Correct tightening torque is a connection-specific requirement in solar photovoltaic (PV) installations. Inverter terminals, combiner connections, disconnects, grounding and bonding hardware, and approved cable terminations may have different manufacturer requirements. There is no single safe torque setting for all solar electrical connections.
Why tightening torque matters
A terminal or bolted joint depends on the manufacturer's specified connection design, hardware, conductor preparation, and installation method. Too little tightening may fail to establish the intended mechanical connection; excessive tightening can damage threads, terminals, conductors, or other components. The correct value cannot be determined from the nominal system voltage or the fact that the equipment is used in solar installations.
Where solar installers obtain the correct torque
Use the current installation instructions and markings for the exact equipment model and connection. Confirm conductor material, size, terminal type, hardware, and any manufacturer-specified tightening sequence or tool requirements. Where the equipment is listed, labeled, or certified, OSHA construction regulation 29 CFR 1926.403(b)(2) requires installation and use in accordance with the instructions included in that listing, labeling, or certification. This is not a universal torque table.
Inverter and combiner terminals
Different equipment families and even different terminals on the same assembly can require different values. Verify each terminal against its own labeling and documentation. Do not transfer a value from a different model.
Disconnects, breakers, and terminal lugs
Confirm that the conductor and lug combination is approved for the equipment and that the specified torque applies to that exact combination. Do not assume a familiar lug size implies a familiar torque.
PV connectors and module hardware
Connector assembly requirements are not interchangeable with screw-terminal torque requirements. Use the specific connector manufacturer's instructions and approved components and tools. Module clamps and mounting hardware also require their own manufacturer documentation; mechanical mounting values are not electrical terminal values.
Before making or checking a connection
Identify all relevant sources of electrical energy, including PV DC, AC supply, and connected storage. Establish the applicable safe-work condition using the employer's program and equipment-specific instructions. A switch position or shutdown indication alone is not proof that every relevant circuit is deenergized. For general-industry tasks within its scope, 29 CFR 1910.333 addresses deenergizing, lockout/tagout, verification, and qualified-person requirements. Construction tasks have their own applicable provisions; assess the work rather than assuming one regulation applies to all situations.
Applying a manufacturer-specified torque
- Identify the exact terminal, approved conductor or fastener, and equipment model.
- Locate the current manufacturer torque instruction and confirm its units.
- Confirm the required value falls within the documented operating range of the selected tool.
- Inspect the torque tool and insulated surfaces; do not use damaged tools.
- Confirm the tool's calibration and inspection status under the manufacturer's instructions and the employer's quality program.
- Use the specified socket or bit and follow both the equipment and torque-tool manufacturers' application instructions.
- Document the connection, specified value, and verification as required by the project or quality procedure.
Torque units are not interchangeable
Inch-pounds (in-lb), foot-pounds (ft-lb), and newton-meters (N·m) describe torque using different scales. A value copied without its unit is incomplete. Verify the manufacturer's stated unit before setting a tool; use a reliable conversion only when needed and preserve the required precision. Do not substitute a tool's maximum range for a connection's required value.
Inspection, retightening, and maintenance
Do not automatically loosen and retighten an existing connection or perform a “check torque” by turning it further. Some equipment and connection designs have specific restrictions on retorque, reuse, or replacement. Obtain the equipment manufacturer's instructions and follow an approved inspection and maintenance procedure. Never disturb an exposed energized connection merely to check its torque.
Insulated torque tools: useful but not a substitute for electrical safety
Where the task calls for insulated tools, select appropriately rated, undamaged equipment. A 1000V-insulated wrench does not establish an electrically safe work condition, remove arc-flash hazards, or authorize energized tightening. Tool selection is covered separately in our Torque Wrenches for Solar Installations guide.
Relevant 1000V Tools products
These are catalog-listed examples of insulated torque tools, not prescribed tools or settings for a particular PV terminal. Verify the actual product specification and connection requirements before use.
- S22TS35 insulated torque screwdriver — evaluate only for compatible connections within its documented range.
- S22TS100 insulated torque screwdriver — evaluate only for compatible connections within its documented range.
- S22TCI-150RA 1/4-inch insulated torque wrench — evaluate only for compatible connections within its documented range.
- S22TCI-150RA38 3/8-inch insulated torque wrench — evaluate only for compatible connections within its documented range.
- S22TCI-250R insulated torque wrench — evaluate only for compatible connections within its documented range.
- S22TCI-750R insulated torque wrench — evaluate only for compatible connections within its documented range.
Related Knowledge Center resources
- Torque Wrenches for Solar Installations — selecting and caring for an appropriate tool.
- Lockout/Tagout for Solar Installations — energy-control considerations.
- Why Solar Panels Remain Energized — understanding persistent PV electrical hazards.
Original sources and references
- OSHA, 29 CFR 1926.403, General Requirements, especially paragraph (b)(2) on installation and use according to listing, labeling, or certification instructions.
- OSHA, 29 CFR 1910.333, Selection and Use of Work Practices, including deenergizing and verification requirements where applicable.
- OSHA, Electrical Safety-Related Work Practices: Inspection Procedures and Interpretation Guidelines, interpretation of the applicable electrical safe-work provisions.
Safety note: This article is educational. It is not a substitute for current manufacturer instructions, applicable codes, an employer's electrical safety program, or qualified-person judgment. No universal PV terminal torque values are provided.