240v outlet and charger installed - charger is hot and saying temperature too high, limiting charge

[wmras]

My electrician just told me he doesn't think that 20 ft would make that much of a difference but is willing to try...given the 70 ft of wire I have currently.

Normally, we do not think too much about wire resistance, but a 40-amp circuit generates a lot of heat loss. Power (watts, heat) = amperes squared times resistance (W = I^2 x R).

For example, the power loss at 40A at 100 ft. equals:

#4-gauge wire Watts = 40A x 40A x 100 x 2 x 0.0003
= 96 watts (~1 watt/ft.)

#6-gauge wire Watts = 40A x 40A x 100 x 2 x 0.0005
= 160 watts (~1.6 watts/ft.)

#8-gauge wire Watts = 40A x 40A x 100 x 2 x 0.0008
= 256 watts (~2.6 watts/ft.)

Your first reaction be that is not much loss, but how long can you hold a lit five watt light bulb in your hand?

Bottom line, larger wire, solid connections, and great receptacle/plug contacts reduce loss, heat, and risk of fire.

Sponsored

 

[KenU]

Normally, we do not think too much about wire resistance, but a 40-amp circuit generates a lot of heat loss. Power (watts, heat) = amperes squared times resistance (W = I^2 x R).

For example, the power loss at 40A at 100 ft. equals:

#4-gauge wire Watts = 40A x 40A x 100 x 2 x 0.0003
= 96 watts (~1 watt/ft.)

#6-gauge wire Watts = 40A x 40A x 100 x 2 x 0.0005
= 160 watts (~1.6 watts/ft.)

#8-gauge wire Watts = 40A x 40A x 100 x 2 x 0.0008
= 256 watts (~2.6 watts/ft.)

Your first reaction be that is not much loss, but how long can you hold a lit five watt light bulb in your hand?

Bottom line, larger wire, solid connections, and great receptacle/plug contacts reduce loss, heat, and risk of fire.

Lowered to 24A for curiosity and lo and behold the temp is way down from the 42A and even 32A. (50 Amp breaker, etc.) 4 gauge wire ordered and will replace the 6 gauge. Will be installed next week. Thanks again for your analysis and explanations.

 

[petrie]

What gauge of wire did they use from the circuit breaker to the plug? I believe it should be 6 gauge and not 8 which is normal for a 240 outlet say for a dryer or washer

Charged my car for the second time yesterday and did not want to deal with the heat problem. I adjusted to 35 amp from 40. There was no notification about temperature and the car finished charging just fine. The charger and wire is still slightly warm to touch but most likely normal. I guess this is a short term solution.

I asked my electrician and he used a #8 gauge wire size. Will asking him to change it to a #6 fix the issue (using a 25ft cable)? Thanks.

 

[wmras]

I asked my electrician and he used a #8 gauge wire size. Will asking him to change it to a #6 fix the issue (using a 25ft cable)? Thanks.

Perfect! Also consider an industrial-grade receptacle.

Sponsored