Electrician Talk banner
1 - 18 of 18 Posts

· Registered
Joined
·
218 Posts
Discussion Starter · #1 ·
Hey guys I just came across a set of drawings for a building with commercial units below and a few resi units above. The engineered drawings are showing service will be 600A 3ph, 200A 3ph for the commercial units, and 100A 3ph for the resi units??

I have never seen 3ph inside a dwelling unit??? Is there a misprint on this set of drawings or are there some exceptions etc....... I can't get a hold of the engineer to verify
 

· Registered
Joined
·
218 Posts
Discussion Starter · #3 ·
I've seen it in some huge houses, but not an apartment. A 100A 208 3 phase service is a lot of watts for an apartment, it would be the same amount as for a 150A 120/240v single phase service.
Whatever the reasoning be, aslong as its allowed ill price it out. Ive always thought it was a no no to have 3ph in a dwelling
 

· Pool Shark
Joined
·
472 Posts
208/120 wye 3-phase is perfectly fine for residential. I've done a few jobs with the residential side of the building uses 208/120 wye 3-phase. In one building the contractor used a 3-phase bolt in panel, and in the other building the contractor used a 3-phase snap in.
 

· Administrator
Retired EC
Joined
·
24,980 Posts
I have seen three phase to the service and single phase panel to the apts but that is harder to balance the loads. I have also seen 3 phase throughout.

It may not be necessary to use 3 phase in the apts if the heating is single phase. They may be able to save money
 

· Registered
Joined
·
218 Posts
Discussion Starter · #12 ·
I have seen three phase to the service and single phase panel to the apts bresthat is harder to balance the loads. I have also seen 3 phase throughout.

It may not be necessary to use 3 phase in the apts if the heating is single phase. They may be able to save money
I think your on the right idea. The drawing shows 3ph furnace and 1ph heat pump and the new owner of the job then decided to put baseboard heaters now for the resi units. I'm sure 125a 1p would be more than enough.
 

· Senior Member
Joined
·
507 Posts
fistofbolts said:
I hope you dont mind if I pipe in with a complete nooby apprentice question here. so it's 3 phase to the service no matter what, and from that you can choose single or triple phase to the individual unit panels?
Pretty much but since there isn't much 3ph equipment you would ever use in an apartment and the loads generally being the same you can just use 208 1ph and save on material cost.

Edit. You could do a total single phase service but 3ph has more advantages until you get to individual suites
 

· Registered
Joined
·
218 Posts
Discussion Starter · #15 ·
I hope you dont mind if I pipe in with a complete nooby apprentice question here. so it's 3 phase to the service no matter what, and from that you can choose single or triple phase to the individual unit panels?
A building/townhouse complex etc can have 1ph or 3ph service depending on how much power is needed. Then from the electrical room its split out, most if not all of the commercial units get a 3ph panel, and most of the time 2 lines and a neutral are taken to the residential units. Usually these units are not that big that 3ph is required but i guess anything is possible if someone wants to pay$$$$
 

· IBEW MEMBER
Joined
·
383 Posts
A building/townhouse complex etc can have 1ph or 3ph service depending on how much power is needed. Then from the electrical room its split out, most if not all of the commercial units get a 3ph panel, and most of the time 2 lines and a neutral are taken to the residential units. Usually these units are not that big that 3ph is required but i guess anything is possible if someone wants to pay$$$$
thank you both for spelling that out. something I wish our jatc would do is focus on more on situations on like that. a lot of basics just get ramrodded through.
 

· Pool Shark
Joined
·
472 Posts
I hope you dont mind if I pipe in with a complete nooby apprentice question here. so it's 3 phase to the service no matter what, and from that you can choose single or triple phase to the individual unit panels?
In electrical terms 3-phase refers to 3 independent rotating coils in a generator. They are out of phase by 120 degrees and are considered balanced.
Single phase refers to 1 rotating coil.

Mains power is a 3-phase distribution for the most part, in some cases DC will be used for longer runs. The utility company will use 1 leg to supply multiple residential homes. This is a single phase service by all intents and counts.
Larger residential homes and condominiums can use all 3-phases from the utility and these are fed off a 208/120 wye transformer.
In industrial locations where the majority of the loads are motors and linear loads the power is fed with 240/120 delta 3-phase. Some deltas have a high leg with a 208v reading from phase to neutral. Wyes always have 208 reading phase to phase and 120 phase to neutral.

The mix up is easy to get started and everyone has their own opinion and definitions, this is why it is best to just not use the term single phase or 3-phase when speaking of breakers, but use the term 1 pole, 2 pole, and 3 pole.
 
1 - 18 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top