JC_ELEC
Member
- Location
- Dominican Republic
- Occupation
- Electrical Engineer
Hello, i'm a bit confused about grounded conductor sizing for parallel feeders. Nec 215.2(B) states the following:
"The size of the feeder circuit grounded conductor shall not be smaller than the equipment grounding conductor size required by 250.122, except that 250.122(F) shall not apply where grounded conductors are run in parallel"
So it says that 250.122(F) shall not apply for parallel runs. So, does that mean that 250.122 won't dictate the minimum neutral conductor size for a parallel run? Here is an example:
In this scenario i have a 1000A 3phase Breaker in a Switchboard feeding a 1000A Panelboard. The neutral load is non-existent but the client wants a minimum sized neutral conductor (don't ask why, it's an example). The conductors sizing are as follows:
- Ungrounded conductors sizing: 5 x #3/0AWG (200A) per phase = 1000A.
- 5 x EMTs (one per parallel set).
- Equipment Grounding Conductor: 5 x #2/0AWG EGC (per table 250.122).
- Grounded/Neutral Conductor: can i size the minimum neutral conductor as 5 x #1/0AWG (minimum size for parallel neutral size per 310.10(G)(1)? Or do i have to size the neutral in each set per the minimum allowed size in 250.122 (in this case 5 x #2/0AWG)?
"The size of the feeder circuit grounded conductor shall not be smaller than the equipment grounding conductor size required by 250.122, except that 250.122(F) shall not apply where grounded conductors are run in parallel"
So it says that 250.122(F) shall not apply for parallel runs. So, does that mean that 250.122 won't dictate the minimum neutral conductor size for a parallel run? Here is an example:
In this scenario i have a 1000A 3phase Breaker in a Switchboard feeding a 1000A Panelboard. The neutral load is non-existent but the client wants a minimum sized neutral conductor (don't ask why, it's an example). The conductors sizing are as follows:
- Ungrounded conductors sizing: 5 x #3/0AWG (200A) per phase = 1000A.
- 5 x EMTs (one per parallel set).
- Equipment Grounding Conductor: 5 x #2/0AWG EGC (per table 250.122).
- Grounded/Neutral Conductor: can i size the minimum neutral conductor as 5 x #1/0AWG (minimum size for parallel neutral size per 310.10(G)(1)? Or do i have to size the neutral in each set per the minimum allowed size in 250.122 (in this case 5 x #2/0AWG)?