Paired cable screens

Lc1 · May 13, 2015

We have a 5pair cable which is overall screened. This cable takes 3 alarm signals from a panel to the DCS, 2 pairs are spare. Does the screen have to be earthed at one side only? And can the screen be left unearthed?

thanks

Hellmooth · May 14, 2015

Pop it into the earth terminal in the panel, leave the other end unearthed, seen many installs where it isn't earthed at all, but I've had issues in the last with interference!

Hellmooth · May 14, 2015

It was the second post I would have liked kept, I meant past instead of last, won't matter too much :yes:

LeeH · May 15, 2015

At any one end.

Should be marked Cream/White.

SheffSimon · May 15, 2015

Lc1 said:
We have a 5pair cable which is overall screened. This cable takes 3 alarm signals from a panel to the DCS, 2 pairs are spare. Does the screen have to be earthed at one side only? And can the screen be left unearthed?

thanks

What are you doing with spare pairs? It's not unusual to take them to protective earth, especially in an ATEX install.

I would also expect to see a separate instrument earth at the DCS, and from there, a screen earth bar.

LeeH · May 15, 2015

SheffSimon said:
What are you doing with spare pairs? It's not unusual to take them to protective earth, especially in an ATEX install.

I would also expect to see a separate instrument earth at the DCS, and from there, a screen earth bar.

As you know, only if it's IS. And if it is, its mandatory.

But this is way overboard for the OP I would have thought.