When I was 17 and an apprentice Electrician, I was talking to my father who was at that time, a Fire Officer, (for 34yrs before previous work injuries caught up with him and forced him into retirement a few years ago), anyway I asked him "Why do all the media reports say the fire was caused by an Electrical Fault?"
His response was that once they had eliminated all other causes, ie accelerants, arson, smoking in bed, kitchen fires etc, they put in the report 'Possible Electrical Fault'
I was always consciencious of my workmanship, but even more so after I heard that, there is no way anybody will ever be able to point the finger at me because they cant find any other reason for a fire.
Skip 12yrs and I am replacing a switch board that had caught fire, (not my work of course) and the insurance companys Forensic Scientist phones me and tells me that he sifted through the mess and found that the time clock for the security lights had been the cause of the fire, the unit was totally destroyed but he could tell by the size of the contacts that they were rated for 15-17Amp, and it was protected by a 20A circuit breaker. He asked me to investigate it further and do a report on my findings as to why it had taken so many years for this fault to happen.
There was 4x 400w lights which is about 1/3 of the breakers capacity and about half of the time clocks. The insulation resistance was 1.5Mohm which is a pass above the 1Mohm required, but it a long way from ideal. The cables had been installed correctly and the conduits on the roof were all glued and the conduit boxes were siliconed shut, other than the clock, all good practises so far, closer inspection revealed that the silicone had deteriorated a little and water had seeped into one of the boxes and condensation had got in and around the connectors, I replaced the connectors, dried the boxes and drilled drain holes in the bottom, pumped silcone into the inside of the conduits and then resealed everything.
The Australian Wiring rules have since closed that loophole and now has a specific rule that states that these are draw through conduit boxes and not termination boxes.
Jump another 6yrs and I am working for a Thermal Imaging Inspection company, using $150,000 Infrared cameras, I was very surprised to find so many hot terminations, I would tighten the screw another 1/4 to 1/2 a turn and reduce the the temperature by 5-15degC back down to the same as the cable.
To give you an example, in a power circuit we generally use a 20A breaker and 2.5sqmm V90 cable which is rated to 90degC. If the circuit is at 16-17A the cable is at around 80degC, to sum it up, a circuit that is loaded to 3/4 of its current capacity the cable is at 80% of its temperature capacity, in ideal installation conditions, (ie free in air, think single cable tied to a catenery wire), add in 10-15degC and you are starting to damage the insulation, and thats not even fully loaded any where near the breakers capacity. By the way quite a few were 110degC, the hottest I ever saw was 270degC and the company record was 987degC on a Gas Processing Ship, and we had the IR photo to prove it.
I agree with the comments on the extension leads, but please dont roll them up on your arm like you would do with rope, this creates twists and kinks to the internal conductors and you can't see the damage until you end up with a strange lump in the outer sheath or until it burns through. I have seen probably 40 or 50 leads like that over the years and have angered many tradies and cleaners with the back pack vacs, when I have to condemn their equipment and they have to remove them from site, yes I do feel bad about doing it but would feel worse if someone died or got injured from a dodgy lead that I had tested and tagged, they quickly learn to roll up their leads properly after that though.
I have noticed that alot of people over there do their own wiring and terminations, and then install insulation in the walls, that derates the current capacity by half which means that the cables should be doubled the size. I cant seem to get half of the Refrigeration Electricians around here to understand that even though they are not allowed to run the wiring for a start (different licences) and I can show it to them in the Wiring Rule Book,
I hope this helps non electricians to understand some of the dangers and I would recommened that you turn off the power and just double check things every now and then, just to be sure,
