NKK Switches S21B Toggle Switch DPST Equivalent & Substitute Parts

Part Overview

The NKK Switches S21B is a panel-mount toggle switch with DPST (Double Pole Single Throw) circuit configuration, rated for 5A at 125V AC and 30V DC. This component is classified as obsolete, making identification of compatible substitute parts essential for ongoing maintenance, repair, and new design applications where equivalent functionality is required.

The S21B features a standard round actuator with 17.50mm length, solder lug termination, and a circular 12.50mm diameter panel cutout. Its electrical life rating of 25,000 cycles and operating temperature range of -10°C to 70°C define its performance envelope for industrial and commercial switching applications.

Substiute Parts

S21B

NKK SwitchesIn Stock: 758S21B Datasheet

Current PartRFQ

S21A

NKK SwitchesIn Stock: 1602S21A Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the NKK Switches S21B is determined by strict equivalence across the following critical parameters:

Mechanical Compatibility:

• Panel mount configuration with identical 12.50mm circular cutout diameter
• M12 x 1 bushing thread specification
• Standard round actuator with 17.50mm length
• Solder lug termination style

Electrical Compatibility:

• DPST circuit configuration (Double Pole Single Throw)
• On-Off switch function
• Voltage ratings: 125V AC and 30V DC minimum
• Current rating: 5A AC minimum (substitute may exceed this specification)
• Operating temperature range: -10°C to 70°C

Environmental & Compliance:

• Non-illuminated configuration
• Moisture Sensitivity Level 1 (Unlimited)
• REACH Unaffected status
• ECCN EAR99 classification

The NKK Switches S21A meets all mechanical and electrical compatibility criteria while offering enhanced current ratings and active product status.

Parameter Comparison

Engineering Selection Recommendations

The NKK Switches S21A is a direct substitute for the obsolete S21B. Both components share identical mechanical interfaces, circuit topology, and environmental specifications. The S21A provides superior current handling capacity (15A AC / 20A DC versus 5A AC) while maintaining full backward compatibility with existing panel cutouts, bushing threads, and termination methods.

The S21A holds active product status with RoHS3 compliance certification, ensuring long-term availability and regulatory alignment for new designs and production continuity. The enhanced current ratings of the S21A provide design margin without requiring panel modifications or rewiring.

Frequently Asked Questions (FAQ)

Q: Can the S21A directly replace the S21B in existing applications?

A: Yes. The S21A is mechanically and electrically compatible with the S21B. Both components feature identical panel mount configurations (12.50mm circular cutout, M12 x 1 bushing), solder lug termination, actuator geometry, and voltage ratings. No panel modifications or rewiring are required.

Q: What is the primary difference between the S21B and S21A?

A: The S21A provides higher current ratings (15A AC / 20A DC) compared to the S21B (5A AC). Both maintain the same voltage ratings (125V AC / 30V DC), circuit configuration (DPST), and operating temperature range (-10°C to 70°C).

Q: Why is the S21B classified as obsolete?

A: The S21B is no longer in active production. The S21A serves as the current production equivalent within the NKK Switches S series toggle switch portfolio.

Q: Are there any compliance differences between the two parts?

A: The S21A includes RoHS3 compliance certification, whereas the S21B does not specify this status. Both components are REACH Unaffected and classified as EAR99 for export control purposes.

Q: What packaging options are available?

A: The S21B was supplied in standard packaging. The S21A is available in bulk packaging configuration.

Q: Are the electrical life ratings identical?

A: Yes. Both the S21B and S21A are rated for 25,000 electrical cycles, ensuring equivalent operational durability across switching cycles.