Tesla Powerwall 2 AC Installation Manual page 72

APPENDIX H: MULTI-POWERWALL INSTALLATIONS
Service Type and Capacity Requirements
The Backup Gateway supports systems of up to 10 Powerwall units, but the maximum number of Powerwalls
may be limited by the site electrical service, utility grid infrastructure, or local requirements; therefore an
impedance test is required to confirm.
Line Impedance Requirements
The sensitivity of the system to line impedance increases with the number of Powerwalls in the system. (See
Impedance Requirements for Multi-Powerwall Systems on page 70
as it relates to number of Powerwalls.)
If grid impedance at a site exceeds the maximum allowable value, do either of the following:
• Decrease the impedance of the site grid connection. This may require coordinating with the local electrical
utility. See "Minimize Impedance" in the Pre-Requisites for Design for suggestions.
• Reduce the quantity of Powerwalls installed at the site to meet the maximum allowable impedance value.
If impedance values exceed the requirement for the installed number of Powerwalls, the system may not
function properly.
Measuring Line Impedance
To determine the line impedance at a site, measure between Line and Neutral where the Powerwalls will be
interconnected to the site electrical system with testing equipment such as the following:
• Fluke 1660 Series Installation Tester (1662, 1663, or 1664)
• Metrel-MI3000 Multifunction Tester
• Megger LTW315 Loop Impedance Tester
Example Line Impedance Test Instructions
For details on line impedance testing, refer to the test equipment manufacturer's instructions. The steps
below are general guidelines only.
WARNING: Impedance tests must be performed on an energized electrical system. Impedance tests
should be carried out only by trained electricians using appropriate safety equipment and safety
practices.
1. Follow manufacturer instructions to calibrate and zero the impedance tester before taking
measurements.
2. Complete the test on L1 first, then move to L2.
3. Connect all three voltage test leads – Line, Neutral, and Ground
4. Follow manufacturer instructions to verify that the correct voltage is present. Switch the tester to a
voltage measurement mode and check Line-to-Neutral and Line-to-Ground voltages.
5. Follow manufacturer instructions and take an impedance measurement where the Powerwalls will be
interconnected to the site electrical system. Switch the tester to the appropriate impedance
measurement mode and take the following readings:
◦ Line-Neutral
◦ Line-Ground
NOTE: The Line-Neutral impedance measurement is the value referenced in
Multi-Powerwall Systems on page
Powerwall 2 AC Installation Manual
70.
for the maximum allowable impedance
Impedance Requirements for
69