3 Phase Bastard Leg

[markebenson]

Installed a new 200a 3 phase panel for stage lighting and sound but of course L3 is useless right now we have corner Delta coming in to the bulding. What hoops will I have to go through to get it changed to Y ?


We have Florida Power and light.

Thx

 

[infinity]

Not sure about what your POCO can do but at 200 amps a transformer might be an easier alternative.

 

[kwired]

Getting POCO to change is one thing, but you also need to consider what loads you have and whether or not changing from 240 to 208 volts will have undesired results for anything. Quite a few things can take this kind of change with little or no problem. Control transformers sometimes have 208 and a 240 volt tap, and you would lengthen their life and/or some of the control components if you changed such taps when making service voltage change.

 

[Little Bill]

Installed a new 200a 3 phase panel for stage lighting and sound but of course L3 is useless right now we have corner Delta coming in to the bulding. What hoops will I have to go through to get it changed to Y ?


We have Florida Power and light.

Thx

I thought you would have a center tapped Delta since you have a high leg.

 

[infinity]

I thought you would have a center tapped Delta since you have a high leg.

Good point. The OP needs to clarify what the actual system is because bastard leg and corner ground are parts of two different systems.

 

[texie]

Installed a new 200a 3 phase panel for stage lighting and sound but of course L3 is useless right now we have corner Delta coming in to the bulding. What hoops will I have to go through to get it changed to Y ?


We have Florida Power and light.

Thx

As mentioned, this is not a corner grounded system. Your post is indicative of a center tapped delta. Very common in FPL territory. I think you will find that it will be near impossible to get a wye system from them unless you can demonstrate least 150 KW of demand and even at that, it would depend on if they had facilities available at the xformer location.

 

[markebenson]

I just looked at the power meter, It has a triangle on it.

 

[gar]

180707-1534 EDT

markebenson:

Stick a screwdriver in the earth outdoors. Using a high impedance meter read the voltage between each power wire and earth. From this information you should be able determine the kind of 3 phase supply you have.

.

 

[kwired]

I just looked at the power meter, It has a triangle on it.

That might indicate it is intended for delta system - but there is still corner grounded, grounded at center of one phase, and non grounded possibilities for a delta source.

 

[roger]

I just looked at the power meter, It has a triangle on it.

That would be the case with any closed Delta configuration, it doesn't tell you if it's corner, center, or ungrounded but as Little Bill pointed out, it can not have a high leg unless it's center grounded.

Roger

 

[markebenson]

Ok i was misinformed and The Pike guys were in the area and confirmed we have delta "Y"

 

[jaggedben]

Ok i was misinformed and The Pike guys were in the area and confirmed we have delta "Y"

Lol, that's really not a thing either. Have you had a chance to measure voltages to neutral and/or ground?

 

[LarryFine]

If the transformers are on a pole, take a couple of pics and post them here.

 

[markebenson]

Lol, that's really not a thing either. Have you had a chance to measure voltages to neutral and/or ground?

Yeah sorry lol. I am not up on the transformer terminology.

But yes each phase to neutral 121.8, 120.4, and 209.4

 

[gar]

189707-2430 EDT

markebenson:

Those measurements tell you that you have a wild leg delta. If there are two transformers, then it is an open delta. Three transformers and it is a closed delta. Between two legs of the supply you have a center tapped secondary with the center tap being nreutral. This neutral should be earthed some where.

.

 

[roger]

Ok i was misinformed and The Pike guys were in the area and confirmed we have delta "Y"

Yeah sorry lol. I am not up on the transformer terminology.

But yes each phase to neutral 121.8, 120.4, and 209.4

Well the Pike guys told you wrong.

Roger

 

[ggunn]

Ok i was misinformed and The Pike guys were in the area and confirmed we have delta "Y"

Delta and wye are mutually exclusive. You can have one or the other but not both.

 

[tom baker]

If you look at the primary overhead distribution, its probably 2 hots and a neutral. To get a three phase 120/208 secondary, your poco would have to bring in the third overhead phase (this is the way its out here in WA) and that would be very expensive.
Look at a delta to wye transformer for your facility, as was pointed out
And our POCO no longer offers wild leg services, but there are still a lot of them around

 

[gar]

180708-1308 EDT

tom baker:

A third hot primary line is not required. From two hots and a neutral of a three phase source you just need appropriate transformers to create a wye output.

.

 

[Jraef]

Yeah sorry lol. I am not up on the transformer terminology.

But yes each phase to neutral 121.8, 120.4, and 209.4

From those measurements, the ONLY possibility is that you have a 240/120V 3 phase 4 wire delta source with a center tapped leg between two of the phases. That is not “Wye” at all and if they were referring to the primary side of the transformer being Wye, that was irrelevant and superfluous information that only confuses things.

So the ONLY two issues you have with this system are that 1) you can only feed 120V loads from two of the phases, and 2) if you feed 240V single phase loads where either pole comes from the “stinger” leg, the breaker cannot have a “slash rating”, meaning it must be rated for straight 240V, not “120/240V” as the cheaper ones are. Other than those two issues, you can use this in any way you need. No need to change anything.