Grounding Between Industrial Control Panels

[tganz96]

I am insatalling a new system which consists of 2 cabinets which have PLC's ,HMI's and Drives in each. One of them is built by anOEM and the other we did in house.

Cabinet A from the OEM and cabinet B from us has 4 conduits between them and are about 170 feet apart. We have 2 ethernet cables between the 2 cabinets and a switch in each to comm between a compact logix in our cabinet and a micrologix 1400 in the OEM cabinet.

We have 24 volt dc wiring between them to interlock the estop system. Should I connect a ground between the 2 cabinets or not and why? the OEM panel is fed from an Iline panel borad and our cabinet is fed from a MCC bucket and the MCC is fed from the same Iline panel board as the OEM panel.

I am just not sure what needs to happen with grounding between the 2 systems.

 

[petersonra]

I am insatalling a new system which consists of 2 cabinets which have PLC's ,HMI's and Drives in each. One of them is built by anOEM and the other we did in house.

Cabinet A from the OEM and cabinet B from us has 4 conduits between them and are about 170 feet apart. We have 2 ethernet cables between the 2 cabinets and a switch in each to comm between a compact logix in our cabinet and a micrologix 1400 in the OEM cabinet.

We have 24 volt dc wiring between them to interlock the estop system. Should I connect a ground between the 2 cabinets or not and why? the OEM panel is fed from an Iline panel borad and our cabinet is fed from a MCC bucket and the MCC is fed from the same Iline panel board as the OEM panel.

I am just not sure what needs to happen with grounding between the 2 systems.

metallic conduit is a perfectly acceptable equipment grounding conductor.

 

[Smart $]

The cabinets should be grounded via a conduit or wire EGC from the power source.

If the conduits between cabinets are metallic, they are typically bonded through mechanical connection and provide the required grounding means.

If the conduits or any part of the run is nonmetallic such that any non-current-carrying metallic parts are ineffectively bonded, you will have to run an EGC or bonding conductor to bond the parts from whichever cabinet that is likely to be the energizing source.

 

[tom baker]

Your PLCs are connnected via ethernet and will be very tolerant of induced noise. However I had 3 control cabinets with compact logix and one PLC cabinet, PLC was on UPS, there was a power outage and the PLC in the main cabinet went off line, not sure how. But we changed to ethernet fiber optic/RJ45 medial switches and ran multimode fiber between all. So far so good.