Heating problem advise please

[glenn_btn]

Hi All hope someone can help

I am having a few problems with my heating. When the heating and hot water come on together there are no problems but if I only put on the heating it wont come on. I thought it was the 3 way valve but when I only switch the hot water on it does only heat that. Does any one think it could be the thermostat, when i switch the heating on not even the boiler clicks on which i guess if it was the 3 way valve it would still come on just not heat the pipes.

Thanks

Glenn

 

[CH4]

Hi Glen,

It could be a faulty timer/programmer ('CH On' switch), room thermostat or micro-switch (within the 3-way valve - the one that connects to the orange cable). Alternatively, a fault in the CH wiring could be the cause.

If you have a Multi-meter, Volt Stick or neon screwdriver, and can establish that mains is present at the output of the room thermostat (when it and the timer are calling for heat), then problem is likely to be within the 3-way valve. The head of which may be replaceable, without the need to drain the system.

If mains voltage is not present at the output of the thermostat, but is at its input then the thermostat is faulty (which can be proved by temporarily replacing the thermostat with a wire link). Otherwise, the timer/programmer is the likely cause.

John

 

[MANDATE]

Best place to check the voltages is in the terminal box used for the heating system. You should be able to identify and check the related valve wires. the room stat output leads to the valve 'white' wire.
HW OFF leads to the 'grey' wire. cylinder stat leads one way to 'grey wire' other way to 'orange' wire and boiler/pump
One micro switch in 3 way valve also feeds 'orange' wire and boiler.
I would suggest the room stat is OK otherwise the valve would not move to mid position
I would suggest removing the valve head so you can see if it moves to the CH only positon. If it does then the fault is the micro switch and if it doesn't then fault is either no voltage on 'grey' wire or micro switch.