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49 ft./15m. limit on HPWC; Has anybody broken this rule?

Discussion in 'Charging and Infrastructure' started by 17.088 ^2, Apr 15, 2017.

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  1. 17.088 ^2

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    This URL:
    https://shop.teslamotors.com/collec...dapters/products/wall-connector-with-24-cable

    ...will have a link to a PDF Installation Guide's URL:
    https://www.tesla.com/sites/default...l_connector_installation_manual_80A_en_US.pdf

    In that manual, on page 29: "Appendix B: Optional Connection for Load Sharing", you will notice in the lower right corner:

    The maximum distance between Wall Connectors is 49 ft (15 m).

    Also seen on page 14: "Tools and Materials Required" is this quote:
    Wiring {use twisted pair communication cable 18AWG (Max diameter: .04 in. (1.02 mm); Max. cross-sectional area:.03 in2 (0.82 mm2) for a maximum of 49 ft. (15 m) between Wall Connectors}


    ==========


    Has anyone had experience with this 49' limit?

    We have a situation where this could easily be violated for two chargers that are spread far apart. (The distance is not an issue as the bird flies or eyeball looks, but instead the distance as the conduit lays; I don't want to rip up a concrete driveway.)

    I'd like to know if anyone has experience with violating the 49' rule, and/or what the real-world actual limit may be.




    17.088 ^ 2


    =====

    p.s.: I understand that Millbank, the electrical meter socket company, makes a great enclosure to protect an EVSE from the elements, etc. I've only seen the picture, and have not found out about price, availability, etc..
     
  2. garsh

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    Then tunnel under it.
    It's not too difficult nowadays to run wiring and even conduit under a driveway as needed.
    There are lots of videos on YouTube demonstrating various techniques.

     
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  3. 17.088 ^2

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    Not practical in my case.
    Costs a lot less to go the long way around AND through the house.
    Unfortunately, that means multiple 2-pole circuits if we get multiple sides of the driveway.
    Eh, that wouldn't be such a bad thing.
    Still, as for the 3rd location, it would be nice to re-use one of the (soon to be) new circuits for that portion (via the "sharing" feature).

    .
     
  4. Badback

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    Nope, don't see anything about a limit on page 29.
     
  5. 17.088 ^2

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    There may be a glitch in one or more pdf readers.
    When I looked again, I did find the quote on page 14,
    but the second one was now on page _28_ (not page 29).
     
  6. MelindaV

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    not being an electrical engineer/installer... I do know you need to increase the wire ga for longer runs. I would expect that translates down to the connection points inside the WC itself. So if the run up to 49' needs to be X ga the connectors were rated for that. If over 49' would need to be Y ga instead but the connectors are still only rated for X ga...
    just my guess

    So if you connect multiples with longer than the rated distances, you would be putting a higher load on the unit than it is designed for, potentially causing a fire hazard and certainly voiding it's warranty.
     
  7. Badback

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    The 49' (15 meters) limit is for the signal wires. They carry very little current so the wire size is not very important. The 18AWG specified is a common shielded cable size and the connector block used is intended for this size. The 15m limit has to do with noise pickup. A longer run will introduce more noise into the electronics than they are designed to tolerate.
     
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  8. KennethK

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    Also, if you can avoid running the signal wire in the same conduit as the AC lines to avoid adding noise, then do it. You may be able to route them differently and avoid your 49ft limit (probably a soft limit with engineering margin built in).
     
  9. Badback

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  10. 17.088 ^2

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    Uh, I think you've got that backwards.

    Ground loops in communication cables generally occur when one grounds _BOTH_ ends of a cable's shield.
    i.e.: One typically only wants to ground ONE end of a shielded cable.
     
  11. Badback

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    That's what I said. "be careful to terminate the shield of the cable at the source end only to avoid ground loops."
     
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