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PSA for people with Powerwalls - Run an off grid test

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Just to be clear, even if you were to feed power back to the grid it would in no way be dangerous. The system has a lot of safeguards in place to stop it from being dangerous and, of course, all of those safeguards are still operational even before you have PTO.

If the transformer were undersized for the amount of backfeed, it could be very dangerous. No one should be operating their system in parallel with the grid before obtaining PTO from the power company.
 
If the transformer were undersized for the amount of backfeed, it could be very dangerous.

Grid-tie inverters shutdown at 264v. There's no way you'd do any damage before that threshold is reached. PTO is administrative BS.

Grid-tie solar on the grid is the proverbial straw on a horses back... except ~100x smaller than the smallest straw... and designed with ~4 different fail-safes to vanish if it detects the tiniest amount of stress from the horse.
 
Agreed on the administrative part. Once the system is installed and passed inspection and deemed "ready".. the PTO is just the approve to turn on. Assuming no other system changes have taken place which would require a re-inspection. Looking forward to some testing. ..and regression testing. lol
 
Except we don't have one. Our TEG connects directly to the meter.

Our "Safety" disconnect required by the county sits between the PV/Powerwalls and the Load/generation hookups on the TEG.

There has to a service disconnect somewhere in the system to manually disconnect you from the utility, but installing a breaker in the gateway is an option for the service disconnect, so it sounds like that’s how you’re configured.
 
Our house already had the correct meter and grid connection in place prior to solar, so all we needed for PTO was approval to turn on the system. Our 3rd party, Tesla-approved, installer did run the system for short periods prior to PTO.

Our system has a breaker inside the TEG panel that disconnects the TEG from the grid - so it's easy to do an "off-grid" test.

Once PTO has been received all PowerWall owners should run a "max load" and "off grid" test. The max load test determines the maximum power consumption of your house circuits with all heavy power usage devices turned on at the same time. This determines the theoretical maximum of power you could draw during an unplanned outage. If this is higher than the PowerWalls can provide while operating off grid (5KW times the number of PowerWalls), then you'll know in advance that you could run into problems during an unplanned outage, and may need to plan for some equipment to be turned off during an outage or have non-essential circuits moved off the TEG.

The "off grid" test can identify issues such as the solar cutoff frequency being too high (causing problems with devices like UPS or motors) or can identify the need to add soft or hard starts to the air conditioner compressors (to eliminate the surge when the compressor starts).

These are tests the installers should run prior to customer acceptance of the system and making the final payment (if possible)...
 
Talked about "testing" with my install guy today. He mentioned not allowing the PW to charge past 90% before PTO in case you hit 100% then feed back to the grid. I presume a proper disconnect from the grid once done you can ignore this 90% mark and truly test off grid. I'm on day 4 of install... PW expected tomorrow and hopefully the last install day.
 
Talked about "testing" with my install guy today. He mentioned not allowing the PW to charge past 90% before PTO in case you hit 100% then feed back to the grid. I presume a proper disconnect from the grid once done you can ignore this 90% mark and truly test off grid. I'm on day 4 of install... PW expected tomorrow and hopefully the last install day.

Yes, that’s true... if you have your service disconnect off then you won’t be able to feed anything back to the grid no matter what... you will be physically disconnected from the grid.
 
I just wrapped a 3 day off grid test. If it hadn’t been for super cloudy weather today + having to do several loads of laundry, I would have stayed disconnected longer. May have been able to squeak by tonight, but chose to get some juice in the PW’s this afternoon/evening and power the house from the utility instead. Really happy with how the system ran. Both AC’s ran all weekend along and had no trouble running along side the other heavy draw appliances. Looking forward to sunny days ahead:).
 
My install completed today and I had a small window to test off grid by throwing the switch in the GW2 to take off grid, but first turn on the inverter as they leave it off. Simple enough and things worked as a charm. Was late in the day so didn't get much chance to test, but did see very low production due to the cloudy day. Will be playing with this more and may follow what @BrettS did and get into a habit of testing by day manually so making sure I turn off. =) If nothing else, this will offset some electric bill while I wait for PTO to get some of the benefits of the system. However I'm looking for for the data that I'm collecting on this. Awesome!
 
So I thought this was kind of interesting. My utility just emailed me the final copy of my interconnect agreement and it included the field inspection report. As I was reading through the field inspection report I noticed the following:

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Again, this may vary from utility to utility, but it certainly looks like my utility has a pretty lax view of operating the system before PTO. If they discover that the system is operational during the field inspection they will tell you to turn it off as you are “not technically permitted to interconnect”, however, finding the system connected won’t cause the inspection to fail.
 
It will certainly vary by jurisdiction and utility. Though I have no idea if they have ever enforced it, I believe our utility somewhere suggested that operating the system before PTO could be grounds to deny the NEM request (not sure about PTO as well.) I suspect they include the extreme language both to dissuade customers from operating before PTO and to have an option to deal with egregious cases. Probably for most cases, it would just be a warning. I even wonder if that language from Duke is because there is a similar policy but some inspector got too aggressive about trying to enforce it on site rather than just completing the inspection and noting that the system was on.

It helps in our area that the utility doesn't do its own inspections. It does reserve the right to do them but instead just relies on the county inspections. So, once you get county approval, they could only notice an anomaly if they were monitoring the usage data for the account, which they do not seem to do. I would definitely make sure the system is completely off when the county arrived, as I think they would be more likely to make life difficult if they determined it was being operated without their approval.
 
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Talked about "testing" with my install guy today. He mentioned not allowing the PW to charge past 90% before PTO in case you hit 100% then feed back to the grid. I presume a proper disconnect from the grid once done you can ignore this 90% mark and truly test off grid. I'm on day 4 of install... PW expected tomorrow and hopefully the last install day.

who was your install guy? They just departed on day 2 of my install in Richmond (sept 16) and should finish up by Friday! They are installing the ‘very large’ package with 4 PW