277V and 120V question
- Thread starter twada
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electricman2
Senior Member
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- North Carolina
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- Retired Electrical Contractor
Re: 277V and 120V question
Yes, provided the voltage rating of all conductors is equal to the highest voltage. 300.3(C)(1) If the grounded conductors for each system are present they must be identified in a different manner per 200.6(D)
Yes, provided the voltage rating of all conductors is equal to the highest voltage. 300.3(C)(1) If the grounded conductors for each system are present they must be identified in a different manner per 200.6(D)
- Location
- Illinois
- Occupation
- retired electrician
Re: 277V and 120V question
I want to qualify the answer a bit. In general you can mix these voltage systems, but not always. If the 120 volt conductors are an Article 725 Class 1 circuit and if they are not functionally associated with the 277 volt power conductors, then they cannot be mixed. See 725.26(B).
Don
I want to qualify the answer a bit. In general you can mix these voltage systems, but not always. If the 120 volt conductors are an Article 725 Class 1 circuit and if they are not functionally associated with the 277 volt power conductors, then they cannot be mixed. See 725.26(B).
Don
Re: 277V and 120V question
OK we know we can by the articles quoted but I will bite and ask the question why would you want to?
I guess I am being pessimistic and can only see bad things happening down the road to the next guy. Although this practice may be allowed by code IMO it is an accident waiting to happen. The damage to equipment would be the least of my worry. I can see no reason to want or need to mix these voltages.
OK we know we can by the articles quoted but I will bite and ask the question why would you want to?
I guess I am being pessimistic and can only see bad things happening down the road to the next guy. Although this practice may be allowed by code IMO it is an accident waiting to happen. The damage to equipment would be the least of my worry. I can see no reason to want or need to mix these voltages.
electricman2
Senior Member
- Location
- North Carolina
- Occupation
- Retired Electrical Contractor
Re: 277V and 120V question
Many times it's a matter of installation cost and convenience. For example in a wastewater treatment plant you may have a 250ft. run to a primary clarifier that requires a 480v 3 phase circuit and a 120v circuit for lighting or receptacles. It's much easier and less costly to simply put everything in one pipe. I have seen this quite often.
Many times it's a matter of installation cost and convenience. For example in a wastewater treatment plant you may have a 250ft. run to a primary clarifier that requires a 480v 3 phase circuit and a 120v circuit for lighting or receptacles. It's much easier and less costly to simply put everything in one pipe. I have seen this quite often.
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