The hot-water system relief valve has become more of a concern here in recent years. For many years the most common system was a non-pressurized installation fed from a cistern in the attic. Pressurized systems (American-style) have really only just begun to catch on here in the last few years (I believe that the local water bye-laws prohibited their use in many areas until recently).
As Roger mentioned, frozen pipes can cause problems even without incompetent plumbing work. Every so often there is a case reported here where somebody has fired up the system after being away for a few weeks during a cold winter, and the system has exploded because the ice didn't have time to thaw before the cylinder reached its critical pressure.
Bill,
The cable rating question is a problem I have with many of our big DIY chain stores. Along the cable racks, they frequently include the ampacity (not a word that's used over here!) along with the size, price, stock code etc. They always seem to just quote the absolute maximum rating, i.e. the one which in the IEE Regs. corresponds to a single cable in free air.
I have yet to see any of them explain that the cable may need to be derated for ambient temperature, cable bundling, enclosure in thermal insulation, etc.
I feel especially strongly about this, because these days our cables are already rated much more liberally than in the past.
[This message has been edited by pauluk (edited 07-24-2002).]
