String Verification Record
Instructions
Use this form to record measurements taken during array installation to verify that all string connections (series and
parallel) have been properly completed.
Required Tools
The following tools are required to perform string measurements as described here:
- Digital multimeter (DMM) capable of measuring DC voltages and currents expected from string blocks
- Current clamp capable of measuring DC currents expected from individual series strings
- DC safety switch to prevent arcing when short-circuiting string blocks
- Solar cable test leads to reach positive and negative ends of string blocks
- Solar irradiance meter
- Ambient temperature sensor
String Verification
Safety Warning: String measurements must be taken by a qualified electrician or PV technician.
String Blocks
- Identify each string block using notation that can be referenced to the engineering drawings
- Enter the physical array each string block is part of
- Enter the number of panels in series and the number of series strings in parallel for each string block
Test Conditions
- Note the date and time that each string block is verified
- Measure and record irradiance in the plane of the panels
- Measure and record the ambient temperature
String Measurements
- Connect test leads to positive and negative string block leads, through the DC safety switch, and to the DMM
- Using DMM, measure and record open circuit voltage (Voc) for the string block
- Using DMM, measure and record short circuit current (Isc) for the string block
- Using a current clamp, measure and record the short circuit current (Isc) of a single series string within the string block
Expected Results
Voc Measurements
- Voc should be relatively constant at different irradiance levels
- Voc of each string block should be equal to the Voc of a single panel times the number of panels in
each series string (+/- 5%)
Isc Measurements
- Isc will vary at different irradiance levels
- The ratio between the string block Isc and single string Isc should be approximately X:1,
where X is the number of series strings in the string block
If measurements from a string block are not consistent with the above, inspect the string block to ensure all
series and parallel connections have been completed properly and re-test.
Attachment 5
String Verification Record
Installer / Integrator
Total system size (kWp DC)
System install site
Installation date (mo/yr)
Safety Warning: String measurements must be taken by a qualified electrician or PV technician.
Test Conditions
String
Block
Array
Panels in
Series
Strings in
Parallel
Date
Time
Irradiance
(W/m2)
Temp
String Measurements
Voc
Isc
(block)
Isc
(string)
0920-30109 rev 1.0 2010-01
Combiner Box-Verification Record
Instructions
Use this form to record individual string block measurements taken at the combiner box array to verify that all string
connections (series and parallel) have been properly completed.
Required Tools
The following tools are required to perform string measurements as described here:
- Digital multimeter (DMM) capable of measuring DC voltages and currents expected from string blocks
- 15 amp Fuse for testing Isc
- DC safety switch to prevent arcing when short-circuiting string blocks
- Solar cable test leads to reach positive and negative bus bar
- Solar irradiance meter
- Ambient temperature sensor
String Verification
Safety Warning: String measurements must be taken by a qualified electrician or PV technician.
String Blocks
- Identify each string block using notation that can be referenced to the engineering drawings
- Enter the physical array each string block is part of
- Enter the number of panels in series and the number of series strings in parallel for each string block
Test Conditions
- Note the date and time that each string block is verified
- Measure and record irradiance in the plane of the panels
- Measure and record the ambient temperature
String Measurements
- Connect test leads to positive and negative string block leads, through the DC safety switch, and to the DMM
- Using DMM, measure and record open circuit voltage (Voc) for the string block
- Using DMM, measure and record short circuit current (Isc) for the string block, closing one fuse holder at a time
Expected Results
Voc Measurements
- Voc should be relatively constant at different irradiance levels
- Voc of each string block should be equal to the Voc of a single panel times the number of panels in
each series string (+/- 5%)
Isc Measurements
- Isc will vary at different irradiance levels
- The ratio between the string block Isc and single string Isc should be approximately X:1,
where X is the number of series strings in the string block
If measurements from a string block are not consistent with the above, inspect the string block to ensure all
series and parallel connections have been completed properly and re-test.
Combiner Box-Verification Record
Safety Warning:
Installer / Integrator
String measurements must be taken by a qualified electrician or PV technician.
Installation Date (mo/yr)
Total system size (kWp DC)
System install site
Test Conditions
Combiner
Box
Array
String
Block
Panels in
Series
Strings in
Parallel
Date
Time
Irradiance
(W/m2)
String Measurements
Temp
Voc
Isc
(block)
0920-30109 rev 1.0 2010-01