Extending Circuits

[ban-all-sheds]

That's the same one I posted pictures of. I've never seen an unjointed length of meter tail burn out

Indeed.

But a circuit with no joints in it isn't a lot of use. I agree there's no point in having an isolator for its own sake, but if one is useful then I don't see why a few more joints to go with the hundreds already present in the installation is something to be worried about.

 

[JohnW2]

But a circuit with no joints in it isn't a lot of use. I agree there's no point in having an isolator for its own sake, but if one is useful then I don't see why a few more joints to go with the hundreds already present in the installation is something to be worried about.

Quite so. As I said, if the alternative being contemplated is Henley(s), then an isolator (involving exactly the same number of joints) would at least occasionally be 'useful'.

Of course, with any screwed joint, the unknown factor is 'who does it'. It's interesting to see that, AFAICS, at least one (possibly both) of the pics RF posted seem to indicate that the (presumed) loose connection which resulted in the 'burning out' was on the meter side of the isolator - hence very probably done by an MOP (or maybe DNO).

As for the 'usefulness' of isolators, if there were one there, I would certainly use it to isolate a CU before working on it, even though the CU's main switch was 'off', wouldn't you? (it would seem silly not to, wouldn't it?!)

Kind Regards, John

 

[RF Lighting]

I remove any henleys, isolators or any other unnecessary joint and replace with a single unbroken length of tails.

 

[JohnW2]

I remove any henleys, isolators or any other unnecessary joint and replace with a single unbroken length of tails.

That's obviously the electrical ideal, if an isolator and/or splitting of the tails is not required - but are you saying that you break the meter seals (assuming that it's not one with insealed access to load side) ??

Kind Regards, John

 

[RF Lighting]

I'm not saying that I do that.

 

[sparkwright]

I would have thought having Henley blocks were convenient, for various reasons.

One advantage would be they wouldn't have to sealed, unlike the meter.

Very useful if a second consumer unit has to be added.

Surely Henleys only fail if the terminals aren't tightened, or the tails are subject to a lot of movement.

 

[JohnW2]

I'm not saying that I do that.

Ah - so you have a technique for "removing any henleys, isolators or any other unnecessary joint and replace with a single unbroken length of tails" without breaking the meter seals?

Kind Regards, John

 

[JohnW2]

I would have thought having Henley blocks were convenient, for various reasons. ... One advantage would be they wouldn't have to sealed, unlike the meter. ... Very useful if a second consumer unit has to be added.

All true - but I suspect that some (like RF?) will argue that such eventualities are unlikely to ever arise during the lifetime of a given installation!

Surely Henleys only fail if the terminals aren't tightened, or the tails are subject to a lot of movement.

Indeed - as is true of any other screwed connection in the installation (including connections of tails to main switch in CU).

Kind Regards, John

 

[scousespark]

I am personally pretty 'neutral' in terms of the isolator issue. However, CUs vary in relation to how well protected are the supply-side connections/terminals of the main switch - one often has to have ones hands very close to them when doing things with neutral and/or earth bars - so I personally always welcome the opportunity to isolate the entire CU (with an external isolator) when 'playing around' within it!

Kind Regards, John

An isolator is just another potential weak point. As stated, they are useful for a CU change, but getting the fuse pulled is not that difficult to arrange.

I am puzzled as to why a diyer would 'often' need to open up a CU to access the earth/neutral bars.

Happy New Year.

 

[JohnW2]

An isolator is just another potential weak point. As stated, they are useful for a CU change, but getting the fuse pulled is not that difficult to arrange.

Sure - you're merely repeating RF's view. However, as I've said, if the alternative under consideration to to have Henley(s), the the number of joints is the same, and the chances of the mechanism of a (very rarely operated) isolator 'failing' is surely vanishingly small.

I am puzzled as to why a diyer would 'often' need to open up a CU to access the earth/neutral bars.

I don't think anyone said anything about 'often' - and, in any event, it's far more likely that an electrician (rather than a DIYer) would be doing things within a CU. However, as I said/asked (and this applies just as much to electricians as DIYers)...

As for the 'usefulness' of isolators, if there were one there, I would certainly use it to isolate a CU before working on it, even though the CU's main switch was 'off', wouldn't you? (it would seem silly not to, wouldn't it?!)

In such a situation, would you really not bother to avail yourself of the additional safety of using the isolator (if one were there) if you were doing things within the CU? As I said, I really don't feel strongly in either direction as regards the 'isolator yes/no' issue - but I'm interested to see how polarised the views of electricians appear to be in relation to the question!

