"Set Square" wrote in
:


The boiler input and output will be at virtually the same pressure.
The output of a pump will be at a higher pressure than the input - and
this pressure will be dissipated by the resistance of the particular
circuit. If only one pump is running, all points on the other circuit
are going to be at the same pressure (ignoring static pressure
differencers due to height differences) - so there's nothing to induce
any flow.

It's that "virtually" the same pressure that was worrying me - the circuit
looked so much like an electrical network I nearly started using Kirchoff
and Thevenin on it! I was certainly taken back to backdoor circuits and
steering diodes - and it _does_ have nonreturn valves.

Seriously, do you have any thoughts about the system; It doesn't seem all
that dear at the moment, comes with the wiring centre, and in priciple
looks better to me.

But I'm extremely inexperienced, in faact, when iit comes to upgradeing
cylinders and CH - none at all

mike