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Topic Title: Guidance on terminal torque
Topic Summary: Is there any?
Created On: 14 February 2013 06:03 PM
Status: Post and Reply
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 17 February 2013 07:35 PM
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DR2366

Posts: 705
Joined: 09 April 2006

Thats interesting as the tag line on the NICEIC shop over a picture of a torque screwdriver is "are you compliant with the 17th edition?". So I suppose in the opinion of your assessor you are, even if you don't have a torque screwdriver at present?

I just wish the whole issue was a little clearer. People seem to be on one side of the fence or the other with the NICEIC and the like sitting in the middle!
 17 February 2013 10:18 PM
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NeilBush

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I heard my first non-compliance warning in December. A fitter was asked if he had a torque driver. He replied that he owned one but did "not have it with him that day" (blag). He was told that he must show it during the next assessment or it will go down as a black mark. That was when he contacted his wholesaler to buy one and I got involved.

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 17 February 2013 10:54 PM
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rocknroll

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As I have already pointed that there is no evidence in any of our databases or mention in the latest trend analysis that there is a problem in this area that requires people to go out and unequivocally purchase and use a torque screwdriver for electrical accessories, other than outlined by the organisations and distributors who have a vested interest, it is in our opinion that where there have been the occasional reports of loose terminals this has been a result of human error, for example forgotten to tighten a terminal because of a distraction like a mobile phone or customer input, or not done the extra check that most electricians do before the accessory has been put in service.

It is also in our opinion that to remove the common sense, skill, judgement and practical ability from the contractor will actually exacerbate the problem and from the technical standpoint torque is applicable to the fastener, material, size, pitch angle, head size etc; and to apply a universal torque is fraught with danger, for some screws this will be too slack and smaller ones too tight creating a problem that is not there.

non-compliance warning


Non-compliance means three things; failure or refusal to comply, as with a law, regulation, or term of a contract.

There is no law and as far as I am aware there is no regulation and not being in the game I am not aware of any contract conditions where this is required by the schemes.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 17 February 2013 11:12 PM
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sparkingchip

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I bought a torque screwdriver at the Coventry show last year, I'm not impressed.

How can you have the same torque setting for a single 1.00 mm conductor as a multi-strand 10.00 or 16.00mm conductor? As commented on in a recent discussion one is being crushed whilst the other is barely nipped up.

Some settings are virtually stripping the heads and snapping the screws, whilst others are leave the conductors loose.

Even with a torque screwdriver the hand of experience intervenes to determine weather the end result is acceptable!

Andy
 18 February 2013 02:41 PM
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NeilBush

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Agreed; a torque driver cannot replace "competent persons" but now gives those competent people the ability to follow "manufacturers instructions" (both are in Reg 134.1.1).

The tolerance which has been spoken of above should have been described to you as +/-6% which is the accuracy all of us torque tool manufacturers must achieve to pass the ISO EN 6789 torque tool standards. So a 2Nm instruction might result in 1.88 or 2.12Nm at worst.

In terms of what torque values the switchgear manufacturers state, that is a discussion which they have to help with. All a driver will do is follow the instructions. The second comment on page 1 has a link to 15 pages of torque values.

-------------------------
I have an interest in Wiha Tools
www.wiha.com/england
 18 February 2013 11:11 PM
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DR2366

Posts: 705
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NeilBush. Any chance I could become a product tester and get torque screwdriver to trial over over an extended period?

I will post a reply to an email I sent to Hager tomorrow.
 19 February 2013 07:22 AM
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Jaymack

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Torque screwdrivers - instructions - tables - followed by the introduction of the need to send away to be calibrated ........ eventually! We're all big boys, any limp wristed users will be quickly rooted out, it's not required to be part of the nanny culture in this instance.

I.M.O., torqueing to limits, is applicable to mechanical/electrical assemblies for heavy switchgear ........ and road wheel nuts etc.

Regards
 19 February 2013 11:34 AM
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Angram

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Rant permitted ?
Torque tools are fine for engineering threads where metals are the same or similar , and at tightening you come to a sudden halt with no clear feedback via the tool unless its a torque tool.

