Proper Control Schematic - Switch Contacts 1

[electricnewbie]

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.

 

[davidbeach]

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.

 

[DRWeig]

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

 

[BJC]

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.

 

[rcw retired EE]

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.