Search

Premium Membership ♕

Limited Time Offer: Save 15% on PRO Plan with discount code: LRN15 and study specialized LV/MV/HV technical articles and studies.

Basics of Safety Switches - SIEMENS
Basics of Safety Switches – SIEMENS (photo credit: superbreakers.net)

Safety Switches

A safety switch is a common type of enclosed switch. Safety switches are generally used for two purposes:

  1. As a disconnecting means for a service entrance
  2. As a disconnecting means and fault protection for motors

The enclosure provides a degree of protection to personnel against incidental contact with live electrical equipment. It also provides protection for the enclosed equipment against specific environmental conditions. Safety switches may consist of a switch only or may consist of a switch and fuses.

Application

Safety switches can be used in any number of applications. The National Electrical Code® (NEC®), for example, requires that a disconnecting means shall be located in sight from the motor location and the driven machinery location (Article 430.102(B)). The NEC® defines “in sight” as visible and not more than 50 feet (15.24 m) distant (Article 100 – definitions).

Regardless of where the safety switch is used, the function is to provide a means to connect and disconnect the load from its source of electrical power.

Non-Fusible Safety Switch

A safety switch with no associated fuses is referred to as a non-fusible safety switch. A non-fusible safety switch has no circuit protection capability. It simply provides a convenient means to open and close a circuit.

Opening the circuit disconnects the load from its source of electrical power, and closing the circuit connects the load. Circuit protection must be provided by external overcurrent devices such as a circuit breaker or fuses. In the following illustration, power is supplied to a motor through a non-fusible safety switch and a separate fuse.


Fusible Safety Switch

A safety switch can be combined with fuses in a single enclosure. This is referred to as a fusible safety switch. The switch provides a convenient means to manually open and close the circuit, and the fuse provides overcurrent protection.

Title:Basics of Safety Switches – SIEMENS
Format:PDF
Size:3.9 MB
Pages:72
Download:Right here | Video Courses | Membership | Download Updates
Basics of Safety Switches - SIEMENS
Basics of Safety Switches – SIEMENS

Premium Membership

Get access to premium HV/MV/LV technical articles, advanced electrical engineering guides, papers, and much more! It will help you to shape up your technical skills in your everyday life as an electrical engineer.
50% Discount 💥 - Save 50% on all 90+ video courses with Enterprise Membership plan.

More Information

3 Comments


  1. Joe Tellez
    Dec 15, 2022

    Can a double throw non-fusible safety switch be used as service entrance rated manual transfer switch?


  2. evacuation lighting Testing Brisbane
    Nov 08, 2022

    A electrical safety switch is a device that quickly interrupts an electrical circuit to prevent serious harm from an ongoing electric shock.


  3. MICHAEL HAMRICK
    Jun 08, 2022

    We have older Square D type safety switches installed for some of our machinery where I work. The front panels can be opened while the switch is in the “ON” position. The newer types have a switch interlock that prevents this. My question is, is there a current safety requirement that requires this interlock be installed, and do we need to change out all of our old safety switches with ones that have the interlock?

Leave a Comment

Tell us what you're thinking. We care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

  +  13  =  nineteen

Learn How to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Enjoy learning!

Subscribe to Weekly Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and guides (PDF).
EEP Academy Courses - A hand crafted cutting-edge electrical engineering knowledge