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Thread: Breaker size for Chevy Volt

  1. #1
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    Breaker size for Chevy Volt

    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

  2. #2
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    If the charge station requires a 40 a then you would need a 40a circuit.

  3. #3
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    Quote Originally Posted by Sierrasparky View Post
    If the charge station requires a 40 a then you would need a 40a circuit.
    Where in the code is this called for?

  4. #4
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    Quote Originally Posted by dnyman View Post
    Where in the code is this called for?
    I don't recall the code section but it has to do with manufactures requirements.

  5. #5
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    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.

  6. #6
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    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.

  7. #7
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    SierraSparky,
    Thanks for the reply.

  8. #8
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    Quote Originally Posted by dnyman View Post
    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
    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.
    Electricians do it until it Hertz!

  9. #9
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    This is one of those situations. If it doesn't work, do it over.

    If you have to run new conductors anyway, why is a $15 CB a problem?
    Tom
    TBLO

  10. #10
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    Quote Originally Posted by dnyman View Post
    ..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.
    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.
    Last edited by ramsy; 09-14-17 at 11:55 AM.
    Roger Ramjet NoFixNoPay

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