Thought these were slight overkill. but...

[studentspark]

http://www.elecsa.co.uk/shop/elecsa/ProductDetail.aspx?PID=8f69b9f6-be78-4597-93a4-a00d00b44218


My last assessment suggested using a torque screwdriver, and stickers to 'seal off' the correctly tightened screw for MCB's and such.

Thought this was a bit over kill. The sticker bit!

Got called back today to a board change I did a year ago. No power to some circuits.
RCD would click back to on , but test button not working, and no power.

The tenant I find out later had an issue today, where they cut through a strimmer lead, and could not switch the power back on.

Thought, that must be the problem. Went through the usual.....

Cut a long story short, every connection to the RCD had been unscrewed, the cables were loose.

Tenant said he had not touched it. Obvious he had

Flat owner not sure what to think, asks could I have left them loose when I changed the board!.


I am going to get some stickers.[/u]

 

[EFLImpudence]

Thought this was a bit over kill. The sticker bit!

They are at £10.80

Plus vat. and postage ?

 

[ban-all-sheds]

AFAICT that's a reasonable price.

 

[Taylortwocities]

Buy some sheets of small self-adhesive labels and make them yourself.

 

[ban-all-sheds]

They won't be tamperproof.

 

[JohnW2]

My last assessment suggested using a torque screwdriver, and stickers to 'seal off' the correctly tightened screw for MCB's and such. Thought this was a bit over kill. The sticker bit!

Going a little off-topic and forgetting the stickers ... am I the only person who is a little uneasy about terminal screws on MCBs, RCDs etc. which have been tightened 'only' to the recommended torque? If I do that, they often feel (with a screwdriver) much looser than I would normally regard as acceptable when tightening by hand. I realise that this may mean that I am manually 'over-tightening', with the possibility of damaging threads, but these recommended torques do seem pretty modest.

Kind Regards, John

 

[bernardgreen]

Labels The ones used to mark prices on items in shops are designed to fall into one or two pieces if removed. This indicates any tampering.

Loose screws One old hand I knew would go back to the customer several months after installing a "new fangled" consumer unit to free of charge check the screws were still tight.

 

[scousespark]

My last assessment suggested using a torque screwdriver, and stickers to 'seal off' the correctly tightened screw for MCB's and such. Thought this was a bit over kill. The sticker bit!

Going a little off-topic and forgetting the stickers ... am I the only person who is a little uneasy about terminal screws on MCBs, RCDs etc. which have been tightened 'only' to the recommended torque? If I do that, they often feel (with a screwdriver) much looser than I would normally regard as acceptable when tightening by hand. I realise that this may mean that I am manually 'over-tightening', with the possibility of damaging threads, but these recommended torques do seem pretty modest.

Kind Regards, John

I assume that some of the R&D budget was spent on determining the values, so I don't have any issue with sticking to the recommended values. I doubt you will be the only person in here who thinks the screws need to be tightened further.

 

[JohnW2]

I assume that some of the R&D budget was spent on determining the values, so I don't have any issue with sticking to the recommended values. I doubt you will be the only person in here who thinks the screws need to be tightened further.

I'm sure you're right, on both counts. In mechanical engineering, specifying tightening torques is as much to prevent overtightening (hence potential damage to, or even failure of, threads) as to prevent undertightening - so the same may be at work here (i.e. the torques recommended for, say, an MCB may be the the greatest which they feel the threads can safely take). I do suspect that many an electrician with a screwdriver might feel the need to 'tighten' terminal screws which had already been tightened to the recommended torques.

Kind Regards, John

 

[ricicle]

Going a little off-topic and forgetting the stickers ... am I the only person who is a little uneasy about terminal screws on MCBs, RCDs etc. which have been tightened 'only' to the recommended torque?

In my engineering days, many engineers were moving away from torque settings and moving towards angles of turning. One piece of rogue debris on a thread could make the torque wrench 'see' that the fastener was tight enough.

 

[JohnW2]

In my engineering days, many engineers were moving away from torque settings and moving towards angles of turning. One piece of rogue debris on a thread could make the torque wrench 'see' that the fastener was tight enough.

That's interesting, but where does one start measuring one's angle from - if one uses 'hand tight' as the starting reference, that will obviously vary a lot between 'hands' - and, indeed, could be fooled by a piece of debris in the same way as a torque wrench could.

One variant I've seen of what you say is to tighten to a specified torque and then tighten further by a specified additional turning angle. However, the purist 'thread engineers' (my father was partially one for the last few years of his life!) will probably always want to have precise quantification of the stresses being applied to a thread when 'tightened as instructed'.

Kind Regards, John

 

[ban-all-sheds]

With brass threads, how about until you just hear it creak?

 

[mfarrow]

Just do them up till the heads snap off, then you don't need to worry about putting stickers on them.

 

[ericmark]

Binding threads, Slack screws, Necking off, and many other problems with the tightness of a screw are a huge industry problem.

With a batching plant we had to check tightness of screws on a service which resulted in cables being crushed to a point where they failed.

but also binding screws have caused lose connections and with a high current the screws no longer bind once overheated due to pour connections.

There is also the missed screw where for example MCB has been loosely fitted by the supplier and not checked by the electrician.

To re-torque once is good but to do it more than once is a problem. The idea of re-visiting after 3 months is sound. And re-torque once is great but only once.

The main thing is if faults are due to installation or from interference. To my mind the recording of loop impedance is critical here. If one records the loop impedance for every socket then if there is an extra socket then clearly the system has been tampered with. But unless one has paper work which lists each socket then one can't show work has been carried out since one completed.

To my mind the paperwork we produce after a job is somewhat lacking and that is why we find it hard to show something has been done since our visit.

OK a loop impedance reading line - neutral may show we miscalculated the number of sockets we could put on one ring. But it also shows where some one has fiddled with the installation.