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Friday, December 16, 2022
Question:
Dear CQD, I really appreciate the Code Question of the Day, and read it every morning. Could you please help clear up a debate in our office. In our locale, the local AHJ has told us that 3 phase power is not allowed for a single-family dwelling unit. If it is allowed, I have certainly never seen it during my time as an inspector. Any insight on this topic would be appreciated, as we cannot seem to agree on this matter. Regards, Steve Bosserman
A
Answer:
Hello Steve, thank you for the kind words and continued participation in the Code Question of the Day. Regarding your debate, the NEC® does not prohibit the use of a 3-phase system on a single-family dwelling unit. Currently, it is a common practice to install a 120/208V, 3-phase service for multi-family dwelling units. It also advisable to check with the local utility, as they may have residential service rules in place that restrict the available voltages for service to single-family dwellings. Additionally, the service equipment cost, and electrical appliance availability are also likely factors that deters individuals from utilizing 3-phase power systems on an average size single-family dwelling unit. Hope this helps.