Omission of overload protection for resistive heating elements.

[EFLImpudence]

I have noticed a couple of times lately that you, Sunray, have said that something might be safe and to the regulations but "I don't like it". I don't know how you decide what advice to give people on the forum and how much better than the regulations your advice should be.

When you (and Bernard) buy a car - I hope it is a new one - do you fit it with, for example, larger brakes and have it de-tuned before driving it?

 

[JohnW2]

I came to the conclusion years ago that regulations are a minimum standard below which no one should sink.

That is surely what they (indeed, virtually any standards/regulation) are, isn't it?

Working to a better standard should not be prohibited ...

I've never come across such a 'prohibition' in relation to any standards/practices/regulations - have you?

.... and anyone who does work to a better standard is ( in my opinion ) far better than anyone whose work is just above the standard set by the regulations.

Again, essentially agreed, but that obviously requires a definition of "a better standard".

"Better" is not necessarily simply a matter of 'safer' or 'neater' etc., since (at least in my opinion) it also should take on board concepts such as "sensible" and, in some situations, "cost-effectiveness" etc.. If someone expends appreciable time, effort and money in going way beyond the 'minimum required safety standard' by taking steps to address extremely small theoretical risks (which many others would not be concerned about), I am not sure that it would always be appropriate to say that was necessarily "better" than the approach of someone who was not quite as 'risk-averse'.

Kind Regards, John

 

[SUNRAY]

I have noticed a couple of times lately that you, Sunray, have said that something might be safe and to the regulations but "I don't like it". I don't know how you decide what advice to give people on the forum and how much better than the regulations your advice should be.

When you (and Bernard) buy a car - I hope it is a new one - do you fit it with, for example, larger brakes and have it de-tuned before driving it?

I was made redundant in 2005 when the company I worked for went into liquidation. My role was workshop manager. Sounds grand but in reality much of the time it was just me, the others were on site. There were 3 panels in production and the administrators asked my boss who should finish the work off. I got the job.

Additionally some of the site work was taken over by installers and they also came to me for advice/assistance. All of a sudden I had significant money in the bank and had to ask advice on what to do about it, I'd accidentally become self employed and receiving phone calls from companies I'd never heard of offering work, so much so that I had to turn loads away. Throughout my S/E work the rates have been offered by them as an incentive for me to work for them and has always been more than what I would have worked for.
This doesn't happen for those who 'just do enough'.

I was working at a BBC site for a controls company, my employer was also in the room and speaking with a competiter controls company who asked for a recommendation for a good panel builder. The reply; "Sunray if you can get him, he's not the quickest but he doesn't have to come back." At that I thought it wasn't a bad reputation. "Oh but you have to offer over the top to get him." They did not know I was working the other side of some partition screens. Later in the day I was working in a plant room containing 3 panels where I'd stripped the Honeywell BMS and replaced with Trend in one and working on the second, the third had been done by A.N.Other. The competiter came in and started asking questions, seeing the difference between mine and the other panel the deal was quickly struck. They both worked properly, they were both safe but the different workmanship was the clincher. I use Hellermann sleeves on the ends of cables - not PVC tape, my cable markers all read in the same direction on the cables/wires and they are lined up. Just those sort of details.

When sizing wiring I'll go up a size if the current is anywhere near the limit etc.

We all have our quirks, our pet loves and hates, my main hate is poor design & quality. As to advice, I hope I'm advising to do the job to a good standard but sometimes I'll come up with an unexpected solution, probably based on the way things used to be done, like 2way switching. A classic case was about a year ago where an elderly guy had problems with 2 sets of 2way switching on the stairs but only one 3C&E for strappers.

As to vehicles, I don't think any of mine have not been modified in some way. Potentially the next may have the silly waste of space centre console reduced in size or even removed, dependant on what's hiding inside it.

 

[bernardgreen]

When you (and Bernard) buy a car - I hope it is a new one - do you fit it with, for example, larger brakes and have it de-tuned before driving it?

For the past 35 years I have bought cars from new and use them as delivered. No modifications.

 

[bernardgreen]

We all have our quirks, our pet loves and hates, my main hate is poor design & quality.

