TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Charger safety

Discussion in 'Charging Standards and Infrastructure' started by kevincwelch, Jul 9, 2012.

  1. kevincwelch

    kevincwelch Active Member

    Joined:
    May 13, 2012
    Messages:
    2,015
    Location:
    Chicagoland
    Not having dealt with these chargers before (and since I am about to embark on installing a NEMA 14-50 in my garage), is it safe to assume that when the UMC is connected to the NEMA 14-50 that the other end is safe until connected to the car? I'm not saying that I am going to stick my tongue on the leads to test it, but with kids, fingers will explore...
     
  2. dhrivnak

    dhrivnak Active Member

    Joined:
    Jan 8, 2011
    Messages:
    2,150
    Location:
    NE Tennessee
    #2 dhrivnak, Jul 9, 2012
    Last edited: Jul 12, 2012
    Yes, unless they try to pull out the NEMA 14-50 plug. If they do one can get a nasty shock. If you are worried about kids I would hard wire the HPC. Or you can use a junction box to make it relatively easy to remove. The junction box would keep fingers away from the wires.

    That said it is no different than the outlets used at most KOA's and there are certainly plenty of kids there.
     
  3. Tommy

    Tommy Member

    Joined:
    Mar 3, 2010
    Messages:
    880
    Location:
    The great OC
    The UMC (Universal Mobile Connector) is not a charger, it is a connector that has safety circuitry built into it to prevent electrocution. There is a set protocol (the handshake) the connector performs once connected to the car before any harmful voltage is delivered; a built in GFI is part of the specification. This is one instance where correct terminology, connector, not charger is important to emphasize as the word "charger" leads one to imagine more risk than is present. OK, off my soap box.
     
  4. Jason S

    Jason S Model S Sig Perf (P85)

    Joined:
    Apr 20, 2012
    Messages:
    1,350
    Location:
    Rocklin, CA
    #4 Jason S, Jul 9, 2012
    Last edited: Jul 9, 2012
    There is a set protocol (the handshake) the connector performs once connected to the car before any harmful voltage is delivered; a built in GFI is part of the specification.

    There's a case of burying the lead. The connection to the car is better than the NEMA 14-50... the connection including the plug and circuit is so very nice.
     
  5. doug

    doug Administrator / Head Moderator

    Joined:
    Nov 28, 2006
    Messages:
    15,914
    Location:
    Stanford, California
    Hmm... I wouldn't go licking the connector. I think there may be some safety relays in the Model S UMC, but I'm not certain. Fairly sure the Roadster 120V Spare Mobile Connector (MC120) had no such relays, nor did the Roadster Foundry type 240V connectors. So there is a possibility that the business end of the connector is live when the other end is plugged into the wall socket.

    There is a pilot signal which prevents the car from pulling to much current during charging, as well as GFCI which cuts power if there appears to be some ground leakage current (like through someone's body). But I wouldn't take "no power till connected" as a given, like you can with the HPC. The HPC definitely includes a power relay since you can hear it click (separate from the relay (contactor) in the car).

    The connectors are designed to be basically finger safe however.
     
  6. Tommy

    Tommy Member

    Joined:
    Mar 3, 2010
    Messages:
    880
    Location:
    The great OC
    I agreee, the best protection against electrical shock is to treat ANY power source you are handling as energized. However, there are safeguards mandated by standards that must be part of any device classified as an EVSE, portable or otherwise.
    From the Leviton website: EVSE Fact Sheet: 240 Volt Home Charging Station | Leviton Information Exchange

    EVSE Fact Sheet: 240 Volt Home Charging Station
    Cord-and-Plug connected EVSE allowed?

    Yes, because Leviton’s EVSE charging stations have been designed to comply with all applicable safety and industry standards and also for code-compliant installations. Leviton’s 208/240 Volt AC-rated cord-connected EVSE are part of a system, identified and listed for the purpose, by Underwriters Laboratories. They are also compliant with the requirements of the National Electric Code: Articles 625.13, 625.18, 625.19, and 625.29.

    NEC Art. 625.13 states: Electric vehicle supply equipment rated at 125 Volts, single phase, 15- or 20- amperes or part of a system identified and listed as suitable for the purpose and meeting the requirements of 625.18, 625.19, and 625.29 shall be permitted to be cord-and–plug-connected
    625.18 requires an interlock that de-energizes the electric vehicle connector and cable whenever the electrical connector is uncoupled from the electric vehicle
    625.19 requires an automatic means to de-energize the cable conductors and electric vehicle connector upon exposure to strain that could result in either cable rupture or separation of the cable from the electric connector and exposure of live parts
    625.29 requires that the unit be located in indoor sites, including integral, attached and detached residential garages; enclosed and underground parking structures; repair and non-repair commercial garages; and agricultural buildings

    Per the requirements, the connector is de-energized when not connected to the vehicle, thou I won't tempt Murry's Law and assume "no power till connected" as a given either.
     
  7. doug

    doug Administrator / Head Moderator

    Joined:
    Nov 28, 2006
    Messages:
    15,914
    Location:
    Stanford, California
    Those standards seem fairly new. Pretty sure the Roadster MC120 does not comply.
     
  8. Doug_G

    Doug_G Lead Moderator

    Joined:
    Apr 2, 2010
    Messages:
    15,850
    Location:
    Ottawa, Canada
    I'm pretty sure the UMC has contactors. That's the reason for the big lump in the cable.

    The 110V "spare" cable is just an extension cord with a funny plug - it will be energized.
     
  9. W.Petefish

    W.Petefish Active Member

    Joined:
    Apr 29, 2011
    Messages:
    1,059
    Location:
    North Texas (DFW)
    Listen to it when in a quiet place. You can hear a "click" from inside it when it engages.
     
  10. Todd Burch

    Todd Burch Electron Pilot

    Joined:
    Nov 3, 2009
    Messages:
    4,731
    Location:
    Smithfield, VA
    Related question: When plugging in/unplugging the UMC to the NEMA 14-50 outlet, do you recommend turning off the circuit breaker? Especially since the GFCI is not built into the 50 amp circuit?
     
  11. dhrivnak

    dhrivnak Active Member

    Joined:
    Jan 8, 2011
    Messages:
    2,150
    Location:
    NE Tennessee
    No need in my humble opinion and have done it many times. That said it is possible to grab the prongs asso you arethe making contacttight with thethe socket so a shock is possible so take prudent care.
     
  12. Todd Burch

    Todd Burch Electron Pilot

    Joined:
    Nov 3, 2009
    Messages:
    4,731
    Location:
    Smithfield, VA
    Thanks!
     
  13. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Joined:
    Jun 21, 2012
    Messages:
    7,019
    You can get a GFCI breaker for additional protection - I use one for my hot tub. However, it won't completely prevent you from getting a hell of a shock of you happen to grab both hot legs at once, or a hot+neutral while pulling the plug; it only prevents you from getting a shock due to a path to ground.
     
  14. Todd Burch

    Todd Burch Electron Pilot

    Joined:
    Nov 3, 2009
    Messages:
    4,731
    Location:
    Smithfield, VA
    Yes....but Tesla says you should not use a GFCI in your 14-50 circuit, because the UMC (or car?) has it built-in and doubling them up causes problems.
     
  15. hcsharp

    hcsharp Active Member

    Joined:
    Jun 7, 2011
    Messages:
    2,532
    Location:
    Vermont
    I installed all my NEMA 14-50 outlets at eye height or higher to help keep them out of reach of toddlers.
     

Share This Page