Yep, Jay is correct. The breaker is sized to protect the conductor (wire). The 30A breaker would protect a #10 conductor. A person can still use a larger conductor for smaller load than the maximum rating allowed. Is it cost effective? Probably not. It also tends to defeat the purpose of the smaller breaker size protection, but it still functions to provide power to the end device. Connecting a 30A appliance using a #6 conductor, protecting the circuit with a 30A breaker will function, however, when the appliance fails electrically, the circuit breaker may not thermally trip quickly enough to avoid a fire type event. -Tom True
Remember, it is not that the glass is half empty, in reality, the glass is merely twice the size that it needs to be! -TNT'82 On Thu, Feb 12, 2026, 11:26 AM Jay Summet via EV <[email protected]> wrote: > > > On 2/12/26 13:40, EV List Lackey via EV wrote: > > On 12 Feb 2026 at 9:22, Thos True via EV wrote: > > > >> If you are connecting a 30A charger, it would be wise to choose a 30A > >> circuit breaker, rather than a 50A. > > > > I'm not a pro electrician, so please forgive me if I'm speaking out of > turn, > > but wouldn't you use a 40a breaker there? > > > > Yes, that is correct. You need a 50 amp breaker for a 40 amp EVSE and 40 > amp for a 30A EVSE to prevent nuisance trips. > > He also didn't mention what wire size to use. But if you install a NEMA > 14-50, you should use the correct (50 amp rated) wire gauge (size can > change depending upon the length of the run, but typically be a 6AWG or > 4AWG for longer runs to reduce resistance losses). > > I suspect it may be against code (but safe) to downsize the breaker > (smaller than the wire/outlet requires). > > So if you have a 30 amp EVSE, using a 40A Breaker isn't a bad idea to > trip faster if the load goes well above expected, BUT, if somebody plugs > anything else into the NEMA 14-50 that expects to be able to get 50 amp > power, it will trip the 40A breaker quickly. > > What you CAN'T do is use the incorrect (too small, lower amp rating) > wire size...that's unsafe, especially if somebody later swaps out the > 40A breaker to a 50A breaker because they see the 14-50 at the other end > and don't pay attention to the wire size. > > Jay > _______________________________________________ > Address messages to [email protected] > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20260212/7e578097/attachment.htm> _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
