one part three phase question

[Les]

or a three phase one part question.

Why would a 900sqft office have this for service? Exterior disconnect three phase. there is an a/c, gas forced air, 5gal electric water heater, three rooms, one bath and nothing else. Could it have to do with quality of power rather than quantity?

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[Marc]

It has to do with the advantages of 3 phase, not with power quality. 3 phase is a more efficient transmission method than single phase, allows the use of 3 phase motors which have massive starting torques if you need it, and you don't have to mess with starting capacitors.

I'd love to have it on my house so I can have a 3 phase HVAC outdoor section. You'd seldom have any problems with a stalled compressor if the motor in it is 3 phase.

Utilities economized their operations decades ago by requiring justification before they'd let you have 3 phase. It takes more transformation and money for them to get it to you.

Perhaps that office got it because of blanket policy at the time, "Commercial buildings are eligible for 3 phase", though it didn't make much sense in that little bldg because it's so small and, I'm guessing, didn't have any large motors.

One thing interesting about that disconnect in the photo is the size of the neutral. It's bigger than the ungrounded conductors. That's a waste of wire unless there's a major issue with harmonics.

Marc

[John Kogel]

Maybe they had a plan for a factory that never materialized.

[Greg Booth]

.........could it originally have been considered for a dental office? Any sign of additional plumbing infrastructure?......Greg

[Jim Katen]

The builder was covering his bases to make the building attractive for a wide range of future users.

To my eye, the neutral looks the same size as the phase conductors. Optical illusion?

[Marc]

The builder was covering his bases to make the building attractive for a wide range of future users.

To my eye, the neutral looks the same size as the phase conductors. Optical illusion?

Maybe. I was looking at the line side.

Marc

[Les]

Thanks, I am familiar with three phase qualities. This is a very small office condo in a building with three other units. This one is the only one with three phase. Why would dental use make a difference? This could not have been anything serving the pub lic - too small.

Thanks for responses

[Greg Booth]

..........the constant voltage delivery of 3-phase (no drop-out during cycle) allows greater radiation production and better penetration. This is what I recall from back-in-the-day (early 70's) install of dental offices in one of our commercial office buildings. Probably does not have merit with today's generation of equipment - we even had one suite that powered all the dental equipment on DC current......Greg

[kurt]

That may be it. I occasionally come upon 3 phase in small office buildings of the sort that might be/are medical facilities. It may have been a positive pitch to medical tenants.

[Bill Kibbel]

I inspect a lot of buildings with medical offices. It's the older x-ray equipment that requires the 3 phase. On a recent inspection, I assumed laser equipment was 3 phase.