Announcement

Collapse
No announcement yet.

Powerwall 2 install.

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • #46
    Sorry, I'm still not getting it. If the PowerWall's are wired such that they could see the entire load of the house (including the air conditioner(s)) I just don't see how such a system could pass engineering design review / inspection. It's not good enough to just say that you'll turn them off (been there, tried that).

    You must demonstrate that the reasonably anticipated diversity of the load is not likely to exceed the current carrying capacity of the UPS/generator WITHOUT human intervention to shed loads. If load shedding is required (because the UPS/generator) is sized smaller than would be necessary, load shedding must be automatic. Hence separate UPS protected and non-UPS protected panels.

    Two PowerWall's can provide 48.3 amps continuous and 60 amps peak (for 10s) at 240 VAC per spec's available (granted if one had access to the Tesla partner portal, more detailed specs are available). Any normally sized air conditioner (3-5 tons) will draw roughly 25-40 amps. Larger homes, say ~3000 square feet an up, often have two HVAC units here on the East Coast -- where its not that hot -- typically with a 3-4 ton for the first floor and a 2-3 ton for the second floor.

    Here's a top of the line 20 SEER York, older, and less efficient units will draw even more when running.
    http://www.upgnet.com/PdfFileRedirec...YTG-B-0517.PDF

    The Condenser alone draws (all 240VAC):
    3 ton 25.7 amps continuous (30 amp breaker), starting inrush will be at least 2x to 3x granted only for a second or two
    4 ton 28.6 amps continuous (40 amp breaker), starting inrush will be at least 2x to 3x granted only for a second or two
    5 ton 33.9 amps continuous (50 amp breaker), starting inrush will be at least 2x to 3x granted only for a second or two

    Plus the blower fan in the air handler will use another 3 to 4 amps @240VAC, plus any other loads that might happen to be active in the house at the time the Poco power goes out.

    All will be well until you're away at work one day, for example, and the compressor tries to cycle on automatically and stalls due to insufficient voltage/current from the inverter causing 1) a brownout in your home, 2) damage to your electronics / compressor while it tries to start with insufficient voltage, and 3) the PowerWall inverters sense the overload and shutdown abruptly dropping all of the other loads in your home (fish tank, security system, Solar PV, etc.)

    Many such UPS systems will try to automatically restart when this happens and the system goes through these start, fail, stop cycles for hours until something fails -- compressor motor, starting capacitor, inverters, etc.

    But, obviously, its not up to me. If your AHJ is willing to sign off on your engineering design AS IS covering the whole house mains panel, then that's up to them and you. But, it doesn't mean its going to work (well). Regardless, I suggest you find this out sooner rather than later as it could potentially cause a lot of re-work in your wiring design.

    I agree it's close. But IMHO, either three PowerWalls or separate UPS/non-UPS panels is what would be needed from my perspective, Especially given little or no current consumption info. Unless the house is particularly small and we're talking room or mini split AC systems.

    Comment


    • #47
      This appears to be the relevant section of the NEC. I have't cross-checked 2008 vs 2011 vs 2014 vs 2017. But starting in 2008, for new installs, the NEC appears to state that if an automatic transfer switch is used (presumably the PowerWall Gateway) that the generator system (doesn't matter if its an actual generator or UPS/battery inverter solution) must be able to carry the full current of the connected load.

      Important Highlights of NEC 702

      Comment


      • #48
        Oops, seems to have gotten cutoff

        Important Highlights of NEC 702

        Comment


        • #49
          Hmm, still getting cut off. Not sure why. Anyway code sections are 702.4 including 702.4 B1 and B2 and 702.5
          http://www.inspectionbureau.com/pdf/...stems-2014.pdf

          Comment


          • #50
            article 220.87 could be a good bet to be in compliance.

            Comment


            • #51
              Originally posted by JSchnee21 View Post
              Hmm, still getting cut off. Not sure why. Anyway code sections are 702.4 including 702.4 B1 and B2 and 702.5
              http://www.inspectionbureau.com/pdf/...stems-2014.pdf
              The manual transfer section seems to provide plenty of leeway for sizing for load intended to be operated at one time, and user of the system being permitted to select the load connected. Is the Energy Gateway automatic? If so 220.87 could definitely be used for compliance at a home that does not exceed the power rating of the Powerwalls, provided a demand logging meter has been set in advance of the permitting - which would seem logical for someone who has budget to buy a Powerwall.

              Comment


              • #52
                My guess is for any home battery system to be accepted by the NEC it will have to be limited to what it can power. Otherwise unless the system is rated 50kWh or more it could be overloaded and drained quickly.

                With a specific critical load system setup, the battery could be used for emergency back up or load shed for those on a TOU contract. In most cases unless the person has a lot of money the battery system would never be sized to cover entire household kWh usage for an extend time.

