Recently I was installing heat tape. The voltage was 208, and I needed 2 circuits. After I pulled in 4 phases I got to wondering if I could have used Three Phases, one to carry the unbalanced load, in the same manner as a multiwire circuit using a phase instead of a neutral. Does the NEC address this situation at all?
Hot carrying unbalanced currant
- Thread starter JerL
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- Chapel Hill, NC
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- Retired Electrical Contractor
Let's assume that a heat tape circuit draws 12 amps at 208 volts. Assuming single phase-- each leg draws 6 amps. Thus if you hooked one circuit to AB phase and the other to BC phase then the load would be Phase A= 6 amps, Phase B =12 amps and Phase C= 6 amps.
This certainly would work but you would have to make sure you don't overload one phase.
This certainly would work but you would have to make sure you don't overload one phase.
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- Wisconsin
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- PE (Retired) - Power Systems
You did not pull in 4 phases.
Although you did pull in 4 phase conductors. This is a very critical difference. If you pulled 2 conductors on L1 and 2 conductors on L2, you only have 1 phase voltage (L1-L2) even though you have four phase conductors. If you pulled 1 conductor on L1, 1 conductor on L2, and 2 conductors on L3, you have 3 phase voltages and 4 phase conductors.
LarryFine
Master Electrician Electric Contractor Richmond VA
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- Henrico County, VA
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- Electrical Contractor
The simple answer to the OP's question is yes. You'd need a 3p breaker instead of two 2p's.
If I'm not mistaken, the current on the shared conductor would be somewhat lower than 12a.
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