Happy New Year.

Thanks ... and ditto to you and yours.

Kind Regards, John

 

[sparkwright]

I have no fixed views on Henleys, only that most of the time they are more convenient, rather than inconvenient.

The main issues with them are;

1) People don't always tighten them up properly.
2) The cables can be pulled and made loose.

Yes, I know I've already said all that, but it does point to another problem;

1) There has been talk about using a torque tool to check the tightness of the screws, but I suspect an electrician would tighten them up than they perhaps the torque tool says.
2) Why do tails so rarely have cable clamps or clips or other restraints to prevent them getting disturbed? Usually they ate dressed neatly, few cable or ties or tape if you're lucky, but could get yanked quite easily

 

[JohnW2]

1) There has been talk about using a torque tool to check the tightness of the screws, but I suspect an electrician would tighten them up than they perhaps the torque tool says.

There seems to be a word or two missing from that sentence, but if you're saying than electricians (and others) would probably tighten them ('manually') to much more than the specified torque, then I agree. As I have observed before, I find it quite frightening how 'loose' arethe terminals of RCDs, MCBs, main switches etc it one tightens them to the manufacturer's recommended torque - if I do that, I can often get quarter or half a turn more 'manually' without much effort.

2) Why do tails so rarely have cable clamps or clips or other restraints to prevent them getting disturbed? Usually they ate dressed neatly, few cable or ties or tape if you're lucky, but could get yanked quite easily

Good question, if they are of significant length and/or 'drooping'. If they take fairly short and fairly straight direct routes between two terminations, then I would say that the stiffness of the cable is such that restraints are not really necessary, particularly if they are 25mm².

Kind Regards, John

 

[scousespark]

An isolator is just another potential weak point. As stated, they are useful for a CU change, but getting the fuse pulled is not that difficult to arrange.

Sure - you're merely repeating RF's view.

Is this thread restricted to answers from RF. (Scousespark)

However, as I've said, if the alternative under consideration to to have Henley(s), the the number of joints is the same, and the chances of the mechanism of a (very rarely operated) isolator 'failing' is surely vanishingly small.

It may be small, but an isolator can fail.

If a homeowner wants an additional CU, then I would say that is the time to fit a henley block.

If either are already fitted, I have no issue using them on jobs.
(Scousespark)

I am puzzled as to why a diyer would 'often' need to open up a CU to access the earth/neutral bars.

I don't think anyone said anything about 'often' - and, in any event, it's far more likely that an electrician (rather than a DIYer) would be doing things within a CU. However, as I said/asked (and this applies just as much to electricians as DIYers)...

In the post I quoted, you stated that one often has to have ones hands very close to them when doing things with neutral and/or earth bars - I was questioning why you would need to often work in a CU. I have rewired my current home once and that is the only time I have had to work in the CU. (Scousespark)





Kind Regards, John

 

[JohnW2]

However, as I've said, if the alternative under consideration to to have Henley(s), the the number of joints is the same, and the chances of the mechanism of a (very rarely operated) isolator 'failing' is surely vanishingly small.

It may be small, but an isolator can fail.

Why such an unusual and tedious format of quoting/response in your post?]
Nothing's impossible, but I would have thought that the probability of the mechanism of (rather than connections to) an isolator failing whilst in use, with contacts closed, is about as close to zero as any other minute risk in this life!

I am puzzled as to why a diyer would 'often' need to open up a CU to access the earth/neutral bars.

I don't think anyone said anything about 'often' - and, in any event, it's far more likely that an electrician (rather than a DIYer) would be doing things within a CU. However, as I said/asked (and this applies just as much to electricians as DIYers)...

In the post I quoted, you stated that one often has to have ones hands very close to them when doing things with neutral and/or earth bars - I was questioning why you would need to often work in a CU. I have rewired my current home once and that is the only time I have had to work in the CU. (Scousespark)

The English language has failed me again - you have misunderstood what I was qualifying with the word "often"! Re-phrasing, the intended meaning of my sentence was "When doing things with the neutral and/or earth bars [which itself is a very rare activity], one very often has to have ones hands very close to [to supply side connections of the main switch]". As I said before, IF (very rarely) one would (albeit very rarely) have to have one's hands very close to those otherwise live parts within a CU, it would seem crazy not to avail oneself of use of an isolator, if one were fitted, wouldn't it?

Kind Regards, John

 

[scousespark]

My quoting went all over the place because I was deleting quote boxes using my Ipad.

If an isolator is in place, I would obviously use it. However, fitting an isolator or a henley, is only a benefit should some some future event takes place.