I suggest you need tactile feedback when tightening brass onto soft copper.

You feel the bite and know you have hit the copper. You can miss the copper entirely and the torque screwdriver will just behave the same way.

Some terminations are tighter than others just to turn the screw in the thread. Some start loose and become tighter as they go down.
I have found some recently which are so tight that the torque would quickly and wrongly stop tightening.

I believe these tools will cause serious problems "going foreward".

Waggling after tightening has already been mentioned.

Interesting to see pozi tips being declared mandatory after all the heavy sales drive for sets of plus minus type screwdrivers for exactly the same application.

If a maker is asked; "How tight"? he can only answer with a metric to cover himself (or her). Does that mean we all rush out and buy torque screwdrivers? Its utterly ridiculous unless you have shares in the tool industry.

OMS and RnR are absolutely right in my humble..

Terence.
 19 February 2013 05:25 PM
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DR2366

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When I asked Hager technical if the torque figures in the instructions changed for different conductor material, size and construction the answer was no the figure stays the same.

The instructions say:
Note: In transit it is be possible that some
connections on this consumer unit may have
slackened. Please ensure that all connections
(that are not factory sealed, or have a
label over them) have been correctly torqued
in accordance with the appropriate standards
for devices, and for other connections
at least 2Nm should be applied.

When I asked what was the recommended inspection interval to check terminal tightness the answer was "As far as inspection intervals depends on usage and environment and to be determined by installer / designer , see regs for clarification"

I'm awaiting the reply to a couple of other questions posed. I will keep you posted.

So is it case of you do it up to the specified figure and then its up to you to decide how often it needs checking. What regs do you think he is referring to, GN3?
 19 February 2013 05:38 PM
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AJJewsbury

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What regs do you think he is referring to, GN3?

I hope not - GN 3 is guidance, not regs. I'd suspect he's referring to BS 7671 Chapter 62 - possibly 622.1 (which of course you might like to use GN 3 to interpret!)

- Andy.
 19 February 2013 05:54 PM
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OMS

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When I asked Hager technical if the torque figures in the instructions changed for different conductor material, size and construction the answer was no the figure stays the same.


If that doesn't tell you it's nonsense nothing will - so the same terminal torque for hard drawn or half hard copper and for aluminium and no difference for solid, stranded or fine wire.

Plastic deformation and creep will totally change any torque setting anyway - but the get out clause is that you decide when you need to re torque.

Ahh well

Regards

OMS

-------------------------
Failure is always an option
 19 February 2013 07:55 PM
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NeilBush

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DR2366 You're finding out some good stuff there. These are things I get asked all day every day so I'm learning a lot.

I can't discuss selling on here, or your bulk purchase idea, or your freebie idea, but can answer the questions as best I can.

-------------------------
I have an interest in Wiha Tools
www.wiha.com/england
 19 February 2013 08:25 PM
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rocknroll

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Now that by inference you have formed an opinion that electricians are no longer capable of using a screwdriver and what is not a problem now could result in your estimate scores of electricians standing outside court with a spoon in their hand to receive their medicine for incorrectly using or not using a torque tool on a domestic consumer unit, there is one question that I think is important, the standards recommend an annual verification and certification of a torque tool, for legal reasons traceability would be an important factor in any of these cases, the annual cost to electricians using the most expensive calibration outlets from RS to the lower order would be around £60-80 on top of all the ridiculous amounts they already annually pay for psuedo regulation and relative misinformation.

I will give you time to consult your sales brief under the heading 'customers who ask awkward or technical questions' for an answer to this.

This is only Part 1, another to follow.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 19 February 2013 at 08:35 PM by rocknroll
 19 February 2013 08:47 PM
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DR2366

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Don't scare him away! he might weaken and give us all a discount code to use online (I'm hoping for a larger one of course).
 19 February 2013 09:00 PM
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sparkingchip

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I fitted two Hager RCBOs into a existing board today, absolutely on mention of torque at all on the instruction sheets, so Hager can't be taking it too seriously can they?