                Comment


                • #53
                  Originally posted by JSchnee21 View Post
                  Sorry, I'm still not getting it. If the PowerWall's are wired such that they could see the entire load of the house (including the air conditioner(s)) I just don't see how such a system could pass engineering design review / inspection. It's not good enough to just say that you'll turn them off (been there, tried that).

                  You must demonstrate that the reasonably anticipated diversity of the load is not likely to exceed the current carrying capacity of the UPS/generator WITHOUT human intervention to shed loads. If load shedding is required (because the UPS/generator) is sized smaller than would be necessary, load shedding must be automatic. Hence separate UPS protected and non-UPS protected panels.
                  What Sonnen did was to include a 200A transfer relay, so the system could pass the entire load of the house when AC is present - and (presumably) switch back to grid if the load greatly exceeds the capacity of the inverter. During an outage of course this will result in depowering the loads, but perhaps that's the "trick" they use to be technically code compliant.

                  Comment


                  • #54
                    Originally posted by jflorey2 View Post
                    What Sonnen did was to include a 200A transfer relay, so the system could pass the entire load of the house when AC is present - and (presumably) switch back to grid if the load greatly exceeds the capacity of the inverter. During an outage of course this will result in depowering the loads, but perhaps that's the "trick" they use to be technically code compliant.
                    The "trick" will be some type of load shed controls that turns off high loads or is only allowed to power critical loads. That is pretty common in the commercial industry but can get expensive for a home owner.

                    Comment


                    • #55
                      I've often wondered if anyone made "smart" load shedding circuit breakers, and indeed Schneider does. I'm not sure if these can be used in a residential setting, but in theory the breaker for the condenser could be set to trip based on a centralized control signal (presumably from the Gateway).

                      See page #5:
                      http://static.schneider-electric.us/...0611DB1107.pdf

                      This might (or might not) be less expensive than installing a separate breaker panel for non-critical loads. Though, I bet you'd have to re-arm the Schneider automatic breaker manually when the Poco comes back on.

                      I assumed the PowerWall gateway was serving as an ATS (Automatic Transfer Switch) -- and not a manual transfer switch.

                      Since I believe this is new construction, CT metering may not be possible, in which case there are other estimation schedules which can be followed.

                      Still wish the OP would go with DC-Optimizers and a StorEdge Inverter over an Enphase solution. I have to believe there's some co-ordination advantage given that Tesla has been working with SolarEdge for some time now.

                      The thing is, given the 60 amps peak from the two PowerWalls, it might almost carry the AC running continuously. My principle concern is the starting current. Additionally, since the OP is planning to get an electric car this will be another high current 240VAC device which will compete for power. Plus any electric ranges, hot water heaters, dryers, well pump, sump pump, pool pump, dehumidifier, bathroom space heaters, etc.

                      Comment


                      • #56
                        Originally posted by JSchnee21 View Post

                        Still wish the OP would go with DC-Optimizers and a StorEdge Inverter over an Enphase solution. I have to believe there's some co-ordination advantage given that Tesla has been working with SolarEdge for some time now.
                        I thought it was only the DC Powerwall that has any sort of integration advantage with SolarEdge. The StorEdge is kind of limited in what it can handle, each unit can only put out 5 kW AC in backup mode, so you'd need one for each battery. Even then, it has an "input" power limit of 3300 W continuous from the battery, so it isn't clear that two inverters each with its own battery could put out more than 6600 W. What has been spec'd out looks much more capable.
                        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                        Comment


                        • #57
                          Originally posted by sensij View Post

                          I thought it was only the DC Powerwall that has any sort of integration advantage with SolarEdge. The StorEdge is kind of limited in what it can handle, each unit can only put out 5 kW AC in backup mode, so you'd need one for each battery. Even then, it has an "input" power limit of 3300 W continuous from the battery, so it isn't clear that two inverters each with its own battery could put out more than 6600 W. What has been spec'd out looks much more capable.
                          I had heard that the DC powerwall will not be built. At least that was from one of Tesla's news flashes a couple of months ago and the story may be different now.

                          Comment


                          • #58
                            Originally posted by SunEagle View Post

                            I had heard that the DC powerwall will not be built. At least that was from one of Tesla's news flashes a couple of months ago and the story may be different now.
                            Discontinued for all markets except USA.
                            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                            Comment


                            • #59
                              Originally posted by sensij View Post

                              Discontinued for all markets except USA.
                              Hmm. Sounds promising but I wonder why just the US should get that product when there are so many other Countries that could use energy storage.

                              Comment


                              • #60
                                Originally posted by sensij View Post
                                I thought it was only the DC Powerwall that has any sort of integration advantage with SolarEdge.
                                Per a SolarEdge rep at Intersolar, they are now concentrating on the LG battery rather than the Powerwall.

                                Comment

                                Working...
                                X