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Thursday, February 7, 2019
Question:
In a bathroom, can a 227v switch for lighting be installed in a 2-gang box along with a 120v switch for an exhaust fan? If so is a barrier required?
Richard Cressotti
A
Answer:
Hey Richard thanks for your question. Yes, switches for 277 volt lighting circuits can be in the same enclosure with switches for 120 volt loads. If the voltage between the adjacent switches exceeds 300 volts, identified securely installed barriers are required as stated in 404.8(B).
So, depending on the systems supplying the two different circuits the voltages can be additive, subtractive or theoretically neither, to each other. Either measure the difference between the two circuits and show the AHJ it does not exceed 300 volts or use barriers that are readily available. If you have the interest and time, using safe work practices, check the actual voltages, with different circuits and systems if possible, and send that information in to us. It might be an opportunity to help improve the NEC wording in future editions.