Have a Client that has a strip mall configuration, 1 structure with 4 individual buildings because a firewall divides them. There is a 208V 3-phase pad mounted transformer serving the ganged meter bank. The meter bank has the bus section in the middle rated at 1200A and 3 meters on the right and 2 meters on the left. Each building disconnect is also located at the meter with each meter having a 200A-3P breaker (side note, the feeds from the meter bank go thru the ceilings on the units then drop down into each unit without having a disconnect where they pass thru another building). Originally, 2 buildings would get 200A and 2 buildings would get 400A though not privy to the original design documents. However, because they did not get 400A meter sockets, 2 of the buildings are supplied by 2 meters and this left 1 building without power as follows:
original:
building A = 200A
building B = 200A
building C = 400A
building D = 400A
Installed:
building A = 200A
building B = no power
building C = 200A, 200A
building D = 200A, 200A
Obviously, the first issue here is that 2 of the buildings have 2 supplies to them and code will allow this to remain. Next issue is we need to get power to the building without power. The installed service conductors are 2 sets of 750 copper. The next issue is the conductors obviously do not have a 1200A rating. Is it possible the conductors were sized based on NEC 230.90.A. exception #3? would that have been allowed for this installation. The intended load did not change just the metering configuration.
Our first recommendation (knowing the 2 supplies to each of the 2 building is approved) would be to add a 3rd set of 750 which would provide 1284 amps. (4 ccc per set, 535A x 0.8A = 428A per set). Then, add an additional meter on the left side with 200A load. Probably $10K to $15K.
However the Client does not want to add the 3rd set unless necessary. Therefore, back to NEC 230.90.A. exception #3, can this be applied in that we would perform a load calculation for the unpowered unit and 220.87, utility data for the remaining units? Even thought the breaker amps are over, the load could still be under the 750's. I guess then then maybe the issue is, is the calc based on 3 CCC or 4 CCC. I don't like sizing the conductors based on the load because the load can change and is unsafe in my mind but trying to look at it from a code standpoint.
I was then thinking of maybe letting everything there the way it is and just bringing a 2nd underground lateral to a 200A self-enclosed meter (without a disconnect) located by the ganged meters. However, I am not fully understanding how this would play into the exhibits shown after section 230.2. I think this would count as 2 services and because all the meters are located on the end of the structure, 1 building's exterior wall would have 2 services. Would look like exhibit 320.11 but with 2 laterals all on 1 building. I am also not sure how having the exterior disconnects plays in; if it changes these exhibits.
My plan to get the feeder (or service conductors) to the empty unit is to trench the floors and stub-up in the unit or go thru the ceilings and provide disconnects in the units passing thru.
Any info would be helpful.
original:
building A = 200A
building B = 200A
building C = 400A
building D = 400A
Installed:
building A = 200A
building B = no power
building C = 200A, 200A
building D = 200A, 200A
Obviously, the first issue here is that 2 of the buildings have 2 supplies to them and code will allow this to remain. Next issue is we need to get power to the building without power. The installed service conductors are 2 sets of 750 copper. The next issue is the conductors obviously do not have a 1200A rating. Is it possible the conductors were sized based on NEC 230.90.A. exception #3? would that have been allowed for this installation. The intended load did not change just the metering configuration.
Our first recommendation (knowing the 2 supplies to each of the 2 building is approved) would be to add a 3rd set of 750 which would provide 1284 amps. (4 ccc per set, 535A x 0.8A = 428A per set). Then, add an additional meter on the left side with 200A load. Probably $10K to $15K.
However the Client does not want to add the 3rd set unless necessary. Therefore, back to NEC 230.90.A. exception #3, can this be applied in that we would perform a load calculation for the unpowered unit and 220.87, utility data for the remaining units? Even thought the breaker amps are over, the load could still be under the 750's. I guess then then maybe the issue is, is the calc based on 3 CCC or 4 CCC. I don't like sizing the conductors based on the load because the load can change and is unsafe in my mind but trying to look at it from a code standpoint.
I was then thinking of maybe letting everything there the way it is and just bringing a 2nd underground lateral to a 200A self-enclosed meter (without a disconnect) located by the ganged meters. However, I am not fully understanding how this would play into the exhibits shown after section 230.2. I think this would count as 2 services and because all the meters are located on the end of the structure, 1 building's exterior wall would have 2 services. Would look like exhibit 320.11 but with 2 laterals all on 1 building. I am also not sure how having the exterior disconnects plays in; if it changes these exhibits.
My plan to get the feeder (or service conductors) to the empty unit is to trench the floors and stub-up in the unit or go thru the ceilings and provide disconnects in the units passing thru.
Any info would be helpful.
