×
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

Proper Control Schematic - Switch Contacts

Proper Control Schematic - Switch Contacts

Proper Control Schematic - Switch Contacts

(OP)
What is the proper way to show Control Switch contacts on DC Control schematics?


Is it best to:
1) show all contacts as a simple open contact symbol, having a contact development show which contacts are closed during different switch positions, labeling next to the contact what state the switch is in when the contact closes

2) show the contacts in their typical position (eg. typically reclose is turned ON therfor this contact is tyipically open) labeling that typical position next to the contact....

|
= 79CO (ON)
|

where...
79CO - (reclose on/off) switch
(ON) - Indicates the switch is in the on position, allowing this contact to be open



3)  Other?  



It seems like every drawing done here is different, so I was just curious to see what is done typically in the utility industry.

Sorry for this elementary question. I hope I worded it correctly. Thanks for helping a newbie.  

RE: Proper Control Schematic - Switch Contacts

All contacts should be shown in their "shelf" state.  That is the state the contact would have when there is no control power to the device, no input/control signals to the device, etc.

RE: Proper Control Schematic - Switch Contacts

Agree with davidbeach on all relays/contactors/other automated things.  Whatever position those contacts are in when still in the shipping box is correct.

Manual selector switches that include an "off" position should be shown in the "off" position. Those that don't have an "off" position (such as "heat/cool") may be shown however you'd like, but be consistent and add notes to anything vague or ambiguous.

Good on ya,

Goober Dave

 

RE: Proper Control Schematic - Switch Contacts

Some switches don't really have a "Shelf state".  In particular GE SBM switches ( and similar) have different states that do not depend on being energized.  A contact may have a differnet state after "Trip" and after "Close" and they all may be different after "Pull to Lock".
The traditional way to put these switches on a drawing is with a table.  

RE: Proper Control Schematic - Switch Contacts

Use a table clearly identifying the contacts.  Add a column indicating where each contact is used - a cross reference to the schematic.

An entry identifying the use helps also - "Block Close", "Inhibit Remote" etc.

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