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What's amperage do I have?

Discussion in 'Model 3' started by elechead, Aug 10, 2017.

  1. elechead

    elechead New Member

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    I'm doing a cost planning for a potential Model 3 and it just hits my head that my home electrical system may not be ready for it. Here's my electric panel. At the top (half hidden in the photo) are 2 switches with the label 100 on them. Does that mean it have enough amperage for a future High Power Wall Connector?

    2017-08-10 18.26.40.jpg
     
  2. astrothad

    astrothad Member

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    This likely means you have a 100-amp panel. Ask an electrician for a professional opinion, but I highly
    suspect you will need to upgrade to a 200-amp panel if you want to charge with anything more than
    110V or 120V charging (3-4 miles of range per hour). I think even 3.3 kW (beginning of level 2) charging
    would be pushing it with only a 100 amp breaker between your panel and the grid.
     
  3. CmdrThor

    CmdrThor Active Member

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    I would not suggest using both stoves, your A/C, and dryer all at the same time .. You definitely need to have an electrician do a load calculation and by the looks of it I don't think there will be a lot of capacity.
     
  4. hmcgregoraz

    hmcgregoraz Member

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    I count up 290Amp at 240V worth of breakers in that panel. The single 15s count for 1/2, while any double, 15, 30, 40, etc count at full size.

    If you really have a 100 amp main breaker (2x 100amp, one on each HOT leg), you may not have enough capacity to put much in for charging.

    There are a few questions/options. Get a decent electrician in to do a load analysis, including properly setting up a recording amp meter on the mains, and getting days/weeks worth of data.

    Sizing upgrading to a 200amp panel and service (probably not cheap, but not too expensive either). This would be more of an investment in the house, depending on what you may want to install in the future (hot tub, etc).

    Based on the labels, the largest breakers are:

    left, 29/31, 40amp - lower stove
    left, 25/27, 30amp - Air Conditioner
    right, 26/28, 40amp - upper stove
    right, 20/22, 30amp - Dryer

    Each of these can burst to near the full load, but really should not draw a load beyond 80% of the breaker for a long time, and even that would be unusual, considering your not tripping your main right now, we can safely assume they are not all pegged at 80%, as that would be 112amps by itself.

    The 4 15amp 240v confuse me a bit, as they are labeled for "plugs" mostly, but that would normally be 120v in the US and Canada.

    So for the load analysis, you can figure if you will be charging your car, when your also cooking in both upper and lower stove, drying a load of laundry, and have the air conditioner running. The load analysis may let you install a 30amp breaker and 30amp outlet (14-30R), which would draw at most 24 amps for the car. I can't see being able to fit a 40 (Canada) or 50 amp breaker for an 14-50R outlet, and charging at 32/40 amps.

    You could also consider getting a dryer buddy, and have it setup so you can either charge or use the dryer, but not both at the same time, which would also let you charge at 24 amps, and would do well. This would probably be cheaper, depending on locations, but less of an investment in the house as a 200 amp service upgrade, or even a dedicated 14-30R

    -Harry
     
    • Informative x 2
  5. 03DSG

    03DSG Member

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    You probably have a 125 amp panel with 100 amp service. You may want to upgrade to a 200 amp service. That way you can have a 60 amp breaker to supply the HPWC and use the max 48 amp onboard charger. If you need fast charging. If not you will have a Nema 14-50 that in the US can supply 50 amps. Still need the panel upgrade unless your stove and clothes dryer are age.
     
  6. 03DSG

    03DSG Member

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    I just got a quote in Cobourg, Ontario. Reason
    Reasonable.
     
  7. elechead

    elechead New Member

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    Thanks you for your reply. I will inspect the meter outside the house tomorrow. I'm estimating all the costs involving in getting a Model 3. If things look reasonable (including a potential upgrade to the the electric system), an electrician will definitely be next. Just for my curiosity: what prompted your suspicion about the power capacity? I have turned on the A/C, stove and dryer at the same time before without issues.
     
  8. hmcgregoraz

    hmcgregoraz Member

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    Using one stove, the dryer, and the AC at the same time is at most 80 amps, but if you step back a minute, think about it this way.

    When your dryer is running, is the heating element running 100% of the time, or does it cycle on and off to get the right temperature? When your stove is running, is it running the heating element 100% of the time, or does it cycle on and off to get the right temp?

    Basically, just like adding users to the same amount of Internet bandwidth, devices tend to share power well, if they cycle. If they are a constant load, they don't share quite as well.

    Charging a Model 3 will run at what ever rate it can (or is set to) until done (maybe a bit of a taper at the end), so on a 30amp breaker, it will pull 24 amps, so the 30amp breaker means a bit more for an electric car, then it does for a dryer.

