Advantage to sinking inputs

[PackagingRich]

Hi all,
We are replacing a old SLC50/2 with a new MICROLOGIX 1220.
Old inputs were wired 24vdc sinking. Is there an advantage to this? Should I keep the same, just wondering.

 

[PackagingRich]

Sry, meant MICROLOGIX 1200

 

[bernie_carlton]

The DC input controller can be wired either way. The advantage of the sinking 24VDC is that it is already wired that way. If it works then fine.

For new controls the switching input should switch the ungrounded conductor (if one is grounded) to avoid false turn on in the event of an accidental signal grounding.

 

[PackagingRich]

I have researched the archives and got a little confused. Should I then ground the 24VDC+, or leave both ungrounded?

 

[bernie_carlton]

1. If it was working before don't change it.

2. If new rules require that you implement grounding of the 24VDC supply then US common practice is to ground the negative side. Be sure to check all input and output devioces for any problems with this.

 

[PackagingRich]

Thanks. Will keep it the same, easier that way.