How does one measure the voltage on a 230v 3 phase line?

[Anonymous]

Gentelmen:

I'm installing a 230v 3 phase (phase sensitive) heat pump unit how does one measure the voltage, across L1-L3 or L1-L2???. The unit is a Florida Heat Pump model em 096. Directions state that the unit is wired 230 but if service is 208v we must move a wire over (provided in panel in ac unit.) Does anyone have any experience with this type of a unit.

Thanks

Tom

[Wgoodrich]

You need to be careful concerning what type three phase you are being served.

208/110
240 only
240 corner grounded
240 hot leg
480/277
480 only


There are many different types of three phase. Open you main service rated panel. Look to see if you have a neutral bare and four wires coming in from utility company.

If only three wire service you need to test from phase 1 to phase 2 then phase 2 to phase 3 then phase 3 to phase 1. Then test from each phase to your equipment grounding conductor separately.

If with four wire service you need to test from phase 1 to phase 2 then phase 2 to phase 3 then phase 3 to phase 1 then each phase to the neutral bar separately.

Tell us the voltages you find in each test then we should be able to tell you if delta or wye or wye/delta or hot leg or corner grounded delta or open delta service.

Then you can adjust your a/c unit to match your type three phase service supplied.

Curious

Wg

[ceramicbrad]

You need to be careful concerning what type three phase you are being served.

208/110
240 only
240 corner grounded
240 hot leg
480/277
480 only

Tell us the voltages you find in each test then we should be able to tell you if delta or wye or wye/delta or hot leg or corner grounded delta or open delta service.


Wg

This was an interesting post. Too bad anonymous decided not to follow up and answer the above question yet posted many others after this.

Confused::confused::confused:

[StanL]

I've read this post and would like an answer to my voltages on what type of outputs they are, Wye, Delta, Star...?

I read the following:
L1-L2 = 236VAC
L2-L3 = 234VAC
L1-L3 = 240VAC
L1-N = 118
L2-N = 118
L3-N = 205

L3-N looks excessive...


Thanks
Stan

[suemarkp]

This is 240V delta. The one leg on this is "special" as you noticed and is called the high leg. It is typically 208V to ground and it not used by itself. To help ensure you don't accidently use it for 120V loads, that wire is supposed to be colored orange. Sometimes this orange colored wire is required to be in a specific position in a meter or panelboard. Even if you have a single phase 208V load to run from it, I don't think the transformers likes it being used (may overload them). The high leg should only be used in circuit that need all 3 phases.

On 240V delta, one side of the triangle provides "normal" house power -- 240V from the ends, and 120V from those ends to the center tap (which is where the neutral is). You use all 3 corners in a 3 phase load. Most delta 3-phase doesn't use the neutral, but there is still a grounding wire in all circuits and feeders which goes to that neutral point anyway.

[Homer]

Since a pic is worth a thousand words, here's a 4-wire Delta transformer secondary.

B is the high leg in this pic.

The "high", or "wild" or "crazy" leg is supposed to be colored orange in the US.

Homer

[StanL]

Thanks for the quick answers. Now I know I can use this source for the power supply testing I need to do.

Thanks again,
Stan