gh0st
Member
- Location
- California
- Occupation
- Designer
I'm having a brain fart...
I have a design I'm looking at where a new 3ph xfmr is installed that only feeds a 1ph load due to owner standards.
If OCPD for the primary conductors are sized such that it meets Table 450.3(B) to also protect the secondary conductors, isn't it Code acceptable to simply bring 2W+G to the new 1ph load (terminating on equipment's 2pole disconnect)? The third phase wire need not be pulled.
Where is gets kind of confusing is that between the xfmr and the 1ph load is another disconnect. We're being told that 4W+G needs to leave the xfmr secondary and land on the intermediate disconnect and 3W+G need to extend from the load side of the intermediate disconnect to the 1ph load. (?! - not sure where that 3rd wire will land) The fusing in the intermediate disconnect is sized to protect the xfmr secondary (70A @ 208V3ph) but load side of that disconnect feeds the 1ph load (100A@208V1ph).
Coming back to my brain fart...will the 70A (3ph) fusing be an issue when the 1ph load is protected with 100A (1ph) fusing at its local disconnect?
Hope this all makes sense... Thanks.
I have a design I'm looking at where a new 3ph xfmr is installed that only feeds a 1ph load due to owner standards.
If OCPD for the primary conductors are sized such that it meets Table 450.3(B) to also protect the secondary conductors, isn't it Code acceptable to simply bring 2W+G to the new 1ph load (terminating on equipment's 2pole disconnect)? The third phase wire need not be pulled.
Where is gets kind of confusing is that between the xfmr and the 1ph load is another disconnect. We're being told that 4W+G needs to leave the xfmr secondary and land on the intermediate disconnect and 3W+G need to extend from the load side of the intermediate disconnect to the 1ph load. (?! - not sure where that 3rd wire will land) The fusing in the intermediate disconnect is sized to protect the xfmr secondary (70A @ 208V3ph) but load side of that disconnect feeds the 1ph load (100A@208V1ph).
Coming back to my brain fart...will the 70A (3ph) fusing be an issue when the 1ph load is protected with 100A (1ph) fusing at its local disconnect?
Hope this all makes sense... Thanks.
