Most cost effective wiring distribution in a condo building

[hotneutral]

If you run the feeders for seven units through one conduit you will have to derate the wires to 45% of capacity due to heat. This means you will have to make the wires much larger to get the capacity you need.

7 x 3 current carrying conductors = 21 ccc. 21 requires a 45% derating. Further derating may be required due to ambient temp in attic.

Only one neutral from the west wing will count and none from the east wing. doesnt Help a whole lot with wire size and derating though.

 

[winnie]

Only one neutral from the west wing will count and none from the east wing. doesnt Help a whole lot with wire size and derating though.

Unfortunately, each feeder consists of 2 hots and a neutral (120/208 'single phase') derived from a 3 phase wye (208/120V) service. This means that all of the neutrals count a current carrying conductors.

The installation suggested by the OP will not fit in the existing conduit.

-Jon

 

[tkb]

But their engineers should already know that.

 

[Coppersmith]

By looking at this spec, the allowed number of #1 in a SC80 Pvc is 13 using THHW or 16 using THWN2 ... you have 18 + ground/s
Table C:10 page 784 - 785 NEC 2020

For the 125 amp services #1 is too small assuming the conductors are aluminum. 1/0 is required, so even less space in that pipe.

 

[hbiss]

The way it's drawn makes me think that they want to pull individual cables (SER?) from the meter bank to the individual units. Those would be run in the 3" and cable tray. That's not going to happen.

It's usual in jobs like this to run those cables up through the building and attic to their units. No conduit or cable tray is used. What complicates this is the wing that has to have them run underground. What I would suggest is 6 conduit runs from the meter bank, under ground to pull box in the other wing. There the transition would be made from the THHW to the six SERs which would then be run up to the attic and acrosss to the units like the other wing. No derating except perhaps for the attic ambient.

If you have firestopping to consider you may want to use MC instead of SER.

-Hal

 

[texie]

In addition to the issues already mentioned, many POCOs will not allow separately metered conductors in the same raceway.

 

[GoldDigger]

In Calif. The Utility is responsible for only servicing their lines into the Pull section upstream from meter period , as usual they own the meter but the line lug connections,hardware and load lugs are the responsibility of the field electrician. When a switch gear or typical panel is installed as a complete unit with pull section, The meter section and distributions all the bussing, torques, connections thermal protections involved within that equipment is a field electricians problem.

Thank you.

 

[classicaldg]

The way it's drawn makes me think that they want to pull individual cables (SER?) from the meter bank to the individual units. Those would be run in the 3" and cable tray. That's not going to happen.

It's usual in jobs like this to run those cables up through the building and attic to their units. No conduit or cable tray is used. What complicates this is the wing that has to have them run underground. What I would suggest is 6 conduit runs from the meter bank, under ground to pull box in the other wing. There the transition would be made from the THHW to the six SERs which would then be run up to the attic and acrosss to the units like the other wing. No derating except perhaps for the attic ambient.

If you have firestopping to consider you may want to use MC instead of SER.

-Hal

Thank you for the answer. I appreciate it. We will not use the gutter. I sent this to our designer. Thanks again.