I share that. I also hate design specifications that ignore the "what if X happens" situations where X is possible. Remotely possibly but never the less not impossible

I was the hardware designer in a team tasked with designing a radio paging system covering the Greater London Area. The client was the Home Office and the user the London Fire Brigade. The specification called for 13 transmitter sites and 4 control rooms. We designed in the capacity for 20 transmitter sites and 5 control rooms. The control system was duplicated and all sites were automatically monitored for faults in equipment or the PW circuits ( Post Office cables ) As the design team members would be providing the first year of out of hours service to the system we added quite a lot of engineering functions to make the service engineer's job much easier. This was justified by one event involving a PW to the transmitter near Heathrow Airport.

All the transmitters had digital delay lines to ensure they transmitted the data synchronously. A report of missed calls suggested the Heathrow transmitter was faulty but tests from the control room reported the transmitter as not faulty. Further testing using some of the unspecified engineering functions discovered that the Heathrow transmitter was 4 milliSeconds out of synchrony with the other transmitters and hence causing lost calls where the Heathrow signal was interfering with transmissions from the adjacent transmitters.

The delay along the Post Office Private Wire had changed, it's route between Lambeth and Heathrow had been altered. That should not have happen to any of the Private Wires used by the paging system. Post Office Engineers said the route had not been altered. LFB pressed the point and mysteriously within hours the PW delay went back to what had been.

That change of route was a "what if X happens" event.

If the design team had not sneaked in those unspecified engineering functions then discovering that change of route and loss of synchrony would have taken a lot longer and many miles of travel back and forth across London. One person in the equipment room at Lambeth found it in less than an a hour.

 

[SUNRAY]

It always amazes me that people will polish the hell out of a vehicle with pride but will moan something is not right for them and put up with it because 'that's how it is'.
Second hand vehicles:
1972, Viva) Fitted radio, front fog lights, reversing lights, rear window heater, boot light, power socket for parking light etc.
1974, Maxi) Fitted radio, cassette player, electronic ignition, bigger tyres, changed dynamo to alternator, ammeter, front and rear fog lights, reversing lights, boot light, power sockets dash and boot, tow bar and electrics, anti theft devices.
1979, cortina 1600 est) Changed radio, fitted electronic ignition, changed inlet manifold and carb, F&R fog lights, power sockets dash and boot, tow bar.
1981, cortina 2000 est) F&R fog lights, power sockets dash and boot, tow bar, CB and ameteur rasdios and aerials.
1983, minibus) Fitted radios broadcast and and 2 way, altered seats, added sound absorbing roof lining and lights, F&R fog lights, roof rack, tow bar.
1985, 2nd minibus) Fitted radios broadcast and and 2 way, altered seats, added sound absorbing roof lining and lights, rear fog lights, changed rear door handle and catches.
1986, marina est) 2 way radios.
1987, Sierra hatch) changed radio to radio cassette, 2 way radios, rear fog lights.
1988, Mondeo est) 2 way radios, added 2 seats in boot, tow bar, roof rack.
1988, Midi van) 2 way radios, added rear seats, tow bar.
1998, Astra est) roof rack, 2 way radios, dash power socket.

New vehicles:
2002, citroen multispace) 2way radios, roof rack, interior lights.
2005, peugeot combi) 2way radios, roof rack, interior lights.
2015, Peugeot outdoor) provision for 2way radios, roof rack, additional dash power socket.

Unmodified vehicles:
1976, Commer Imp
1977, Bedford CA. Albeit repainted.

I started looking at a vehicle pre lockdown which has a huge and very fashionable centre console, making the front seat leg room quite narrow, the sales staff were horrified when I suggested removing/altering it. I said I'd require exploded views of it (ie from service manuals etc) before I'd consider purchase.

 

[SUNRAY]

For the past 35 years I have bought cars from new and use them as delivered. No modifications.

And perfectly understandable if you are able to find a vehicle which has everything just as you need/wish it to be.

 

[bernardgreen]

My only significant addition to a new Triumph Spitfire 1972 was the fitting of a 7 Watt red fluorescent lamp as a rear fog lamp.

 

[EFLImpudence]

My point was that the manufacturer will usually have designed the car to the minimum standard required for its purpose.

Surely this would not be good enough for you two.

 

[bernardgreen]

My point was that the manufacturer will usually have designed the car to the minimum standard required for its purpose.

Surely this would not be good enough for you two.

