Good practice - preventing loose connections

[David M]

So I was called out to a faulty light today. turned out it was just a loose connection.

Anyway it got me thinking about poor termination procedures when fixing back accessories. One of the first things I taught my previous apprentice about installing items was to check for loose connections before fixing back. What had surprised me at the time was that he was never taught or shown at college how to ensure he had prevented a possible loose connection.

As an example after I've terminated a socket outlet I gently and neatly fold back the cables and push the face plate into position making sure that no wires are trapped. I then ease the face plate forward just enough to check the termination screws for tightness before fixing the plate back. Often you find that one or more of the terminals have loosened due to the movement of the wires as you locate the face plate. I do this with every single accessory I install. I check every terminal for tightness on all and any item before I replace the lid or cover. Now I assume you guys do pretty much the same.

What had surprised me was my apprentice whilst in college was never taught to follow this or a similar procedure. The baffling part is, there is so much concern (rightly so) about potentially dangerous hazards which could result in fires, electric shocks and so forth, yet something as basic as teaching first year apprentices how to ensure good connections is overlooked?? :thinking:

It could be that this particular lecturer during the practicals had missed this crucial lesson. But if it is a nation wide problem do you think it needs addressing or am I just over reacting? (little touchy today)

 

[stevethesparks]

Removing and old consumer unit yesterday, I'd say 90% of the terminals were loose. I also found the shower neutral had been loose too (pic). There was also no continuity on r1 and r2 of the ring circuit, upon removing two items in the kitchen, the lives had both dropped out of the terminals.
So no, I don't think you are over-reacting.

 

[Pete999]

I had an argument at ELEX last year in Coventry about this very issue, pointed out that IMO most of the blame was at the feet of the trainee establishments, not all of them I hasten to add, this argument stemmed from a discussion about the spate of fires in consumers units, got a bit of a cold reaction from most of the cast, I can only think they were protecting their own backs, this is how I perceived the discussion, I could be wrong, but my gut feeling, well better not go into that for fear of a backlash. That's my take on the issue for what it's worth.

 

[telectrix]

strange that 99% of these CU fires have occurred since the advent of Electrical Trainee training courses, virtually none in the last 40 years of plastic CUs. draw you own conclusions. as in post#1, recheck connections, after a wiggle. 90% of the time tails will need a turn or more after a good wiggle. how many Electrical Trainee's are taught this?

 

[7029 dave]

Yes I still think (only my view), that cu's are not very well made these days, not like the 2 screw terminals of days gone by. Products today are pure carp.

 

[Marvo]

I think there's a strong case for making thermal imaging and visual checking a regular requirement. Thermal imaging equipment is now at the point where the price is accessible for most small businesses and it's very effective when it comes to highlighting high resistance terminations.

 

[Octopus]

Yes I still think (only my view), that cu's are not very well made these days, not like the 2 screw terminals of days gone by. Products today are pure carp.

Hit, nail and head springs to mind!

 

[Darkwood]

I just installed 15 x 6way boards in bedsits, 90% of the main RCD outgoing terminals were onto the busbar and N link were loose - its down to people not checking properly before energising and putting into use that we see these fires and a large part of the reason the ammendment 3 changed the board construct, if this was driven hard into trainee's rather than a casual mention then there wouldn't have so many burn outs and overheating that I have witnessed has increased significantly over the last few decades... mass manufactured cheap crap also lends itself to the problem and allowing DIY stores to sell consumer units etc to Joe public even though they should not actual change it themselves - if we have issues we trainee's and Electricians not checking the terminals, what can we expect of a DIYer.

 

[7029 dave]

Point taken, of course human error will come into it, always give the pull test, but some products are rubbish, take the 2poll isolator, no brand mentioned, single pinch spade connection you can tighten them up fully, pull and wiggle it will fall out, I strip the cable say 25mm tail, then flatten it out, it does not move, keep it circumferential it will drop out. Just a Little tip.

 

[Pete999]

strange that 99% of these CU fires have occurred since the advent of Electrical Trainee training courses, virtually none in the last 40 years of plastic CUs. draw you own conclusions. as in post#1, recheck connections, after a wiggle. 90% of the time tails will need a turn or more after a good wiggle. how many Electrical Trainee's are taught this?

I agree wholeheartedly with Tel on this, this was the focal point of my argument/discussion with the panel at ELEX think they must have been scripted on their replies, in fact I'm sure of it

 

[Lucien Nunes]

Poor quality products are a problem but you would hope that would put sparks on their guard and focus their minds on making the best connection possible with the available materials. Back in the day, one of the main craft skills that was considered crucial for every electrician was how to make sound connections. From sweating on lugs to making tensile inline splices (and insulating them), it was one of the fundamentals of the job. Woe betide the lad whose instructor found he hadn't bent up the ends of his Britannia joint square before soldering! Granted, no-one really needs to know how to vulcanise a rubber joint or sweat a lead octopus any more but things have gone too far the other way - newbies waxing lyrical about torque gauges etc and bandying reg numbers about but given a screwdriver and a piece of choc block they can't get current to flow from one cable to another without catching fire. Poor show, I call it.
/rant.

 

[David M]

One of the problems is the lack of understanding of the potential danger and risk such a poor connection can create over time. One guy once said to me that he doesn't worry about his terminations as when he tests it will show up. What about terminations you don't test? Or those you just assume are tight like in cu's as mentioned in this thread. What a cowboy!

Yeah sure when testing some circuits a poor connection may show in the readings but we all know that in a new install you can still get a compliable resistance reading even with a loose connection because the copper is clean and most likely in contact with a clean brass terminal. But over time during use this poor termination deteriorates and that resistance soon increases thus creating a potentially dangerous hazard.

You'd be surprised how many trainees and some electricians I've met who don't understand this. Or rather don't concern themselves with it, or don't see the issue until you point out the potential danger it can create.

 

[slingshot2000]

Further to the above; how many terminals are actually brass nowadays and not just brass plated, or even just brass coloured ?
Remember when the strip of metal joining the two "screw-hole earths", across the rear of a socket was actually copper?

 

[7029 dave]

Further to the above; how many terminals are actually brass nowadays and not just brass plated, or even just brass coloured ?
Remember when the strip of metal joining the two "screw-hole earths", across the rear of a socket was actually copper?

Good point.

 

[Davisonp]

Good point.

I did a job two years ago where working on one circuit in a CU I routinely checked the connectors on the other MCB’s to find 6 were loose including the two pictured below. The two lighting circuits had presumably been forgotten completely and since I was the first person to work on the CU since the occupiers moved in 5 years previously they were very luck not to have had a problem.
Some people are just careless.