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Dual Tesla HPWC Installation

Discussion in 'Model S: Battery & Charging' started by SSonnentag, Jul 20, 2018.

  1. SSonnentag

    SSonnentag Supporting Member

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    I finally got most of the parts (and the time) to start installing dual chargers. Today I got the bulk of the work done. The lower conduit is for the communication wires. Next weekend I’ll be able to finish it up. I’m missing two parts I need to connect to power, but those are scheduled to arrive via Amazon this next week. So at this point it’s mainly down to running the 80 feet of conduit, pulling the 3 gauge wire and popping in a 100 amp breaker.
     

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  2. P85_DA

    P85_DA Supporting Member

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    Beautiful ! Is it possible to run comm wires in the top conduit ? Or did u route at bottom for aesthetic reasons ?
     
  3. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    Max 50 amps per Hpwc?
    Wondering of there is a way to allow one to ramp up to 80 (or at least 48 for a model 3) if the other not used
     
  4. SSonnentag

    SSonnentag Supporting Member

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    It will allow up to 72A (car limit), but will split the 80A for 40A per car when both are charging.
     
  5. SSonnentag

    SSonnentag Supporting Member

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    Tesla recommends running the comm wire separate from the power to prevent interference. I got shielded twisted pair wire, and was considering running it with the power wires, but it didn’t fit too well and I already had the other conduit and fittings anyway. So it is run as per Tesla’s specs.


    It sorta looks like a big smiley face.
     
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  6. boaterva

    boaterva Supporting Member

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    The manual states the max distance between the HPWCs is 49’ and that you can run the signal cable with the power wires if the insulation is higher than the voltage. Most insulation is 600V which would be sufficient.

    See page 28 of the Gen 2 manual.

    Edit; lol thought we were talking about HPWCs 80 feet apart. That install is simple enough, of course. Mine (see sig) has them on opposite walls of garage.
     
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  7. P85_DA

    P85_DA Supporting Member

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    ..thanks although I like his smiley face look I wanted to run in single conduit :eek:
     
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  8. JD01

    JD01 Member

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    Wonderful job! Your work looks amazing.

    Would you mind posting your rationale for going so big? I only mention it because newbies might be scared off by the cost of trying to replicate what you've done. It's a wet dream for enthusiasts but for the masses..? It's overkill. Most will have 48 amp chargers in their cars and drive less than 50 miles/day.

    Yes, you can run the comm wire through the conduit with electrical wiring. The installation guide is a little murky on this topic so discussed it with a Tesla installer while he was doing my solar/powerwall site survey. He said they do it all the time when running a 2nd conduit is inconvenient or less than aesthetically pleasing. For the DIY crowd, regular 2 conductor twisted pair (like what you'd use for a hardwired alarm system) works fine and for interior installations you can skip the comm wire's conduit altogether. Tesla only uses conduit indoors to give the installation that "clean and professional" look. He made it abundantly clear that conduit was required for exterior installations and he strongly recommended the shielded wire Tesla uses when running the comm and electrical wires together. He saw I already had 2 HPWCs sitting in my garage and gave me 25' to make sure I had the right stuff.
     
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  9. SSonnentag

    SSonnentag Supporting Member

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    #9 SSonnentag, Jul 21, 2018
    Last edited: Jul 21, 2018
    Our S100D and X100D both have 72A onboard chargers. We’ve been sharing a single 40A wall charger, but that gets old really quickly as you have to manage the charging vs letting two wall chargers manage it for you. So since I was going to add a second charger anyway, I decided to just upgrade the existing conduit and wiring to 100A. I could have simply added a second charger and a junction box to let the cars share the 40A, but decided to go all out.

    Building code (here anyway) requires a disconnect near the load when the circuit is greater than 50A.

    The conduit, wire, disconnect and breaker came to roughly $1000. The two HPWCs bump the total up to $2000. The permit was an additional $250 for a grand total of $2250.

    If you are on a budget, you could get by with a 50A circuit and eliminate the $232 100A disconnect and about $150 for the heavier wire. This would knock $382 off the cost. In my opinion, that isn’t enough of a savings to warrant dropping from 80A of charging to 40A.
     
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  10. SSonnentag

    SSonnentag Supporting Member

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    #10 SSonnentag, Jul 21, 2018
    Last edited: Jul 21, 2018
    Now, if you already have a wall charger and you purchase a second Tesla, you could get by with spending $500 for a second charger and probably around $100 for the necessary junction box, conduit and wiring to connect the two chargers. Then you would be able to share 40A of charging power between two vehicles.

