Automation Canada Quarterly Volume 2 Issue 5 - 10

WEIGHING YOUR OPTIONS

UNDERSTANDING THE OPTIONS FOR
MOTOR DISCONNECT SWITCHES
Motor disconnects are more than simple on-off devices to satisfy
lockout-tagout requirements. They have become an integral part of the motor
control circuit as disconnects increasingly offer control functions, such as
auxiliary contact interface, added selector switches and push buttons.
Disconnects can be fusible or non-fusible and can have different pole
arrangements and environmental ratings. Multiple disconnects can be packed
into one enclosure, saving space and cost while allowing you to address varied
requirements, including harsh food processing or washdown applications.
The following paper discusses the specification steps you should keep in
mind when selecting a motor disconnect, as well as the various electrical,
installation and enclosure options that will determine how your disconnect
functions in its operating environment.
SPECIFYING YOUR DISCONNECT
With all the different motor disconnects on the market, the best choice for
your application isn't always obvious. But if you follow a few simple
specification steps, you'll end up with the right disconnect switch every time.
Evaluate the operating environment. While it's good to pay attention to the
electrical characteristics of a motor disconnect, it's just as important to carefully
evaluate the disconnect's operating environment-a step that is often
overlooked. The operating environment will determine what type of housing
material will work best in your plant or on your shop floor.
High-quality motor disconnect switches are available in both metallic and
non-metallic. MENNEKES products use UL Listed metallic and non-metallic
enclosures, both with a NEMA 4X rating, so they offer watertight protection for
harsh environments. Many NEMA 4X enclosures can withstand challenging
operating conditions, including those with corrosive chemical exposures and
caustic cleaning substances. If both metallic and non-metallic can meet the
same NEMA rating, typically the manufacturing environment will make the
choice clear.
Where stainless steel shines. Stainless steel and other metallic enclosures are

C A N A D I A N A U TO M AT I O N

increasingly favored in areas with the potential for direct food contact. One
reason involves stainless steel's tolerance of repeated washdown cycles. The
other reason is that food processors prefer metallic enclosures in production
line areas since metal detection systems can pick up foreign matter if there is
breakage. Metallic enclosures also have better impact resistance, so
high-traffic and end-of-line applications in packaging, manufacturing and
pharmaceutical facilities often use stainless enclosures.
High-performance polymers. The vast majority of motor disconnect
applications are well served by disconnects with a non-metallic enclosure.
These polymer housings have a lot going for them. Non-metallic housings
generally cost less than a comparable metallic housing. Nonmetallics also cost
less to install-in part because they are easier to punch and rough-in for fittings
and conduit than metallic boxes. Unless you need stainless for a specific food
processing area or for impact resistance, polymer housings will likely offer all
the performance you need for less money.
Keep in mind, however, that not all non-metallic disconnect switches are
created equal. While a NEMA 4X disconnect has a watertight rating, the type
of polymer used for the enclosure has significant performance consequences
especially when it comes to chemical, weather, flame and impact resistance.
We make all our enclosures from a very high-performance polymer that is UV
stabilized and has a UL 94 -5V flame rating. Our UL Listed enclosures indicate
that they have passed rigorous impact and conduit bending tests.
DETERMINING A DISCONNECT'S ELECTRICAL DESIGN
Open any catalog of motor disconnect switches, and you may be
overwhelmed by all the different electrical options. Does your disconnect
need to be fusible? Is it a 1Ø or 3Ø switch requirement? What HP and voltage
are needed? Do you need an installed pilot device? The list could go on and
on-and for good reason. Nowadays, motor disconnects increasingly have to
meet challenging electrical or installation requirements, and in many cases,
you may need a specialized switch to meet those requirements.

VOLUME 2, ISSUE 5

10
https://www.mennekes.com/ https://www.mennekes.com/products/motor-disconnect-switches https://www.mennekes.com/
Automation Canada Quarterly Volume 2 Issue 5

Table of Contents for the Digital Edition of Automation Canada Quarterly Volume 2 Issue 5
