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Getting a Wall Connector, what Amperage circuit breaker do I need?

Discussion in 'Model S: Battery & Charging' started by viper2ko, Oct 12, 2017.

  1. viper2ko

    viper2ko Member

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    Getting the Tesla Wall Connector. I have a NEMA 14-50 plug installed currently. I am only charging 1 model S. What do I tell the electrician I need, a 40 or 60 amp breaker or higher?
     
  2. Leopold Stotch

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    Calgary, AB
    Uploaded pics from the manual of settings that the HPWC is capable of. Get the biggest breaker size you can or whatever fits your charging needs based on the km/hr chart shown.
    Note* if your panel can not handle a big breaker due to load restrictions. it is probably favourable to get a load sharing device between your tesla and your oven or clothes dryer that automatically stops car charinging when appliance is in use then restarts charge afterwords. This may get you a bigger breaker size for the charger
     

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  3. BrettS

    BrettS Member

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    The wall connector will work with any size breaker up to 100 amps and obviously the bigger the breaker the faster your car will charge, however there are limits. Keep in mind that the charging current will be 80% of the breaker size. So with a 50 amp breaker you will get 40 amps to the car. With a 100 amp breaker you will get 80 amps to the car, etc.

    So the first thing to consider is how much power your car can take. If you have a car with a 40 amp charger, then it’s probably not worth installing more than a 50 amp breaker.

    You also need to consider how much of a load your electrical system will take. Even if your car can take up to 80 amps your current electrical system might not be able to handle that without an upgrade. Your electrician can help you figure out that.

    And finally there is the wiring to consider. You say that you are replacing a 14-50 outlet, which is 50 amps and the wire running to that outlet is meant for a 50 amp circuit. If you simply replace that outlet and use the existing wiring then you will be limited to a 50 amp breaker. If you want to go higher you will need to replace the wiring at a higher cost.
     
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  4. Rocky_H

    Rocky_H Active Member

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    The question is kind of backward. The wall connector is a switchable device that can be run on many levels of circuits, so it's more like pick what size circuit can fit within your electrical system first, and then install the wall connector on that.

    As @BrettS mentioned, this is really easy to put on the line you already have. You already have a 50A sized circuit there. Just remove the outlet from it, cap off the neutral wire, which isn't used by the wall connector, attach the wall connector to the remaining three wires, and set the switch inside for a 50A sized circuit.
     
  5. arcus

    arcus Member

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    It's worth mentioning that you will also be limited by the charger in your car (48A for single, 72A for dual charger). So unless you are planning to make this installation future proof (2nd car?) it won't be cost effective going for any breaker > 50/60A if you have a single charger in your car.

    If you are planning to expand in future (Model 3 perhaps?) it would make sense to invest in higher rate of breaker to facilitate second HPWC in a master/slave configration. They will "talk" to one another and share the same circuit.
     
  6. comanchepilot

    comanchepilot Member

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    The size of the breaker is irrelevant - the size of the wire is the limiting factor.

    The rated current capacity of the wire going from the panel to the plug / EVSE is the controlling limit- not the breaker.

    Remember- most modern homes have a 200 amp supply, if you are running a 60amp breaker to a 60 amp line to a 48 amp constant load you're taking away 30% of the available current in the house.

    Think what else might kick on -

    You have a 50 amp AC system
    20 amp pool pump
    20 amp regrigerator
    30 amp clothes driver / range or stove

    and you are at 180amps peak which far exceeds the sustained limit of your panel - and means you turn on a couple of computers, large screen TV's and a stove etc etc etc, i.e., normal household load, and you're gonna blow your main breaker.

    Many older house are 100 or 150 amp service.

    You can't just toss on a higher breaker and have it work at the higher current level.
     
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  7. Rocky_H

    Rocky_H Active Member

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    That was a little hard to follow, as your first two sentences went with your last one about breaker and wire size, but then everything in the middle was about capacity and load calculation for your house.
    I disagree where you say "The size of the breaker is irrelevant - the size of the wire is the limiting factor." They're both part of the same thing. You need to have the breaker and the wire both sized properly for what level of circuit it's supposed to be.

    I do have a smaller-ish house that has a 125A main panel. But part of the load calculation is that you can allow some loads to be either/or if they are going to generally not going to be run at the same time. I am not going to be running my stove/oven after 1AM, for instance, so it doesn't have to be added along with the car charging circuit, which runs overnight during that time. Load calculators can be found online that can show how that stuff works.
     
  8. comanchepilot

    comanchepilot Member

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    @Rocky_H - I was responding to the question asked - not to electrical code rules in general.

    The OP asked what amp breaker he should put in - period.

    My response was that the breaker size will be dictated by the gauge of wire going to the plug, unless he wants to pull new wire.

    If he has standard Romex for 220v he's limited to a 40 amp breaker.

    If he has bigger wire going to the box, he can go up to his 60 amp size.

    You seem to understand about this - so why am I having to explain myself?

    As for the load discussion, I was providing an explanation as to WHY you may not be able to put in a 60 amp breaker. Or why it would not be advisable anyway.

