Three Phase service

[arnettda]

I did a load calculation for a addition to a existing building that I thought was a single phase service. Historical data shows 25 kw of load. My load calculation for the new building was 29 Kw So my new load would be roughly 251 amps. It turns out my service is actually three phase. Any help on determining my new three phase load?
My other question is the 3 phase service is 120/240 with a high leg. I talked with the POCO and he does not believe they will want to change this as there are multiple building fed off this bank of transformers. I would like to install a 320 class 3 phase meter socket to feed existing three phase panel and then use Phase A and B in meter socket to feed a new single phase panel next to three phase panel? Phase C in existing panel is pretty much useless so to me it would be cleaner if I could just install the new single phase panel. There is not a 200 amp single phase meter to be found from my supplier. Any guidance would be greatly appreciated. Thanks

 

[zbang]

How much of the existing and new loads are single vs three phase, and is it worth the effort to move single-phase loads to a new panel?

 

[arnettda]

I did a load calculation for a addition to a existing building that I thought was a single phase service. Historical data shows 25 kw of load. My load calculation for the new building was 29 Kw So my new load would be roughly 251 amps. It turns out my service is actually three phase. Any help on determining my new three phase load?
My other question is the 3 phase service is 120/240 with a high leg. I talked with the POCO and he does not believe they will want to change this as there are multiple building fed off this bank of transformers. I would like to install a 320 class 3 phase meter socket to feed existing three phase panel and then use Phase A and B in meter socket to feed a new single phase panel next to three phase panel? Phase C in existing panel is pretty much useless so to me it would be cleaner if I could just install the new single phase panel. There is not a 200 amp single phase meter to be found from my supplier. Any guidance would be greatly appreciated. Thanks

The only three phase load is the roof top unit. Sorry I forgot that.

 

[electrofelon]

I come across these frequently. Often it is nice to install a small three-phase panel and then a larger single phase panel (assuming there are limited three-phase loads and limited L-L with no neutral loads). Might want to confirm with your power company that class 320 three-phase sockets are acceptable, in my experience many don't allow them and will want a CT cabinet for anything above 200. But yeah that's a nice way to do it two sets coming off the meter, one three-phase set and one single phase set.

 

[augie47]

One 3 phase panel and one single phase panel fed off a 400 meter is fairly common in this area.
Note that with our POCO the high-leg phase is "C" in the meter (By NEC, "B" in the 3 phase panel)
As felon notes, some POCOs will require CT metering but ours does not on 400 amp.

 

[electrofelon]

One 3 phase panel and one single phase panel fed off a 400 meter is fairly common in this area.
Note that with our POCO the high-leg phase is "C" in the meter (By NEC, "B" in the 3 phase panel)
As felon notes, some POCOs will require CT metering but ours does not on 400 amp.

I've always wanted to use a class 320 three phase socket but the big CT cabinet lobby has not made that possible for me

 

[jap]

In our area some POCO require a 320a meter bases for up to 600 amp services stating their CT's are not accurate on larger services with smaller loads if they determine that to be the case.

In some cases we have to run 600 amp services through 320a rated self contained meter bases.

I wish they would start CT'ing everything.

Self contained meter bases, or metering in general in our area is a high commodity at this time and getting very hard to come by.

JAP>