"Dave Plowman (News)" wrote in message
...
In article ,
Keefiedee wrote:
As water in a central heating system passes over the heat exchanger in
the boiler, a small percentage of that water will boil on the hot metal
surfaces. During this boiling a layer of irregular bubbles forms which
eventually join together and act as insulator between the gas firing
and the water within the radiator circuit.

So just where does this wasted heat disappear to?

It doesn’t, it just doesn’t get into the circulating water
as well as it should do.