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Switches: Fundamentals of safety switches and disconnects

What are safety switches?  

Safety switches are used to open and close a circuit as a disconnecting means for service entrance or to facilitate lock-out/tag-out procedures for motors and other critical power systems equipment.

In today’s world it’s a high priority to create a safer environment for everyone close to and working on electrical equipment. With this intention, safety switches have evolved to offer more robust protection for equipment and personnel. When equipment requires maintenance, safety switches manufacturers make it quick and easy to disconnect and/or reconnect the power. With the power disconnected, operators can safely work on the equipment downstream; there’s no need to worry about coming in contact with live voltage.

Safety switches are a necessity in all commercial and industrial applications, per the National Electrical Code (NEC) established by the National Fire Protection Association (NFPA). According to NEC article 430.102B, a safety switch must be located in sight from all motors or manufacturing equipment. The NEC defines “in sight” as visible and not more than 50 feet from the equipment it controls. A safety switch can also be used at the service entrance, which is a point at which electricity first enters a building. This allows for power to be disconnected from a whole building at one time.


What is the difference between fusible and non-fusible safety switches?

Fusible safety switches combine fuses with the switch in a single enclosure, providing an easy means to manually open and close the circuit while the fuses protect against overcurrent and short circuit. In comparison, non-fusible safety switches do not incorporate any fuses into their enclosure and do not provide circuit protection. The sole purpose of a non-fusible safety switch is to provide an easy means to open and close a circuit.

What are the different types of safety switches?

General duty safety switches

General duty safety switch

Used in residential, commercial and light industrial applications, these switches are load-break rated and suitable for light-duty motor circuits and service entrance applications, unless otherwise noted. 

Heavy-duty safety switch

Used in commercial, institutional and industrial applications where reliable performance and service continuity are critical, these switches are most often rated 30 – 1200A with a visible double-break rotary blade mechanism. All heavy-duty switches are  load-break rated. For added safety, Eaton’s interlocking mechanism ensures the door cannot be opened when the handle is in the ON position; however, a built-in defeater mechanism provides user access when necessary.

Heavy-duty switches pin and sleeve receptacle

Pre-wired and interlocked to polarize receptacles for three-phase, three-wire grounded type power plugs, receptacle switches are used for portable power applications such as welders, infrared ovens, batch feeders, conveyors and truck and marine docks. 


Receptacle safety switches

Heavy-duty safety switches with surge protection

Safety switches with integrated surge protection are used in light commercial, commercial and industrial markets, providing superior protection at the service entrance and/or branch circuit level. Integral to the switch, an SPD provides significantly better performance compared to a device that’s externally mounted, resulting in better protection for connected equipment.


Heavy-duty safety switches with shunt trip

Configured to meet the needs of safety applications in industrial and commercial environments, shunt trip safety switches can be signaled to electronically operate the trip mechanism and interrupt the flow of power when a defined electrical condition is detected via protection relay (i.e., ground fault). When using an emergency stop, safety interlock or similar means, the remote operation capability of the shunt trip switch no longer requires personnel to manually open the switch with the handle, enhancing safety and improving productivity.


Shunt trip safety switches
Double throw safety switches

Double throw safety switch

Used to transfer service from a normal power source to an alternate source, or to switch from one load circuit to another, these safety switches have two interlocked switches with a common connection. The design ensures both switches cannot be closed at the same time, preventing them from being operated in parallel. Double throw switches are offered in general duty, heavy-duty and quick-connect options. Eaton’s stacked switch design (available for a variety of fusible units) reduces not only wall space requirements, but also overall installation cost by reducing the number of fuses required (three fuses instead of six for a 3-pole device).  

What are specialty safety switches?

These switches offer features to meet the customers’ unique needs.

1. Quick Connect safety switch

Provides a safe and quick means of connecting portable generators to facilities, transferring the building to backup power or providing temporary connection of portable loads. Quick connect switches are available in single- and double-throw designs. These switches are available in 100 – 1200A ratings. 

