# 480V lights



## Big John (May 23, 2010)

How is the delta grounded?

-John


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## Antmc22 (Jun 30, 2011)

Big John said:


> How is the delta grounded?
> 
> -John


That I am unsure of this is a very old waste water plan and I'm awful unfamiliar with a delta set up. As long is there is no load my A phase has 250v B has 330 and C has 250. It's like once load is applied the voltage goes ghost. I've never seen anything like it.


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## Big John (May 23, 2010)

Antmc22 said:


> ...It's like once load is applied the voltage goes ghost. I've never seen anything like it.


What happens to the voltages on all three phases once load is applied?

-John


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## nolabama (Oct 3, 2007)

This comer grounding thing gets folks a bunch. I am glad I dont have any of it.


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## Big John (May 23, 2010)

The only reason I'm shying away from corner-ground is I can't explain the 3 TVSS fuses, but I might be able to with an ungrounded.

-John


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## Antmc22 (Jun 30, 2011)

Big John said:


> What happens to the voltages on all three phases once load is applied?
> 
> -John


A and B phase hold true it's only on C.


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## tates1882 (Sep 3, 2010)

Antmc22 said:


> Today I repaired a lighting circuit that was broken by the GC while digging. The pipe contained 3 hots and a ground which fed fed the 480 lighting. It should have been a simple fix but instead it has boggled me. Once the new feeders were pulled in and reconnected it should have been nothing more than throwing the breaker right. Well once I turn the breaker on and the HOA to hand the tvss blows all three fuses. Well I decide to break the circuit which breaks off two diff. Ways at the first pole light. I break the circuit, turn it on, go outside and check voltage all is good. Here's the problem I apply one of the other light loads to the circuit and C phase drops out I mean voltage just disappears once the load is applied. Both A and B phase hold fine and function as needed. The system is a 480V delta what am I missing? What could this be?


You sure the lights are 3 phase. I've done 480v lights but only ever seen them single phase. Maybe you had 2- 480v single phase circuits with no ground or if its that old and rigid, the pipe is the egc.


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## Antmc22 (Jun 30, 2011)

tates1882 said:


> You sure the lights are 3 phase. I've done 480v lights but only ever seen them single phase. Maybe you had 2- 480v single phase circuits with no ground or if its that old and rigid, the pipe is the egc.


You are correct they are single phase. There being fed from a 3 phase beaker and feeding multiple lights using AB AC BA BC CA CB like 208V lights


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## tates1882 (Sep 3, 2010)

Antmc22 said:


> You are correct they are single phase. There being fed from a 3 phase beaker and feeding multiple lights using AB AC BA BC CA CB like 208V lights


 Sounds like high resistance connection or the fault caused internal failure at the breaker. Measure the resistance across the breaker with a good dmm. If C pole is different from A and B then its smoked the breaker. Losing the TVSS fuses is weird, thats why I was thinking 4 hots with no ground or the pipe as the EGC. One of the ballast could have shorted to ground, I would start with the first pole behind the break and work my way back to the service.


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## btharmy (Jan 17, 2009)

Did you check in the lights on either side of the damage. Most lighting circuits damaged by excavation are pulled tight in the lights on either side causing possible damage/shorts.


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