Existing split bus panel

[nizak]

Is it code compliant to add a sub panel to an existing split bus panel or do they need to be replaced entirely?

I need to add 4 circuits. If I swap out the split bus I’ll need to bring the service up to code with Emergency disco new grounding and surge protection. To complicate things even more, the existing meter base is bricked in.

The panel is rated 125A and fed with #2 Cu.

The load on the house is roughly 90 amps per load calculation.

It would be fed from one of the 4 “mains”.

Thanks

 

[don_resqcapt19]

I know of nothing that would prohibit the use of one of the service disconnects to feed a new panel.

 

[suemarkp]

I would think it is ok, but local rules could change that. You may need surge suppression in that new subpanel if you dont have it anywhere in the existing service.

 

[qcroanoke]

If its

I would think it is ok, but local rules could change that. You may need surge suppression in that new subpanel if you dont have it anywhere in the existing service.

If it's being inspected......
That may have been the reason for the question.

 

[tortuga]

Just check the available fault current. most mains these days are 20 - 25 kAIC, but those old 2-pole mains in a split buss are likely 10 kAIC or less? Probably not a issue on residential.

 

[Master Nater]

i suppose that might fall under which code cycle you're operating under. either way, it should fall under grandfather clause, as it is existing. but it's possible that if your inspector is a stickler, he may require you to justify that you're not over-loading the service conductors by adding too much load onto the main bussing, with a calculation of added load on top of documented historical usage, like the earlier versions of the NEC required on these multiple service disconnect services.

 

[kwired]

i suppose that might fall under which code cycle you're operating under. either way, it should fall under grandfather clause, as it is existing. but it's possible that if your inspector is a stickler, he may require you to justify that you're not over-loading the service conductors by adding too much load onto the main bussing, with a calculation of added load on top of documented historical usage, like the earlier versions of the NEC required on these multiple service disconnect services.

I can't think of anything to cite in any NEC edition, that would prohibit additions to this existing panel other than maybe adding single pole breakers to the mains section and creating more than 6 main disconnects. Could be localities that have their own rules preventing this.

 

[Master Nater]

I can't think of anything to cite in any NEC edition, that would prohibit additions to this existing panel other than maybe adding single pole breakers to the mains section and creating more than 6 main disconnects. Could be localities that have their own rules preventing this.

i'm not sure why you feel the need to comment on every one of my comments, but let's go with it. i just ran into this situation with a larger commercial service with existing main bussing. in previous editions of the NEC (and no, i don't have them here, as it's the weekend) the code required an addition to the main bussing to be justified by one of two methods. either doing a load calculation on the entire building, and thus knowing how much more room is left to install additional load on the main bussing, OR getting historical usage for a year with either 15 minute or 30 minute intervals, and then using that peak usage history to determine how much more calculated load can safely be added.

despite popular ideas, the combined rating of the 6 OCPD landed on the main bussing do not have to stay under the service conductor's ampacity. only the calculated and/or historical load. so, no, he cannot just add whatever he wants. it has to be justified, as those service conductor's only protection are those multiple service disconnect OCPDs. simply adding whatever he wants, would be like upsizing the service disconnect to whatever he wants.

but again, it all comes down to what code cycle he's under. (nobody ever tells us this)

 

[curt swartz]

If there is an issue with the inspector can you install a 125A breaker to feed the new panel and move the other loads to the new panel? That way you would not be replacing the existing panel triggering other upgrades.