Instrument Earthing

[nkwe]

1.If I'm using pair cable to supply 110v ac solenoid,Can I use screen core as Earth or should I float the sreen on field and provide separate earthing to the instrument?If yes to using screen core as earth,Is it not going to create Earth Loop?

 

[RayRogers]

I don't know either the Industry or application you are working on; but PLEASE don't proceed without getting professional advice. It sounds like you are in an area where the safety and legal issues are hazardous.

Ray

 

[INSTRUMEN]

It is preferable to earth the instrument and keeping the screen core as floating.

 

[MarkTX]

I am not familiar with this terminology screen core. 30 years ago all the 110/120VAC solenoids I worked on were two wires. We evolved int three wires, one for ground, because if the hot wire shorted to the solenoid case, it would make the case hot. If the case was not grounded anyone touching it would be shocked. It makes a lot of sense for safety. As the solenoids were replaced over the years I have run into places where the green wire was terminated on the ground screw on the conduit. I don't know if this will meet code today, it is a safety issue if the conduit is not grounded. The systems I see today all have three wires for 100vac. But I run into very few of these because most systems have switched to 24VDC solenoids. The best is to check the local code. What was acceptable years ago is often a no no today.
Mark

 

[sridharJalei]

You cannot use the screen wire as a ground wire. Normally the screen wires are grounded at only one place and that too at the control room end. DCS or PLC panels. You can use a 3 core cable and ground one core at the solenoid valve. But in many applications I have seen, 110 VAC solenoids are powered with 2 wires only. Single pair cable with screen is not required for 110 VAC solenoids. yes, if it is 24 V DC solenoid, it is advisable to go in for single pair screen cable so that it can be run on the same cable tray along wit other signal cables.