Large Dwelling Unit subpanel size?

[olc]

A large house (12 bedrooms). How do you think I should size a the subpanelbds? Just use the area served for the lighting and receptacle load (and add other loads)? Or calc actual connected load (using 180VA per receptacle which seems an over kill with receptacles spaced for dwelling unit)?
What do you think.

It is a house but there will be a commercial elevator with a 20HP motor (believe it or not) so there will be 3 phase and the main panelbd will be 3 phase. I am trying to decide whether to make the subpanels (which will be load centers) 3 phase or 1 phase. Any thoughts on that, please chime in.


FYI - It is a large house but is a sort of group home for active seniors (high end).

 

[Dennis Alwon]

I would scatter sub panels so that my home runs are not long and place them in a practical spot. I usually will do one panel for one side of a home and another for the other side-- usually 60 amps but sometimes I will run 100amps or more depending on feasibility with other loads.

I try and take the larger loads, such as, heating, a/c back to the main panels.

If this meets the requirements of a dwelling then 180va per receptacle is not necessary.

 

[augie47]

If the service is 208Y120 I'd definitely take advantage and make my subpanels 3 phase.

 

[kwired]

What are the loads? If most of this area is just bedrooms you really don't have a lot of load there. Might not be worth installing subpanel(s) or if anything just one if it is a long way to the service. Too many details are unknown to give a good answer.

A 100 amp 208/120 three phase feeder has similar kVA capacity as a 150 amp single phase feeder.

 

[charlie b]

I have designed several high-end homes. I agree with Dennis and Gus; put small (3-phase) panels close to where the loads will be. The hard part for me was always convincing the architect to give me the space I needed. For reasons that elude me, they don't ever seem to appreciate the aesthetics of a branch circuit panel. :happysad:

 

[growler]

A large house (12 bedrooms).

It is a house but there will be a commercial elevator with a 20HP motor (believe it or not) .


FYI - It is a large house but is a sort of group home for active seniors (high end).

It may look a lot like a house and may be used for residential purposes but it sound more like a commercial property to me.

To locate panels you would need to know a lot more than number of bedrooms. I would assume that each bedroom would have a private bath (jet air tub?). Does this place have a kitchen, laundry, gym, pool, a lot of site lighting or any offices. How much AC and what type.
Is there going to be pool house or garage with vehicle chargers?

 

[olc]

I have designed several high-end homes. I agree with Dennis and Gus; put small (3-phase) panels close to where the loads will be. The hard part for me was always convincing the architect to give me the space I needed. For reasons that elude me, they don't ever seem to appreciate the aesthetics of a branch circuit panel. :happysad:

I agree that architects don't appreciate the, IMO, fine aesthetics of mechanical and electrical equipment.

 

[olc]

Thanks for the replys.

It is a big house. I am treating it as commercial in certain respects.
There is no question of the subpanels. There will be three.
The main panel will be a commercial panelboard (in the service room) but the subpanels will be load centers recessed in walls (the house is completely finished).
The only question is the subpanel sizing and whether 3 phase.

The advantage of 3 phase at the subpanels is it will balance the phases better and in one case allow 100A (vs. 200A at single phase).
I was wondering if there are any disadvantages to having 3 phase at the subpanels.

 

[kwired]

Thanks for the replys.

It is a big house. I am treating it as commercial in certain respects.
There is no question of the subpanels. There will be three.
The main panel will be a commercial panelboard (in the service room) but the subpanels will be load centers recessed in walls (the house is completely finished).
The only question is the subpanel sizing and whether 3 phase.

The advantage of 3 phase at the subpanels is it will balance the phases better and in one case allow 100A (vs. 200A at single phase).
I was wondering if there are any disadvantages to having 3 phase at the subpanels.[/QUOTE]

Three phase panel and three phase feeder breaker are more expensive then single phase panel and two pole breaker - of same amp rating - plus you will pull three conductors instead of two for ungrounded conductors. But you need to consider that you can use smaller conductors for same load, phase balancing, etc. which offsets those disadvantages. A lightly loaded feeder isn't as cost effective to go three phase as a more heavily loaded feeder. Running several lightly loaded feeders may still be more cost effective to go with single phase feeders and balance phases by balancing how the feeders connect to the supply - like is typically done on multifamiliy supplied by three phase but with single phase to each dwelling.

 

[FountainGuy]

I would definitely run 3-phase subpanels. The only negative thing that I thought of is if you have 230V or 240V single phase loads. With 208V power, sometimes the manufacturer of that load may not allow/warranty using 208V 1-PH power for a 230V or 240V 1-PH load. If this is the case, you would need a buck-boost transformer for that load, an additional expense.

 

[kwired]

I would definitely run 3-phase subpanels. The only negative thing that I thought of is if you have 230V or 240V single phase loads. With 208V power, sometimes the manufacturer of that load may not allow/warranty using 208V 1-PH power for a 230V or 240V 1-PH load. If this is the case, you would need a buck-boost transformer for that load, an additional expense.

Most heat pumps/air conditioning units are rated 208 or 240 volts, so are ranges, dryers, water heaters, or electric space heating, though resistance units will have a lower VA rating at 208, usually just means longer cooking, drying or heating time to do the same work. That is the majority of what you are going to need to be concerned with at such voltage in a dwelling application.