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Using UMC vs HPWC for all charging at home

Discussion in 'Model S: Battery & Charging' started by Ohm's Law, Jun 23, 2015.

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  1. Ohm's Law

    Ohm's Law Member

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    What is the expert opinion on using just UMC in your personal garage rather than mounting a HPWC if you do not have dual chargers and only plan to charge at 40A?

    Any pros and cons you can suggest to help make the decision easier?

    thanks,

    -OL
     
  2. Sosius

    Sosius a.k.a. Uptown Frunk

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    No real advantage to HWPC in your situation, except that it looks kind of cool. I use a HWPC, but I do not have covered parking, I was able to get 100/80 Amp service, and I bought the dual chargers.
     
  3. Cosmacelf

    Cosmacelf Active Member

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    The vast majority of Tesla owners use the UMC. I use the UMC, but decided to buy a second UMC to always leave in the car (since my brain is a sieve). The HPWC is more robust and built better than the UMC - some small minority of UMC owners have had overheating problems with their UMC - the odds of having a problem with an HPWC is far less.
     
  4. InternetDude

    InternetDude Member

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    I have a HPWC but I have at 30A so technically it's probably a LPWC LOL

    I'm happy I have it so the UMC is always in the car. With my last car, a Prius plugin, I hated that I had to swap the charging cable in and out of the car all the time.

    If you're thinking of buying a second UMC, just buy the HPWC instead. It's well-built IMHO.
     
  5. Lloyd

    Lloyd Active Member

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    I have both. I charge at 30 amps from my UMC. I charge at less than 40 for less heat generation, and I don't need more for overnight changing. I only use the HPWC occasionally when I need to add some miles quickly, or for guests/travelers wanting a quick charge.
     
  6. dkonigs

    dkonigs Member

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    My house only has 100A service, so I'm using the UMC on a dryer outlet (actual dryer is gas) for charging. I went this route, because installing an HPWC or even a NEMA 14-50 would require more major electrical work than I wanted to deal with right now.
    When/if I find myself living somewhere that has a high enough rated service to support an HPWC practically, I'll probably get one installed.
     
  7. Todd Burch

    Todd Burch Electron Pilot

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    50,000 Model S miles in 2.5 years. I've never encountered a situation where having an HPWC in my garage would have helped me out of a bind--the UMC is enough for almost anyone.
     
  8. m6bigdog

    m6bigdog Member

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    IMHO, the UMC is for occasional charging away from home where there is not a J1772 charger available. Using the UMC for daily charging is tempting fate, waiting for the adapter or receptacle to fail.
    The HPWC has a huge advantage and is all about safety (hardwired & robustness) so it is not just about fast charging rates; as at home/overnight/unattended charging 240V, 20-24 amp charge rate would most likely charge just about any MS to the daily charge limit needs overnight. Either way it is better on the home electrical to not place unnecessary stress on it when 20-30 amps of charge current will do the job just fine. That is, it will require more maintenance to operate the HPWC at 80 amps or the UMC at 40 amps on a NEMA 14-50 for daily charging and the high current charging is of no actual advantage.

    I will leave the HPWC's 80 amp charge rate for the occasional destination (hotel/store, etc.) with a HPWC and an 80 amp service for when it is the fastest charge rate available.
    As for the dual charger? Not much of an advantage for home/overnight charging but irreplaceable for the occasional 15-20Kw destination charging opportunity when you need the faster charging rate and AC is the only service available.
    Of course when on the road nothing is faster than the Supercharger or CHAdeMO DC charging.
     
  9. davidc18

    davidc18 Member

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    I put in a NEMA 14-50 outlet and then wired a 14-50 plug into the HPWC and plugged that into the 14-50 outlet. If the HPWC goes bad, I have the 14-50 as a backup. I don't have dual chargers so the 40 amp max works just fine. We installed the HPWC on the advice of another forum member after he demonstrated how nice it was to have the charger located right at the charging port.
     
  10. ArtInCT

    ArtInCT Always Learning

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    When I have my garage wired for the Tesla, the primary charging outlet will be a HPWC. I will however have one 40 AMP NEMA 14-50 wired as well for a backup outlet should there ever be an issue with the HPWC.

    At present, I am not planning on having a second charger on the Tesla as there are not too many >40 AMP stations in my normal travel area.
    MY typical total daily miles are about 45 on average.
     
  11. jerry33

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

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    I use the UMC. However, I charge at 33 amps so nothing gets too warm. Unplugging only occurs on trips, when there is the possibility that I'll need to charge away from home, or when the car goes in for annual inspection. This means that the receptacle gets cycled 10-12 times a year. Receptacles are good for at least 100 cycles. When I get a spare $750 (plus $300 for the electrician), I'd put in an HPWC for the extra cord length (the sub-panel is already in place) but I'd still charge at 33 amps. (33 was chosen because below 32 is reputedly inefficient compared to above 32.)
     
