Neutral in feeder tied to different service panel.

[jcbabb]

I've come across an existing building that has (2) Main Service panels, each with a main breaker, and each fed from the CT can and located in different locations (let's call them Main A and Main B). Someone has added a sub-panel connected to a breaker in Main B. They routed the line conductors from Main B to the sub-panel's bus, then ran a separate neutral to the sub-panel that is connected to Main A. I don't have any knowledge as to why this was done, but I'm scratching my head for a code citation to use against it.

 

[Dennis Alwon]

Does 300.3(B) help you

 

[jap]

I'd start with 300.3.

Jap>

 

[jcbabb]

I read that, but wondered if 300.3 (B) allowed it if the neutral was routed in PVC. I don't fully understand the 'Nonferrous Wiring Methods'.

 

[Dennis Alwon]

I read that, but wondered if 300.3 (B) allowed it if the neutral was routed in PVC. I don't fully understand the 'Nonferrous Wiring Methods'.

Ferrous raceways are magnetic such as emt and rigid metal. Non- ferrous would be aluminum raceways

 

[jcbabb]

Ferrous raceways are magnetic such as emt and rigid metal. Non- ferrous would be aluminum raceways

Sorry I didn't clarify. I don't fully understand the section 300.3 (B) 3 titled 'Nonferrous Wiring Methods' or its implications in this case. I understand what ferrous versus non-ferrous means; I'm just not sure if simply routing the neutral in a separate non-ferrous raceway was enough to meet the exception. It seems at a surface reading that it would comply, but I don't understand why that might make it so.

 

[Eddie702]

I don't believe that is correct.215.4B &303.B

 

[Dennis Alwon]

Sorry I didn't clarify. I don't fully understand the section 300.3 (B) 3 titled 'Nonferrous Wiring Methods' or its implications in this case. I understand what ferrous versus non-ferrous means; I'm just not sure if simply routing the neutral in a separate non-ferrous raceway was enough to meet the exception. It seems at a surface reading that it would comply, but I don't understand why that might make it so.

I believe you are correct. Take a service conduit with parallel conductors and you must install all the conductors of the circuit in each conduit run. For instance, one conduit for have all the phase plus neutral, however if you use non ferrous raceway such as PVC then you are allow to run each phase in individual raceways. Phase A in one conduit, phase B in the other, phase C in the next and all the neutrals in another. You see this with open bottom switchboards.

Apparently with ferrous metal raceways using separate raceways will cause the conductors to heat up.