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HPWC Failure - melted wire.

Discussion in 'Model 3: Battery & Charging' started by dwalme, Oct 11, 2019.

  1. dwalme

    dwalme Member

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    Last night I plugged in my Model 3 around 50% battery like I do each day (charge to 80% daily).

    Went to go to work this morning and I notice I'm at 28% battery. I see the HPWC has no power. Breaker is on but nothing from the HPWC. So I take my Jeep to work and deal with it later.

    Tonight I open up the HPWC to see that one of the hot wires is completed melted through the jacked all the way to where the wires enter the HPWC. The breaker never tripped at the panel and the wire seems to be ok just inside the conduit and at the panel side.

    Wire is THHN 6 Awg and 25 feet from the panel. I charge at 48 amps each day and the HPWC was installed in May.

    Anyone else see this before? Any thoughts to what might have caused this?

    Car seems ok, but I haven't driven it yet. I've been charging on 120v 12amp mobile connector.

    IMG_20191011_200633a.jpg IMG_20191011_200812a.jpg IMG_20191011_202351a.jpg
     
  2. GHammer

    GHammer What a long strange trip its been.

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    Having installed three of these, I can tell you the wire clamps in the wall connector are a little tricky. It's possible the wire was inserted on the wrong side of the clamp and wasn't fully torqued to the wire.
     
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  3. ucmndd

    ucmndd Well-Known Member

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    Judging from the melted plastic on the failed wire and the amount of insulation stripped from the “good” one, you had insulation pinched in the terminals, creating a bad connection that eventually failed.

    When you fix it, do two things.

    1) strip the wire down farther
    2) Use ferrules
     
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  4. dwalme

    dwalme Member

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    Thanks for the tips.

    I don't see how the wire could be on the wrong side of the clamp. I'll have to look closer at it. They were both clamped in tight.

    I agree the jacket wasn't stripped back as far as it could have been. I'll make sure to strip it back further next time.

    Any thoughts to whether the wall connector is still good? None of the wall connector wires seemed to be impacted other than a small burn mark on the ribbon cable for the cover lights.
     
  5. GHammer

    GHammer What a long strange trip its been.

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    I've seen a couple of threads on this issue, I can see how it happens.
    HPWC Self Install: Terminal block not gripping the wires? WTF?
     
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  6. eprosenx

    eprosenx Active Member

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    Yes. This is a classic failure mode for poorly terminated wires. Either the wire was on the wrong side of the clamp or it was not torqued down properly or insulation was caught under the clamp and so it was not making good contact.

    I have the exact same wire size and setup and mine is flawless.

    It is hard to say if the Wall Connector is damaged or not. Clearly what happened is not good and a lot of heat was generated! The “safe” answer here from a liability standpoint would be to say to replace the unit. Though given the cost, I might inspect everything really carefully and contemplate attempting re-use.

    I am kind of surprised that the Tesla did not detect this and back down the charge speed due to voltage drop. I am guessing it was just under the threshold and that with your setup there was nearly zero other voltage drop from long wire length etc...

    Also, it would seem likely that the Wall Connector does not have any internal thermal sensors to detect things like this. Good to know.

    Note that I think this is only the first or second time we have seen Wall Connectors fail like this. They are generally pretty rock solid!
     
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  7. Evbwcaer

    Evbwcaer Member

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    I'm not an electrician... I had some corrosion on my 14-50 connections. I still don't understand why, the outlets are totally dry and indoors. Anyway, I suggest putting something like OxGuard on the connections to help prevent corrosion and promote conduction. After cleaning off the corrosion and applying OxGuard, my connections are now cool.
     
  8. mswlogo

    mswlogo Well-Known Member

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    Exactly. I’ve installed two myself.

    They are a bit “blind” to install and not the best design to help installer cross check they are stripped just right and fully seated in.

    Now that mine (and a friends I installed) has been in for 9 months it probably wouldn’t hurt to double check tightness. Sometimes the wire under the lug can settle and effectively loosen from even small temperature cycles.

    This is not the first example of one cooking like that either. It is the fault of the installer ultimately, despite a less than ideal design.

    Overall the unit is very nicely built though.
     
