×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Class 2 control center

Class 2 control center

Class 2 control center

(OP)
If multiple (seperately derived) class 2-control wiring enter a single "control panel" what are the code implications? Since the 120V motor controls are derived from independent sources of power, servicing the units can intoduce the potential of electrical shock.. etc/ no clear means of disconnect. Not clear to me per 2002 NEC?

RE: Class 2 control center

It is not clear what you are asking , everything alway applies in the nec it depends on what you want to do.

RE: Class 2 control center


One reference may be NEMA Std ICS 1-2000 Industrial Controls and Systems, General Requirements §7.5, cataloged at www.nema.org or, possibly others in the ICS 1 series.
  

RE: Class 2 control center

If you have a motor- OF ANY TYPE!- and there is potential to get hurt from mechanical movement you need an isolating disconnect. And yes damper motors are motors as well - really strong tourqey hurtful little motors if I remeber right. Specifically if the source of power (be it a breaker or fuse or whatever) is over 30'(south of the 49TH) or 9.5m (north of the 49TH) from the motor and that source is not lockable in the "off" position you need a disconnect.
Why argue, common sense tells you it is easier to service whatever it is regardless of the number of sources within the device.

RE: Class 2 control center

(OP)
There is a requirement to control several petrol pumps located inside a Class 1, Div 1, CD area remotely from a  non-class area. The motor starters, switched to auto, the class II 120V control leads all enter a common start-stop station. I was curious to the disconnect requirements of these separately derived class 2 voltages when servicing the control panel, not the motors.

RE: Class 2 control center

I believe it is acceptable for you to simply provide adequate labeling indicating the presence of multiple foreign voltage sources if it is not practical to disconnect them all when the door is opened. There are spring-loaded door switches available that will open the circuit when the door is opened, but theat becomes cumbersome in control stations in particular.

When there are only a few, I use these, with the "pull-to-cheat" feature so that I can test circuits with the door open.

http://catalog.sensing.honeywell.com/datasheet.asp...

"Venditori de oleum-vipera non vigere excordis populi"


RE: Class 2 control center

(OP)
At least in the current state of emergency breakdown maintenance at our facilities. These switches would last until the next "emergency”, a few cuss words, and be bypassed as the first trouble shooting method. I like labeling the leads. Control technicians should be well versed in the hazards associated with troubleshooting these types of systems, If not, they have no business of opening any panels. (The lawyer’s would disagree however)

a star for trying however,

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources