Replacing a Honeywell T6360 with a CM907 problems

[005506duffer]

I recently replaced an old Honeywell T6360 thermostat with a CM907 programable stat. I have followed the instructions connecting the old 1 & 3 wires to A & B and isolated the old No 2 and earth wires, however with the programmer (ST6400) set to CH Constant and HW Auto the heating performs correctly but we don’t get any HW. Thinking it may be the motorized valve I put back the old stat and everything worked OK. I’m sure I’ve wired it correctly; so I’m assuming the issue is the unused old wire 3 – any ideas?
I contacted Honeywell but they just said the programmer controls the HW!
BTW we have a modern Thermo compact boiler and a megaflow HW tank.

 

[D_Hailsham]

Which motorized valve do you have?

 

[005506duffer]

Thanks for your interest.

We have Honeywell Motorized valves, 1 is by the HW tank I presume it controls when hot water flows into the loop to heat the water.
The other is close to the boiler which I guess is controlling the CH.

 

[D_Hailsham]

As you have a megaflow the valve near the cylinder probably looks like this:

View media item 11762

Is the other valve similar to the one above, or does it look like this?

View media item 5946

 

[005506duffer]

Hi,
The one by the HW tank is as per your top picture and the one by the boiler is also similar to the top one i.e. on both the flow is in/out.
Regards.

 

[005506duffer]

Hard to believe, in desperation I replaced the old programmer for a ST9400, put back the CM907 and bingo it all worked perfectly.