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Am I good at 32A?

Discussion in 'Model 3: Battery & Charging' started by dankumm, Jun 29, 2018.

  1. dankumm

    dankumm Member

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    Hi All we just got our model 3 and I know it can take 32 amps which is what our Bosch Power Express Charger is set to. Problem is, the charger user manual says 32A charging requires an 8 gauge wire. The marking on the wire is weird and says 3C 10 (AWG) + 3C 18 (AWG). Is this equal to or better than 8 (AWG) as I don't know why they'd split it up like that. I called Bosch technical support who couldn't even verify the gauge of the wire of their own charger but instead said if the car is not complaining and the charger is not tripping a breaker you are probably fine. Sorry but this is outside my comfort zone and rather be safe than sorry so.......am I good keeping it at 32a or should I turn it down to 30 or even lower? Thanks in advance guys!
     
  2. ewoodrick

    ewoodrick Member

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    First, the response that the car not complaining and you aren't tripping a breaker is outright dangerous. The can be the exact way that fires happen.
    So my issue is that Bosch shouldn't be the one whose wire you are reading. What's inside the charger can be different. What's important is the wire size between the charger and the panel. Who put the charger in. It is that company, that installer that you need to talk to.
     
  3. PeterHG

    PeterHG Member

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    You should only accept an answer from the licensed electrician who (presumably) installed your charger
     
  4. nwdiver

    nwdiver Active Member

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    Which wire are you reading? The wire that was installed connecting the Bosch to the breaker or the Bosch to your car? The HPWC cable uses #6 for 80A but needs to be installed with #3 to use 80A. Two different scenarios...

    If your EVSE was built using #10 wire then you're fine. It was UL tested and passed...
     
  5. dhrivnak

    dhrivnak Active Member

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    The short answer is no but you are likely OK. I would double check and make sure whe wire does not get hot. I think the designation is 3 conductors at 10 gauge (power wires) and 3 smaller 18 gauge signal wires.
     
  6. eprosenx

    eprosenx Member

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    It sounds to me like you are looking at the wire that goes from the EVSE (Bosh box) to the vehicle. This will be factory rated to the max rating of the charger itself. It is acceptable for it to be of a lower gauge since it is higher temp rated and it lays in open air - not in the walls of conduit where heat can build up.

    The real question is what gauge of wire is feeding to the Bosh unit from your circuit breaker panel and what size circuit breaker is in that panel?

    To charge at 32 amps you need to be on a branch circuit with a breaker and the wiring rated for 40 amps since electric vehicles are "continuous loads" (so you must calculate the load as if it was 25% larger than it is).

    The wire size required for 40a can depend on a lot of factors, but since 10 gauge is only allowed on 30a circuits, you are forced into 8 gauge wire. Even 8 gauge wire with only a 60c insulation rating is good for 40 amps, so yeah, 8 AWG copper is what I would expect.

    So yeah, I would have zero concerns using the full 32 amps as long as it is on a 40 amp breaker with 8 AWG copper wire feeding it.
     
    • Like x 2
  7. dankumm

    dankumm Member

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    Thanks guys for all the fast and informative responses. To answer all your questions it was actually Bosch who came out and replaced the wire as part of an update a few years back which is why I'm surprised they can't tell me the gauge of the wire they installed. The circuit breaker and wire from the box to the charger is the one thing I'm certain and not worried about as it is on a dedicated 40 amp circuit. To clarify the wire in question and the wire they replaced is the one running from the charger to the car....sorry for not being clear. You are right that is is 3C 10 AWG + 3C 18 AWG. I take this to mean the conductor portion which matters here is 10 AWG and so I suspect this is not the 8 gauge required for 32A per their manual and I should turn the amperage down to 30. If true that irks me because the charger is rated at 32A why would they only give me a 10 AWG wire that can only go to 30A and then tell me that if the 32A setting is not tripping anything I should be fine. Ah well, whats 32 vs 30 amps gonna do for me in the long run. I'd rather not burn my house down. If I have anything wrong please correct my ignorance. You guys rock!
     
  8. iluvmacs

    iluvmacs Member

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    They are only referring to the wire used for installation. Different wire types have different ratings. If the wire they provided is 10AWG, then it is rated (and safety agency certified) for use at whatever max current the controller allows. I wouldn't worry about it.
     
    • Like x 1
  9. eprosenx

    eprosenx Member

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    My apologies, I think you are missing the point here:

    10 AWG on the cord from the charger to the car is nearly 100% positively fine at 32a. The "ampacity" of wire is not only dependent on the wire gauge, but also on the rating of how high of heat the insulation can withstand and how much the cable can dissipate heat. There is no way Bosh would come out and replace your cord with one that could not operate safely at the highest rated ampacity of the charger.

    I am pretty sure what you are reading in the manual is referring to what gauge of wire you need to run to connect the electrical panel to the charger. Since it is either in the wall or in conduit you are not allowed by the NEC to run it as hot as you can the wire from the wall to the car and so hence to keep it cooler they require larger wire. (8AWG)

    You should have no issues running this at the full 32 amps.

    P.S. Feel free to post pictures here of the wire including high enough resolution pictures such that we can read all of the writing on the cable in question. We might be able to go look up the specs for that specific type of line cord and find manufacturers specs that say it is rated to the level necessary to charge at 32 amps.

    P.P.S. The cord to the car getting warm is expected at its max rating, but hot is not ok.
     
    • Like x 2
  10. dankumm

    dankumm Member

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    Thanks again to everyone. Obviously my paranoia due to lack of electrical knowledge and extreme desire to keep the house standing overruled simple logic on my end and I was hearing/reading the wrong things. Re reading the manual after your guidance it all now makes so much more sense!
     
    • Like x 1
  11. nwdiver

    nwdiver Active Member

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    I'd bet the Gen 2 UMC uses #10 wire, it's rated to 32A. Gen 1 could pull 40A and had 2 parallel #10 wires (4 total) which is super-weird but made it much thinner than any other 40A EVSEs...
     
    • Like x 1

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