No heating,but have hot water?

ok, so you have changed the 2 port valve for heating.
do you have 2, 2 port valves?
did you replace the actuator on the 2 port valve, as some honeywell valves come as 2 separate parts (actuator & valve body)
when you turn the heating on does the actuator move?

my first instict would be that the microswitch in the actuator isn't making, even if it is new.
if you get heat from the radiators with hot water on then that pretty much tells us that the valve is opening, so therfore i'd think it's pretty safe to assume the timer and room stat are sending power to open the valve, it's just that the power isn't getting to the boiler, which point's to the microswitch.
however if you've been in about the wiring centre, it may be possible that you've got some wires in the wrong place, it's easily done.

first thing to check is that the orange wire coming from the actuator is going into the terminal for thelive to the boiler & the pump (usually brown).
if you have 2 2 port valves then both orange wires should be in the same terminal in the wiring centre.

hope that helps.

Ian
February 2010

I am an unqualified muppet so ignore my answer....
At least treat it with great suspicion...

You have made four changes and might possibly have fixed the original fault but may have introduced another - either a defective part or a wiring error - as you worked.

The boiler fires and works fine - you know this - what it is not doing is responding to a call for heat for Central Heating only.

The Switched Live that represents the call for heat comes originally from the programmer - then the room stat - then into the mid position valve (MPV) on a White wire and eventually (when only C/H is required) as the motor drives the valve to full travel - from switch 2 of the MPV on the Orange wire.

When Both H/W & C/H are required the route of the Switched Live (call for heat) is different. And your boiler fires OK in these circumstances...

I would look to the MPV - the orange wire and SW2 - Orange needs to be live to fire the boiler for CH only.
AS FAR AS I KNOW

This link may help...

http://www.gasheating.co.uk/Mid-Position-Valve.html

Again - I must stress I know nothing - have no qualifications or experience and am therefore potentially misleading and dangerous.

Good luck...

Peccavi
February 2010

HI there, You have checked that on the zone value orange wirer is live when the clock calls and the room sat is on ? Yes I also that is that you have an S plan ? DId you look at the pump ? hope this helps

capitalboilers.co.uk
February 2010