400 Amp 3 phase service

[guitarchris]

Let me start this by stating that we do 98% resi work. Most of the commercial work we do is interior work or maintenance. That said we have been asked to do service upgrade on a restaurant. We are separating the existing service off of a trough that serves several other tenants in the same building. We want to leave all the other items alone, as it is as old as the hills and a mess. It is 3 phase coming in and 2 legs coming off of a 5 jaw meter to a 200A single phase panel that serves the restaurant. The A/C that are on the roof are tripping the main when all is on.

I plan to build a 208/120 400A 3 phase service with a standard 3 ph meter base with a 18 circuit 3ph 200A panel beside the meter. Then a 3 phase 200A main breaker disconnect on the other. Can I just come off 2 legs of the 3 phase breaker/ disco to feed the 200A single phase panel inside the restaurant? If I can could I just come off two legs at the meter to feed a single phase disconnect to save on cost? How about the panel, can it be single phase, pulled off 2 phases? None of the equipment is 3 phase (including A/C's).
I'm just looking for the simplest, cleanest, cost effective method for my install. If I was doing this on a single phase resi scenario I would use a meter panel combo for ease of install, I don't think such a thing exists for 3 ph. I don't live in the commercial world, so help a bother out!
I'm

 

[Dennis Alwon]

You certainly can use 2 phases of a 3 phase breaker but why not just use a 3 phase panel. That may give you the capacity you need without going 400 amps.

Are you sure the a/c is tripping the main due to overload or could the a/c unit be the issue. I would hate to see you build a whole service and find out the a/c is the issue.

 

[cadpoint]

I'll assume this is a 208 wye? 208 delta only leaves two workable legs of 120V.

3 ph wye

vs

3 ph Delta

How many meters are in place now?

I think you should get the AHJ invovled ASAP, if it's Wake County, I'm almost going to say that your out of luck - because the job isn't engineered. The City of Raliegh is even worse. All county's don't ask for all the same things! Some County's will allow seperate "electricial" or other "types" of pulled permits on resturants. Some have various degree's but you've been advised.

I also a agree in toto with Dennis, Frankly I think you'll raise eye-browes with the splitting of the service circuits. I don't think you'll be able ever balance the loads but will infact cause or induce an in-balance if so isolated.

Don't forget to GFCI the kitchen!

Most all counties in NC have their requirements for permits on-line, Good Luck

 

[guitarchris]

I do plan to get the AHJ involved. I'm in the planning stage now. That's the next step.
It is 120/208 wye.

I want to leave the inside panel as is, just re- feed and seperate the grounds & neutrals.

 

[guitarchris]

Denis, the A/C (one of the 3 units) definitely might be the problem, that was my first comment. The customer is dead set on upgrading.
If I went to a 3 phase panel I would have to swap out the inside panel in fairly close quarters, which is doable but not ideal. Then I think we would have to rework the service changing the meter (the current one is a 5 jaw). It would be almost the same amount of work.

the current service is one of two in use, and a couple other meter bases that are abandoned. All that is one OH drop to a trough feeding those meter pans. There is another 200A, newer, service that is adjacent to this one. They did exactly what I have in mind by not messing w/ what is there and starting fresh.

Nothing about this job is ideal and I have tried to walk away, but they keep calling me back. The current service is a mess. The current panel is in the kitchen, between two pieces of equipment and they want zero downtime. The no downtime means working a Sunday on as much as we can do, then early Monday having to re-feed existing panel and coordinate w/ poco and AHJ for reconnect by 11Am opening.......insane, but doable.

 

[cadpoint]

Before you go any farther. Do a cost of a total rip-out verses what the client and you think you can do. It frankly doesn't come down to what the Client will pay for but what they are getting into &what will be required to meet, since your now involved!

The main overhanging drama is that the Hood will be 208? Was this a designed resturant or a space that was taken over by a resturant?

My friend says just rip everything out, and put in what is needed; OK let me clarify that in most cases he can blow out a 42 space panel based on 200 Amp service trying to service a resturant! It seems your good at 400 but your not carrying the full service forward, but that spliting out service is a no go; he also recommends EE drawings. Now the Client has slipped into the NC Dept of health requirements...
since now you know , they should know...It's not the owner call to defer a good service upgrade.

 

[kwired]

The A/C that are on the roof are tripping the main when all is on.

The first thing I would do after ruling out something wrong with the A/C unit(s) as well as a hot terminal on the main is to do some load calculations as well as measurements of existing loads. Does little good for the immediate symptoms to upgrade if there is some other problem and if the 200 amp single phase to this restaurant is near its capacity from what I understand you are still going to feed it with 200 amp single phase - so you gained nothing in capacity. Or are you losing a 200 amp main that feeds all occupancies?

 

[guitarchris]

The first thing I would do after ruling out something wrong with the A/C unit(s) as well as a hot terminal on the main is to do some load calculations as well as measurements of existing loads. Does little good for the immediate symptoms to upgrade if there is some other problem and if the 200 amp single phase to this restaurant is near its capacity from what I understand you are still going to feed it with 200 amp single phase - so you gained nothing in capacity. Or are you losing a 200 amp main that feeds all occupancies?

It would be a 400 service with a 200A breaker/disco (feeding existing panel)at meter and another 200A panel beside the meter. The A/C units circuits will be taken off of the existing 200A and on to the new 200A panel. The existing panel feeds the one restaurant.

