Solar Panel Installer how-to
How to Measure a String’s Open-Circuit Voltage
Checking Voc confirms modules are wired correctly before connecting to the inverter. Follow electrical safety rules.
Checking Voc confirms modules are wired correctly before connecting to the inverter. Follow electrical safety rules. In short: confirm; set; wear, then complete the remaining steps below.
Step by step
Confirm the inverter and DC disconnect are off and the string isn’t connected.
Set your meter to DC volts with a range above the expected voltage.
Wear required PPE and keep hands clear of connector contacts.
Measure across the string’s positive and negative leads.
Compare the reading to the expected Voc (module Voc × number of modules, adjusted for temperature).
Investigate any reading that is significantly low or reversed in polarity.
Safety reminders for solar panel installers
- Use fall protection on every roof
- Treat PV conductors as energized whenever light is present
- Prevent heat illness with water, rest and shade
- Lift panels with a partner and in safe weather conditions
Key terms
Photovoltaic (PV) · Module · Array · Inverter · Microinverter · String: see the full solar panel installer glossary.