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?

 

[James]

All very good questions.

I do not own a torque screwdriver and have never used one.

I still rely on my wrist although I don’t have any calibration certificate for it.

 

[Marvo]

I'm sure you could borrow someones torque screwdriver and self calibrate your wrist against it

I don't carry a torque screwdriver on site either but I have a range of very accurate versions in our workshop that are about 15 years old and too expensive to carry around. I'm thinking about getting one of these new snazzy looking red and yellow plastic ones although I wouldn't use it very often with the type of work I do. I'm just interested how they're used in the UK and what the recognised usage practices are now they've been popular for a while.

 

[SparkySy]

I have and use a torque driver for a few years now.
I have found more and more manufacturers listing required torque either in the instructions or on the product next to the terminals (that's if they aren't push in) so that it's obvious.
As to whether or not I agree with that setting is another matter as some of them seem to be extremely low.
So I do if there are settings listed anything else is down to the torque elbow!
Sy

 

[nicebutdim]

I have and use a torque driver for a few years now.
I have found more and more manufacturers listing required torque either in the instructions or on the product next to the terminals (that's if they aren't push in) so that it's obvious.
As to whether or not I agree with that setting is another matter as some of them seem to be extremely low.
So I do if there are settings listed anything else is down to the torque elbow!
Sy

Just over 1Nm on outgoing side of certain breakers seems a tad low for higher ratings with stranded cables, but likewise I (mostly) tend to set torque where manufacturer has clearly requested it.

 

[davesparks]

what the recognised usage practices are now they've been popular for a while.

I suspect a common usage practice is to dig it out and brush the dust off once a year, just in time for the annual visit from the NICEIC.

 

[SJD]

If you don't have one in your tool bag, and you ever find yourself in court defending an installation such as a consumer unit that has e.g. overheated or caught fire, how do you explain how you did the terminals up to manufacturer's instructions. My college tutor used to tell a story about this, of someone being cross examined about the contents of their tool bag after such an occurence, they didn't see where the questioning was leading.

 

[Dustydazzler]

I have 2 vde versions and the only time that they ever see the light of day is on a board change , I do all the connections up by hand then go round at the very end and torque everything up.
To be fair its just another one of those items you shell out £100+ for an it lives in a box for 99% of its days.
I probably did 500 boards before I ever got a torque screwdriver and as far as I know none of them caught fire ( yet )

 

[IAmSparkytus!]

As above, only use mine on distribution boards.

3.5nm on some terminals seems a lot and I quite often find the screwdriver slipping and starting to round the screw head before the driver clicks to confirm torque.

On the flipside, one board I’ve worked on asks for all connections on the earth bar to be 2.0 or 2.5nm (can’t remember which) and the main earth pops right out

being honest I much prefer the old fashioned DIY way of going with your gut instinct

 

[Dustydazzler]

Quite often I find my self doing the torque up and still checking again afterwards by hand as I don't trust the torque screwdriver

I honestly don't think you can beat an experienced hand/arm when it comes to making good connections

 

[Marvo]

Quite often I find my self doing the torque up and still checking again afterwards by hand as I don't trust the torque screwdriver

I honestly don't think you can beat an experienced hand/arm when it comes to making good connections

Is that a lack of trust in the accuracy of the screwdriver or lack of trust in the manufacturers published torque spec?

When you say you recheck by hand afterwards do you mean you 'tug test' the wires or you go again with a normal screwdriver?

 

[davesparks]

Howany electricians using torque screwdrivers actually know how to use them properly?

 

[LukeD]

If you don't have one in your tool bag, and you ever find yourself in court defending an installation such as a consumer unit that has e.g. overheated or caught fire, how do you explain how you did the terminals up to manufacturer's instructions. My college tutor used to tell a story about this, of someone being cross examined about the contents of their tool bag after such an occurence, they didn't see where the questioning was leading.

Always have whats legally required. Down to you if you want to use it , But have it

 

[littlespark]

I’ve got a torque driver, only gets used on boards though. I don’t go back and retighten with a regular screwdriver…. That’s just pointless.
I will, however, check every terminal in a board even if I’m just working on one circuit… although that only finds loose connections, not over-tightened ones.

Someone else on here has my ones twin.

It came with a #1 and a #2 +/- bit which I manage to break the tip off the smaller one on an RCBO at not very much N/m setting (warranty replacement, got both sizes in return)

Also the one I have doesn’t fit any other brand of driver bit. Just slightly too small.

And final gripe, the increments go up in .2 so 1.0, 1.2, 1.4 etc
When most published torque settings for MCBs and the like end in .5


In a response to some other comments….

“I’ve done loads of boards without a torque driver, and none have gone on fire”……
That you know of. Maybe further work has been done, which has been blamed.

“Always have what’s legally required. Down to you if you use it”
This is sadly true. How many instances of drive by EICRs have we seen where the £1000 MFT has never left its box.

 

[Dustydazzler]

Is that a lack of trust in the accuracy of the screwdriver or lack of trust in the manufacturers published torque spec?

When you say you recheck by hand afterwards do you mean you 'tug test' the wires or you go again with a normal screwdriver?

Go back round checking with a normal Screwdriver