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

Two new HPWC amperage configuration question

Discussion in 'Model S: Battery & Charging' started by scottfl, Jun 11, 2016.

  1. scottfl

    scottfl Member

    Joined:
    Jun 11, 2016
    Messages:
    33
    Location:
    sarasota
    I recently had two HPWC professionally installed on a single 100A circuit (see photo) in my garage. The electrician set the master unit to a maximum output current of 40A (rotary switch position 8). In this setting, it was only able to charge a single updated MS at 40A rather than 48A. Would it be safe to advance the rotary switch to 48A (position 9) or no? I understand that it is only safe to use only 80% of the 100A circuit (40A x 2) but I wonder if the load sharing smarts of the new HPWC is smart enough to keep things in check in the higher position.


    IMG_2446.jpeg
     
  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,762
    Location:
    Texas
    The difference in charging speed that the 8 amps will give you is insignificant from a practical point of view. I'd not bother with it. I also wouldn't count on it to adjust for an incorrect setting.
     
  3. dhrivnak

    dhrivnak Active Member

    Joined:
    Jan 8, 2011
    Messages:
    2,150
    Location:
    NE Tennessee
    Not really if you will be charging both cars at the same time. 88 amps will often trip a breaker after a couple of hours. Time at high charge rates heat up the breaker causing false trips. Hence the 80% rule for sustained loads. If the overlap is less than an hour you can likely do it.
     
  4. AoneOne

    AoneOne Member

    Joined:
    Sep 21, 2013
    Messages:
    151
    Location:
    Fox Chapel (Pittsburgh), PA
    • Like x 1
  5. scottfl

    scottfl Member

    Joined:
    Jun 11, 2016
    Messages:
    33
    Location:
    sarasota
    Yes and that's what I thought at first, however the manual is confusing since in appendix B (page 29) it states that the maximum setting of the master for load sharing is position 8 [40A]. Can you or someone else clarify?
    1. Set one Wall Connector as the master by setting the Rotary Switch Position from 1 to 8 depending on the maximum available output current. Set up to 3 Wall Connectors as slaves by setting the Rotary Switch Positions to F.
     
  6. aesculus

    aesculus Still Trying to Figure this All Out

    Joined:
    May 31, 2015
    Messages:
    1,970
    Location:
    Northern California
    I reported this as a issue a number of weeks ago and Flasher Z asked the factory and they confirmed it was a mistake in the manual.

    Dial them both up.

    I assume you have #2 or #3 wires to each unit from that junction box?
     
  7. scottfl

    scottfl Member

    Joined:
    Jun 11, 2016
    Messages:
    33
    Location:
    sarasota
    Thanks! I was hoping it was a mistake in the manual. Do you have a link to a previous thread that you and Flasher Z discussed it?
     
  8. aesculus

    aesculus Still Trying to Figure this All Out

    Joined:
    May 31, 2015
    Messages:
    1,970
    Location:
    Northern California
    New Wall Connector :)
     
  9. scottfl

    scottfl Member

    Joined:
    Jun 11, 2016
    Messages:
    33
    Location:
    sarasota
  10. Rocky_H

    Rocky_H Member

    Joined:
    Feb 19, 2015
    Messages:
    890
    Location:
    Boise, ID
    The part I don't see specifically spelled out is: Were they installed with the twisted pair interconnect for them to communicate as master/slave? It looks like there is a light gray conduit running between them that might be it. If they were set up properly with that communication, then you can turn them both up to the full level (80A output). They will coordinate to make sure the total of the two together stays within that 80A limit. That is the purpose of the new interconnected system, so that if either one is used, it can get the full rate of the circuit, but if they are both connected they will reduce their levels.
     
  11. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    1,644
    Location:
    Oregon
    Actually you set one to the full level and the other to "slave".
     
  12. Rocky_H

    Rocky_H Member

    Joined:
    Feb 19, 2015
    Messages:
    890
    Location:
    Boise, ID
    Oh, yes, that's right. I had forgotten that's how the settings go.
     
  13. scottfl

    scottfl Member

    Joined:
    Jun 11, 2016
    Messages:
    33
    Location:
    sarasota
    As a late follow up, you guys were right. I set one to slave and the other to 80amps. Works perfectly with two Tesla's charging. Thanks again for the advice.
     

Share This Page