3PH Service for Building - House Panel Rating?

designer82

Member
Location
Boston
I'm working on an apartment building with a 3PH-4W service coming into the Main Disc.

There's a meter center with single phase meters to the individual dwelling units. For the house panel I can have a 3 phase Disc./Panel or a single phase.

Does it matter at all? There are no actual 3 phase loads needed in the building.

Thank You
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I can't see where it can make much difference unless there is a considerable load.
 

Carultch

Senior Member
Location
Massachusetts
For the house panel I can have a 3 phase Disc./Panel or a single phase.

Does it matter at all? There are no actual 3 phase loads needed in the building.
If no three phase loads are needed, the common loads panel could be either single phase "open wye", or three phase from the full wye system.

A three phase house loads panel will have advantages, as it is a provision for a three phase load in the future. The larger the total load in the house panel, the more advantage there will be to selecting three phase over single phase.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
With the exception of the apartment panels I would not install any 1 phase panels when 3 phase is available.
 

Npstewart

Senior Member
I run into this a lot because I do a lot of apartment work. However, most apartments I do usually have an elevator so I always end up with a 3 phase house meter. Also, the house meter usually feeds a pool which sometimes uses 3 phase pool pumps.

For the apartment unit panels I always use single phase. Apartment units aren’t usually subject to change so I don’t have to worry about accommodating future loads, and, because I can usually use a smaller conduit which helps a lot for various reasons. I would have to imagine that the panels are slightly cheaper too.


Sent from my iPhone using Tapatalk
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If it makes sense for the house panel why wouldn't it make sense for each apartment?
Typcial apartment house design uses 1Ø, 120/208 feeders for individual apartments similar to a small house. There is usually little reason to use 3Ø unless you have an elevator as Npstewart suggested.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
The reason why apartment complexes are fed 3 phase is so that they loads can be better balanced between the 3 phases. But there is no use for actual 3 phase power in an individual dwelling.
 

kwired

Electron manager
Location
NE Nebraska
What kinds of house loads are there? Just some outdoor or hallway lighting, probably pretty minimal load - single phase panel is likely fine. If house load contains a laundry area or some heating/cooling loads, three phase panel possibly desirable depending on how much of those loads there is, even if there is no individual three phase loads.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
The reason why apartment complexes are fed 3 phase is so that they loads can be better balanced between the 3 phases. But there is no use for actual 3 phase power in an individual dwelling.
I would tend to agree there is no "need" for it, but I wonder if the smaller feeder wires might make it attractive in at least some cases.
 

kwired

Electron manager
Location
NE Nebraska
I would tend to agree there is no "need" for it, but I wonder if the smaller feeder wires might make it attractive in at least some cases.
Might be more of a factor for install cost if you need more than maybe a 125 amp three phase or 200 amp single phase feeder.

125 amp three phase feeder @ 208/120 can supply 45kVA worth loads, 200 amp single phase feeder also @ 208/120 can supply 48 kVA of balanced line to neutral load but only 41.6kVA of line to line load.

Probably somewhat of a wash on cost (smaller conductor but also one more conductor, plus extra cost for a three pole vs 2 pole breaker) but start increasing feeder size even more and it may make more economic sense to go with a three phase feeder even if no three phase loads are supplied.
 
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