What is this - an external isolator?

[JohnW2]

Surely it would make more sense to not introduce ferrous metals into the equasion, would it not?

If it's a ferrous metal box, then such a material is right at the centre of the equation (and, per regs, has to be 'connected to earth' somehow), whether one likes it or not - or are you suggesting that we should use brass boxes?

... which raises an interesting question - if one did use a brass box, would you still feel the need for a banjo?

Kind Regards, John

 

[SUNRAY]

As I understand it, you effectively are (electrically) are ...
Yes, if one does that (which I suspect a good few don't), and particularly if one uses three nuts (which I imagine even less people do), then the two mechanical joints will be (mechanically) 'isolated' from one another.

No I know a good few don't which is why I've had to repair so many of the ruddy things.
Suddenly your arguement has changed to what I have been saying all along

However, that does not alter the fact that if all the joints are mechanically (hence also electrically) sound, that there will then be an electrical path through the steel in parallel with that through the brass (or vice versa, if one wants to look at it like that).

Kind Regards, John

Indeed one could look at it thay way but going by your ideas there is no requirement to bolt the banjo to the enclosure and one could conceivably rely on the mechanical gland to enclosure joint for the enclosure earth and the banjo for the remainder of the electrical earthing requirements, ie the internal earthing arrangements taken directly from the banjo may not have any connexion to the enclosure save the gland.

 

[SUNRAY]

If it's a ferrous metal box, then such a material is right at the centre of the equation (and, per regs, has to be 'connected to earth' somehow), whether one likes it or not - or are you suggesting that we should use brass boxes?

... which raises an interesting question - if one did use a brass box, would you still feel the need for a banjo?

Kind Regards, John

I do still use a banjo, well these days I'd use an earting nut which really can be mechanically isolated, as I've always been taught not to rely on the mechanical joint for the electrical connexion.

 

[JohnW2]

Yes, if one does that (which I suspect a good few don't), and particularly if one uses three nuts (which I imagine even less people do), then the two mechanical joints will be (mechanically) 'isolated' from one another.

No I know a good few don't which is why I've had to repair so many of the ruddy things. Suddenly your arguement has changed to what I have been saying all along

My 'argument' hasn't changed. I was merely agreeing with your statement that using two nuts partially isolates, and using three nuts fully isolates, the mechanical joints from each other.

However, my 'argument' has never been about isolation of mechanical joints from one another. Indeed, if one has no banjo (or a banjo with one nut), there are not two mechanical joints to isolate from each other.

Indeed one could look at it thay way but going by your ideas there is no requirement to bolt the banjo to the enclosure and one could conceivably rely on the mechanical gland to enclosure joint for the enclosure earth and the banjo for the remainder of the electrical earthing requirements, ie the internal earthing arrangements taken directly from the banjo may not have any connexion to the enclosure save the gland.

Yes, but this "relying" language is confusing and misleading since, if the joints are all mechanically (hence also electrically) sound, then the electrical paths which involve the box and those which don't involve the box are permanently in parallel - so one cannot really say that a connection between anything and anything else 'relies on' just one of those parallel paths.

There is also scope for some confusion of language which arises from the fact that you seem to be assuming that 'earth' is coming from the SWA's armour and that this is providing "the electrical earthing requirements" of the CPCs (and box). However, it's perfectly possible (and common) that 'earth' is being supplied by one or more of the incoming CPCs and that it is they that are providing "the electrical earthing requirements" of the SWA armour (and the box).

Kind Regards, John

 

[JohnW2]

.... or are you suggesting that we should use brass boxes? .... which raises an interesting question - if one did use a brass box, would you still feel the need for a banjo?

I do still use a banjo, well these days I'd use an earting nut which really can be mechanically isolated...

I'm not sure what your answer means in terms of my questions which you are answering (and quoting) - if you were working with a brass (or maybe other non-ferrous metal) box, would you still feel the need for a banjo?

these days I'd use an earting nut which really can be mechanically isolated, as I've always been taught not to rely on the mechanical joint for the electrical connexion.

