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HPWC - Safety Advantages?

Discussion in 'Model S: Battery & Charging' started by iadbound, Jun 28, 2014.

  1. iadbound

    iadbound Member

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    I've been reviewing the HPWC sticky and searching about the forum, but I can't seem to find the exact answer to my question. I recall that the Wall Connector had some safety advantages over the UMC+14-50 combo. Could anyone (FlasherZ?) enlighten me on this issue? I'm leaning Wall Connector just for the finished look, permanent installation, and faster charging, but I thought there were some safety benefits too. Thanks.
     
  2. 100thMonkey

    100thMonkey Member

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    I use the UMC-14/50 combo daily without issue, but I am cautious on the occasion that I plug and unplug it, that's where a potential safety issue could be, you are coming close to live 240V's with some arcing potential. the HPWC is hardwired, eliminating that potential contact point. at the car plug end, both the UMC and HPWC are protected, meaning they only become live when they are plugged into the car. If you imagine wanting to plug and unplug the UMC a lot to take it with you, then it's more of an issue, mine stays plugged in for weeks and months at a time.
     
  3. tga

    tga Active Member

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    I don't think unplugging a 14-50 is really any more dangerous than unplugging a regular (5-15) plug. In both cases, there's a slight risk your finger could "sneak around" the edge and contact an energized 120V blade, but you need to be pretty careless/sloppy to do that. Remember, each hot on a 240V circuit is 120V with respect to ground (and, by extension, your body). The size of the breaker is really immaterial to the risk, since even a 15A non-GFCI breaker won't save you from getting zapped.

    Now if we're talking about unplugging a circuit under load (ie, while charging), than yes, the 14-50 would arc more. But you really shouldn't do that, except in an emergency (like something at the other end of the cord is on fire or electrocuting someone).
     
  4. JPP

    JPP Active Member

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    FWIW, I own 2 NEMA 14-50 adapters for my UMC. I leave 1 plugged into my NEMA 14-50R on the wall, and do my disconnect at the UMC connector. I keep the 2nd adapter in the black bag for the UMC. I do not believe that the NEMA 14-50 is rated for lots of insertion/removal cycles, and would rather have the wear and tear be at the UMC/adapter level, easier for me to repair/replace without getting an electrician out.
     
  5. iadbound

    iadbound Member

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    Thanks for the replies. I was thinking that the HPWC had some fault tolerance, testing, etc. that the UMC didn't have.
     
  6. jerry33

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

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    This is about reliability in general. I don't believe there is much danger in plugging and unplugging the UMC.

    The main differences are that there is no adapter on the HPWC, and it's hardwired. This makes for fewer places to have problems. The math works out like this:

    If each connection has a 1% failure rate (assumption), then the HPWC has four (breaker to wiring, wiring to HPWC, HPWC to cable, cable to connector).
    The UMC has eight, (breaker to wiring, wiring to receptacle, receptacle to adapter, adapter to connector, connector to cable, cable to GFI, GFI to cable1, cable1 to connector1).

    0.99[SUP]4[/SUP] = 96% reliable
    0.99[SUP]8[/SUP] = 92% reliable

    However, the UMC's failure rate is more likely to be 2% rather than 1% due to the portable nature of the UMC.

    0.98[SUP]8[/SUP] = 85% reliable. This number seems more in line with the reports (and yes, I realize that some of the connections, such as breaker to wiring, would have the same failure rate regardless of whether it was a UMC or HPWC.)
     
  7. rapoport3a

    rapoport3a Member

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    Just make sure you have a good HPWC. There are reports of faulty ones overheating. Not in large number, and not causing a fire, but something producing high temperatures at a junction, in which cases Tesla has replaced the unit.

    Because we had to upgrade our service from 100 amps regardless, we decided on the HPWC over the 14-50, partly because we get a government rebate for the HPWC which almost covers its cost (but none for the 14-50).
     
  8. iadbound

    iadbound Member

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    Thanks for the heads-up. The electrician I selected is actually the go-to guy for our local Tesla service center -- he troubleshoots home charging issues for them. So hopefully I won't have to worry about the actual install, but a bad unit will obviously be hard to spot in advance.
     
  9. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    #9 FlasherZ, Jun 30, 2014
    Last edited: Jun 30, 2014
    Most people have covered the main points, I think. The HPWC is UL listed as EV supply equipment, and the J1772 adapter is listed as an electric vehicle plug/receptacle/couplers. The UMC is not listed, although we don't know why -- it could be that the appropriate UL standards aren't defined, we just don't know. Having it listed just means it was tested by a lab to meet certain specs in the category it is listed. I could probably get the UMC listed as a "safety power unit", but that doesn't really mean much. While I have some concerns about the adapters used on the UMC, it seems like Tesla has addressed those with the new rev of adapters (I have yet to hear of a failed / melted new adapter or charging cut-offs / problems using the new adapters).

    Personally, I like the construction of the wall connector much better than the UMC, but I can't quantify the safety aspects of it. The biggest issue for me was having a single UMC and needing to wrap it up any time I knew I'd need it on the road. That could easily be solved by purchasing a second UMC, though.
     
  10. iadbound

    iadbound Member

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    Thanks. I know you have devoted a lot of time to charging issues. It sounds like the HPWC is a winner, but that the UMC has also improved. My electrician has nothing but good things to say about the HPWC as well.

    My order finalizes today, and I've got the HPWC and dual charger in the configuration. I think I will stick with it.
     
  11. tliving

    tliving Member

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    If its for looks thats one reason to get it but its a lot to pay for looks. I drive 100 miles a day and my car is fully charged up before I go to sleep on a NEMA 14-50. While I don't use the dual chargers for normal charging I think they're a better investment than the HPWC. More thoughts here:
    Charger Confusion | Tesla Living
     
  12. iadbound

    iadbound Member

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    The finished look is nice. I'm also taking advantage of time of use pricing (4 hour window at just under 6 cents per kwh), but it will take a while to recoup the costs of the equipment. As for costs, they are considerable because I have to replace my main panel because it is an older, unsafe model. Given everything I've got to do, I decided to max out the charging options, including doing some future proofing, HPWC and 14-50. The 14-50 will also act as a backup or future charger. My wife also encourage me to maximize my charging options, just in case. Frankly, if I had not needed to do all of this other work, I would have just run one 14-50.
     

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