Torque Talk

[Marvo]

Long time no see and I hope you're all doing well.

I see that torque screwdrivers have become the height of fashion in the UK over the last couple of years. I wondered what general practice has been adopted regarding their use.

Are electricians expected to;
Have a torque screwdriver on site at all times?
Check torque of all terminations in CU's / DB's they open or just any new terminations they make?
Check the torque of all terminations in any accessories they open?

Also;
Is acceptable to do torque testing live in a CU (assuming a VDE screwdriver)? Is a risk assessment required for live torque testing?
If torque testing is performed in a DB/CU do you just check screws for tightness or do you loosen off all terminations first then re-torque to the correct figure to eliminate overtightened connections as well as loose ones?

 

[Rockingit]

Hey Stranger! Good to see you - was beginning to wonder if all was OK.

As for Torque screwdrivers..... I've got one, bottom on the toolbag, never been asked to show it on any inspection ever! It's not VDE and it's also never been calibrated, but it does do a really good job of holding my extra-wide flat bit for doing up tray bolts

 

[slartybartfast]

The wiring regulations (Regs) themselves do not mandate the use of torque screwdrivers.

However they state at 134.1.1 that "the installation shall take account of manufacturers' instructions".

The word "Shall" in British Standards means a requirement, or in plain English a MUST.

So the Regs state that you MUST take manufacturers instructions into account.

However it is odd that the Regs do not explicitly mandate that the manufacturers' instructions are adhered to.

Even if you MUST adhere to manufacturers' instructions, they do tend to be rather vague and very poorly written. Very few state categorically that connections MUST be set to specified torque.

Quite why this is so vague is beyond me, rather inexcusable of British Standards in my book.

Read into that what you will. I read into all this that torque screwdrivers are optional but can see that in some cases use of them is good professional practice; maybe that is the real intent behind the vague language from British Standards.

 

[DPG]

The wiring regulations (Regs) themselves do not mandate the use of torque screwdrivers.

However they state at 134.1.1 that "the installation shall take account of manufacturers' instructions".

The word "Shall" in British Standards means a requirement, or in plain English a MUST.

So the Regs state that you MUST take manufacturers instructions into account.

However it is odd that the Regs do not explicitly mandate that the manufacturers' instructions are adhered to.

Even if you MUST adhere to manufacturers' instructions, they do tend to be rather vague and very poorly written. Very few state categorically that connections MUST be set to specified torque.

Quite why this is so vague is beyond me, rather inexcusable of British Standards in my book.

Read into that what you will. I read into all this that torque screwdrivers are optional but can see that in some cases use of them is good professional practice; maybe that is the real intent behind the vague language from British Standards.

You've answered your own point about why the regs say that manufacturer's instructions do not have to be strictly adhered to - if we did that with some of the badly written/translated rubbish that often comes with items these days then it wouldn't go well !

 

[slartybartfast]

You've answered your own point about why the regs say that manufacturer's instructions do not have to be strictly adhered to - if we did that with some of the badly written/translated rubbish that often comes with items these days then it wouldn't go well !

Quite why this is so confusing is mind boggling....

 

[DPG]

Quite why this is so confusing is mind boggling....

What's confusing? The regs say manufacturer's instructions should be taken account of. That's not confusing.

 

[slartybartfast]

What's confusing? The regs say manufacturer's instructions should be taken account of. That's not confusing.

Well it is. Very confusing. Read my post of a few minutes ago. In summary, "taking account of" does not mean "must be complied with" and also instructions are generally crap....hence the confusion.

 

[DPG]

Well it is. Very confusing. Read my post of a few minutes ago. In summary, "taking account of" does not mean "must be complied with" and also instructions are generally crap....hence the confusion.

I think I'm missing your point here.

We should take account of manufacturer's instructions, but not necessarily rigidly follow them.

That's straightforward to me. Look at them, but if they are incorrect, badly translated, or geared towards another country's electrical system then adapt as appropriate. A competent electrician will be able to do this.

Let me know if I've missed something

 

[slartybartfast]

I think I'm missing your point here.

