Disconnect Switch Selection

[Knappy]

Hi, I'm not sure if this is the right place to be posting this but I was wondering if someone could lay down some general guidelines to keep in mind when selecting a disconnect switch for a PLC panel.

For example, I have to select a disconnect switch for a Panel that has a MicroLogix 1200 PLC, a motor (12.4/9.5 A), and 4 heaters (220V 300W each).

Anything you can add would be a great help. Thanks.

 

[Skogsgurra]

Select a switch that is designed for the short-circuit of the mains feeding the panel. There are usually fuses or a breaker with overcurrent trip in the feeder. As long as your switch can withstand the fuse/breaker rating it is OK. No use to select breaker according to actual load.

Gunnar Englund

http://www.gke.org

 

[jdkasper]

Other things to consider are:

External or panel mounted (interlocked?)
How often it will be actuated
Compliance with Lockout/Tagout
Enclosure type (suited for environment)
Susceptibility to damage (believe me, it will happen)

 

[dbaird]

If this is for an industrial machine in the USA you are required to to abide by NFPA 70 "Electrical Standard for Industrial Machinery"

Chapter 5 covers disconnects.

http://multiterra.mooload.com/file.php?file=files/1137696459/NFPA+79_Chapter+5.pdf

David Baird

Sr Controls Designer
EET degree.
Journeyman Electrician.