Overview:
1) Installers should also reference the technical installation documents from the manufacturer website for specifications.
Tesla:
IronRidge: Listing to UL 3741
Aire Flush Mount Installation Addendum
(Guidelines for other mounting systems should be procured from their manufacturer’s website).
2) Installers are responsible for obtaining certifications required to be a certified installer with Tesla prior to installing inverters, Powerwall+ & Powerwall 3.
MCI (Mid-Circuit Interrupter):
The Tesla Mid-Circuit Interrupter (MCI) is used within PV strings and arrays to meet the Rapid Shutdown requirements of NEC Article 690.12
The quantity and placement of MCIs within the string varies. Rules for installing MCIs are detailed.
No minimum number of MCI's required for inverter or Powerwall+ to function.
Tesla MCI Requirements - 600V Application
IronRidge (XR Flush & Aire Mount Systems) & ECOFASTEN (ClickFit & Rockit Systems) Only
1 MCI-1 on both ends of the string
1 entering the array and one at the end.
Additional MCI-1s required where strings span Sub arrays.
Min Voltage per string = 60V
Max Voltage per string = 550V
Can only use MCI-1
Example 1: Module Voc (with temperature correction) = 45V
Max number of panels per string = 12
Sub-arrays >2’ apart require an MCI on both ends if PV conductors are not positioned beneath the arrays (eg: String E).
Example 2: Module Voc (with temperature correction) = 56V
Max number of panels per string = 9
Sub-arrays >2’ apart require an MCI on both ends if PV conductors are not positioned beneath the arrays (eg: String H).
Tesla MCI Requirements - 165V Application
Arrays that qualify as PVHCS
1 MCI at one end of each string.
Can be on either end (positive or negative).
1 MCI after no more than every 3rd module
Can be installed in between less than 3 modules depending on needs of layout
Example: In cold climates, when Voc for 3 modules might be greater than 165 VDC.
No more than 5 MCIs per string.
Min Voltage per string = 60V
Max Voltage per string = 550V
Can use MCI-1 or MCI-2
Example 1: Module Voc (with temperature correction) = 45V
Voc for 3 modules lower than 165V
Need 1 MCI every 3 modules
Max number of panels per string = 12
Sub-arrays >2’ apart require an MCI on one end if PV conductors are not positioned beneath the arrays (eg: String E).
Example 2: Module Voc (with temperature correction) = 56V
Voc for 3 modules greater than 165V
Need 1 MCI every 2 modules
Max number of panels per string = 9
Sub-arrays >2’ apart require an MCI on one end if PV conductors are not positioned beneath the arrays (eg: String H).
Tesla String & Design requirements
String Diagram
Ensure string diagram on the plan set matches install on site.
Ensure MCI location is marked and MCIs were installed correctly per references above.
String length
Min - Max voltage per string (60 - 550V)
Min module count per string
# of modules x Voltage per module should be greater than 60V.
Max module count per string
# of modules x Voltage per module should not exceed 550V.
Use LightReach's Tesla MCI calculator to determine sizing.
Azimuth & Tilt effects
All modules in a series string should
Have same azimuth (+/- 3 degrees tolerance)
Have same tilt (+/- 3 degrees tolerance)
All modules in a parallel string
Can be different pitches and azimuth
Each string should have the same number of modules (String voltage must be same to parallel together)
Ensure jumpers are used when parallel strings exceed 13 amps for individual MPP (image below for reference).