In message , John
Rumm writes
Pete wrote:

I have one, and I find it quite difficult to get the flow right to
give optimum amount of hot water.
Would it be worth putting an in-line valve on the cold inlet to the
boiler and then adjusting it such that I could set it to the flow
which would be optimum temperature when taps turned on full? ie it
would limit the flow to a max value which would produce hottest water.

Yes this can work (although obviously you need to adjust the flow
restriction as the groud water warms up in the summer). You may find
the boiler already has a service valve on the cold inlet that you can
partially turn off.

If yes - could I adjust by trial and error or could I adjust and set
to a known litres/minute to get the optimum flow.

You could do either.

How could I find
out what that optimum flow would be - I guess it would be part of the
spec of the boiler?

Look up the power of the boiler, and see if that is input power or
output. If it is input then look up the efficency of it on the SEBUK
database and reduce the actual power by the precentage indicated.

That will give you a number of kW - or 1000s of Joules per second that
the boiler can put into the water. Divide that by 4200 and by the
desired temperature rise, to get the number of kg (i.e. Litres) per sec
the boiler can heat to that temp, then multiply by 60 to get litres per
min. You can then set the flow rate with a bucket and stopwatch.

(personally I would go with the twiddle until about right technique!)

Note that if you set the flow a little too low it does not matter too
much since the water will be hotter, and you just add more cold instead.

Shouldn't be if it's modulating correctly


--
geoff