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30 amp breaker

MorrisonHiker

Well-Known Member
Moderator
Mar 8, 2015
10,553
10,580
Colorado
I have a 30 amp breaker for my dryer with a NEMA 14-50 Outlet. How fast will that charge a MY?
Hopefully you have a 14-30 outlet if you have a 30 amp breaker.
30 amps X 240 volts = 7,200 watts, or 7.2 kilowatts (kW). Assuming your Model Y uses about 280 watt hours/mile (like mine), this outlet would charge at about 26 miles of range per hour.
For EVs (continuous load), you can only use 80%, so it would be 24 amps usable, not 30 amps.

A 2021 Model Y LR is rated at 270 Wh/mile: 24 amps * 240 volts / 270 Wh/mile = 21.3 mph.

A 2021 Model Y Performance is rated at 300 Wh/mile: 24 amps * 240 volts / 300 Wh/mile = 19.2 mph.
 
Hopefully you have a 14-30 outlet if you have a 30 amp breaker.

For EVs (continuous load), you can only use 80%, so it would be 24 amps usable, not 30 amps.

A 2021 Model Y LR is rated at 270 Wh/mile: 24 amps * 240 volts / 270 Wh/mile = 21.3 mph.

A 2021 Model Y Performance is rated at 300 Wh/mile: 24 amps * 240 volts / 300 Wh/mile = 19.2 mph.
Thank you morrisonHiker
 
Yes - a portable charger with the 14-50 will try to draw 32A. (it's max capable). that should pop the breaker. Get a 14-30 plug for your portable charger, or on your car's charging options limit it to 24A. (And check that regularly to be sure the car has not decided to reset itself...) But only as a stop-gap. Get the correct plug and it will limit the charger's draw.

Electrical code says "DO NOT DRAW MORE THAN 80% OF RATED CIRCUIT/BREAKER AS A CONTINUOUS LOAD" As MorrisonHiker says.

I have a Gen2 charger and got a 50A cord 14-50 from Amazon, so I could plug it in instead of hard wiring. But the Gen2 Wall Charger has a dial to set max current limit.
 

jcanoe

Well-Known Member
Oct 2, 2020
5,327
5,815
Maryland
30 amps X 240 volts = 7,200 watts, or 7.2 kilowatts (kW). Assuming your Model Y uses about 280 watt hours/mile (like mine), this outlet would charge at about 26 miles of range per hour.
Your calculation of the maximum power from the dryer circuit is correct however when used to charge an EV the maximum allowable amperage is limited to 80% of the circuit rating. When charging the Tesla vehicle using the 30A dryer outlet the maximum draw is limited to 24 amps. 24A X 240V = 5760W or approximately 6kW.

Tesla's charging table charging shows that using the NEMA 14-30 (not 14-50, that receptacle, plug is for a 50A circuit) will add approximately 21 miles of range to the Model Y per hour of charging. This is quite adequate for most daily charging needs.

Gen 2 NEMA Adapters
 
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jcanoe

Well-Known Member
Oct 2, 2020
5,327
5,815
Maryland
I have a 30 amp breaker for my dryer with a NEMA 14-50 Outlet. How fast will that charge a MY?
Safety first; if you have a 30A breaker and assuming the wire is for a 30A circuit, i.e. 8/3 gauge wire then you cannot use the NEMA 14-50 receptacle as this requires a 50A circuit. If you are using a NEMA 14-50 receptacle on a 30A circuit this is not to code and unsafe. Any electric vehicle service equipment fitted with a NEMA 14-50 plug will enable charging at up to 32A or in some cases up to 40A from what is supposed to be a 50A rated circuit. Drawing more than 24A from a 30A rated circuit, over the multiple hours it typically takes to fully or even partially charge an EV, could cause the wiring to overheat and start a fire. For a 30A dryer circuit the correct receptacle needs to be one rated for 30A, i.e. NEMA 14-30 (Note: the NEMA 14-30 receptacle requires a ground wire.)
 
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