Powerwall 2 install.

[JSchnee21]

Hi @sriram97,

Just following up. How's your install and inspections going? There's another recent poster @Saxxon who is also considering a PowerWall 2 solution. Could you provide some more info on your project? Is one solar installer performing/coordinating all of the parts of your project? Or are you working with separate contractors for each part? Aka a solar installer for PV piece (panels, racking, DC, and inverter), a separate electrician for the AC load centers / conduit, what what about for the storage?

Did you buy the PowerWall 2's direct from Tesla or through your PV company (or electrician)? Are they "in stock" or was there a long lead time?

Did you ever get to the bottom of whether or not automatic load shedding would be required to pass inspections?

Thanks,
Jonathan

[jflorey2]

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.

[SunEagle]

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.

[sensij]

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.

[SunEagle]

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.

[sensij]

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.

[JSchnee21]

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/docs/Circuit%20Protection/Molded%20Case%20Circuit%20Breakers/0600%20A%20Frame%20PowerPact%20L/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.

[SunEagle]

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.

[jflorey2]

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.

[SunEagle]

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.

[adoublee]

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.

[SWFLA]

article 220.87 could be a good bet to be in compliance.

[JSchnee21]

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/Emergency-Systems-2014.pdf

[JSchnee21]

Oops, seems to have gotten cutoff

Important Highlights of NEC 702

[JSchnee21]

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