sailonjazz
Member
- Location
- Charletown, RI
:?Hello to all. I've been gleaning very good information from this forum for a while but feel i need more advise than i can find in the posts. I have been licensed since 1986 and have done a lot of industrial and commercial work but find myself a little out of my depth of field. I have been tasked to engineer a remodel of an existing space in a very large building. The building has a 1200a 480v 3 ph service consisting of a 1977 ITE series 5 switchgear and panel board with 3 open spaces next to a JL3-F400 breaker rated at 30 KAIC. My 120 volt loads total 65836 va, 44364 va is 240v lighting and the rest is some light duty fans. I also have 2 480v 3 ph HVAC roof units drawing 21.5 amps and 24 amps each. The new area is 175' of pipe run away from the electric room.
My original plan, working backwards, is to have a 400 amp main 120/240 1 ph 42 cir panel-board able to feed a 200 amp sub panel. Fed with (3) 600 kcmil and (1) #3 gnd, or (6) 4/0 and (2) #6 in parallel, from a 75 kva 208/480v - 120/240v transformer. The transformer would be bonded with a 1/0 jumper to building steel and fed with (2) 3/0 and (1) #6 gnd from a 200 amp 2-pole breaker. This breaker would be installed in a 400 amp 480 volt 3 ph MLO panel also containing (2) 30 amp 3 ph breakers for the two HVAC roof units. I intend to feed this panel with (3) 350 kcmil and (1) #4 gnd from an ITE JL3-F400 with a 250 amp setting.
So finally to my questions. I am concerned about balancing my 3 ph panel.
1) Could i use a 3 ph 120/240 v panel along with a 3 ph transformer. This would bring my sizing down.
2) Should the 480 v 3 ph sub panel have a main breaker.
3) Are my calculations messed up
My original plan, working backwards, is to have a 400 amp main 120/240 1 ph 42 cir panel-board able to feed a 200 amp sub panel. Fed with (3) 600 kcmil and (1) #3 gnd, or (6) 4/0 and (2) #6 in parallel, from a 75 kva 208/480v - 120/240v transformer. The transformer would be bonded with a 1/0 jumper to building steel and fed with (2) 3/0 and (1) #6 gnd from a 200 amp 2-pole breaker. This breaker would be installed in a 400 amp 480 volt 3 ph MLO panel also containing (2) 30 amp 3 ph breakers for the two HVAC roof units. I intend to feed this panel with (3) 350 kcmil and (1) #4 gnd from an ITE JL3-F400 with a 250 amp setting.
So finally to my questions. I am concerned about balancing my 3 ph panel.
1) Could i use a 3 ph 120/240 v panel along with a 3 ph transformer. This would bring my sizing down.
2) Should the 480 v 3 ph sub panel have a main breaker.
3) Are my calculations messed up