Opinion of a 3 phase panel in an condominium unit

[Cartoon1]

I have a multiple story building for a total of 35units. 2 of those units are very large that has 2 ranges, 2 a/c, and 2 instant water heaters. The service for the building is a meter center that is 208/120V 3 phase. Most units ore getting 2 of 3 (single) 208/120 phase with a 225A panel (based on their load). For the 2 larger units that i have: i was thinking of doing 225A 3/phase 208/120V instead of 400A 208/120 2 of 3 hot (single). Is this it a better solution to do 3 phase 225 or go to a single 400A panel? I was thinking a 3phase 225 load center can still be recessed in some wall compared to a 400A single phase panel. Is there any violations of running a 3 phase to some of the condos that I'm missing?

Thank you

 

[infinity]

We have typically run 3Ø to very large apartments or condos even when a majority of the smaller units are 1Ø. No code issue in doing so. What kind of metering are you using? Is there a provision for 3Ø?

 

[electrofelon]

I once did an old mill that was turned into "live/work" type units. We ran a mix if single phase and three phase to them. I probably would have run three phase to all of them but someone else had started the project and the unit panels were already set. I think your plan is good. if you go to 400 anything it will have to be a true panelboard which are certainly nice but cost more and take 6" of depth to flush mount.

 

[kwired]

Outside of having an individual single phase that would require a pretty large circuit, which is likely kind of rare to have over 60-100 amp circuit for this, I'd probably run the three phase feeder as well.

 

[electrofelon]

Just for completeness, if you did run single phase, perhaps the way to do it would be to tap your 400A feeder to two 200A main breaker load centers, if you didnt want to go the true panelboard route.

 

[LarryFine]

Not only do I agree on the 3ph idea, you should recommend 3ph to the HVAC contractor.

 

[Cartoon1]

We have typically run 3Ø to very large apartments or condos even when a majority of the smaller units are 1Ø. No code issue in doing so. What kind of metering are you using? Is there a provision for 3Ø?

using the the square D ez pak, i suspect they have up to 225A 3 phase option but im not sure yet.

 

[hillbilly1]

Not only do I agree on the 3ph idea, you should recommend 3ph to the HVAC contractor.

HVAC contractors don’t like three phase, because they can do single phase units much cheaper. I wired a Church building three phase just for a three phase elevator and HVAC units. HVAC contractor put in single phase units, elevator contractor put in a single phase elevator!

 

[tortuga]

I agree with the others a 3 phase panel, if there is not a penalty on the metering side, sounds nice.
One small consideration is you can't use 310.12, nor the optional calc in 220.82 to size the feeder.

 

[kwired]

HVAC contractors don’t like three phase, because they can do single phase units much cheaper. I wired a Church building three phase just for a three phase elevator and HVAC units. HVAC contractor put in single phase units, elevator contractor put in a single phase elevator!

You can however balance multiple single phase units across the phases.

Single phase is what they prefer for household type units of 5 ton or less. If you have larger units three phase becomes somewhat usual though.

225 amp 208 volts still gets you somewhat close to same kVA ability as running 400 amp single phase @ 208 volts, uses less copper, smaller frame breaker or smaller frame fuses/disconnect switches/

 

[tortuga]

What I'd do is run the load calc in using the general method and divide by 208 X 1.732 or 360.2 V
Then run the optional calc and divide by 208 for open wye.
For a quick example do two quick back of the napkin calc's for a 6000 SQFT condo with;
6 kitchen small appliance circuits
2 Laundry circuits
2 Dryers
2 Ranges 12.5kw
2 Instant Hots 1.5kw
2 Disposals .9 kw
1 Dishwasher 1.8 kw
3 HVAC Units 5.2kw each

With the optional calc @ 208 single phase (open wye) I get ~242 Amps
With the General calc @ 3 phase get ~150 Amps

 

[Jraef]

I will be the devil's advocate here...

Some RESIDENTIAL USERS can get confused about 3 phase... VERY confused.
That's all...

 

[hillbilly1]

You can however balance multiple single phase units across the phases.

Single phase is what they prefer for household type units of 5 ton or less. If you have larger units three phase becomes somewhat usual though.

225 amp 208 volts still gets you somewhat close to same kVA ability as running 400 amp single phase @ 208 volts, uses less copper, smaller frame breaker or smaller frame fuses/disconnect switches/

I had to double the size of the feed to the elevator because of that. HVAC units too. To top it all off they all were at the opposite end of the building!

 

[kwired]

I will be the devil's advocate here...

Some RESIDENTIAL USERS can get confused about 3 phase... VERY confused.
That's all...

outside of single family dwellings, the users generally have no business messing with it though.

 

[macmikeman]

Cmon you two, most electricians have had to take tests to get licences in the trade and there will be lots of questions regarding 3 phase work, plus usually they have to provide details of experience levels in more than just residential to get that license.

 

[kwired]

Cmon you two, most electricians have had to take tests to get licences in the trade and there will be lots of questions regarding 3 phase work, plus usually they have to provide details of experience levels in more than just residential to get that license.

There are places that have licenses that are limited to residential work only, often is limited to say 400 amp or less as well.

Quite frankly with all the rules added in past 15-20 years that applies mostly to dwellings, I kind of have to wonder which is easier code wise residential or non residential.

 

[hillbilly1]

Cmon you two, most electricians have had to take tests to get licences in the trade and there will be lots of questions regarding 3 phase work, plus usually they have to provide details of experience levels in more than just residential to get that license.

The guy sitting next to me when I was taking the Florida journeyman’s test, was taking the residential test, his was mostly pool questions.

 

[Cartoon1]

Thanks!! This gives me a good idea on everyone thought process. I'm definitely going 3 phase for the bigger units now.

 

[petersonra]

I have a multiple story building for a total of 35units. 2 of those units are very large that has 2 ranges, 2 a/c, and 2 instant water heaters. The service for the building is a meter center that is 208/120V 3 phase. Most units ore getting 2 of 3 (single) 208/120 phase with a 225A panel (based on their load). For the 2 larger units that i have: i was thinking of doing 225A 3/phase 208/120V instead of 400A 208/120 2 of 3 hot (single). Is this it a better solution to do 3 phase 225 or go to a single 400A panel? I was thinking a 3phase 225 load center can still be recessed in some wall compared to a 400A single phase panel. Is there any violations of running a 3 phase to some of the condos that I'm missing?

Thank you

I think putting a 208/120 3 phase panel in makes the most sense. The cost of the feeder and the panelboard will probably be less.