    You know that you are not supposed to running an electric stove after 1a when the car is charging. Exactly what percentage of the population has ever done a load analysis? Or even knows? I dare say as the millennials get older there will be more electrical problems because they don't have a clue about this stuff.

    I'm in the same position you are in - I've got a 2800 square foot house built in 1971 with a 125 amp panel.

    I replaced a working 9 seer HVAC system with a 14.2 seer system that has a starting load of only 40 amps and put it in on my old 50 amp breaker because we have a 40amp J1772 EVSE for the B class. Part of the reason was to free up the ability to charge the car and have AC at night - here in my part of SoCal when you NEED AC at night - you need AC at night. Maybe total of 20 nights a year - but when you need it - its damn hot.
     
  9. Rocky_H

    Rocky_H Active Member

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    Ah, because your whole answer went on the assumption that it was going to use the existing wire run in the place where it was without actually stating that, and which the OP didn't exactly state either, whether he wanted to use that wire or just put in a new circuit. Your further explanation makes sense now if you take the existing wire as a given.

    The electrician will do the load calculation anyway, so it will be done, even if most homeowners know nothing about it. I was just giving the tip that the person can go ahead and pre-check on that ahead of time if they want, rather than having to wait and find out about it later from the electrician or just be wondering what they can or can't do. The person is here right now asking questions to get this information. Why should we hide the information about load calcs, which they can do ahead of time to be more prepared in deciding what they want to do? Forewarned is forearmed.
     
  10. Moshne

    Moshne Member

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    The variable settings on the wall connector are irrelevant if Los Angeles. You didn’t mention where you are, so it’s worth having your electrician double check the code. We installed my wall charger on a 50A circuit and the city inspector wouldn’t approve the install. Their read of the code is that because the device can utilize 80A, it has to be wired for it, regardless if you internally throttle it to 40A.

    It’s turning into quite the headache, as it’s not quite as simple as changing the wiring. I live in a condo with a relatively low service amperage to my unit so adding a dedicated 100A line for it isn’t possible without installing a new line off the common power.
     
  11. RScottyL

    RScottyL Member

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    LOL, my house was built in 1968, so as you can see, when I get an electric vehicle, I will definitely need to upgrade my main service panel!

    2017-10-14 17.42.00.jpg
     
  12. davewill

    davewill Member

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    I don't usually recommend such shenanigans, but in your case, I'd be tempted to put a 14-50 or 6-50 receptacle on the wall and tell the inspector you're going to use the mobile connector... Then put the appropriate plug on the wall connector and plug it in.
     
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  13. tls

    tls Member

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    This is not the right way to think about load at a service entrance / main panel. To get to "180 amps peak" you totalled a bunch of non-continuous loads, then added a 60A charging circuit as if it were actually drawing 60A rather than actually being a 48A load with a 60A breaker and wiring due to the continuous load rule. And you still came out lower than the 200A rating of the service/panel, even for this notional "peak" load.

    What that should have actually quite amply demonstrated to you is that all those loads fit in a 200A service with plenty of room to spare.

    Many have done it; it's legal; it's safe; if you sit down with one of the actual worksheets used to size electrical service for residences and total up the loads properly according to the instructions on the sheet, you'll see it's fine.

    The real question is, how fast does the OP want to charge? Unless his car has dual chargers, there's no reason to set up the HPWC for more than 48A -- 60A breaker -- or even 40A. These loads will fit on the 200A service of most homes without trouble, unless there has been another major retrofit such as multi-zone central air, electric heat, or a kitchen conversion from gas to electric since the service was sized and installed -- and often even then.

    If dual chargers are involved, though, there's more of a real question, since you're talking about adding 70-80A of load, on a 90-100A breaker according to the continuous load rule. I would personally recommend running through one of the load-calc worksheets you can find online (treat the EV charger as a "continuous" motor load if the worksheet doesn't know about chargers; it will scale such a load by 125%).

    Look at the numbers you get out, then consult an electrician. You can have a conversation with him or her starting from a well-informed position, rather than in a vacuum.

    For what it's worth, I was able to add *two* chargers -- a HPWC on a 100A breaker, and a J1772 charger on a 30A breaker in a more convenient location -- at a property with 400A service for two detached houses, a jacuzzi, a pool, and electric laundry and kitchen equipment in both buildings. It worked out fine on the load-calc sheet, the electrician had no problem with it, and we've never had an issue.

    Not even with two of us charging, on Thanksgiving day, with both ovens broiling away, a load of clothes in the dryer, and the kids leaving the fridge door open all the time. Very few loads are truly continuous.
     
    • Informative x 1
  14. Julie's MS

    Julie's MS Member

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    Mar 6, 2017
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    Location:
    Ottawa
    A load Miser might be worth considering instead of upgrading your service to your house and your main service panel.

    D-LM

    I came across this article online which explains how it works. I am sure there are also other companies making these Load Misers.

    Dividing available energy from your electrical panel

    ;)
     

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