I have solar panels, two inverters and a Tesla Backup Battery. I also have a home on 3-phase.
Recently we had a new power pole installed in our street which required the electricity to be shut down to the street. It was a bright sunny day and we were really surprised to find that our battery would not recharge from our solar panels.
On questioning Tesla who installed the battery we were told that the energy companies have instituted a policy of “energy balance” where the inverters and battery need to be wired to each phase separately meaning that when the grid goes down, the battery cannot be recharged from the solar panels. To do this, we would need to wire the inverters and the battery to the same phase and this has been deemed 'illegal" by the energy provider
We intend to challenge our supplier (Ausgrid) as Tesla seems to think that they can make an exception to this ruling… but doesn’t this defeat the purpose of transitioning to cleaner energy to some degree?
I think if you had identified your requirement for backup power during a mains outage then your installation would have catered for that e.g. included the necessary Tesla Gateway.
For safety reasons, your source of generation must be isolated from the mains when the mains is down.
Many households with standard grid connected PV installed also mistakingly believe that the PV system will power the house when there is a blackout/no supply from the grid.
Standard grid connected PV systems are designed to shutdown when there is a blackout/no supply from the grid. This is to ensure the mains connection isn’t potentially live posing a significant safety risk to anyone working on the local distribution network or returning the network into service. This is because the PV system/inverter is electrically connected to the grid. It appears that this is how your system has been installed.
There are hybrid PV systems where inverters have isolation or a blackout mode, but one would need to check with their local distribution network operator they can be connected - and such inverters if allowed to be installed would specifically need to be requested as part of the PV system installation.
Where we live, our three phase inverter had to be connected to each phase for export. We were told it was a distribution network requirement. However, installing a single phase inverter, we could have opted for which phase it was connected for export. If your distribution network operator is Ausgrid, they will have requirements for three phase inverters connected to three phase mains connection.
Edit: as it appears you may have a non-standard connection, it might we worth looking at the connection approval the installer would have obtained from Ausgrid. They should have given this to you on or soon after installation. See if there are any special conditions attached to the approval. If there are conditions, see if any relate to inverter configuration such as isolation during power loss. If there aren’t any special conditions, the standard Ausgrid connection requirements would apply. If you are concerned about the connection setup, see if there are contact details on the approval as this would be your best bet when contacting Ausgrid.
The requirement to connect each source of energy generation on seperate phases is stipulated by the Industry standard of best practice - Service and Installation Rules of NSW. Your system has 3 inverters, one the Tesla Powerwall inverter, and the other two the PV inverters. A PV inverter plus Powerwall on the same phase count as two sources in a 3 phase system.
It’s unlikely Tesla will get a dispensation as it would change the rules for all of NSW. Your accredited supplier would have been aware of the limitation that your Powerwall would not recharge from PV during an outage when submitting the installation design for approval by your distributor. As the customer the same should have been communicated at the time of offer.
P.S.
Assuming you do not get a dispensation to reconfigure your approved installation - There are several possible solutions assuming you want the added security of being able to recharge the Powerwall from your PV during an outage. That is in addition to the backup it currently provides. They would be best discussed with an accredited Solar and Battery system designer familiar with the NSW distribution authority requirements. It will require additional expense.
The battery while power is in islanding mode can only supply one phase circuit of your house. Our choice was to supply the lights/fans and the power supply that feeds our bedroom (for essential medical equipment) and lounge/dining/kitchen area.
If you want to supply all three phase circuits you would need 3 batteries or have a system specially and specifically made to supply all 3 phase circuits at once. For the battery to supply all 3 phases would possibly very quickly drain it’s capacity if there are high draws on the power e.g. hot water, air conditioning and similar.
The problem of having 3 Tesla batteries is that they each have a 5kW inverter and this alone would mean you reach the 15 kW limit for 3 phase and that wouldn’t include the inverters you have for the panels. This may mean you would have to restrict the output to ensure you comply with the requirements of the Grid connection. A specialist in this area of technology would be best to contact to ensure any compliance issues are dealt with.
If the battery is not being charged while the system is isolated from the grid, it may be an mis-wiring of the sensor circuit of the Tesla battery system. When our battery was first installed, and we had an outage for 3 days we noted that the battery was not recharging during the day. We got the technician back (from the installer’s business) and they located the issue. On rectifying the problem, the battery is recharged when in islanding mode and the Sun is shining. Of course this still only supplies the single phase circuit we selected. So it is worth having that checked to ensure the Tesla system is detecting outages correctly.
Our main power box showing the non essential breakers (which are not powered in an outage) and the backup breakers (those that the battery supplies in an outage)
The Tesla Gateway box showing the Backup and non essential breakers (note inverter 2 for panels goes through the Gateway so it is isolated from the Grid when in islanding mode).
Thank you. The way you have it set up is similar to you. ie o. One phase only We have several essential items to keep running during outages. Our issue is that the PV inverters do not charge the battery during an outage. Tesla tells us that this is due to the Energy suppliers rules
Interestingly SolarQuotes who Choice often references recently responded to a very similar question. It provides further insight to what may be your situation.
Note:
Even when your system is connected to the grid and operating normally the PV inverters connected on the other two phases do not charge the Tesla Powerwall. The Powerwall is charged from the grid (mains supply) via the third (seperate) phase it is connected to. SolarQuotes mentions net metering which provides import and export from the PV are correctly accounted for.
As you don’t have a 3 phase inverter I am sure you can get the same setup as we have that charges the battery from one inverter and it’s panels when an outage occurs. The Tesla system cannot use more than a single phase, so only 1 of your inverters will be able to be connected to the Powerwall to be used to charge the battery, the other inverter will shutdown in an outage.
It has to be a single phase inverter from the panels for this to work and it does require the Gateway to be setup to support that single phase inverter. As you can somewhat see on our Gateway it has been wired and setup to support the #2 inverter from the panels. This inverter is connected to the Gateway to support charging while an outage is occurring during daylight hours. This was not a difficult request of the installers when we had the work done, nor did it add much to the cost (I think in the realm of about an extra hour of work and about $200). It was just after the install, there had been a mis-wiring of a sensor that meant that until it was rectified the Tesla system did not “see” the inverter was able to be used, once that was fixed it has worked flawlessly.
