Breaker size for Chevy Volt

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dnyman

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I just bought a Chevy Volt and I want to install a 240 V charger. The Volt charging system is limited to 3.6 KW max. I have s spare 30A 240 V breaker in the panel. I got a deal on a charger that is rated for 30A. This is overkill for the 15A load that I need. The installation instructions call for a 40 A breaker. Does the code call for a 40A or do I size for the cars load. I really don't want to use a larger breaker than I need. This is on a dedicated circuit that is hardwired to the charging station.
Thanks
 
My $0.02- seems OK to wire it for 30A knowing you can't use the charger to its max capacity. There is a chance there is still an inrush on the charger that could trip a 30A breaker. Only the manufacturer will know, and they probably won't say anything under 40A will work. No safety issue so I don't think NEC will care. Like wiring a 1HP motor to a 20A circuit. It's allowed by NEC but you may trip the breaker.
 
ok I found it.
By code you must install to manufactures requirement ... So if the instructions or listings say "requires 40 or 50 amp "
then you must do so.

110.3 b
(B) Installation and Use.
Listed or labeled equipment shall be
installed and used in accordance with any instructions included
in the listing or labeling.
 
dnyman said:
I just bought a Chevy Volt and I want to install a 240 V charger. The Volt charging system is limited to 3.6 KW max. I have s spare 30A 240 V breaker in the panel. I got a deal on a charger that is rated for 30A. This is overkill for the 15A load that I need. The installation instructions call for a 40 A breaker. Does the code call for a 40A or do I size for the cars load. I really don't want to use a larger breaker than I need. This is on a dedicated circuit that is hardwired to the charging station.
Thanks
Click to expand...

How EXACTLY do the instructions read?

"Requires individual branch circuit with 40A OCPD"
"Recommend a 40A breaker"
"..."
???

110.3(B) requires you to follow mfg instructions. That written, mfg instructions can be somewhat vague or use incorrect terminology, like the word "dedicated".

If the instructions require a 40A breaker, then you should use a 40A. Using a 30A would be an NEC violation, that if I had to rate on a scale of 1-10, 1 being a technical violation and 10 being "your house will burn down any second", using a 30A here in place of a 40A is a zero. Nuisance trips are the only potential problem here.
 
dnyman said:
..The Volt charging system is limited to 3.6 KW max. I have s spare 30A 240 V breaker in the panel. I got a deal on a charger that is rated for 30A. This is overkill for the 15A load that I need.
Click to expand...
If charger operates at 3.6kw/120vac then load ampacity is 30A x 1.25 for continuous loads = 37.5A --> 40A Breaker

Further, doing 30A continuous with #10cu Romex operates near 64'C, overheating the MAX 60'C listing of NM cable conductors & some fuse-box equipment.

The only way ampacity is closer to 15A, is if your charger operates at 240vac, requiring use of both hot legs, not just one.
 
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What the OP is calling a charger is properly called an EVSE. It is just a relay to control AC power along with some electronics to communicate with the electric vehicle. The EVSE advertises to the car the maximum current that is available, and then the car asks the EVSE to close the relay. The charger, as in the circuit element that converts AC to DC and determines the current draw, is located in the EV itself. In the case of the Volt, it is (I infer) 120V/240V at up to 15 amps.

So the proper way to utilize a 30A circuit is to get an EVSE that can be set to advertise only 24A, since the EVSE is considered a continuous load by the NEC. As a practical matter, if you put a 30A EVSE on a 30A circuit, then the worst that should happen is nuisance tripping if you plug in a car with a 30A charger. That will not happen with the Volt and its 15A charger.

Cheers, Wayne
 
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