Wiring interaction between two enclosures with different power sources

Is there any issue introducing wires from a different power supply to my enclosure?



Currently, I have an HMI that will be powered by one source and push buttons in the same enclosure that will be attached to another power supply. These push buttons are used to interact with a three wire motor starter circuit. Different contacts on the push buttons will go to different power supplies, but no single contact will go to both power supplies.



Does the fact that there will be wires from two different power sources in the same enclosure bring up any issues?


Thank you for any assistance!

Probably the best way is to enclose the connections in a screw lid enclosure within the other panel with a notice to isolate elsewhere, the standard appears to be orange for those cables depicting they are powered from an external source, if there is any interface with existing equipment in the panel this should be isolated by relays etc within the enclosure there has been other threads here regarding this.
Where possible use a low voltage i.e. 24v this reduces the risk of electrocution.

When there are connections that send an external voltage into the cabinet, and it is not the main incoming power supply, then you must indicate to the electrician that the wiring and terminals might have a dangerous voltage when the main power switch is off.
This is done by using terminals with extra labeling and maybe extra covers over the terminals, and the wiring from the terminals into the control cabinet must be with a color reserved for externally powered circuits - usually yellow or orange.
It generally doesnt matter if it is a low voltage or not. If it is externally powered, then you indicate it with the yellow/orange color.

Apart from the safety issue, normally you want to isolate the electrical systems from each other. Usually by interposing relays or isolation amplifiers.
edit: In your case, it is enough isolation that there are contact sets on the push buttons that are used only for the external control system.

Typically you would often use volt free contacts for this. ( aka a relay)

also, ensure that the 0V rail is tied together so that 0v is 0v in all cabinets.

IEC 60204-1:2018 §5.3.5 if you like to have a read

mad4x4 said:

also, ensure that the 0V rail is tied together so that 0v is 0v in all cabinets.

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Not necessarily.

Are you thinking of equipotential bonding ?

look at nfpa 79 - electrical standard for industrial machinery.
color code for interface wiring.
james