Plastic 3 phase Rotary Isolator Earthing

[robbo777]

Hi All

What method do you use for earthing armoured to armoured on a platic 3 phase rotary isolator? Assuming I will have one armoured on top of the isolator and one on the bottom.

At the moment I use the banjos and on the inside of the isolator using an m6 bolt I'll lug the earth cable and join them but there's got to be a better method than this.

Always open to better suggestions

Many Thanks

 

[Leesparkykent]

Piranha earth locking nut.

 

[Darkwood]

Use earthing locknuts. .. little bit expensive but save it on time faffing about with earth rings.

 

[Deleted member 26818]

Put the banjo on the inside if there's room.
Use a 5 core cable.

 

[robbo777]

Piranha earth locking nut.

Perfect, I never knew these existed. exactly what I was looking for.

Many Thanks

 

[Risteard]

Put the banjo on the inside if there's room.

Really it should be sandwiched between two locknuts inside a plastic enclosure to prevent creep which could compromise the earth integrity.

 

[Deleted member 26818]

It's not sandwiched between two lock nuts on the outside, so why should it make any odds on the inside?
Perhaps you just need stronger arms?

 

[davesparks]

It's not sandwiched between two lock nuts on the outside, so why should it make any odds on the inside?
Perhaps you just need stronger arms?

It should be if it is on the outside of a plastic enclosure, the problem is that plastic is a soft material so no matter how tight you make the nut at installation the plastic could move and the connection become loose. Also plastic is susceptible to temperature changes, so could in theory soften under fault conditions and loosen the connection.

 

[Lucien Nunes]

Exactly. An earth connection that just sits there being slightly loose and the moment you actually want to pump some current through it the plastic softens and it goes open completely. I never rely on clamping through the plastic wall of a box for making a banjo connection. 99% of the ones I've tried have been loose, sometimes you can push the banjo round with one finger once the bolt is out. It was double-nut every time until the advent of the earthing nut which is better still.