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Feel stupid - popped a panel breaker. Not sure why exactly though.

Discussion in 'Model S: Battery & Charging' started by David_Cary, Mar 25, 2016.

  1. David_Cary

    David_Cary Member

    Dec 17, 2012
    Cary, NC
    Ok - I feel stupid but lesson learned and perhaps someone can avoid my mistake

    I have a newer house with 400A service. 2 panels that are 200A - right? Well - the heat pumps are on the main outdoor panel. The 2 subs are in the basement. They are full size panels.

    Well the breaker to the sub is 80A. I have 2 cars on the sub - a 20A charger and the 40A Tesla EVSE. I've had this set up for 4 months and charged both together many times.

    Well, last night I forgot to plug the cars in. I have a TOU rate that ends at 6am and I have peak kw pricing so Tesla charging leads to a $50 surcharge if done during the day. I got up at 4:45 and plugged in both cars, ran the dishwasher (efficient as can be - .5A tops) and turned on the coffee maker - 1-2A tops for a few seconds here and there.

    My egauge peaked at 16 kw - which I have exceeded many times before (although when I have been over 20 - it was hot water which is on the other panel).

    Either way - not 80A - right? I'm guessing the refrigerator compressor fired up? 80% continuous I get so maybe that was it - 64A. But looking at the monitor I never really breached 16kw - if I did, it was seconds and not continuous. I did run at 15.8 for 10 minutes. I'm sure these things aren't exact but I would have thought the breaker could handle that.

    Lesson learned - I can't use 200A from that panel. Don't push it in general. But still curious why it popped. I dialed down the Tesla to 20A. I am at 120 miles and I'll be fine - long day but have charging options. The Leaf isn't going far today - and wife can charge when the sun hits the panels....
  2. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Jun 21, 2012
    You don't mention the type of coffee maker that you have, but a typical coffee maker that is doing a brew cycle will draw up to 1500W (12-13A on one of the line conductors) for a few minutes. A Keurig brewer uses about that much for 3 minutes duirng its initial warm-up cycle. If the refrigerator circuit and the coffee maker circuit were on the same line conductor in the split-phase arrangement, it could exceed things.

    That said, breakers are not perfect. They don't trip the moment you get .001A over the rated current, so a few seconds wouldn't cause it unless you've nearly doubled the current. I've seen some breakers bad, directly out of the box, that trip at lower currents.

    If it continues, I would consider replacing the breaker.

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