A
Andrew Gabriel
70 years ago there was a type of wirenut which was ceramic and had a
molded-in conical thread, which did not work nearly as well as modern
wirenuts with a metal conical threaded insert. I am not sure where you
are that they are illegal, but in North America almost every building has
wirenuts in lighting wiring in multiple places, and all but perhaps a few
badly installed wirenuts have redundant, gas-tight connections both
between the wires and the conical threaded insert, and directly from wire
to wire, with each contact area being larger than the wire cross
section. Take one apart after 40 years or more and you will still see
bright copper at both contact areas, solid proof of a gas tight
connection.
In discussions of the detailed causes of electrical fires, I have never
heard any reference to wirenuts being a significant problem, nor did a
web search turn up anything, so as of now I see no factual basis for the
claim that there is any problem with wirenuts other than the possibility
of faulty installation by untrained amateurs - and that happens with all
wiring methods!
Well, no actually. A lot of work has taken place over the last ~60
years to make our wiring accessories safe and reliable when used by
untrained amateurs, which is a big market in the UK (which also
makes them much safer when used by professionals).
Safety and ease of use have been big selling points here for the
last 60 years, and manufacturers have continuously tried to
out-compete each other in this area, which results in continuous
product improvement. When I take a walk down the electrical isle
in the US (such as Home Depot), it's like stepping back 60+ years
to what we used to have before that.
Some 10+ years ago, I was in an Electrical Engineering meeting in
New York. That gave me the opportunity to ask one of the large
manufacturers why there's such a difference between the state of
UK and US wiring accessories, given that they manufacture products
for both countries. The answer was partly what I said above - buyers
will buy based on quality and safety and ease of use in the UK,
which is where manufacturers compete. In the US, buyers will only
buy on price, so whilst he could make a safer duplex outlet at 75c,
no one will buy it because there's a bin full of 50c ones there.
US Elecetrical Engineers know they have an electrical fire rate
which is well in excess of all other countries in similar economic
bracket, but there's no appetite to tackle the causes, merely to
paper over them with things like arc fault interrupters. Many other
countries do not need arc fault interrupters - you might like to
ask yourself why that might be...
Much of what I say for the UK applies to much (but not all) of the
EU too.