Hello,

I would like to upgrade my gravity hot water system to a fully pumped
one. I have been reading the faq and honeywell diagrams.

Should I use two 2-port valves (1 CH; 1 HW) or should I use one 3-port
valve? Using a 3-port valve halves the cost but the faq said 3-ports
were more unreliable. How unreliable are they?

Is there any advantage to splitting the house in two and having one
valve for upstairs CH and one for downstairs? It might be useful to
run CH upstairs only overnight on a low thermostat setting, just to
keep off the chill; it would be a waste to heat downstairs when
everyone's in bed. Are there any other times it would be useful and
worth the expense?

I am unsure how to wire a 3-port valve. The 2-port seems
straightforward and has a built in switch. I am not clear that the
3-port valve has a switch to signal it is open; does it?

The pages I read suggested connecting the orange wire (only B port
open) to the pump. I'm sure I have misunderstood because if that's the
case what switches the pump on when you use port A only or A and B?

There seems to be some controversy: should CH be port A or port B, and
why should it make any difference? Is it that the valves fight against
a spring and that as long as the B port is open the mechanics are
fighting against the spring?

Is the idea that CH is on port A which is unenergised and the HW is on
port B, the theory being that the HW will warm up quickly so that the
valve is not energised for long? If so, does this mean that using
2-port valves is more energy inefficient?

Thanks,
Sam.