Then out of interest I took the cable cut out from the Hager plastic consumer unit and held it in my long nosed pliers with a cigarette lighter underneath it, another consumer unit that burns rapidly producing thick choking fumes would be fair assessment from this simple test.
 19 February 2013 09:25 PM
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DR2366

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Consumer unit

Is this the future of consumer unit terminals? I wonder what the torque figure is? Two screws, think I've seen that before somewhere before.

Oh no! it says 3 - 5 Nm on the main switch !!!
 19 February 2013 09:44 PM
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DR2366

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Sparkingchip, RCBO terminals are 1.7Nm I have it on a pdf sheet!

fitted 12 of them last week and your right about the lack on info on the instructions. It would seem that ignorance of manufactures instruction might not be a good defence but if its that important stick it on the device.
 20 February 2013 02:58 PM
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NeilBush

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The calibration interval period wording is this:

"If the user has procedures for test devices then torque tools should be included in these procedures. Interval period should be chosen on factors such as required accuracy, frequency of use, conditions during operation etc. The interval should be adapted by evaluating the experience gained. If the user does not have a control procedure then 12 months or 5000 clicks is the default value"

So most people will be once a year, which costs between £15 to £22.

Please note it does NOT say "12 months or 5000 clicks WHICHEVER IS THE SOONER". So, ignore if you've read that in PE this month, it isn't correct. You DO NOT NEED to count applications, just get a new certificate once a year.

The certificate which you get with a torque tool will have the date on from when it was calibrated at the manufacturing facility. Your "one year" begins from the first application, which can be presumed to be on the date of purchase. So, your purchase receipt is actually worth photocopying and keeping on file if you're to be absolutely bulletproof.

Go onto Yell.com and search for "calibration services" to find who does it near you. It doesn't need to go back to Germany or wherever.

There are two best practices for those who want to get the longest life from the clutch. First is to tighten until you hear one click. Subsequent clicks are a waste of time and tool life. Second ideal is to unwind the tool to it's lowest setting when not in use. Best practices for those who want to get the greatest return from their spend.

What is part 2 of the question?

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www.wiha.com/england
 20 February 2013 04:26 PM
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rocknroll

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Thankyou for answering that question although I think £15-22 might be a bit on the lean side or is that what you would guarantee you would charge, so once again not only does the poor domestic electrician have to shell out £120 for a screwdriver but has been captured with an annual ongoing charge and paperwork to contend with, a bit like buying one of the computer programs they use only to find every year they have to shell out £100 for updates.

Part 2.
On Monday I picked up a well known consumer unit from a very very nice gentleman in one of the electrician's friendly distributorships in Bridport, it was 2x8 way with 2 RCD's and a main switch, on examination there were 7 different types of critical fasteners, applying the general torque data for the fastener (material type, thread and pitch size, head size etc; ) the range was inbetween 0.32Nm to 5.2Nm, the factory pre-tightened critical fasteners were in excess of 5Nm, the instructions that came with the unit and it was one of the latest editions did not have any instruction regarding torque just that the terminals should be tight and then rechecked when in service once you got through the usual need to use a competent electrician. Yesterday afternoon after taking the unit back we checked 3 other proprietary brands and the manufacturers instructions had no mention of torque only reference to the terminals being tight as above.

I can see a business opportunity here, a bacon bap calibration day , I can supply the test equipment and necessary computer equipment, OMS can be the technical adjuster and we might be able to hire Zs with her rocknroll pinny to man the barby.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 20 February 2013 at 04:32 PM by rocknroll
 20 February 2013 04:48 PM
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OMS

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I can see a business opportunity here, a bacon bap calibration day , I can supply the test equipment and necessary computer equipment, OMS can be the technical adjuster and we might be able to hire Zs with her rocknroll pinny to man the barby.


LoL - now you aren't taking this very serious issue very seriously - I'm more than happy to loll about making "technical adjustments" and trying not to laugh, I'm guessing you are too - but come on, Zs in a pinny - that's stretching things a bit far even for you - we couldn't charge enough to cover that, old son -

OMS

-------------------------
Failure is always an option
IET » Wiring and the regulations » Guidance on terminal torque

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