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Wiring for Wall Connector Power Sharing?

Discussion in 'Charging Standards and Infrastructure' started by jimmyz80, Mar 10, 2017.

  1. jimmyz80

    jimmyz80 Member

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    I've read through the installation guide for the new Wall Connector, and I just can't wrap my head around what the actual wiring would look like to utilize the power sharing feature.

    Currently in my garage I have a 14-50 outlet that's connected to the main breaker panel outside with 6-2 NM wiring through my crawl space and a 50A breaker. If I were to remove the outlet and mount the Wall Connector over the J-box to hardwire it, I just don't see how you would then daisy chain the power along to a second Wall Connector. It doesn't seem like there would be room in the J-Box to pigtail 6AWG, nor does it seem like a smart idea to me (giant wire nuts???).

    Is the only way to do this correctly to install a sub-panel in the garage using the existing wiring and breaker, and then run two 50A circuits from that sub-panel to each of the Wall Connector locations?

    Another related question... I see that 6-2 NM can handle 55 amps, and as far as I can tell you're allowed to size up to a 60A breaker since 55A breakers aren't a standard size. In this case could I just size the breaker up to 60A with the existing wiring, and then safely Power Share two Wall Connectors from that circuit? It seems safe to me since the EVSEs should only ever be pulling 48A from the 60A circuit anyway, never exceeding the 55A rating of the 6-2 NM.

    Thanks!
     
  2. 182RG

    182RG Free The Service Manuals From Tyranny

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    NEC 240.4B. The round up rule. #6 is fine with a 60A breaker.

    I personally would use a sub panel or box with a terminal block that supports multiple load connections. Not a fan of giant wire nuts. Something like this:

    IMG_0053.JPG
     
  3. brkaus

    brkaus Active Member

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  4. boaterva

    boaterva Supporting Member

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    My electrician just did this with a box (3" by 4" by 10"? about that) where he ran the 1" conduit from the subpanel to the first HPWC and then back to the second one. It had three way tap devices that I'd not seen before, but he used them to connect 'around' each wire to create the connection for the third wire.

    (The subpanel was for the backup 14-50 to come off the 100 A feed from the main panel; the 14-50 has its own 50 A breaker with a little device to ensure that only one breaker is on at any one time.)

    The data wire to control the 'sharing' goes between each of the HPWC pairs, and most of us would have only one pair, of course. (I've seen in the manual that this is where all the confusion about 'daisy chaining' comes from, since it is the language for the data connection, not the power connection.)
     
  5. jimmyz80

    jimmyz80 Member

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    Doesn't the round up rule only apply to the OCPD (breaker) and not the conductor (wire) though? My impression is that if I had a 55A load on 6/2 NM, then I'd be allowed to use a 60A breaker by rounding the breaker size up. But since the load would be 60A in this case, I don't believe I can legally use a 55A conductor (6/2 NM).

    I've seen many similar discussions around people trying to use 2/3 NM for 100A wiring, but it's not allowed since 2/3 NM is only rated for 95A. Same story, just lower amperage.

    Seems like according to code the best I can do on 6/2 NM is 50A. Does that sound right?
     
  6. boaterva

    boaterva Supporting Member

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    I'm pretty sure I saw that exact question answered in @FlasherZ 's excellent FAQ (and the answer is, no, you can't round up wire sizes...).
    FAQ: Home Tesla charging infrastructure Q&A
     
    • Like x 1
  7. 182RG

    182RG Free The Service Manuals From Tyranny

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    In your first post, you stated that the max load was never going to exceed 48A. 54A or less is fine with 6/2 NM on a 60A breaker. Most charts that exist show 50 or 60A breaker is fine for #6 in the 60 degree temp range. If you are concerned, use THHN in conduit, instead of NM to give you more headroom.

    IMG_0054.JPG
     
  8. jimmyz80

    jimmyz80 Member

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    The max load never will exceed 48A if that's what I set the wall connector to. But due to it being a continuous load, I have to apply the 1.25x multiplier which means everything needs to be sized for 60A. That chart you posted is also the only one I've ever seen that shows 60A for 6AWG NM wire. Literally everything else I've seen shows 55A.

    http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM10
     
  9. 182RG

    182RG Free The Service Manuals From Tyranny

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    That chart is from the NACHI site. It's in many other places online. I recommend you consult an electrician, and understand what will pass inspection.

    Personally, I wouldn't use NM. I'd use (and have used) THHN in conduit for sub panels. Good luck.
     
  10. jimmyz80

    jimmyz80 Member

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    Well then the home inspectors are following misguided information that doesn't match the NEC table and disregards manufacturer ratings.
     

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