> In this tropical paradise, very few home are boiler heated. But I 
 > suspect that
 > the legal, insurance and bureaucratic complications of using a 
 > pressure vessel
 > in a home [regular Inspection and Certification] would result in 
 > these "pressure cookers" being very rare indeed!
Hot water heating boilers are very common in the US, Alec. They run at no 
more than city water pressure, usually much less. I believe that they 
incorporate a pressure regulator on the water feed line. They also 
incorporate extensive controls to keep the temperature from ever actually 
boiling the water, only heating it. The 'radiators' are usually baseboard 
units today.
Steam heat was common many years ago, again using low-pressure boilers. They 
had one or 2-pipe systems, with the condensate either returning down the main 
feed pipe (usually oversized) or down a seperate condensate line. A pump 
takes the water from the feedwater tank and puts it into the boiler as 
determined by a float switch mounted on a pipe external to the boiler.
I've never seen a steam heat system in a modern home however.
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