Anyone know any spec's or installation information or advice regarding the installation of an Instrument & clean Earthing system for a new PLC we are to install to replace a pneumatic system.

Current earthing is plant & MCC dirty earths

Thanks in advance
Greg

 

Greg,

The PLC manufacture is going to be able to provide detailed installation, power and grounding information in their manual or via technical support. Typically your earth ground for PLC power can be connected directly to the existing enclosures ground terminal or stud.

If your concerned about the integrity of the overall system grounding, you can clean the MCC ground bus, clean all ground connections, re-attach the ground wires, ensure that the ground wire and ground rod are intact (replace as required). - I would recommend this be done by a licensed electrician, not by you, since you are probably not a licensed journeyman electrician - which if you were, you would not be asking this type of question.

I would be recommending surge protecting devices, maintenance of all grounding terminations and an overall review of the grounding system.

Otherwise, you should be consulting with the PLC manufacture, a licensed electrician, the NEC and local or state electrical inspectors.

Other than doing a good job of providing a solid ground connection from the PLC to the appropriate ground stud and ensuring the integrity of the overall grounding system, you probably don't have to do anything else, follow local code and NEC requirements, seek advice or service from a licensed electrician who is experienced with installations in your specific environment.

Many instrument manufactures recommend a ground wire be connected to their instrument chassis, one as part of the required power connections, two a protective requirement and even local code may require that a ground wire be provided.

Fell free to drop me a note offline.

[email protected]


you can also go to:

www.mikeholt.com, has tons of technical and NEC related information.

 

Refer to the PLC supplier for earthing requirements as they ussually have their own requirements (ohm value, independent system, etc..)

 

Hi,

You will need a 'clean' earth (US ground) which is seperate from the MCC 'dirty' earth. Earth pit readings for DCS are usually 1 ohm or less, your PLC will probably require the same. Manufacturer will confirm.