EGCs in parallel

[m sleem]

Having 1000a OCPD fed by 4 sets each 4xsingle core 400mm2(4x4x1c400mm2) all in parallel, as per table 250.122 the EGC would be min 70mm2. My college says: for bundle installation, better to have EGC with each bundle, means 4 x1c70mm2 which is extra cost.
My question is, can we split the 1c70mm2 EGC into 4x1c25mm2?

 

[eprice]

I'm not sure what you mean by bundle. If these are separate raceways, then 250.122(F) requires a full sized EGC in each raceway.

 

[charlie b]

First, if I correctly understand that the four parallel bundles will be run in four separate conduits, then the answer to your question is no. Reference the second paragraph of 250.122(F). The EGC in each conduit has to be full size, meaning each one has to be based on the 1000 amp OCPD.

Secondly, a 400 mm2 conductor will have an ampacity of 400 amps or more, so four of them have an ampacity of 1600 amps or more. That seems a bit of overkill for a 1000 amp circuit. Why are you using such large wires?

 

[m sleem]

First, if I correctly understand that the four parallel bundles will be run in four separate conduits, then the answer to your question is no. Reference the second paragraph of 250.122(F). The EGC in each conduit has to be full size, meaning each one has to be based on the 1000 amp OCPD.

Secondly, a 400 mm2 conductor will have an ampacity of 400 amps or more, so four of them have an ampacity of 1600 amps or more. That seems a bit of overkill for a 1000 amp circuit. Why are you using such large wires?

All cables will be run in one tray & the reason behind the oversizing is voltage drop.

 

[m sleem]

I'm not sure what you mean by bundle. If these are separate raceways, then 250.122(F) requires a full sized EGC in each raceway.

The meant by bundle is ''cables installed in group, each group consisting of (phases,neutral) in trefoil shape"

 

[petersonra]

Having 1000a OCPD fed by 4 sets each 4xsingle core 400mm2(4x4x1c400mm2) all in parallel, as per table 250.122 the EGC would be min 70mm2. My college says: for bundle installation, better to have EGC with each bundle, means 4 x1c70mm2 which is extra cost.
My question is, can we split the 1c70mm2 EGC into 4x1c25mm2?

you can't use wire of IEC standards in NEC applications unless the wire is dual rated as some kind of NEC conductor.

in a later post you mention they are all in one cable tray. many times cable trays are rated as egc and so you might not need a wire type egc at all.

you can't break up an egc into smaller parallel conductors like you can wires that actually carry current.

400 mm2 is about 750 kcm. if you had four of them in parallel you would probably need about a 4/0 or maybe even a 250 kcm egc. see 250.122 (B).

 

[m sleem]

many times cable trays are rated as egc and so you might not need a wire type egc at all.

I can find it in 250.118.

you can't break up an egc into smaller parallel conductors like you can wires that actually carry current.

Please provide the reference.

 

[don_resqcapt19]

I can find it in 250.118. ...

Look at 392.60

 

[petersonra]

Please provide the reference.

take a look at the last sentence of 250.122 (F)