24vdc power supply

[Lc1]

We have a drawing that shows a solenoid valve panel( containing approx 40 valves) being powered from an adjacent control panel by a 24vDc PSU however this is shown as a 2 core cable connection but I was thinking it should maybe be a 3 core with the third core being an earth connection.
Not sure if there is something I am missing?

Thanks

 

[DPG]

I wouldn't imagine the extra low voltage cables need an earth. Just a pos and neg.

 

[Darkwood]

You are looking at the control voltage of 24v DC, this falls in the realm of safe to touch extra low voltage and doesn't require the negative to be grounded or a reference earth... however it is sometimes done either permanently or temp' to aid testing and maintenance to give a reference point to identify faults easier, also to shut down monitored systems in some fault conditions.

Caution to be taken if you convert it and ground the negative is the fusing arrangements if the power supply itself is not monitoring for S/C or overload.

 

[Lc1]

Thanks for the replies.
Cheers