radiator balancing with multiple zones

[D_Hailsham]

[The minimum flow rate quoted by manufacturers is normally calculated for the peak output with the stated temperature differential. So Vaillant quote 20.3 litres per minute for the 428 with a 20C differential. (My calcs give 20 litres per minute.)

That's a minimum flow rate at full power for getting the heat out of the boiler!

Agreed. But with an on/off boiler its either running at full whack, which needs the stated flow, or not at all.

Its not the same as the minimum flow rate to enable the boiler to control its heat output.

I don't understand what you mean Are you talking about a modulating boiler?

 

[Agile]

Agreed. But with an on/off boiler its either running at full whack, which needs the stated flow, or not at all.

I don't understand what you mean ? Are you talking about a modulating boiler?

All modern domestic boilers modulate, condensing or not!

Tony