcm. You are allowed to use the insulation of the conductor for figuring the deration in the feeder conduit, but you must not exceed the 75-deg c ampacity of the conductor at the terminations. In addition at 300ft you may have voltage drop issues.

 

[hornetd]

Re: Need advice on 400A service

Are you
A)running a 400 ampere feeder and then tapping off in the auxilliary gutter to two 200 ampere panels, each with a main breaker,

or are you

B)running two two hundred ampere conductor sets from the four hundred ampere service disconnecting means?

If the answer is B you will have to run them from individual 200 ampere Over Current Protective Devices (OCPDs) located at the service disconnect or run them as conductors in parallel to four conductor splice blocks in the auxilliry gutter and run the individual conductors from the splice blocks to the two panels in compliance with the tap rules.

Does it really save money to run two 200 ampere conductor sets in the four inch pipe?
--
Tom