Handy electrical installation techniques

[Tim S]

John Rumm coughed up some electrons that declared:

On a separate note, it might be worth adding, to the section with the socket tester something like:

"Warning, no socket tester of this type will detect neutral-earth reversal.

Most socket testers are unable to provide any indication of the quality of the circuit. A socket or the circuit it's on can be in a dangerous condition and still show as a pass on one of these devices.

They are useful as a quick and easy spot check but more rigorous testing procedures are needed to fully test a circuit."

Cheers

Tim

[John Rumm]

Yup, dive in... (the article has not had any protection set, so you can edit even without an account at the moment. Having said that, its better if you do log in since it makes seeing who changed what much simpler)

[John Rumm]

ok, slapped it on the end with a bit of re-ordering...

[Tim S]

John Rumm coughed up some electrons that declared:

Cheers

Tim

[ARWadworth]

A good point, but if you plug an appliance in to an RCD protected socket with a neutral/earth reversal at the socket and turn the appliance on the RCD will trip(1).

Adam

(1) anything apart from an appliance that has got it's plug wired with an earth/neutral reversal(2).

(2) That is if the RCD works anyway. I have seen quite a few failures on RCDs.

The test button on an RCD should be done every six months on the day the clocks alter. This way you get to test the RCD (not a proper test but a start) and get to reset your clocks. Midnight is a goodtime to do this as many clocks restart at 00:00 when the power is restored.

[John Rumm]

(1.5) and also appart from any class 2 appliance with no earth connection at all (or a plastic earth pin). ;-)

[Mike Clarke]

[snip]

A class 2 appliance should still trip it if the *socket* has a neutral/earth reversal. All of the return current will go back down the CPC wrongly connected to the neutral terminal and the RCD will see a massive inbalance.

[John Rumm]

not if you have wired the neutral in the plug to the plastic earth pin! ;-)

[Tim S]

It's not a technique, but I think it would be worth including this in one of the electrical wikis as a warning...

It's a perfect illustration of what happens to antique rubber cable:

it by chance today. Yes it's dead.

Cheers

Tim

[John Rumm]

Nice, I would slap a copy of that in the cables article under the VIR section...

[Tim S]

John Rumm coughed up some electrons that declared:

Hi NT,

Looks like your domain then, checking the edit history.

Would you like to grab a copy?

Cheers

Tim

[Appin]

The message from Tim S contains these words:

Not exactly sure what we're looking at there.

The grey cable seems to be neatly fastened in a buckle clip.

But what exactly is the score with the black rubber? Split with age or what?

Just to be politically-incorrect, I have to say that while we've probably all seen plenty of examples of perished rubber insulation, especially where it's been subjected to heat, all rubber is not equal. A few years ago I had to look at a few 415v tubular convector heaters that had failed -- not surprising, considering they were from the early

1950s. Wired in, believe it or not, with rubber cable. No cold tails, either. But what was astonishing was that the ends of the wiring were absolutely perfect. Flawless. Supple and flexible as one could wish. Fixed the faults -- in each instance, element burned out very near the end, easy enough to reconnect without significant loss change in resistance -- I examined the cables to several other heaters in the same installation -- exactly the same story. Quite clearly, some rubber insulation lasts even though most fails.

[Tim S]

Appin coughed up some electrons that declared:

Crumbled mostly, and a nice bare bit of copper showing.

I know the photo's not very clear. When I get to clearing the cabling in that area, I'll cut the cable out and take a better picture.

I know a few people who haven't...

Cheers

Tim

[Appin]

The message from Tim S contains these words:

OK, I've got it now. Black outer sheathing exposing red-insulated core with some of the red insulation gone, exposing bare copper. Was it perishing alone that got it into that state or had it been nibbled by rodents etc.?

They must have had a very sheltered life! :-) Or maybe are relatively young and/or have never worked on older buildings.

[John Rumm]

Tis ok, I have done it:

[Tim S]

Appin coughed up some electrons that declared:

Mice are a possibility, but the thing that isn't clear from this photo is how crumbly and unstable the rubber is. As I said, I'll try to do it justice later on.

[Tim S]

John Rumm coughed up some electrons that declared:

What *is* the protocol for updating uk.d-i-y Wikis that are predominately authored by others? One doesn't always like to go steaming in... ;->

Cheers

Tim

[John Rumm]

When it is an established article that is in some semblance of completeness, then just go steaming in. The wiki software has the tools to work out what changed and how, so no real harm can come of it. If you want to make big organisation changes (say split an article, or delete lumps of it, reorganise sections etc, then its worth posting the outline of what you suggest in the "talk" page associated with the article. That way other editors can see what is happening, and also contribute / comment. You can also use the talk page as a dumping ground for useful stuff that you want to do something with, but can't quite work out just what as yet!

With articles that are in the process of being written and have an "under construction" message on them, its usually better to try and collaborate with the principle author to avoid duplicating effort etc, but even then, small changes and typos etc you can fix without causing much grief.

[Tim S]

John Rumm coughed up some electrons that declared:

Cheers John,

I'm comfortable with Wiki editing, just wasn't sure of the politics :)

I'll sort myself out next time following your advice.

Ta

Tim

[meow2222]

Hi Tim

Thanks for that. It looks fairly mild though, as far as I can see that cable looks like it would still function. The major problem IME with rubber is when all the insulation falls off, the whole lot, leaving nothing but bare metal conductors suspended mid air. I've seen too much of that.

NT