Alan B said:

I am coming across more curve consumer units with Lewden RCBO's in and they are causing me a dilemma.

As you will see in the picture the line conductors pass straight in front of the neutral terminal screw, the only way to check torque on the neutral is to remove the line conductors or risk damaging them.

Has anyone asked the manufacturer's advice yet? What is the recommended maintenance approach from them?

Alan B said:

So far providing the line terminals are tight I have not checked the neutrals as I believe i would be doing more harm than good

I think that's a fair point. However, it could also be argued (although I'm not sure how effectively) that, if you are loosening the line conductors to re-torque them, there's not much difference removing them and reconnecting after checking neutral conductors.

IQuote. "Investigators have concluded that the fire was accidental and the probable cause was a defect in an electrical distribution board located in a cupboard in the basement.

The report states that the distribution board ‘could be assumed was delivered from the manufacturer with this fault."

Most manufacturers have stickers on their switchgear that say CHECK TIGHTNESS OF FACTORY FITTED SCREWS AFTER INSTALLATION.  We would normally do this anyway, as the equipment may have been thrown about and rattled about during delivery to suppliers and then travelling to site.

Also, after removal, I NEVER re-terminate solid copper wires if the ends have been in any way crushed or damaged, by say a tight screw. The indented solid copper conductor is liable to break after being moved. I strip the insulation off and cut the damaged section of wire off. Also I am a great fan of doubling over the conductor to provide greater area for a screw or clamp to contact with. This also reduces the chance of the conductor becoming loose if the wire is moved in the future.

Z.

Don't let I squared r heating degrade equipment, check the tightness of all terminal screws. P.S. I do not own a torque screwdriver and never have. I have had no problems at all with that. How often do you get your torque screwdriver calibrated?

Z.

"P.S. I do not own a torque screwdriver and never have." A torque screwdriver a.k.a a Unicorn. Does anyone own one?

Back in the day, folk were taught for hours and hours of practice to tighten screws correctly, strip wire correctly, engineers to use a micrometer without a ratchet 

Precision by "the rack of the eye, the feel of the fingers" A Jedi Knight, 

Mind you, the quality of terminals was not the end product of a race to the bottom back then

Zoomup said:

Also, after removal, I NEVER re-terminate solid copper wires if the ends have been in any way crushed or damaged, by say a tight screw. The indented solid copper conductor is liable to break after being moved. I strip the insulation off and cut the damaged section of wire off. Also I am a great fan of doubling over the conductor to provide greater area for a screw or clamp to contact with. This also reduces the chance of the conductor becoming loose if the wire is moved in the future.

I think that you are contradicting yourself here.

I agree with chopping off the last 1/4" or so if the conductor has been indented significantly, usually in the earth or neutral bar rather than the RCD/RCBO. That's why I like to leave circuit tails slightly long. Admittedly, however, doing this once a decade isn't going to cause much shortening.

Bending the ends over 180º weakens the conductor at the hairpin so there are pros and cons to this technique.

Actually Chris, I am a doubler too. I always at least double (sometimes I Quaddle) , I think one careful bend tight will not usually over-stress copper conductor and the benefit is better contact - In an ideal world we would aim to have almost the whole circumference on the round terminal hole in surface contact with the circumference of the conductor. We can`t actually achieve that but adding more conductor material in the hole goes part wat towards it I think. I don`t like twisting because it sometimes encourages untwisting but a light twist on 7 stranded conductors or a bit more on flexes perhaps helps to keep it tidy and sort of contained under the screw sometimes

Once certainly should be able to feel the elastic deformation of a (reasonably small) screw. I suspect that screws are often under-tightened. 2.5 N m needs a fairly strong wrist.

Many years ago a time-served railway fitter told me, "one, two, or three grunts" was the measure.

Railway spanners are something else though. I volunteered alongside a railway chap at a large scout event once, and it is the only occasion I have seen a 3/4 inch steel bolt tightened to sheer failure by hand socket set - it was part of a hired temporary roadway. In fairness to him  it seemed to work rather better without it.

Mike.