3 pole breaker utilized for lighting circuits.

[ElectPro..spect]

building was built in the 70's.....may play a part. 277/480 3phase 4w panels, feeding the lights. most of the breakers in these panels are 3 pole 20's. the breakers only have 1 switch(common trip) located on the middle pole(B phase)
why would lighting circuits be fed from a 3 pole? i know it is not legal now, considering it is exsisting, it can remain? yes there is a light. control system.

 

[iwire]

It was legal, it is still legal and in some cases required.

Are the lights 480 or 277?

 

[ElectPro..spect]

Yes, the light are 277, I guess if the lights were 480 it would need a 2 pole or 3 pole. But a 3 pole for individual branch cir.?

 

[ElectPro..spect]

im sorry for not being more explanatory, and appreciate any knowledgable information. retro-fitting a warehouse appr. 750k sq.ft from old HPS to new 6 lamp flour..circuits are all 277v in the form of L7-20P twistlock at the end of the circuit(new lights are s.o. whipped, hung, plugged in)many of the exsisting circuits feed appr. 7 fixtures. becuase the circuits are protected by a 3 pole breaker, if one circuit goes, the remaining 2 go as well. this is correct? we can retrofit the panels as well, with new single pole 20, but why was this done in the first place? thx again for the time and help.

 

[ElectPro..spect]

Im sorry for not being more explanatory, and appreciate any knowledgable help. Im retro-fitting a 750k sq ft warehouse from old HPS to new flour. exsisting circuits are 277v in the form of L7-20P twistlock (new lights are s.o. whipped, hung, and plugged back in in place of old fixture) exsisting circuits are feed from a 3 pole breaker, so if 1 circuit goes, the remaining 2 go as well. this is correct? we can retro the panels with new single pole 20, but why was this done in the first place? agian thanks for the time and help.

 

[iwire]

im sorry for not being more explanatory,

No problem.

retro-fitting a warehouse appr. 750k sq.ft from old HPS to new 6 lamp flour..circuits are all 277v in the form of L7-20P twistlock at the end of the circuit(new lights are s.o. whipped, hung, plugged in)many of the exsisting circuits feed appr. 7 fixtures. becuase the circuits are protected by a 3 pole breaker, if one circuit goes, the remaining 2 go as well. this is correct?

In that case it sounds like the fixtures were supplied by a multiwire branch circuit, 3 hots (A,B and C phase) with one neutral.

Back when that system was installed the NEC would have allowed 3 single pole breakers, now under current codes you could use single pole breakers with a handle tie acrros all 3 of them. However I have not seen handle ties for 277 volt breakers, that being the case most of us use 3 pole breakers.

we can retrofit the panels as well, with new single pole 20,

If they are multiwire branch circuits doing that will be a violation unless you find handle ties for thos single pole breakers.

but why was this done in the first place?

Why not?

Yes, the light are 277, I guess if the lights were 480 it would need a 2 pole or 3 pole.

A common way to save wire with 480 volt lighting is to use a 3 pole breaker and run all 3 phase in the conduit and tap each single phase light fixture from alternating phases.

• First fixture connected to phases 'A&B'
  
• Second fixture connected to phases 'B&C'
  
• Third fixture connected to phases 'A&C'
  
• Repeat as many times as you need to.

 

[Barndog]

Im sorry for not being more explanatory, and appreciate any knowledgable help. Im retro-fitting a 750k sq ft warehouse from old HPS to new flour. exsisting circuits are 277v in the form of L7-20P twistlock (new lights are s.o. whipped, hung, and plugged back in in place of old fixture) exsisting circuits are feed from a 3 pole breaker, so if 1 circuit goes, the remaining 2 go as well. this is correct? we can retro the panels with new single pole 20, but why was this done in the first place? agian thanks for the time and help.

One reason it may hae been done is to elimanate getting shocked on a three phase neutral. Its my understanding that the code now states if you use a shared neutral youmust either use a three pole breaker or handle tie the singles together. If you dont want to go that route. you could install single pole breakers and pull a seperate neutral for all circuits. if you are going from HPS to 6 lamp flour. you will have a lower amp draw on the circuits allowing you to almost double your number of fixtures on each circuit