I don't do much commercial so I wanted to make sure, plus I didn't see any 3 phase equipment in the property. You should be able to put a volt meter across any two combinations of these hot legs and get 208 volts, correct?

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(Title) "Re: This is 3 phase service, right?"

Correct.

No. You 'may' get 208 volts from one phase to ground, but then you will not get 208 volts between each phase.

There are 3 phase systems which are delta connected or wye connected, and which have different voltages and different voltage combinations.

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

Phase to phase measurements should all be the same.

A-B=B-C=C-A

Incorrect.

That's what I was saying - it depends on the 3 phase configuration.

What you are saying would only be true with a delta connected, corner grounded (not center tapped) 3 phase system, in which case *nothing* would be 208 volts. You might have a 240/240/240 3 phase system, but as soon as you center tap one of the 240 phases to get 120 for lighting you create a different voltage configuration.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

This building appears to have all standard 120/240V service panels, lighting, appliances, HVAC, etc. Is there anything I should be looking for regarding the 3 phase service? Should I be checking voltages anywhere or anything else?

Please explain Jerry.

If the voltage A-B, A-C, B-C are not all equal the connected 3-phase load would operate properly.
No argument with halving the voltage if a center tapped is used but that doesn't change the the voltage across each full winding of the WYE or Delta wound transformer.

The key to understanding three-phase is to understand the phasor diagram for the voltages or currents. In the diagram at the right, a, b and c represent the three lines, and o represents the neutral.

Let's try this: http://www.kilowattclassroom.com/Arc...WYEPhasors.pdf


Look at that diagram and ignore the "Corner Ground (if used)", and look at it with the "center-tapped lighting transformer (4-wire system)" ground.

Each phase has 240 volts, right? (Yes.)

The center tapped phase has 120 volts / 120 volts, which is 240 volts total, right? (Yes.)

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

So, if I see 208 volts at the panels, let's say for an a/c condensing unit, then I need to make sure I use the ampacity for 208V on the dataplate. Are all household 220 V appliances designed to be able to run on 208V also?

That is correct.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

I'm sure you understand perfectly well from your point of view but let me ask you this:

On the original photo If I measured between any two poles on the disconnect I would expect to measure the same voltage between left and center, left and right and right and center.
Would you agree?

PS. Been gone most of the day without computer access so I have not been able to keep the flow going smoothly on this post.

No.

It depends on where the other ends of those conductors are connected. Those conductors go back to the 3 phase transformer, and, depending on how the transformer is connected will be what you are asking.

That's what I was trying to explain.

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

Jerry, I see no indication of a high leg on the wires to that disconnect so I think it's likely they are the same voltage phase to phase.
Of course metering it would clear all doubt.
If there are any connected 3-phase loads they would have to be equal.

I think we lack enough information to determine what's really going on in this particular photo. Thanks for the interchange.

To answer the original question, though ...

The answer is still ... No.

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

And we still disagree as no information(wiring diagram) has been posted demonstrating your contention.

BTW-You still have not answer the question regarding any connected 3-phase loads.

To answer the original question, though ...

The answer is still ... No.

[quote=Michael Larson;27589]And we still disagree as no information(wiring diagram) has been posted demonstrating your contention.[/quote

Michael,

What voltages are available on three phase wiring systems? (Assuming a delta or wye and no center taps or grounded corners.)

When you answer that, you will see why you will not get 208 volt phase to phase to phase between all of the phases.

Which question?

You can have 3-phase loads and single phase loads on a 3-phase system, and it all works with the 3-phase system connected the correct way.

I sure wish Corey would jump in here, he most likely can explain it better than I am.

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

Commonly, 480 VAC or 208 VAC measured phase to phase.

I hope someone else will come along and explain this to both of us.

I have never seen a 3-phase motor or load that didn't require each phase to phase voltage to be equal each other.

Michael,

I don't think Both of you need this explained.

Would you finish your User CP to include your location?

Thanks,

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It Might have Choked Artie But it ain't gone'a choke Stymie!
Billy J. Stephens HI Service
Memphis TN.

Try going here: Three-phase electric power - Wikipedia, the free encyclopedia

"After numerous further conversions in the transmission and distribution network the power is finally transformed to the standard mains voltage (i.e. the "household" voltage). The power may already have been split into single phase at this point or it may still be three phase. Where the stepdown is 3 phase, the output of this transformer is usually star connected with the standard mains voltage (120 V in North America and 230 V in Europe and Australia) being the phase-neutral voltage. Another system commonly seen in North America is to have a delta connected secondary with a center tap on one of the windings supplying the ground and neutral. This allows for 240 V three phase as well as three different single phase voltages (120 V between two of the phases and the neutral, 208 V between the third phase (known as a high leg) and neutral and 240 V between any two phases) to be made available from the same supply.

Then go here: Wye Systems

And here: Delta System

And here: Delta and Wye Circuit Equations

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )