Randomperson1362 t1_ir1mt8r wrote
Reply to comment by [deleted] in Wiring EV Charger by Loon610
I'm not an electrician, so don't listen to me, but what is the harm in going with smaller wire?
Lets say you have 60 amp wire, then in a junction box you add connect 40 amp wire to lengthen the circuit. Assuming a 40 amp breaker* is that an issue?
Obviously using a 60 amp breaker is a very bad idea.
Princess_Moon_Butt t1_ir1ztv8 wrote
Exactly. If you use wire that's rated for less than the breaker's capacity, yes, that's bad.
This guy's talking about using a 40-amp breaker, with a mix of 60-amp wire and 40-amp wire. There's no concern there, because the most that will go through that 40-amp wire is 40 amps.
eerun165 t1_ir1vd96 wrote
Wire size can be increased in size to account for voltage drop.
Decreasing wire size from its corresponding breaker is a fire risk. The wire is not rated for the higher current and will heat up (think of the small wires in a toaster).
Viper67857 t1_ir324xm wrote
It's still a 40A circuit on a 40A breaker, it just has wire rated for 55A along most of the run. Using a couple feet of 8ga at the end will not hurt anything.
You already downsize the massive 200A cables coming into your service entrance with 15-20A wires going to most of your devices, then those devices may have some tiny 20+ga wires inside them. You use what you need for the individual load, you don't just carry on the larger cable for consistency.
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