"Mary Fisher" wrote in message
t...

"Steve S (another one)" wrote in message
...


If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated to
60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.

I wonder why you have to boil stuff for several minutes to kill bacteria if
an initial burst of heat will do the job?