Heavy duty quick connect safety switches
Elevator control switch

2. Elevator control switch

This simple, all-in-one solution helps remove the mystery out of meeting the many codes associated with fire protection and safety in elevator shafts. Elevator control switches arrive completely assembled for quick installation, eliminating the labor and time needed to assemble individual components. In addition, they make it easy to meet code requirements for selective coordination in a fully-fused system. 

3. Double door safety switch

Providing a simplified solution to risks associated with exposure to line-side power, line isolation safety switches are used in almost any environment where the desired result is additional layer of protection.

These fusible heavy-duty safety switches provide a compartmentalized design and an internal barrier that separates the upper switching compartment (line-side) from the lower fuse compartment (load-side). This allows operators to access the fuse compartment with no exposure to line-side power, providing enhanced safety during fuse replacement. 

Double door safety switches

4.  Line isolation (OLI) safety switch

Similar in concept to a compartmentalized safety switch, line isolation switches for control panels can reduce operators’ exposure to line-side system voltage (i.e., 480 Vac) when opening a control panel. This type of specialty switch (i.e., OLI) provides an external disconnecting means for industrial control panels. It allows operators to access the control panel without exposure to the line-side voltage, thus enhancing safety and possibly allowing for reduced PPE which improves worker dexterity and mobility.

Are safety switches suitable for different environmental conditions?

Below are the common types of enclosure ratings described by NEMA.

  • Type 1 general purpose enclosures are constructed for indoor use. They  protect the equipment inside from ingress of solid foreign objects (falling dirt).
  • Type 3R enclosures are typically used in outdoor applicatins to provide protection against falling rain, sleet, snow and external ice formation. 
  • Type 4 enclosures are intended for general purpose indoor or outdoor use, primarily to provide a degree of protection against windblown dust and rain, splashing water and hose-directed water, and to be undamaged by the formation of ice on the enclosure.   
  • Type 4X enclosures, often constructed of stainless steel, are intended for indoor and outdoor use, primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water and hose-directed water; provides an additional level of protection against corrosion; and to be undamaged by the formation of ice on the enclosure.
  • Type 12 enclosures are constructed (without knockouts) for indoor use, primarily to provide a degree of protection against dust, falling dirt and dripping noncorrosive liquids.


Applications where the safety switches are commonly used

Safety switches are commonly used in commercial buildings, healthcare and institutions, water/wastewater, industrial and oil and gas applications.

Oil and gas
Commercial buildings
Healthcare and institutions

Custom safety switches

At Eaton various factory modifications are available to meet customer’s unique requirements. Our Switching device Flex Center can design and modify safety switches, enclosed circuit breakers and rotary disconnects for needs that are not met by standard products. Solutions can be custom designed for harsh environments, enhanced safety and convenience, and to meet the needs of specific applications. 

Types of customization include:

Flex center image.jpg

1. Customer-driven specs

  • Custom painted enclosures
  • Nameplates
  • Special labeling
  • Custom lugs
  • Switching and 200% neutrals
  • Fire pump disconnects

2. Packaged solutions

  • Unique mounting options
  • Non-standard receptacles
  • Installed fuses
  • Elevator control
  • Factory-installed field kits
  • Meters
  • Cover controls/relays/terminal blocks
  • Shunt trip switches
  • Space-saving designs

3. Enhanced reliability

  • 304 and 316 grade stainless enclosures
  • Mill duty switches
  • Seam welding
  • Stainless steel mechanism
  • Irrigation switches
  • Fungus proofing
  • Lock-on provisions
  • Surge protection

4. Safer designs

  • Key interlocks
  • Quick connect products
  • Voltage indicators
  • Viewing windows
  • Left-handed switches
  • Finger-safe barriers
  • Interlocked receptacles
  • Hook stick handles
  • Visible blade

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