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Posted By Topic: screened cable

May 17 2015 19:39

I have a customer with a milkshed backing gate that is supplied by a 3c+E+screen 2.5mm flexible cable. The cable is perished and needs replacement.

The run is from the MSB, roof cavity to the outside where is runs through a metal pipes and receives considerable flexing in a couple places about 30 times a day.

So, with that information (and I could provide more if required) does the cable in fact need to have a braided screen?

I would have thought a cable designed for the sort of movement would be sufficient, no screen required. Am I mistaken.

May 17 2015 20:32

No screen is required for this application.
When it was installed the original electrician probably used the only heavy duty flex that was available at the time.
These days there are many more flexible cable options for this application.

May 17 2015 20:39

Sounds like maybe the cable is supplying a variable speed drive (VSD), so ensuring you have the right cable is important.

When replacing it consider why it has perished first. Chemicals/sun/ flexing.

We use first flex cables. Plenty of choice.

May 17 2015 21:03

Highly unlikely that a dairy farm backing gate is controlled by a vsd.
Just having a 3 phase one is considered an upgrade in some farms.

May 17 2015 22:23

sure your prob right, but do look at the right cable for the flexing.

May 18 2015 01:53

VSDs are very common now and that\'s a good example of where one would be used. Gentle-does-it is the motto when it comes to cows.

Ask the farm manager how it\'s controlled.

If a screened cable is not used when there is a VSD powering that motor then it\'ll totally crap all over the local radio links, in particular it\'s common to have datalogging equipment all over farms now.

May 18 2015 08:43

Not only that, but unscreened or incorrectly screened cables used with VFDs can result in hazardous touch voltages, because standard earthing doesn\'t carry HF well.

May 18 2015 20:22

Thanks guys. No VSD on this one. My suspicion is in line with Sarmajors. It was probably all that was around at the time.

Firstflex had a solution.