It is good enough for me in this age of technical complexity in the modern vehicle.

 

[SUNRAY]

My point was that the manufacturer will usually have designed the car to the minimum standard required for its purpose.

OO wow what a thought...

Left for long enough to make lunch for thought process...

I personally don't see the comparison. I've worked with vehicle design and construction regs a number of times when building and modifying trailers and vehicles, after construction every vehicle is inspected by a DOT inspector which the new owner pays for. Unlike MOT test the DOT inspector is not permitted to inspect his own new vehicle. It may not seem like it but quality of work is assessed, totally unlike our electrical requirements.

So yes the manufacturer will do what he can to save costs where 'it doesn't matter' but equally car buyers now are far more discerning and demand all sorts of added comfort, facilities and silly toys. Draught proofing, sound deadening etc are not required in most vehicles but it's all there to some degree.

When purchasing a new vehicle I will look or my requirements, then inspect the vehicle (usually a sample) and decide to purchase, if it doesn't come up to my needs I'll move on and hopefully purchase something PDC. Then I have the issue of converting it to my needs/desires which is usually fairly minimal (See previous list).

The same purhasing process is true for pretty much any manufactured & purchased item.

The difference with wiring installation is any old herbert (No offence intended to those named Herbert) can do a 2 minute course, purchase a certificate and hopefully insurance and start work. Said person can do the most appalling trash, scribble on a piece of paper that it's correct and walk away... and they do just that... without any real official second opinion. That situation can not happen with a car and for that matter most other mass produced products.

 

[JohnW2]

When sizing wiring I'll go up a size if the current is anywhere near the limit etc.

Fair enough, but as I recently wrote to bernard, being 'exceptionally cautious' is not necessarily 'better', particularly in cases (cable 'limits' almost certainly being an example) in which one is adding one's additional caution to a 'limit' which already includes a very generous 'safety margin'. Some may feel that if it had been deemed appropriate to have the 'minimum standard' as "thou shalt not drive faster than 30mph on this road", that it would actually be 'better' never to drive at more than 10 mph on that road.

Furthermore, it's not uncommon that there are actually downsides to 'exceptionally cautious'. Even with electrical cables, using a much larger cable than necessary will increase fault current, possibly to the detriment of components of the circuit other than the cable under fault conditions.

"Over-engineering" is, in general, not necessarily 'better', and is often the consequence of the perpetrator not being knowledgeable, skilled or experienced enough to understand (or be able to determine) what is 'adequate' - as was probably the case with the Victorians who built some parts of my house with 13½" and 18" brick walls, 12" x 4" floor joists and some 2"-3" water pipes!.

Again in terms of 'downsides', I don't think you would get any praise or prizes at all (and may not even retain your job!) for designing an aircraft, spacecraft, racing car or even road vehicle which was 'much stronger' than the 'minimum requirement', if that were achieved by making it much heavier than was otherwise 'necessary'. The truly skilled person will be able to produce an optimum design, which achieves 'adequate' strength, but with minimal weight. Similarly, you may again not keep your job for long if you designed products which went a long way beyond 'minimum required standards', to an extent that many others may not be considered 'necessary', if it resulted in a product that was more expensive to manufacture.

Of course, reflecting the 'potential downsides' issue, 'minimum standards' often come with both minimum and maximum 'limits', which makes the situation a bit more complicated. Whether tightening a nut/bolt or deciding which dose of a medicine to prescribe, to over-tightening the nut ("to make sure that it doesn't come loose") or to overdose with the medicine ("to be sure that it works") can be at least 'as bad' as the opposite.

As with so many things, it largely comes down to common sense. The person who will keep his/her job for a long time, and whose work will be 'admired' and hopefully well-rewarded, is not the one who always 'over-engineers' (in the name of safety, reliability or whatever) beyond the minimum required standard (regardless of issues such as cost and/or other 'downsides') but, rather, is the person whose is knowledgeable, skilled or experienced enough to understand (or be able to determine) what is a reasonably 'adequate' compromise (which may not address 'incredibly improbable' theoretical scenarios).

I'm sure that, if I really wanted to, there are quite a few things I could do to make my house appreciably more 'lightning-proof' than it is - but I don't

Kind Regards, John

 

[bernardgreen]

Said person can do the most appalling trash, scribble on a piece of paper that it's correct and walk away.

