ECN Forum Forums Code Related Discussion NEC & other Code issues 310.4

A building has an existing 400 amp service with a 3" rigid riser existing.

They make the service 800 amp and add another 3-1/2" riser with the same conductor type, size, insulation, length, and terminated in the same manner.

Would this be a violation?

Does the raceway having the same physical charactristics include the size of the conduit?

Red tag from me

Ryan--Would you mind elaborating a little. Just curious about the interpretation.

Thanks

SteveT, I'm curious how you turn a 400-amp service into an 800-amp service without replacing the gear. It sounds like you're describing some kind of add-on.

Dave

3" and 3 1/2" seem to be different physical characteristics to me.

Steve I imagine Ryan is thinking of this part of 310.4


Tiger one quick and easy way is to provide 800 amp metering and add a second 400 amp service disconnect switch next to the original.

They are replacing the gear.

I was just thinking the different physical characteristics tended more towards meaning the same type of metal, or not one metal and one PVC.

Does anyone have a reason why this would or could be unsafe? (Assume the raceways are properly bonded and such)

I personally don't think there would ever be an issue with this install. But you are trying to avoid any differences between the paths. If you have a smaller pipe you would have a change in heat disipation and inductance for example, which might result in one path taking a larger amount of current.

Size is definitely a physical characteristic of a raceway.

I thinbk that cite came from a discussion of "parallel" feeders. What I see, instead, are two separate service drops, going to two separate disconnects.

If these are then combined at a panel, I see all sorts of "multiple feed" issues."

If they are segregated from each other, all the way to the outlets, then we have two separate services on one building.

As I understand parallel feeds, they have to start, and end, at the same places.....not a separate disconnects.
If that is the case, I would have preferred a larger riser, with larger wires, coming from a single disconnect to a single weatherhead. Then, if the PoCo wanted to run a parallel feed, they would join at the weatherhead.