Delta or Wye?

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jerrymiller66

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Location
Dallas, TX
Working on some canopy lights yesterday in a gas station. 120V, metal halide. Partial outage. Noticed something I hadn't seen before. The panel fed these lights as well as some regular convenience outlets. I noticed B phase had been skipped throughout. Tested it and found it to be a high leg, 208V in fact. This configuration is a delta, am I correct? I understand the reason for skipping B phase....for one, these lights are fed with 120V, you don't want to shoot 208 to them if you've tapped them at 120, and, of course you don't want 208 going to your outlets unless that load calls for 208 at the wall,...which nothing does here.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Working on some canopy lights yesterday in a gas station. 120V, metal halide. Partial outage. Noticed something I hadn't seen before. The panel fed these lights as well as some regular convenience outlets. I noticed B phase had been skipped throughout. Tested it and found it to be a high leg, 208V in fact. This configuration is a delta, am I correct? I understand the reason for skipping B phase....for one, these lights are fed with 120V, you don't want to shoot 208 to them if you've tapped them at 120, and, of course you don't want 208 going to your outlets unless that load calls for 208 at the wall,...which nothing does here.

This would indeed be delta high leg. Either fed via an open or closed delta transformer bank. Only 3 phase loads may connect to the high leg or those that are straight 240 volt single phase. Anything 120 volt takes the A and C phase. Just of note if you are working on the meter can by chance high leg will be on the C slot of the meter but once inside it goes to the B position of any breaker or panel in newer installs.

You did the right thing and test.:thumbsup: Always test, even if that service is single phase. Voltage testing giveaway the system type and any issue it may be having.
 

jerrymiller66

Member
Location
Dallas, TX
This would indeed be delta high leg. Either fed via an open or closed delta transformer bank. Only 3 phase loads may connect to the high leg or those that are straight 240 volt single phase. Anything 120 volt takes the A and C phase. Just of note if you are working on the meter can by chance high leg will be on the C slot of the meter but once inside it goes to the B position of any breaker or panel in newer installs.

You did the right thing and test.:thumbsup: Always test, even if that service is single phase. Voltage testing giveaway the system type and any issue it may be having.

Appreciate your prompt and civil response. Just trying to learn like everybody else. Thanks again
 
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