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Topic Title: Guidance on terminal torque
Topic Summary: Is there any?
Created On: 14 February 2013 06:03 PM
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 15 February 2013 06:46 PM
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Avatar for Legh.
Legh

Posts: 3478
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Originally posted by: NeilBush

The IET recently reported on the HSE fire stats from terminal tightness on the early Smart Meter roll-out:

http://eandt.theiet.org/news/2...smart-meter-safety.cfm


It appears that it was the installation of the new 'Smart ' meters. I can't imagine that it would be BS7671 trained electricians which would make such a basic error.........

Legh

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 15 February 2013 06:55 PM
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rogersmith7671

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My understanding of the problem is this;
Pre-assembled consumer units, no need to worry.
Consumer units that need some on site assembly, such as the buss-bar, the rcd links/split board links and the MCB'c will only meet the consumer unit standard if they have been assembled in accordance with the manufacturers instructions. this i understand has always been the case since the revised consumer unit standards came into force, and sometime before the 17th ed BS:7671.
Modern equipment has always required modern installation methods and therefore tools to carry them out.

Regards.
 15 February 2013 07:03 PM
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kj scott

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Originally posted by: rogersmith7671

Modern equipment has always required modern installation methods and therefore tools to carry them out.

Regards.


How about screwdrivers, in the hands of competent persons.

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http://www.niceic.biz
 15 February 2013 07:05 PM
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Legh

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Pre-assembled consumer units, no need to worry.


Oh contra. The one thing we were taught and learned was to check manufacturer's terminations. Remember , the operatives that put these things together are not necessarily trained electricians and why not. Electricians charge the appropriate rate for the job. Manufacturers will not stand that hourly rate.

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 15 February 2013 08:01 PM
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rogersmith7671

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"My understanding of the problem is this;
Pre-assembled consumer units, no need to worry. "

About assembling them, that's already been done, but your'e right you will need to check. Presumably with the fancy new screwdriver.
Competent persons will always seek out the right tools for the job, which is why i assume they (the persons)are a requirement these days.
 15 February 2013 08:34 PM
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kj scott

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The torque screwdriver has only appeared for electricians use in the last couple of years; and surprise, surprise the scam providers start recommending them; and also sell them. No conflict of interest there then.

Loose connections are not due to the lack of a torque setting, but lack of care, RnR makes some very valid points above; and the cause of connection failure would be difficult to prove.

There is also incomplete/inadequate information available from the manufacturers to apply the use of torque screwdrivers consistently. Further if required in distribution boards and consumer units, what about accessories and equipment?

You can't replace operator experience.

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http://www.niceic.biz
 15 February 2013 09:05 PM
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Jaymack

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A screw amongst other interpretations, is simply a long mechanical wedge held in position by friction. Loading of electrical connections are mostly cycling intermittently with a consequent expansion and contraction, this must eventually reduce the friction on the mechanical wedge and loosen the terminals, with an increasing heating effect - the I²R loss.

In theory, spring clamping terminals are continually under compression, and should be superior to screw terminals over the long term, but I have not found this to be this case, e.g. on lighting fittings.

Regards
 15 February 2013 09:13 PM
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DR2366

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If it were so clear cut why aren't the govening bodies just saying you need to use/own a torque screwdriver when doing any termination to comply with manufactures instructions.

I have no issue in geting an new toy to play with (cheap toys are more fun), but I would like to know that it made my installations safer. After the debate I'm not sure it will.

Will home owners be invalidating their home insurance if they fit electrical accessories and don't have the correct tool to comply with the fitting instructions?

Edited: 15 February 2013 at 11:06 PM by DR2366
 15 February 2013 10:28 PM
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dickllewellyn

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For me, the main benefit of owning a torque screwdriver is that I'm no longer having to change MCBs with stripped threads, or broken terminals due to over tightening. I have also had a torque screwdriver long before the current crop of insulated ones came about.

I'd also note though, that when installing a proteus 3 phase board a while ago, the neutral nut was tightened to the supposed correct torque, and pulled right off the board. Pointless giving us a figure if the kit isn't strong enough to take it!

I was also quite surprised recently to talk to a guy in the tools industry who tested my wiha driver for accuracy, to hear just how wide the tolerance is on torque setting equipment.

For me personally, it's an ***** covering tool. I don't feel it make me a better electrician, I do feel it makes me compliant with what is expected of me.

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Richard (Dick)

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 15 February 2013 10:41 PM
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Legh

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if they fit electrical accessories and don't the correct tool to comply with the fitting instructions?


Its called a screwdriver - they have been around for a while, I think!

Unless you wear a jock strap and a gimp mask while terminating a flexible cable etc................
Complete rubbish !

If the manufacturers need to justify their 'under engineered' manufacture,which as I believe its called 'Quality', by providing the necessity of some form of torque measurement then by all means continue. We will follow like sheep to ensure that the insurance companies don't nail us.

However,
There will be a point where 'Trigger' will rear it head, so to speak .

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 15 February 2013 11:17 PM
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DR2366

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If there are any gas fitters/installers on the forum, are there similar requirements regarding fixing torques in the gas appliance industry?
 15 February 2013 11:49 PM
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stateit

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I'm perfectly happy,as dickllewellyn says, to have an '@rse covering screwdriver'.

Twice in the past few months I've had commercial customers had to have shutdowns due to burning out DNO cut-outs.

Both times I received a phone call from the client asking what the **** was going on.

And I knew from the described symptoms that it wasn't my fault but the DNO cut-out's fault.

The bu*ger was the 2 hour wait after my calling the DNO for them to come out. And the clients looking me up and down as if it was my fault and that my saying 'the fault's at their end' was an @rse covering excuse.