We should take account of manufacturer's instructions, but not necessarily rigidly follow them.

That's straightforward to me. Look at them, but if they are incorrect, badly translated, or geared towards another country's electrical system then adapt as appropriate. A competent electrician will be able to do this.

Let me know if I've missed something

You are missing the OP's opening gambit - asking if Torque screwdrivers are mandated....and think it is fair to say that they are not !

 

[DPG]

You are missing the OP's opening gambit - asking if Torque screwdrivers are mandated....and think it is fair to say that they are not !

No, they are not. The regs don't mandate which specific tools to use, only that things are installed correctly and tested correctly.

 

[Lucien Nunes]

The manufacturers' instructions have to allow for the situation where a newly qualified installer wishes to fit their component to the highest standard. It might be the first real installation work in their career, with very little experience to guide them on how terminals behave. By providing torque figures the manufacturers can help ensure them achieve a good installation and begin to learn what is appropriate for each of 101 different types of terminal, based on factory tested torques instead of guesswork.

An experienced installer whose approach combines craftsmanship and engineering, takes the time to examine and test their finished work and that of others, reads up on how devices are made, analyses failures etc. might have as good an idea of the appropriate torque as the manufacturers themselves. They will account for factors that are excluded from the sterile lab environment in which the published figures are devised and fine tune according to variables that cannot be included in a one-figure-fits-all torque setting printed on the side of an MCB.

I am interested to know the correct torque and will test it to decide whether I think it is appropriate. Sometimes, as mentioned above, I find recommended torques somewhat low. I trust my own judgement and would happily defend a departure from the published figure because I consider myself sufficiently competent in the craft and science of termination, and believe I could demonstrate that competence if required.

 

[littlespark]

Here's an example... tyre fitters.

They run up the wheel nuts on your very expensive alloy wheels... Then finish them with a torque wrench, set at the correct value.
This ensures that its not too loose, that the vibration of driving loosens them more, and they fall out... nor too tight, as they would damage your alloys.

Its the same type of forces on the screw terminals within a consumer unit. Not too loose, not too tight...You dont want the cable wiggling out... nor do you want the circuit breaker cracking apart because someone turned the driver too much.
Luckily the manufacturers helpfully give you the optimum values.

I would rather see a tyre fitter use a torque wrench on my wheels, that im going to drive away in.... rather than him doing it by 'feel' alone.... using a manual wrench, and him saying "Aye, that'll do"



Don't tell me.... you change your own tyres.....
As we tend to say around here: Get a professional to do it!

 

[timhoward]

I think both arguments carry some weight.
Fitting to the specified torque will avoid damage and usually provide an adequate connection and peace of mind.
However I'm a firm opponent to the general erosion of common sense and responsibility, and I'd want any sparks to be happy they had made a good connection too. Sometimes, especially with larger conductors, the recommended torque doesn't feel quite enough.

Don't tell me.... you change your own tyres.....

Actually I used to, and I had a torque wrench and hosted a wheel balancing machine that various like minded folk were free to use any time. (Citroen BX owners used to struggle to get big-name firms to change their tyres as the engine needed to be kept running to keep the suspension up and health and safety didn't allow this when on a ramp. )
However I'm regularly told by my wife and children that I'm abnormal so I'm probably not a good case study.

 

[LukeD]

Ive seen breakers where they have been done up too tight and you see the casing "splitting open" :-(

 

[IAmSparkytus!]

Ive seen breakers where they have been done up too tight and you see the casing "splitting open" :-(

I’ve actually had this happen on distribution equipment where I’ve followed manufacturers torque recommendations.

Another reason why ultimately I prefer the gut instinct method.

 

[OnlQQker]

It's a bit like plumbing, you get a feel for it.

I use the same method, tighten up gently making sure no cross threading is taking place, then give it another tweak, and a final tweak before fixing in place.

Usually the third tweak produces nothing in the tightening procedure but gives peace of mind.

I wouldn't trust torque screwdrivers, you might think it's tight because it's torqued to the correct reading, but everything can be faulty.

Good old fashioned feeling can never be wrong, unless you get arthritis.