Apartment complex voltage

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Sparky5150

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I have to design the electrical system for an apartment complex which I'm not too familiar with, office building yes, resi not so much.

Anyway I'm trying to figure out if I should bring 240 single phase or 208 3 phase to the meter centers.

If I have a need for a 1200 amp 240 single phase service can the power co. connect this? Do they have a transformer large enough?

Is there a problem with multiple meter centers feeding one building?

Should I go 208 3 phase if there are 36 units?


Thanks for any help, I know this is a complex question, just looking for a little advice from the designers who work on multi family on a regular basis.
 
I always try to use 3-phase on any new design of significant size. But there's always an exception.

You can feed each apartment's panel with single phase and balance the loads at the main.

Just make sure the stove, dryer, water heater, etc. are rated for 208V.
 
Sparky, the power co. will probably tell you what they will deliver, once you tell them your power requirements.

Personally, I like 3-phase for that much power.
 
contact your local poco. some have limits as to how large a single phase service they will connect. if you stay with single phase, the poco may place a 167kVA at best a 200Kva single phase transformer.
 
On sizable services for mid-rise resi here - all you will get is wye. Then much of the available peter packs will split up the phases for you.
 
I don't care for using 2 legs of a 3-phase source to power single-phase loads. I know it's done all the time without problems. The main reason I don't care for it is 208-volts is on the low end of the operating voltages for most motors. If the PoCo has a VD on the transmission line, you will probably be below the lower limits of what the equipment will operate at. If you have a 240-volt source you can tolerate low voltage from the PoCo much better.

With MWBC, that neutral is a CCC. You lose any VD advantages that you would have with a single-phase MWBC.

JMO
 
hardworkingstiff said:
If the PoCo has a VD on the transmission line, you will probably be below the lower limits of what the equipment will operate at. If you have a 240-volt source you can tolerate low voltage from the PoCo much better.
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The power company is suppose to supply power within a range of the target voltage. Plus or minus a certian percentage. Manufacturers design to this tolerance. Utilities in the US are fairly good at supplying within this range. I wouldn't select 240V because of an assumed voltage variation of under voltage while ignoring the benefits the 208V system would have over a 240V system.

I think there would be lots of problems if the voltage was over or under. How do you say which one is better? Under voltage burns up motors and over voltage can burn up other devices, like resistive heaters. Some devices will fail if it sees either over or under voltage.
 
Many people feel that equipment is designed to accept over/under voltages of 10-15%. Since 208 volts is 87% of 240 volts (90% of 230 volts)they justify using 240 volt equipment on 208 volt circuits using this assumption. If the voltage drops below 208, then they are in real trouble. The answer is to use equipment rated for 208 volts on 208 volt systems. Anything else is not according to the listing and labeling of the equipment. If it is intended for use at 208 volts it will say so on the label.
 
I would design a 3-phase 208 main service with single phase service to each tenant. Specify 200 volt appliances and let the power company know when the plans are submitted to permitting by sending them a copy. 208 isn't ideal for resi, but the size of your service will all but require it.

good luck
 
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