    -Harry
     
  9. Thomas Edison

    Thomas Edison Member

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    #9 Thomas Edison, Aug 10, 2017
    Last edited: Aug 10, 2017
    You shouldn't worry that it means you can have a safety issue. If overloaded the main 100amp breaker will just flip and the whole house will shut off. Then you know you turned on too many things at a time. If you set your car to charge over night with a nema 14-50 then you should be ok.

    Edit: When you have all that stuff turned on that you mentioned, you should go to the panel and listen for any buzzing sounds.
     
  10. Rygnerik

    Rygnerik New Member

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    Those might be separate 15 amp 120v circuits. If you have circuits with a shared neutral, you want them on common-trip circuit breakers, so you can't end up in a situation where you've got hot wires running through a junction box that you think the breaker is turned off.
     
  11. david_42

    david_42 Member

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    "The 4 15amp 240v confuse me a bit, as they are labeled for "plugs" mostly, but that would normally be 120v in the US and Canada."

    I've seen installations where the top and bottom outlets are separated, so you can pull 30 amps from one box.
     
  12. hmcgregoraz

    hmcgregoraz Member

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    That would make sense. That would be good for load calculations as I highly doubt that the outlets are really going to pull 2x12 amp or 2x15 amp. Maybe bursts like a high wattage microwave oven and a toaster oven at the same time.

    I have seen some places that wire like that, just not much where I have dealt with home electrical. Plus I tend to deal more with 240v 3 phase, and 240v single phase for high end IT equipment.

    -Harry
     
  13. tga

    tga Supporting Member

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    Yep, that's what's going on. It's called a "multi-wire branch circuit", aka "MWBC", commonly used for kitchen outlets, where you're running two circuits to the same location. You can run two circuits with a single piece of 3-wire romex, saving money on wire and labor. The 2 circuits are powered from opposite legs (hots) and share a common neutral. The neutral winds up carrying the difference in load between the two circuits. So if you draw 12A @ 120V on one circuit, and 7A @ 120V on the other, the neutral carries 12A-7A=5A. The breakers need to have a common trip (the handle tie) per NEC.

    To the OP's question - don't worry about it. You don't automatically need a service upgrade. I have 100A service, electric stove, dryer, and well pump (but no A/C). I charge at [email protected] on a 14-30. If you use delayed charging to charge at night, nothing else will be running, anyway (except for maybe your A/C).

    I may upgrade my service when I build the big garage addition, but I'll be doing a bunch of electrical work anyway (lift, compressor, etc), and I'll be moving the service entrance to the new garage, so I might as well upgrade it during the move. Plus, my inner Tim Allen wants to be able to charge at 80A...
     
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  14. gregd

    gregd Active Member

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    Is your Dryer within reach of the car's likely parking place? If so, you can charge from the dryer plug by using a "Dryer Buddy". That will prevent you from using both at the same time (which would be too much for the circuit), and save a bunch of money. Otherwise, I would suggest the upgrade, as your panel is probably at capacity. Mine was similar (125 amp service, feeding 2 A/C units, and the dryer, plus the normal plugs and lights), and the electrician said it was full.

    You didn't note the age of the house, but you might want to look up the brand of panel that you have. I found out that mine was no longer being sold, because they had a tendency to "fail", as in "catch fire". Zinsco brand, but there were others. That made the decision to upgrade the panel really easy. Google search for "Is my <brand> panel safe?".
     
  15. SoundDaTrumpet

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    #15 SoundDaTrumpet, Aug 11, 2017
    Last edited: Aug 11, 2017
    I am going to ask the OP this specific question: Is the clothes dryer gas or electric?

    I mention this because it sounds like you have natural gas (NG) available from reading your post: (1) no electrical heaters circuits shown, furnace circuit shows 15A; hence, fuel burning heating, (2) no electric water heater circuit shown, and (3) you are from a northern climate. You do have electric stove/cooktops though, but NG plumbing to the kitchen may not be in fashion at the time the home was built.

    If you have a gas dryer may explain why you aren't popping your main breakers. My home has both hookups for natural gas and electric dryer (NEMA 14-30 receptacle). (This is not to be confused with the regular wall plugs for the washer and dryer on a separate laundry circuit.) Since I use a gas dryer, I automatically gain 30A available for my electric vehicle charging station (EVCS) in addition to the extra amperage available on my electrical service. I assume that during home construction this 30A was included in the NEC load calculation.

    The panel you have use the same circuit breakers as my year 2000-era house, and the panel is Siemens.

    I had a neighbor that moved away into a large 1990-era home with 100A service running similar loads like the OP yet with a pool pump on top of it. They can only charge with L1 on their Fiats. My former neighbor did some homework; at my shock, a service upgrade from the utility was astonomical (compared to what was quoted for my home) because the service conductors were direct burial! (no conduit) and the transformer was a half a block away underground within the property line a few houses away.
     

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