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Thread: Does Tesla powerwall have to comply with NEC 2014 702.4.(B)(2)?

  1. #1
    Join Date
    Oct 2014
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    Does Tesla powerwall have to comply with NEC 2014 702.4.(B)(2)?

    Hello,
    Section 702 is not just about prime movers. Reading 702.2 definition, this section applies to Energy Storage Systems. Does Tesla powerwall have to comply with NEC 2014 702.4.(B)(2)? Can it connect to the main panel and feeds bunch of loads of the main panel? I don't see load management/load shedding strategy here given that fact that a powerwall can only output 7kW at 240V. Tesla says they have an mobile app to turn on/off specific loads but how is it possible if the contractor connects the single powewall directly to the main panel?

    Thanks.
    Last edited by fandi; 06-13-18 at 10:56 AM.

  2. #2
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    Quote Originally Posted by fandi View Post
    Hello,
    Section 702 is not just about prime movers. Reading 702.2 definition, this section applies to Energy Storage Systems. Does Tesla powerwall have to comply with NEC 2014 702.4.(B)(2)? Can it connect to the main panel and feeds bunch of loads of the main panel? I don't see load management/load shedding strategy here given that fact that a powerwall can only output 7kW at 240V. Tesla says they have an mobile app to turn on/off specific loads but how is it possible if the contractor connects the single powewall directly to the main panel?

    Thanks.
    702.4 Capacity and Rating.
    (A) Available Short-Circuit Current. Optional standby system
    equipment shall be suitable for the maximum available shortcircuit
    current at its terminals.
    (B) System Capacity. The calculations of load on the standby
    source shall be made in accordance with Article 220 or by
    another approved method.
    (1) Manual Transfer Equipment. Where manual transfer
    equipment is used, an optional standby system shall have
    adequate capacity and rating for the supply of all equipment
    intended to be operated at one time. The user of the optional
    standby system shall be permitted to select the load connected
    to the system.
    it seems to me the app idea would be compliant with 702.4 (B)(1) so 702.4 (B)(2) would not apply. Also the user could select what loads to use by turning on/off circuit breakers.
    Bob

  3. #3
    Join Date
    Oct 2014
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    Quote Originally Posted by petersonra View Post
    it seems to me the app idea would be compliant with 702.4 (B)(1) so 702.4 (B)(2) would not apply. Also the user could select what loads to use by turning on/off circuit breakers.
    Thanks, Bob.

  4. #4
    Join Date
    May 2011
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    4,403
    The Powerwall system does not use a manual transfer method. I don't think one can invoke that section.
    Last edited by jaggedben; 06-13-18 at 07:26 PM.

  5. #5
    Join Date
    Apr 2018
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    AƱasco, Puerto Rico
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    Powerwall limitations

    You have very little control over the Tesla system with their gateway. The gateway is the center of the system: everything connects first to the gateway - the grid, the house and the panels. The gateway decides who gets what and from where. If your battery is charged and your grid is off or disconnected, the battery will run your house within load limits continuously for probably 24 hours, depending on load. Of course, at some point during those 24 hours, you should have sun or even just bright daytime light and that will be divided by the gateway - some to the house, the rest to the battery. After sundown, the gateway senses no solar and switches the load (house) back to the battery, almost seamlessly. Not much sun one day? Turn on the grid if the battery is low and the gateway will divide the grid power between the house and recharging the battery. If you have a 'net metering' sell-back arrangement with the power company, the gateway will try to feed the excess back to the grid once the batteries are charged. We use the phone app to monitor the battery level and just shut off the grid when charged into the 90's since we don't have nor want the net-metering system, for several good reasons.

    What we are experiencing is that this system does everything it supposed to do, as far as what I describe above, but it is also doing something it SHOULD NOT DO, which is shutting down completely. battery off, no power to house, sun or no sun, high load or no load, battery charged fully or not.

    System just goes dead. Usually it resets itself quickly but last week it shut down and won't restart under any efforts. I think I have a defective something here...gotta be either the battery or the gateway...what else could shut this down and leave no evidence, like sparks, burns, that smell of electrical stuff burning? None of that, just light out. It's a PW2 with Tesla Gateway, recently purchased and firmware recently upgraded to latest available. We're not overloading it, it's in a cool dry spot, our wiring is up to date, no wiring errors have been detected and the system has been doing this from the start, 5 months ago. Any ideas here?

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