2 port motorised valves

[sbikes]

A brief understanding is wanted here so I will not be to specific. With a vented fully pumped system providing central heating and hot water to the cylinder via 2 2ports motorised valves, if these motorised valves are faulty would this prevent the boiler from lighting.

Cheers lads...

Please all answer at once. I wont mind.

 

[gas4you]

Yes.

There is a microswitch in the valves that send the 230V to the boiler/pump to tell it to fire.

Check the orange wire off the valves for 230V.

 

[Rob]

Usually they fail off. They can fail so that the boiler is constantly on!

 

[Onetap]

Yes.

There is a microswitch in the valves that send the 230V to the boiler/pump to tell it to fire.

Check the orange wire off the valves for 230V.

True.
S-plan wiring diagram here;
http://content.honeywell.com/uk/homes/systems.htm