Exploring the Basics of Safety Switches and Disconnects: Ensuring Electrical Safety in Your Facility

In any industrial or commercial setting, ensuring the safety of personnel and equipment is paramount. One critical aspect of electrical safety is the proper implementation of safety switches and disconnects. These devices play a crucial role in protecting against electrical hazards, preventing accidents, and facilitating maintenance work on electrical systems and machinery. In this blog post, we'll delve into the basics of safety switches and disconnects, exploring their functions, types, and importance in maintaining a safe working environment.

Understanding Safety Switches and Disconnects

Safety switches, also known as disconnect switches or isolators, are devices designed to quickly and safely disconnect electrical power to a circuit or piece of equipment. They serve as a means of isolating electrical circuits, machinery, or appliances to prevent electric shock, fire, or damage to equipment during maintenance, repair, or emergency situations.

Functions of Safety Switches and Disconnects

Isolation: Safety switches provide a physical break in the electrical circuit, ensuring that no power is supplied to the connected equipment or circuit when in the off position. This isolation is essential for preventing accidental contact with live electrical components.

Emergency Shutdown: In case of electrical faults or emergencies, safety switches offer a quick and reliable means of shutting off power to affected circuits or equipment, minimizing the risk of further damage or injury.

Lockout/Tagout (LOTO): Safety switches are often used in conjunction with lockout/tagout procedures to ensure that equipment remains de-energized during maintenance or servicing, preventing unauthorized activation and safeguarding personnel working on the equipment.

Types of Safety Switches and Disconnects

Fused Disconnect Switches: These devices incorporate fuses into the disconnect switch mechanism, providing overcurrent protection when excessive current flows along with the ability to disconnect power, preventing damage to equipment and minimizing safety risks.

Non-Fused Disconnect Switches: Non-fused disconnect switches offer a means of isolating power without the inclusion of fuses. They are commonly used in applications where overcurrent protection is provided elsewhere in the circuit.

Circuit Breaker Disconnects: Circuit breaker disconnects combine the functions of a disconnect switch and a circuit breaker, allowing for both disconnection and overcurrent protection.

Importance of Safety Switches and Disconnects

Electrical Safety: By providing a means of isolating power, safety switches and disconnects help prevent electric shock and electrocution hazards, safeguarding personnel working on electrical systems.

Equipment Protection: Disconnecting power during maintenance or repair activities helps prevent damage to equipment and extends its operational lifespan.

Fire Prevention: Properly functioning safety switches can mitigate the risk of electrical fires by quickly disconnecting power in the event of a fault or overload.

Compliance with Regulations: Many regulatory standards and codes mandate the use of safety switches and disconnects in industrial and commercial settings to ensure compliance with safety requirements and prevent accidents

Key Considerations When Choosing Safety Switches

Voltage and Amperage Rating: Select safety switches that match the voltage and amperage requirements of the electrical system they will be protecting.

Enclosure Type: Consider the environmental conditions (e.g., indoor, outdoor, hazardous locations) when choosing the appropriate enclosure type for the safety switch and select the appropriate NEMA rating for the disconnect switch.

Fused or Non-Fused: Ensure that you select the correct type for the applications of your electrical system.


Safety switches and disconnects are indispensable components in electrical systems, serving to protect both personnel and equipment from electrical hazards. Understanding their purpose, types, and key considerations is essential for ensuring a safe and compliant electrical environment. By prioritizing safety and selecting the right safety switches for your application, you can mitigate risks and create a secure work environment. Remember, when it comes to electrical safety, there's no room for compromise.

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Identifying Westinghouse TAP-ITAP-ZTAP Bus Plugs


westinghouse TAP, ITAP, and ZTAP bus plugs

One of the most common challenges in our industry is accurately distinguishing between the different series of vintage Westinghouse/Cutler-Hammer busway systems. Despite their nearly identical appearances, the TAP, ITAP, and ZTAP series are entirely distinct and cannot be interchanged.

Fortunately, there are quick and straightforward methods for correctly identifying the specific vintage series you require. In the following discussion, we will explore these differences, highlighting easy-to-spot clues on the plugs to help you correctly identify the type you need.

Identifying the types:


3 wire / 4 wire
For use with Westinghouse Standard-Design Busway 225A thru 1000A


Stab configuration: Aligned in a row; neutral offset from stabs.

TAP bus plugs feature stabs that align with each other. In the example above, this three-wire version features 3 stabs vertically aligned with one another. Note that the neutral stab will be offset from the stabs. The part number prefix on the front label will begin with TAP. Any deviations from that prefix designate that it is NOT a TAP series bus plug. It should also be mentioned that the prefix TAP is also used on ZTAP plugs, so another giveaway to differentiate a TAP series bus plug is by hanger width. The hanger width on the TAP series measures 9 ⅝ inches. If the hangers measure 11 ⅝ inches, it is a ZTAP bus plug. More on that below.



3 wire / 4 wire

For use in Westinghouse Pow-R-Way I & II Busway 225A thru 4000A


Stab configuration: Staggered/Offset

The quickest and easiest way to identify an ITAP bus plug is by noting the stab configuration. In ITAP plugs, the stabs are offset from one another. In the 4-wire example above, you can see staggered stabs. The product label on the front will feature a part number that begins with the prefix ITAP. Any deviation from this designates that the plug is NOT part of the ITAP series.



3 wire / 4 wire
For use with Westinghouse Low-Impedance Busway 1000A thru 4000A

Stab configuration: Aligned in a row; neutral stab aligned with stabs.

