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Turning the boiler up to increase efficiency?
QUESTION:I heard some bloke at an energy efficiency company advising people to
turn their boiler control UP (leaving their room and cylinder stats
alone). ie: If the switch on the boiler went 1-6 and it was at 3, turn
it to 4 or 4.5.
He said this is because the boiler gets hotter quicker, heats the tank
quicker, and reduces cycling. Thus saving energy. But won't this mess
with the condensing point of a condensing boiler?
His argument is: tank calls for heat, boiler and pump start, boiler
reaches temp and turns off, tank still wants heat, pump still goes,
primary side water and boiler cool, hence the waste.
It all just doesn't quite sound right, somehow!
ANSWER: That might be true with a conventional boiler if the cylinder is able
to accept all of the boiler output.
There isn't a Holy Grail at the condensing point. Nirvana isn't
achieved. All that happens is that the *rate* of increasing
efficiency with reducing temperature increases - i.e. a knee in the
curve.
It's a jumble.
If it's a modulating model (typically should be), a cool water cylinder
will present a substantial heat load and the boiler will run balls out
condensing heavily because the return water is cool.
For a radiator load with TRVs reducing flow, the boiler will modulate
down to match the load.
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