400-600 amp service 120/208v 3-phase

S

Scheffler Energy

Member
Location
Minnesota USA
Occupation
Master Electrician
Hello,

I am looking for some advice on the best way to build a 120/208v - 3 phase service for a farm site I'm looking into installing a 400 or 600 amp service my question is what would be the best way to accomplish this. My plan is to mount a CT cabinet with a utility meter connected to it for the CTs from the CT cabinet is it better to go to one large 400amp disconnect and then from the load side of the disconnect go to two 200 amp panel boards or for a 400 amp service come out the CT cabinet and go to two 200 amp disconnects and then to two 200 amp panel boards and for a 600 amp service go from the CT cabinets to one large 600 amp disconnect with triple lugs on the load side and go to three different panel boards or come from the CT cabinet and go to 3 different 200 amp fused disconnects and then to three 200 amp panel boards? My mind is telling me the best way to do this is use 200 amp fused disconnects to accomplish this any advice or pictures of the best way to do this would be very appreciated. Thanks ! I want to build an outdoors metal strut rack with rigid pipe and uni strut.
 
If it is a farm you likely need a site isolating device per 547.41(A). Unless this is feeding just one building or structure then you could run service conductors to service equipment at that building or structure.

The loads to be served sort of have some impact on what you might use for multiple disconnects. If you have one large load (or at least need one large feed to a particular building) you may very well need a 400 amp disconnect for that particular feed but other building(s) don't need that sort of capacity.

I can think of a couple places I have wired up grain handling/storage that had 400 amp feed, then when they added drying equipment it needed a 200 amp feed for that equipment so we added a second disconnect for the drying equipment next to the existing 400 amp disconnect. POCO of course ended up needing to install a larger transformer as well to handle the added load. Would likely still done about same setup if all that same equipment were there at initial installation rather than going with a 600 amp main and then 200 and 400 amp sub feeds out of it just because of how things set up at these sites. The drying equipment was sort of it's own supply and only had a few control circuits for the most part that left it to interact with other items away from the drying equipment.
 
So after speaking to the utility the metering is all done at the transformer so I think running 3 different feeds to the transformer from 3 separate 200 amp disconnects on a equipment rack is gonna be the best way to do it. That’s will leave room for future expansion. Thanks for all your insight I’m still always learning!
 
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