The year 2020 provided me with the unique opportunity and the time to produce a series of videos on topics that you told me were of interest to you. I recorded them from my house, and livestreamed them over the course of several months. There were a lot of you that might not have been able to tune in, and others who did, but would enjoy the chance to see them again. We'll be sending them out monthly in a newsletter series. Enjoy and feel free to share!
 Sizing feeder or service conductors for a dwelling isn’t simply a matter of totaling the loads or breaker ratings. The Code recognizes that not all loads run simultaneously and feeder and service conductors are sized with this in mind? First, do a load calculation using the optional method to figure out your demand load [220.82]. Then it’s time to select a conductor based on your result, but unlike most other circuits, not using Table 310.16!
Dwelling units service conductors supplied by a single-phase, 120/240V system and feeders conductors supplied by a 120/240V or 208Y/120V systems can be sized using Table 310.12. The service and feeder conductors supplying the entire load associated with a dwelling unit can be sized in accordance with Table 310.12 where there is no conductor ampacity adjustment or correction as required by 310.14 [310.12(A) and (B)].
Table 310.12 cannot be used to size service conductors for a multifamily dwelling building in accordance with 310.12(A) because the service conductors supply multiple units not the load for a single unit. Similarly, Table 310.12 cannot be used to size feeder conductors for a panel serving only a portion of the dwelling unit. It’s good to remember that feeder conductors for an individual dwelling unit are never required to be larger than the service conductors [310.12(C)].
One last thing to remember is that the service or feeder neutral conductors for a dwelling unit are permitted to be sized smaller than the phase conductors [310.12(D)] as long as the requirements of 220.61 and 230.42(C) for service conductors, or the requirements of 215.2(A)(2) and 220.61 for feeder conductors are met.
Join Mike on this video to catch all the details as he discusses residential service and feeder conductor sizing!
Click here or on the image to watch the video [13min:03sec]. |
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