For the sake of this discussion lets assume that the A/C's are functioning normally and that existing service needs upgrading. If further investigation finds that the A/C's are screwy we will possibly scratch the upgrade. As of now, I have been asked to price upgrading the service and need your advice on the best methods/materials.

 

[Dennis Alwon]

As of now, I have been asked to price upgrading the service and need your advice on the best methods/materials.

From what I understand of your install it should be fine. I don't see why you cannot come off the 3 phase meter with a single phase disconnect. That will definitely save money. The only problem may be an imbalance.

Why are you installing a 3 phase panel and 3 phase meter if the restaurant does not have any 3 phase loads?

 

[guitarchris]

The main overhanging drama is that the Hood will be 208? Was this a designed resturant or a space that was taken over by a resturant?

Building is old, This section has been a restaurant/bar for ages. I'm clueless to restaurants, what does the hood have to do with upgrading the service?

 

[guitarchris]

From what I understand of your install it should be fine. I don't see why you cannot come off the 3 phase meter with a single phase disconnect. That will definitely save money. The only problem may be an imbalance.

Why are you installing a 3 phase panel and 3 phase meter if the restaurant does not have any 3 phase loads?

Wouldn't at least the meter base have to be 3ph. I met with the poco engineer and he implied that a single phase MB couldn't be used. Would the poco just bring in 2 legs? I inquired at my supply house (Womack) to see if I can get a 400A 5 jaw meter base. They weren't sure if they make one, as they haven't sold one that they remember. If no 5 jaw is made, I'm guessing I'd have to go with a traditional 400A 3ph meter base. If I'm allowed to come off with a single phase disco and another single phase panel, I'm all for that...I might even have a nice CH outside panel I could use.

Sorry for my ignorance, I appreciate all the help.

 

[renosteinke]

Panels are listed by the services they are rated to have supply them. Look to the 'fine print' on the panel cover and I don't think you'll find too many single-phase panels listed for use with a 208Y service. (Delta is an entire different discussion).

"Fine print" aside, it just strikes me as sloppy to not use a three-phase panel. OK, that might mean you can't use the cheaper "Homeline," and have to stay with the QO ... but do you really want to introduce a different breaker to the building?

As for the hood reference ... in commercial kitchens, everything 'under the hood' has to shut down when the Ansul trips. It's a lot easier to do this if all those circuits come from the same panel. A service change is a great opportunity to clean up the existing mess.

 

[fridaymean]

Why not sell them on a 400A SINGLE phase service. Since there are not current 3 phase loads, three phase is unnecessary. If they want if for future equipment, it would make sense. But cost being the most important factor these days. Single phase would be the way to go...

 

[kwired]

Why not sell them on a 400A SINGLE phase service. Since there are not current 3 phase loads, three phase is unnecessary. If they want if for future equipment, it would make sense. But cost being the most important factor these days. Single phase would be the way to go...

What is best would really depend on what the load calculations are.

400 amps x 208 volts x 1.73 for three phase allows us to have about 144.1 KVA of load.

600 amps x 240 volts for single phase allows us to have 144.0 KVA of load.

400 amps x 208 volts for single phase allows to have about 83.2 KVA of load. Plus you have one phase of the system that is not used if it is two phases of a three phase system, that will require larger transformer to supply the same load than if it were balanced across three phases.

400 amps x 240 volts for single phase allows to have about 96.0 KVA load.

If your load calculation came to 120KVA then it may cost less to use 400 amp three phase equipment than to use 600 amp single phase equipment

POCO may favor three phase over single phase for load balancing purposes

 

[tx2step]

Maybe I missed it, but I never saw the OP say whether the existing service is 120/208 3 phase wye, or if it is 120/240 3 phase delta. I'm kinda betting it's 120/240 delta and that's why the existing panel is single phase.

If existing equipment is 240v, some of it may not be happy at 208v. Especially an a/c unit that's already having trouble starting & tripping cb's already.

 

[Riograndeelectric]

your utility company may want verification of load calcs for the existing loads on the restaurant as well as the AHJ before commencing with any work.

what about the Fault current? you will have to also have to calculate the Short Circuit fault current ratings on the new service.

your Utility company may prefer you to use CT'S instead of a K base meter.
the 400amp meter is only good for 320A continuous loads

 

[kwired]

Maybe I missed it, but I never saw the OP say whether the existing service is 120/208 3 phase wye, or if it is 120/240 3 phase delta. I'm kinda betting it's 120/240 delta and that's why the existing panel is single phase.

If existing equipment is 240v, some of it may not be happy at 208v. Especially an a/c unit that's already having trouble starting & tripping cb's already.

OP verified that it was 120/208 3 phase in post #4. Makes no sense to me that they supplied it with three phase and then never utilized all three phases, unless it was fed from a delta system originally and had very limited three phase load at one time. POCO transformer may be overloaded on 2/3 of windings and no load at all on the other third or is oversized and still no load on one third of windings.

 

[Dennis Alwon]

Makes no sense to me that they supplied it with three phase and then never utilized all three phases, .

There are other tenants in the building so they may need the 3 phases. I don't see why you would need a 3 phase meter. I would contact the poco. Three phase meter and only 2 legs being used is a waste of money.

 

[Cow]

Seems like quite a money saver going single phase only, but you add so much more capacity switching everything to 3 phase and it'll help keep the load balanced like mentioned above.

Personally, I'd probably push for 3 phase components. Restaurants are constantly adding equipment...

 

[guitarchris]

Well, if I went w/ 3 phase are you saying stick with 200A?