Extremely similar in appearance to TAP plugs, there are fortunately two tell-tale signs to identify a ZTAP bus plug: the neutral stab position (fourth wire) and hanger bracket width. With ZTAP plugs, the stabs are again aligned with one another, however, it’s critical to note that the neutral stab will also be aligned with the stabs. The example above shows that this is a three-wire plug with a neutral stab at the top.

The other big giveaway that this is a ZTAP plug is the hanger width. As you can see in the example, the hangers extend beyond the width of the plug on both the top and bottom. In the ZTAP series, the hanger dimensions measure 11 ⅝ inches wide versus the TAP series hanger width of 9 ⅝ inches.

It is also critical to note that you cannot go by the product label to identify a ZTAP bus plug. The prefix on the label, confusingly, will also begin with TAP. It is only by the neutral stab position and hanger width that you can correctly identify a ZTAP bus plug from a TAP bus plug.


We're here to help

We hope that this quick guide helps provide a quick overview of the various Westinghouse bus plug types. If you still have any questions regarding the type that you need, please email us or give us a call and our sales team will be happy to assist you.

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A Brief Introduction to Motor Control Centers

It's been a while since we discussed one of our main product categories in an overview post. In the past, we've covered topics like bus plugs to provide general information about the products EMSCO offers. In this post, we'll delve into the basics of Motor Control Centers (MCC).

Basics of Motor Control Centers (MCCs)

At its core, a Motor Control Center consists of a series of buckets housed within a larger structure. In industrial and manufacturing environments using electric motors, a system is necessary to control these motors, and that's where the motor control center plays a crucial role.

How They Operate

Feeder buckets are responsible for powering and controlling the electric motors, typically with one bucket per motor. Given that industrial processes often involve numerous electric motors, multiple buckets are required to manage the entire system. The structure serves as the vertical housing, conveniently holding and controlling all feeder buckets in a central location.

The buckets within the structure come in various sizes and configurations, such as fused or circuit breakers. Additionally, these buckets are fully removable, providing flexibility for the electric system to adapt to changes in industrial processes. For instance, adding or removing motors is simplified by adding or removing buckets from the structure or swapping them out for the appropriate components.

In Need of Parts?

If you're looking to replace, upgrade, or install a new MCC system, your search ends here. We offer a wide range of vertical sections of motor control centers, ranging from 400 amperes to 3000 amperes, with main or main lug compartments. Our extensive stock includes all major brands like Square D, GE, Allen Bradley, and more. With a plethora of buckets in stock, both fusible and breaker styles, in sizes 0-6, single and twin feeder buckets, EMSCO is certain to have the components you require.


Established in 1948, Electric Motor Supply Company (EMSCO) is a leading dealer of used and refurbished industrial electrical systems and components. Our vast inventory, housed in our 250,000 square foot warehouse in Minneapolis, MN, ensures we have the exact part you need. From over 25 miles of bus duct, thousands of bus plugs, to various transformers, circuit breakers, and beyond, our experts are ready to assist with all your electrical requirements.

Picture of Allen Bradley 2100 Series FVNR Size-1 Starter Fusible Disconnect MCC Bucket R&G

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An Introduction to Bus Plugs

Bus plugs are a critical component of industrial power distribution systems. This blog post explores what bus plugs are, how they function, and the advantages they offer over traditional wiring methods. Learn how bus plugs can enhance flexibility, safety, and efficiency in your facility's power distribution.


In most residential and commercial settings, power is distributed through hardwiring in the walls. In industrial settings, however, the large open floor plans make it difficult to distribute power in this way. That's where bus duct and bus plugs come in.

In industrial settings, bus duct is often used to distribute power to various areas of a facility. Bus duct [also known as busway] is essentially metal enclosures that contain conductors for distributing electricity and generally come in 10-foot sections that connect to one another to create the exact length necessary for a run. They can be installed overhead or under the floor, and they're designed to be flexible, so they can be easily repositioned or rearranged as needed.

However, just having bus duct isn't enough to distribute power to all the equipment in a facility. That's where bus plugs come in.


Bus plugs are essentially large industrial electrical plugs that connect to a section of bus duct overhead and then feed electricity down to the equipment below.

Bus plugs typically come in a variety of sizes and styles to fit different types of bus duct and equipment. They're designed to be easy to install and remove, so they can be quickly repositioned or replaced if needed.


One of the benefits of using bus plugs is that they allow for greater flexibility in terms of the layout of a facility. Because the bus duct and bus plugs can be easily repositioned, it's possible to change the layout of a facility without having to rewire the entire electrical system. This can save a lot of time and money in the long run.

Another benefit of using bus plugs is that they provide a higher level of safety compared to traditional hardwiring. With hardwiring, it's possible for a fault to occur in the wiring, which can lead to electrical fires or other hazards. With bus duct and bus plugs, the conductors are contained within metal enclosures and the bus plugs are equipped with either fuses or circuit breakers, which provide an extra layer of protection against faults and other issues.

Overall, bus plugs are an important component of industrial power distribution systems, allowing for greater flexibility and safety compared to traditional hardwiring.

We hope this has served to give a basic understanding of what exactly a bus plus is, how it works, and why it is used. If you’re looking for replacement bus plugs for your system, look no further! EMSCO stocks the largest selection of used and reconditioned bus plugs from all the major manufacturers (GE, Square D, and more) and from all vintages, from obsolete to modern systems. Simply browse our store or give us a call to find the model you need.

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Updated March 2024