Sinewave: Thanks for the diagram. I have ONE x V4073A 1039-7 motorised valve, so I'm certain that I must have a Y-Plan. Whare does that information get me?
OK, I think I'm there. When Power is applied to the white wire going into the V4073A DivertEr valve (as it labels itself), the motor inside does not move. That means I either need a whole new Head unit at £80 costing only a bit less than the whole valve, or I just need a new motor which costs £12.35 incl VAT.
THANKS TO EVERYONE WHO HELPED. THE MOTOR IN THE DIVERTOR VALVE WAS BURNT OUT. (THAT'S WHY THE FUSE BLEW.) David
haha... well done guys... To clarify... The orange wire will become live when HW is on OR when mid postion valve moves fully to heating only postion. On the honeywell valve, the manual lever only moves the valve half way, so the orange wire will not energise when lever moved by hand. On some makes the microswitch will make when manually opened, some it doesn't. We'll be stuffed if honeywell remove that useful link! Its amazing by asking the right questions, the answers can be got!
Diverter Valve! second that. normal sequence will fill the cylinder to temperature and then the zone valve will divert the hot water to the rads, try operating it manually with the little lever on the side when the cylinder is up to temperature, your pump should then kick in and heat the rads.
you're describing a HW priority system. A 2 position 3 port valve DIVERTING valve (3 wires) can only rest in HW only position or motor to CH only position. As Navy says, will wait for cylinder to reach temperature before motoring to CH position, when the rads will open up! This is the W plan on honeywell link. A 3 position 3 port valve MID POSITION valve (5 wires) will rest in HW only position, then motor to both ports open, then to CH only position. In this system can the radiators can heat the same time as the hot water, and is the Y plan as in honeywells link, and the faulty valve type in this thread.