Provided all the lights and sockets work then the customer assumes that because all the electrics are working normally the installation is safe.

 

[bernardgreen]

as was probably the case with the Victorians who built some parts of my house with 13½" and 18" brick walls, 12" x 4" floor joists and some 2"-3" water pipes!.

Sorry to disagree John but the Victorian builders did not over engineer things, they built quality and long life into the buildings and engineering projects. Those Victorian buildings and mechanisms have lasted and will continue to last for far longer than modern constructions.

but, rather, is the person whose is knowledgeable, skilled or experienced enough to understand (or be able to determine) what is a reasonably 'adequate' compromise

They will keep their job because they produce a result at a lower cost by paring everything down to the least material and labour costs.

Some very "knowledgeable, skilled" people have come a cropper when they took cost saving just a bit too far.

 

[SUNRAY]

Fair enough, but as I recently wrote to bernard, being 'exceptionally cautious' is not necessarily 'better', particularly in cases (cable 'limits' almost certainly being an example) in which one is adding one's additional caution to a 'limit' which already includes a very generous 'safety margin'. Some may feel that if it had been deemed appropriate to have the 'minimum standard' as "thou shalt not drive faster than 30mph on this road", that it would actually be 'better' never to drive at more than 10 mph on that road.

Furthermore, it's not uncommon that there are actually downsides to 'exceptionally cautious'. Even with electrical cables, using a much larger cable than necessary will increase fault current, possibly to the detriment of components of the circuit other than the cable under fault conditions.

"Over-engineering" is, in general, not necessarily 'better', and is often the consequence of the perpetrator not being knowledgeable, skilled or experienced enough to understand (or be able to determine) what is 'adequate' - as was probably the case with the Victorians who built some parts of my house with 13½" and 18" brick walls, 12" x 4" floor joists and some 2"-3" water pipes!.

Again in terms of 'downsides', I don't think you would get any praise or prizes at all (and may not even retain your job!) for designing an aircraft, spacecraft, racing car or even road vehicle which was 'much stronger' than the 'minimum requirement', if that were achieved by making it much heavier than was otherwise 'necessary'. The truly skilled person will be able to produce an optimum design, which achieves 'adequate' strength, but with minimal weight. Similarly, you may again not keep your job for long if you designed products which went a long way beyond 'minimum required standards', to an extent that many others may not be considered 'necessary', if it resulted in a product that was more expensive to manufacture.

Of course, reflecting the 'potential downsides' issue, 'minimum standards' often come with both minimum and maximum 'limits', which makes the situation a bit more complicated. Whether tightening a nut/bolt or deciding which dose of a medicine to prescribe, to over-tightening the nut ("to make sure that it doesn't come loose") or to overdose with the medicine ("to be sure that it works") can be at least 'as bad' as the opposite.

As with so many things, it largely comes down to common sense. The person who will keep his/her job for a long time, and whose work will be 'admired' and hopefully well-rewarded, is not the one who always 'over-engineers' (in the name of safety, reliability or whatever) beyond the minimum required standard (regardless of issues such as cost and/or other 'downsides') but, rather, is the person whose is knowledgeable, skilled or experienced enough to understand (or be able to determine) what is a reasonably 'adequate' compromise (which may not address 'incredibly improbable' theoretical scenarios).

I'm sure that, if I really wanted to, there are quite a few things I could do to make my house appreciably more 'lightning-proof' than it is - but I don't

Kind Regards, John

I agree with every single word of that.

The question of increasing wire size is a double edged sword, yes it costs, yes it's heavier, yes it takes space. Yes it reduces heat dissipation.

Again a lot of my work is control panels and having 200 wires in a trunking is quite normal. The derating factor figures for tri rated wire go as far as bunches of 12, example at 45°C 0.5mm² is rated at single; 11A/ bunch of 12; 4A , 1mm² as 17A/8A and 2.5mm² as 30A/17A.

I don't know if you can make out much in this picture but that burn out was 16mm² ring of Tri rated (100A/56A) which was estimated to have been running (by the panel manufacturer) within the CCC, as it happens on Chrstmas day and having been in service <2 months.

They wriggled and wriggled but my Report was eventually enough for the various insurance companies to accept is was a manufacturers error.

IIRC that is a 300 A supply.