Well, unless you solder/braze (and, even then, the joint is meant to be mechanically sound before one solders/brazes), one has to rely on some sort of mechanical joint for the electrical connection - so I presume that what you're saying is that one should not rely on a mechanical joint formed by the thread of a nut or nuts on the body of the gland. If so, then if I understand you correctly, that would presumably apply with any of the methods you have been advocating (with banjos).

Even with a Piranha nut, the electrical connection is primarily reliant on the mechanical joint of the threads, although the grub screw helps to maintain the mechanical (hence also electrical) integrity of that joint, in addition to providing a bit of a path through itself.

Kind Regards, John

 

[SUNRAY]

There is also scope for some confusion of language which arises from the fact that you seem to be assuming that 'earth' is coming from the SWA's armour and that this is providing "the electrical earthing requirements" of the CPCs (and box). However, it's perfectly possible (and common) that 'earth' is being supplied by one or more of the incoming CPCs and that it is they that are providing "the electrical earthing requirements" of the SWA armour (and the box).

Kind Regards, John

My previous did in fact raise exactly that point and lookedsomething like this:

... one could conceivably rely on the mechanical gland to enclosure joint for the enclosure earth and the banjo core for the remainder of the electrical earthing requirements, ie the internal earthing arrangements taken directly from the banjo core may not have any connexion to the enclosure save the gland.

but I changed it to avoid yet another tangent.

 

[SUNRAY]

I thought I'd answered the question, does this make it easier?

If it's a ferrous metal box, then such a material is right at the centre of the equation (and, per regs, has to be 'connected to earth' somehow), whether one likes it or not - or are you suggesting that we should use brass boxes?

... which raises an interesting question - if one did use a brass box, would you still feel the need for a banjo?

Kind Regards, John

I do still use a banjo, well these days I'd use an earting nut which really can be mechanically isolated, as I've always been taught not to rely on the mechanical joint for the electrical connexion.

 

[SUNRAY]

Well, unless you solder/braze (and, even then, the joint is meant to be mechanically sound before one solders/brazes), one has to rely on some sort of mechanical joint for the electrical connection - so I presume that what you're saying is that one should not rely on a mechanical joint formed by the thread of a nut or nuts on the body of the gland. If so, then if I understand you correctly, that would presumably apply with any of the methods you have been advocating (with banjos).

Even with a Piranha nut, the electrical connection is primarily reliant on the mechanical joint of the threads, although the grub screw helps to maintain the mechanical (hence also electrical) integrity of that joint, in addition to providing a bit of a path through itself.

Kind Regards, John

I thought we'd got past this one.
Mechanical connexion = the physical stabilizing joint, designed to offer mechanical support.
Electrical connexion = the path used for electrical current to flow. This may take the form of soldering, brazing, nuts and bolts, crimped etc, but not intended to offer any mechanical support.

To put this into perspective, let's build a unistrut frame and mount several enclosures, one would not use the electrical path which happens to exist between them as part of the earthing arrangement... or would you?

 

[JohnW2]

I have been reading posts like these without thinking enough to 'challenge' them ...

Initially you are advocating botching by not being be arsed to bother to install any sort of earth connexion in contravention of 'best practice' or MI's and presumably dumping the items supplied in the gland pack in the scrap metal bag.

Securing the banjo between 2 brass nuts, and never just a single nut and certainly not steel, provides a degree of mechanical isolation from the mechanical joint with the enclosure.

In reality it's all down to quality and workmanship and, I'll add a term here that I know you love so much John, Best practice.

However, I've now had a rummage through my shelves and find that every SWA Gland Kit I have contains just one shroud, one banjo and one nut per gland - and, looking around on-line, that seems to be what the great majority of gland kits being sold consist of.

Does this mean that those who manufacture and sell Gland Kits have a different view of 'Best Practice' from you - or are they 'trying it on' by encouraging people who want to engage in 'Best Practice' to throw every second gland body, banjo and shroud into the "scrap metal bag' in order to get a second nut for the one they actually used?

