208 1 ph

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If you have motors that are going to run continuously (like say a day camp facility that has several swimming pools utilizing about 12 pool pump motors total) those motors will run more efficiently than if they were running on 120V or 208V, 1 phase. If you look at the nameplate ratings on a pool motor as an example (even for a residence), it will show the difference between running it at 120V and 230V. So, let's say that a simple residential pool motor if wired for on 120V will operate at 10 A, if you wired it and used 240V it will operate at 5A. When you have a commercial application and if you used a similar style and rated motor (only a 3-phase type) it will run at something less than 5A (probably 3.3A or something close).
 
Analysis HVAC said:
What is the advantage, (if any) of only using single phase 208 vs 3 phase? I have 20 years of HVAC experience, but I am dumb as a carrot when it comes to the finer points like this.
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The 3Ø motor may allow you to use smaller conductors. For example compare a 10 HP motor at the following voltages from the NEC tables:

1Ø-120v=100 amps
1Ø-208v=55 amps
3Ø-208v=30.8
 
anecdotal, I realize. For some time I worked for a large industrial complex with hundreds of motors. The single phase ones failed 5 to 1 over the 3 phase, usually capacitors or start switches.
 
goldstar said:
If you have motors that are going to run continuously (like say a day camp facility that has several swimming pools utilizing about 12 pool pump motors total) those motors will run more efficiently than if they were running on 120V or 208V, 1 phase. If you look at the nameplate ratings on a pool motor as an example (even for a residence), it will show the difference between running it at 120V and 230V. So, let's say that a simple residential pool motor if wired for on 120V will operate at 10 A, if you wired it and used 240V it will operate at 5A. When you have a commercial application and if you used a similar style and rated motor (only a 3-phase type) it will run at something less than 5A (probably 3.3A or something close).
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Initial equipment investment is what can be different. Efficiency is a different ballgame.

You use same energy to drive same load regardless whether it is single phase, three phase, 120 volts 480 volts or even diesel powered engine. Now efficiency design of the motor can vary, but induction motors are all in similar range on efficiency.

Total capacity needed, the need for more then about 10 horsepower for a single motor, availability of three phase from the utility are all factors into whether you will even have three phase available on the premises.

augie47 said:
anecdotal, I realize. For some time I worked for a large industrial complex with hundreds of motors. The single phase ones failed 5 to 1 over the 3 phase, usually capacitors or start switches.
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Capacitors, start switches, potential relays - are a big maintenance issue at times. If you have limited load, seasonal load, etc. may still not be worth paying POCO extra every month or the initial investment for a three phase supply.
 
If the system voltage is 3 phase 208 then imo, it is bad design to use single phase because it is much harder to distribute the load evenly on the phases. But as others have said 3 phase units cost more.
 
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