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  9. ajdelange

    ajdelange Banned

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    It's a good idea to take a picture of these things from time to time with an IR camera while under load, of course. If you decide to reuse this unit definitely do this as given the evidence of the wire it's pretty clear that the terminal got pretty hot too.

    And it's probably a good idea to check terminal screw torque from time to time too.
     
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  10. mswlogo

    mswlogo Well-Known Member

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    You should not need anything on Copper only setup. This was very unlikely corrosion.

    If you used aluminum (which I would avoid on a 14-50 outlet) you must use anti oxidation. And you need to make sure the outlet is compatible. If you used copper it shouldn’t be corroding that fast if conditions are dry as you said. Something sounds a bit off if it was corroding dry with copper.
     
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  11. mswlogo

    mswlogo Well-Known Member

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    #11 mswlogo, Oct 12, 2019
    Last edited: Oct 12, 2019
    If not to late can you post a pic of the end of the black wire?

    Also the white wire (with no load BTW) looks suspicious. What caused that impression on the insulation? It’s a hint that it wasn’t stripped back far enough. I forget how that is clamped down. But the clamp might be on the insulation. Bad.

    Was this DIY or licensed electrician?

    Nothing wrong with DIY install. Proper enclosures and breakers are your safety. And end pro’s make mistakes.

    EDIT: The Neutral was capped with a wire nut. Forgot it’s not even hooked in. So that’s fine. Still like to see the end of the black wire.

    You could legally use the Neutral for the burned out hot Red. Just mark both ends with black tape. And remove the red burned one or cut it short. Try to verify black was not damaged though. Depends how long the run is. You could pull all wires a foot out or so to inspect then pull them back.

    It’s are to know if Wall Connector is damaged though. And it will be very vulnerable to good contact. After cooking and possible melted plastic in the lug. Not easy to clean.
     
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  12. Teedub21

    Teedub21 Member

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    Those wires are a PITA to get in there correctly. We used 4awg on mine and it took a few attempts to get those wires seated properly. It really isn’t a good design from an install point of view.
     
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  13. ajdelange

    ajdelange Banned

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    That's an excellent suggestion but as the white is being used in place of the red conductor it should be marked with red tape.
     
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  14. mswlogo

    mswlogo Well-Known Member

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    Marking Red or Black doesn’t matter. They are being marked as “hot” (not neutral) I believe is all that’s required. If you like red, go for it. Red and black are completely interchangeable on either end. In fact, personally, marking red would confuse me, because it’s trying to tell me that it’s not just another hot and needs to be treated special. Black just says I’m hot just like the other black ( and interchangeable).
     
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  15. Evbwcaer

    Evbwcaer Member

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    I have copper wire torqued into a copper fitting (by "fitting" I mean the female receiver for the male blade). Only on the black wire was there any corrosion, white/chalky with a hint of green. All other connections looked clean/shiny/dry. I don't understand the chemistry.
     
  16. ajdelange

    ajdelange Banned

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    I'm not sure what the code would say about that and as I don't have it with me I can't check. A bit of research on the net indicates that the NEC is pretty free about how wires are colored with only a requirement that neutral be white and ground green but cautions that local codes may have the specific color requirements of earlier editions.

    Thus we rely on common sense. The cable OP is repurposing had red and black conductors. Those are industry standard for two hots. Throughout my houses red indicates one phase from the transformer and black indicates the other. If I see two black wires I assume they are on the same phase and thus would expect them to be at the same potential. Same with a pair of red or red marked wires (I have lots of those in metering, transfer switch, generator, load shedding etc panels as they are often wired with black wire off the spool rather than a cable with conductors with different color insulation). Certainly in the current situation I would not be confused as there are only two feed conductors coming but my question remains as to why you would suggest going against standard practice here.
     
  17. Wennfred

    Wennfred Supporting Member

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    I see you’re charging at 48 amps, I believe the cap is 44amps for the LR M3, what size Circuit breaker are you running?

    Fred
     
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  18. Wennfred

    Wennfred Supporting Member

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    1954227C-F516-499D-A8B5-4E053684BCFD.jpeg
     
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  19. SilverSp33d3r

    SilverSp33d3r Member

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    I know you said you charge at 48 amps but what size breaker is installed?
     
  20. GHammer

    GHammer What a long strange trip its been.

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    By your posted chart you can see 48 amps is the max.
     
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