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Melted EVSE Disconnect Switch

Discussion in 'Technical' started by woof, Dec 21, 2014.

  1. woof

    woof Model S #P683 Blue 85 kWh

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    Three years ago when I had an EVSE put in the garage, the installer put an "Air Conditioning Disconnect Switch" directly above the Aerovironment EVSE. I'd never seen that before, but it was handy as the breaker was all the way on the other side of the house in the basement.

    Well, today as I was charging my i3 I was greeted with that wonderful "melted plastic" smell. It took me a while to figure out what was melting (I assumed it was the i3!) but eventually discovered I was unable to pull out the disconnect switch. After much effort to pry off the plastic covering (which it turned out was melted into the switch) I was greeted with the following mess:

    IMG_1002.jpeg
    So the EVSE is out of commission until I correct this.

    I'm not sure what went wrong here as the switch is rated for 240 VAC at 60 Amps. The breaker is 40 Amps, and the EVSE never draws more than 30 Amps. The EVSE never stopped working but I obviously decided to remove the switch for safety.

    So now I have a covered box above the EVSE, and some burned wires that need to be trimmed back.

    What would be the best way to get the EVSE back in service? I'm thinking wire connectors of some type to bond the wires together. I'm loath to install the same type of switch, although that would be easiest as the box is fine and good to go.

    Ideas?

    IMG_1006.jpeg G84-940cl.jpg
     
  2. tezco

    tezco Sig P85

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    I suspect the terminals weren't torqued to the proper specs. You may need some sort of disconnect to meet code if the EVSE isn't within sight of the breaker.
     
  3. kennybobby

    kennybobby Member

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    #3 kennybobby, Dec 21, 2014
    Last edited: Dec 21, 2014
    Notice the wide gap of the sliding blade contacts of the two right-most terminals, which have lost their spring tension and ability to make an electrical contact. i have seen this numerous times in main service terminals behind the meter.

    The blade contacts are likely made of tin-plated copper bent to pretend to be a spring and provide the clamping force on the blade. High currents cause the connection to get warm and the copper expands and tends to unroll back to it's original flat shape before it was formed (copper is not a good spring material).

    After many cycles the gap of the spring opens such that there is only a few contact points and lots of arcing, which results in a higher resistance junction, which results in even higher temperatures in the joint, and then more expansion, and wider gap, etc. until the end result is smoking and burnt insulation and plastic such as you have found.

    Sliding electrical contacts such as spade lug terminals are also notoriously prone to failure such as on motorcycle rectifier/regulator units used with 3-phase alternators. My rule of thumb is to avoid sliding electrical contacts in AC systems whenever possible or check them often.

    i couldn't find a datasheet for the eaton cutler ACD to determine the actual terminal material, but their documentation does show it with a 60 Amp rating, but for 240vac it uses a max hp rating of 10 Hp. That equates to only 7460 watts and cuts the current down to ~31 Amps. So the knife blade contacts may be too thin for your application.
     
  4. woof

    woof Model S #P683 Blue 85 kWh

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    Thanks for the help guys.

    I saw that "10 HP" rating and thought it quite strange. Why rate something at 240V/60A but then say "just kidding"? The i3 can only draw 6.6 kW max anyway, so it happens to be under that 10 HP rating. I went to Home Depot looking for a replacement...they didn't have the Eaton one, but had a GE one that seems better built. However, I cannot use it as it didn't have knockouts on the top where steel conduit enters the existing box and I'm not up to that level of rework.

    I think I'm just gonna replace the whole thing with a terminal block...any reason I shouldn't do that?

    Also, does anyone have a good suggestion for a tool for stripping the massive hard coated wires in there? No wire stripper I've got comes close and I don't want to nick the copper with the wrong tool.
     
  5. tom66

    tom66 Member

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    10 HP is probably the interrupt rating. Switches are rated by interrupt power and continuous load current...
     
  6. nwdiver

    nwdiver Active Member

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    I use box cutters to strip large gauge wire. Just wear gloves and keep the wire between your fingers and the blade.
     
  7. mitch672

    mitch672 Active Member

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    you can get barrel connectors at Home Depot to handle that gauge wire and just connect L1 Hot to L1 Hot, and L2 Hot to L2 Hot... or get yourself a "unibit" and drill out the hole you need, or let me know what size the conduit is, I have a set of Greenlee knockouts punches in the basement... still requires like a 1/4" or 3/8" pilot hole though.
     
  8. woof

    woof Model S #P683 Blue 85 kWh

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    Okay, job complete. It only took:

    3 trips to Home Depot
    5 hours of internet research for tools and techniques
    4 Advils
    2 "AC Disconnect" boxes
    4 "splice connectors"
    8 heat shrink tubes (various diameters)
    1 cramped hand
    1 cut finger
    (unknowable) swear words

    My first attempt was to use the GE disconnect box (with no knockouts on the top), but after thorough investigation realized that even if I made a hole as Mitch suggested there was no way to route the wires from the top due to the placement of the disconnect mechanism. So, then I got a replacement Eaton box, with the idea of just replacing the melted disconnect parts. This would have worked but by the time I cut out all the burned out pieces of copper wiring there wasn't enough length to wire it (well, a pro probably could have, I couldn't). So, plan C (as suggested by Mitch) just splice the darn wires together. This was harder than it should have been. While there are a zillion ways to join electrical wires together, once the wires get bigger and the currents higher the choice of connectors goes south. Finally found some "splice connectors" which is just an aluminum tube with set screws. Insulating them was tricky, but I finally settled on heat shrink tubing. The back and forth on the 'net about if that's UL safe or not were just astounding, almost as bipolar as the discussions on is the Volt a real EV. But I digress. After finding some (outrageously priced) UL listed "splice kits" that are just the same aluminum bar and some heat shrink tubing, I decided it was good enough for me.

    In the electronics lab, on a bench top, I'm pretty good. I can wire and build stuff rather well. But in the garage, with crappy light, standing on a ladder, working in a tiny metal box that kept falling closed on my fingers...just trying to connect 4 thick wires together...let's just say I'm the worlds most expensive electrician. I bought 4 times the materials needed and took many more hours than the job called for. I'd have fired myself if I had hired me.

    But it works!
     
  9. kennybobby

    kennybobby Member

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    Haha, you have fallen victim to the 3-trip rule of DIY home projects. Doesn't matter what the project (electrical, plumbing, etc.) you will end up making 3 trips to home depot, usually over the weekend with the last trip late on sunday afternoon.

    First trip to buy all the parts and supplies you need, the second trip to exchange a wrong size part or buy something that you forgot, and the third trip to buy the part again after it breaks while you are trying to install it.
     

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