  12. mibaro2

    mibaro2 Member

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    For the past year, I've use the UMC daily on my 14-50 outlet in my garage. I charge at 33A because I don't need it faster than that.
    I bought my car when HPWC's were still expensive.
    If I was buying my car now, the HPWC's are so cheap now that I would get the HPWC for the look and longer cord. Would still set it to charge around 40amps.
     
  13. TTT

    TTT Member

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    You probably should have used a poll.

    I use UMC at home and charge at 40amps overnight starting at Midnight because I'm TOU (Time Of Use) with my utility company. My Nema 14-15 outlet is very close to my charge port so after every charge I put the UMC back in the trunk so that I won't ever forget it when I go on long trips.
     
  14. mknox

    mknox Well-Known Member

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    #14 mknox, Jun 24, 2015
    Last edited: Jun 24, 2015
    Concur. I use my UMC daily, but am on my third replacement. I was considering a second UMC so I could leave one in the car, but for $100 more, I think I'll go for the HPWC even though I only have a 50 amp circuit in the garage.
     
  15. thedaysbetween

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    +1. Moving to an HPWC (with a 50A breaker) seems like the right thing. I am on my third UMC as well.
     
  16. HankLloydRight

    HankLloydRight Fluxing

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    You mean 10,000s of cycles. I don't know where this rumor started, but these 14-50 and 14-30 receptacles are heavy duty units and can withstand tens of thousands of duty cycles. I'm constantly moving my UMC between my house and my g/f's house and many road trips and have had ZERO problems. If a NEMA 14-50 receptacle failed after just 100 cycles, it's phenomenally defective. Think of all the NEMA receptacles at RV parks -- they are used constantly and not replaced every week.

    This doesn't make sense. If a NEMA 14-50 circuit is properly wired and the main panel can support the extra amperage, there's no "extra stress" placed on the system between using 30 amps versus 40. I don't understand what "more maintenance" would be required charging at 10 additional amps.


    The bottom line is that the UMC is perfectly fine for everyday charging use up to a full 40amps without any added concern. The HPWC has a few benefits over the UMC, but is not required unless you need the faster charging and have dual chargers.
     
  17. jbcarioca

    jbcarioca Active Member

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    True!

    Another option is to buy a Tesla connector to permanently wire into your power source. That will work regardless of voltage or amperage available, up to the HPWC capacity, since it is the same cord and connector. That costs $200 or so. Because my Tesla lives in a multi-unit building I did that just to have the added security that no non_tesla use could happen with my electricity. Certainly unnecessary, but a trifle simpler and more secure than use of the UMC for daily use in a public area. The added benefit is that my assorted connectors remain neatly and conveniently is their bag in the trunk of my car. I would probably not have done a HPC anyway because my car is in the garage overnight and can easily charge with my available 32 amps/208 volts.

    If I had any need at all for faster charging I'd certainly opt for the HPWC, but that is a lot of wiring and installation expense for minimal necessity. If I am in need of fast charging I have convenient access to a CHAdeMO station, as well as Supercharging available for trip topups if needed. It obviously depends on where one lives and the need for faster charging at home.
     
  18. mknox

    mknox Well-Known Member

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    True to a point. Traditionally, outlets like this powered intermittent loads like stoves, RV trailers and such. EVs present a continuous, high current load that can present more of a challenge for loose connections, dirty blades on the plug and so forth. Also, periods of continuous load will generate more heat, and repeated heating and cooling cycles can eventually lead to the connections loosening inside. It's a good idea every now and then to kill the power and check that the screws holding the conductors are torqued down tightly.
     
  19. jbcarioca

    jbcarioca Active Member

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    You are correct, of course. However my own experience suggests it is a good idea to periodically check all electrical connections. Particularly in humid environments corrosion can interfere even with tight connections. Vibration also does the same.

    I'm influenced, no doubt, from having lost important electrical functions on airplanes at inconvenient times. Once when flying a difficult instrucment approach and losing crucial avionics due to water contamination I have since checked my house connections and distribution panels once a year. When having high continuous draw the impact of the heat and cooling will draw excess moisture and loosen connections. The higher the energy load the more such maintenance is required. Not much, but still required. A short or intermittent contact in a HPWC at 80 amps/240 volts is not desirable.
     
  20. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    A big advantage to the HPWC is that if you have a 15, 20, 30, 40, 50, 80 or 100 Amp Breaker on the circuit, you can set the HPWC DIP Switches appropriately and the HPWC will offer 80% of the breaker rating as the available current (12, 16, 24, 32, 40, 64, or 80 Amps). With the UMC, you may need adapters for outlets and breakers other than 50 Amps, and you will certainly need to rely on the car's GPS memory of the correct reduced current at the charger location.
     

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