    In my case this would have saved me about $900, but knowing myself as I do, it would always bug me.
     
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  11. P85_DA

    P85_DA Supporting Member

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    BTW your shiplap gives a nice farm-house look ...now my wife wants that too :eek:
     
  12. JD01

    JD01 Member

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    Well stated. Thanks!

    Local codes vary but in most places a sub panel counts as the "nearby" disconnect if you're using a 60 amp circuit or less. Anything more than that and you have to install a disconnect like the one pictured above.

    Also, the above configuration allows the OP to draw an enormous amount of power. He'll be able to fully charge his car from empty to full in a little over 5 hours. If his daily commute is 50 miles, he'll be able to top off every day in just under an hour (which for most people is totally unnecessary unless you're sharing with a spouse ;)).

    If you're planning to go solar at some point, be aware that most solar installations are less than 10 kW so your car will likely draw more than your panels can produce. His set up will pull approximately 17 kW for one car at 72 amps compared to 11-ish for one car at 48 amps.

    Further, a single powerwall can only handle 5 kW. So in addition to the time of day you're charging and the size of your solar system, you should consider how many powerwalls you'll need if you want to make sure your baby's eating as much tree food as possible.
     
  13. gregd

    gregd Active Member

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    Nicely, done!

    My only comment is to not underestimate the difficulty pulling and working with #3 wire. I hope your conduit is large enough (wide bends), as this stuff is really stiff. I used #4 for my 14-50 install (for future headroom), and almost regretted it.
     
  14. boaterva

    boaterva Supporting Member

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    I have the same setup (see pics in sig) in prep for two cars but limit the car to 40 amps charging so as not to stress anything unless needed for a quick recharge. Always good to have options!

    The sub panel (where the breakers for the feeders for the HPWC 100 A and the 14-50 50 A circuit come off) also serves as a cutoff
     
  15. LukasSwan

    LukasSwan Member

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    Agree. When selecting RW90 cable get it with many strands. The few strand versions are very difficult to get into the terminal blocks of the charge station and tighten down.
     
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  16. SSonnentag

    SSonnentag Supporting Member

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    #16 SSonnentag, Jul 23, 2018
    Last edited: Jul 23, 2018
    Not being an electrician, I had already purchased the THWN-2 #3 wire for the ground before realizing the ground wire doesn't have to be quite as large as the power wires. :D After fiddling with one of the ground connections in the first HPWC, I managed to get all but one strand of the wire inside the connector and fastened down. All of the others went in easily enough, but that one connector just didn't want to accept all 19 strands of copper . . . 18 will have to do.
     
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  17. SSonnentag

    SSonnentag Supporting Member

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    So after a total of 16 hours (removal of old conduit, 14-50 outlet and J1772 charger, followed by installation of new and larger conduit, disconnect switch and dual HPWCs), the project is complete and everything is working well.

    To do this over again, I'd upsize the conduit to make pulling the wire easier. Even with only 1 90-degree turn and a couple of tiny dogleg jogs the #3 wire was a royal pain to pull. The longest single pull was 60 feet. Anyway, it feels great to have the job done. :D

    At 80A, the voltage sags from 243V to 234V (3.7%), more than I was hoping for, but acceptable.
     
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  18. Rockster

    Rockster Active Member

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    I don't want to derail the thread but I have a very similar, dual setup. I didn't want to run conduit on the wall surface so I opened the wall and then replaced the drywall when I finished. My electrical panel is very close to the HPWC's, so I'm seeing no voltage drop at 80 amps. (The blue conduit holds the shielded twisted pair used for communication.)
    IMG_1089.JPG IMG_1426.PNG IMG_1812.jpg
     
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  19. TechVP

    TechVP Active Poster

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    Hi Joe, can you quote the markings on the COMM cable that Tesla supplied for you?
    That cable has to be 600v, 18 gauge, 90 deg. C, and shielded. Hard to find all of those criteria. Usually you can find all of those at 300V rating... but not as easily found at 600V.
    Would love to know what they are using... as I am searching still for a cable that meets the requirements listed in the HPWC manual.

    BTW, congrats on your install.
    -TechVP
     
  20. Rocky_H

    Rocky_H Active Member

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    I'm pretty curious on that as well, since the first time I read the specifications in the manual for that signal wire I was shocked. Those requirements are absolutely ridiculous for a tiny little twisted pair wire.
     

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