Kind Regards, John

 

[JohnW2]

I thought we'd got past this one. Mechanical connexion = the physical stabilizing joint, designed to offer mechanical support. Electrical connexion = the path used for electrical current to flow. This may take the form of soldering, brazing, nuts and bolts, crimped etc, but not intended to offer any mechanical support.

Sure, but so what?

We are specifically talking about electrical connections achieved by 'nuts and bolts' or nuts tightened against rigid things. In that situation, the electrical connection depends entirely on the integrity of the 'mechanical joint' achieved by tightening the nut(s) - so mechanical and electrical integrity are essentially the same thing.

To put this into perspective, let's build a unistrut frame and mount several enclosures, one would not use the electrical path which happens to exist between them as part of the earthing arrangement... or would you?

Probably not. However if it were a 'frame' constructed out of steel conduit, properly connected to steel back boxes of the accessories, then I imagine that at least some would say that it was OK (and probably compliant with BS7671) to use those conduits as "parts of the earthing arrangement", wouldn't they?

Kind Regards, John

 

[SUNRAY]

I have been reading posts like these without thinking enough to 'challenge' them ...
However, I've now had a rummage through my shelves and find that every SWA Gland Kit I have contains just one shroud, one banjo and one nut per gland - and, looking around on-line, that seems to be what the great majority of gland kits being sold consist of.

Does this mean that those who manufacture and sell Gland Kits have a different view of 'Best Practice' from you - or are they 'trying it on' by encouraging people who want to engage in 'Best Practice' to throw every second gland body, banjo and shroud into the "scrap metal bag' in order to get a second nut for the one they actually used?

Kind Regards, John

It hadn't occurred to me this has now spanned over 2 treads, I answered your qestion in "Other peoples work" post #84 viz:

The old packs used to supply 2 brass nuts, the plan was to fix the gland in place, add the banjo and second nut so the eletrical connexion was performed by 2 nuts and not pressure against the enclosure,the lazy work done by so many eventually led to dropping one nut unfortunately.

For the record, when I'm doing this sort of work I carry spares...

 

[JohnW2]

I thought I'd answered the question, does this make it easier?

Perhaps, but since I doubted that you actually do use brass boxes, I wasn't sure whether or not "I do still use a banjo" was an answer to my question.[it would hjave been 'easier' (at least, clear) had you written something like "I would still use a banjo"].

Anyway, now that is cleared up, can you help me understand why you would use a brass banjo when attaching a brass gland to a brass box?

Kind Regards, John

 

[SUNRAY]

Perhaps, but since I doubted that you actually do use brass boxes, I wasn't sure whether or not "I do still use a banjo" was an answer to my question.[it would hjave been 'easier' (at least, clear) had you written something like "I would still use a banjo"].

Anyway, now that is cleared up, can you help me understand why you would use a brass banjo when attaching a brass gland to a brass box?

Kind Regards, John

That's an easy one to answer, just go back 4 posts to #68

 

[JohnW2]

It hadn't occurred to me this has now spanned over 2 treads, I answered your qestion in "Other peoples work" post #84 viz: .... For the record, when I'm doing this sort of work I carry spares...

So what's the answer to my question, then? ... given that the suppliers of gland kits no longer provide 2 (and never did supply 3) nuts per gland, does this mean that they disagree with your view of 'Best Practice' or are they trying to rip people off by making those who don't carry spare nuts throw away nearly all bits of half the gland kits they buy?

Kind Regards, John

 

[SUNRAY]

So what's the answer to my question, then? ... given that the suppliers of gland kits no longer provide 2 (and never did supply 3) nuts per gland, does this mean that they disagree with your view of 'Best Practice' or are they trying to rip people off by making those who don't carry spare nuts throw away nearly all bits of half the gland kits they buy?

Kind Regards, John

It means they have established that parts of their packs are being thrown away [second nut] by people not understanding or refusing to follow MIs and accordingly reduced the quantity of nuts supplied as a means of increasing their profit.