After ages building up an enormous amount of mutual trust with them. Blimey, they even give me Xmas pressies, not the other way round.

When the ***t hits the fan you are the one who's going to have the finger pointed at you. And it ain't nice.

If I'd had a torque screwdriver at least in that time I'd be able to say to them'all my terminals were to proscribed tightness'.

I've already ordered a set earlier today* as I think they are a Good Tool To Use.

[edit]* And looking at certain eBay sellers just now, they've sold quite a few today as well![/edit]

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S George
http://www.sg-electrical.com
 16 February 2013 07:47 AM
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MrP

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"Torquing" terminals only happens when stuff goes wrong

Worked on a project for the NICEIC in 2006/7 3rd party audits for Bramhall construction Council house rewires, I think at the time they were doing something like 4,000 rewires a year and there was a big problem with Wylex consumer unit switch disconnectors/main switch with tails and terminals burning out due to not being tightened sufficiently.
Contractors were issued with torque screwdrivers but it didn't solve the problem
Because the sparkies were on a price and some could shift doing a house rewire day after day, boy those guys could shift earning big bobs, connecting the board up with a cordless screw driver was common place, plus knocking the house to bits didn't help, the terminals just became loose, there was little or no verification and on the whole test sheets were an interesting read.
I would expect bus bar connections to be torqued, on my little site Schneider bus bar is going in, it has a red indicator on the connecting bolts and is designed to break off when the desired torque is reached.
If there is a high resistance joint and the red tag has broken off it's the manufactures problem.


MrP Home in 12days
 16 February 2013 09:08 AM
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DR2366

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That's interesting Mr P. What was the outcome after it was determined that the terminals were still coming loose?
 16 February 2013 10:41 AM
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tomgunn

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Originally posted by: stateit

Originally posted by: tomgunn



What we used to have in this ruined island was choice / nay FREEDOM - freedom to express our own thoughts - freedom to do what comes naturally not to be bossed about by someone who, in all probability, has never seen a screwdriver - have the effrontery to actually come up with some stupid idea however illogical and then make it a law so the poor old sparks has one more ridiculous item to worry about! Good god man - can you not see how daft this is? You need to make sure that the screws are tight and you can do that by 'feel' like I 'feel' like screeeeeeeeeeeeeaming sometimes at lifes inability to see common sense - just because this bloke who thought this idea up didnt get his leg over the night before he thought 'I know - I'll take it out on the sparks - haha!'!





Is this meant to be set to a crescendo of Parry's 'Jerusalem' Tom? Probably climaxing in volume and holding at that volume somewhere about 'You need to make sure...'



[IMG][/IMG] [IMG][/IMG] [IMG][/IMG] [IMG][/IMG] [IMG][/IMG]




Hahaha - quite right! I have told my kids that when I'm dead I want the Jerusalem song played, ( before its banned by foreigners as being seen as too British and not in alignment with the current amount of immigrants here - so I'd better fall off of my perch sooner than later!!! ), also Fleetwood Macs formula 1's theme tune 'Chain' Rumours album.

I have got this terrible feeling whats going wrong with this country over the past two years - and its somewhat worrying!! And whats wrong is the meat we are eating - we are getting mad-horse disease. So, stop eating horses and all will be back to normal, ( nayyyyyy ), and maybe someone will bring back the RYB instead of the current 3 core colours, ( for those that dont know these colours they are as follows; medium GREY - dark GREY and of course light GREY so no confusion there then! ).

Tom

-------------------------
Tom .... ( The TERMINATOR ).

handyTRADESMAN ... haha

Castle Builders

Why did Nick Clegg cross the road? Because he said he wouldn't!

I can resist anything..... except temptation! ( Karl Gunn ).

Edited: 16 February 2013 at 10:57 AM by tomgunn
 16 February 2013 11:18 AM
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MrP

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DR
It wasn't the torque drivers didn't work it was the fact the sparkies were on a price as stated in my post there was very little true verification, of course its very difficult to gauge how affective the drivers were with the only focus on to get the rewire completed and start the next one.
The Wylex consumer units came loaded, the spakies would fit the tails then hold in place against the wall and with SDS drill fix though the consumer unit, secure using a cordless drill all that drilling and shaking it's no wonder that the screws were loose, couple of days later a man who was also on a price came to "test" it and check for amongst other bits main terminal integrity via the torque driver.
While the torque drivers seemed like a good idea at the time , you still need a man to verify and unless someone specifically pays for it it's not going to happen to any great effect.


MrP Still 12 days to going home
 16 February 2013 04:52 PM
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WiredScience

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This makes interesting reading - apologies if it's already been mentioned.

http://www.esc.org.uk/industry...htness-of-meter-tails/

It seems that even when correctly torqued, satisfactory connections depend on proper preparation of the conductors and a decent design of the terminals. Not surprising really.
 16 February 2013 05:13 PM
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sparkingchip

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Of course it always helps if the cable conductor is actually inside the cage and hasn't slipped up the back of it, so the cage is correctly torqued up, but empty!

Andy
 17 February 2013 11:20 AM
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DR2366

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Wired Science, thanks for the link it made interesting reading.

Perhaps the front cover of the ESC best practice guide in the link below is a subconscious message that if you use just a screwdriver the screws fall out! Maybe the next issue will see a nice torque screwdriver in its place!

I couldn't see anything in the guide to stress the requirement to follow manufactures instructions on installation.

Has anyone had an assessor comment on the need or not to own a torque screwdriver?

Consumer unit Best practice guide
 17 February 2013 01:24 PM
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daveparry1

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I asked on my last assessment about 6 months ago and he said they (nic) had no plans to require them,

Dave.
IET » Wiring and the regulations » Guidance on terminal torque

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