3 way valve question

[lencuff]

Don't know if we have a problem or not? Have a 3 way valve fitted to the heating/water system BUT once the water needs heating up, the central heating goes off. I thought that with a 3 way valve you could have both on at the same time if required?

[toscal]

I don't think so. Normally its either hot water or heating. With the hot water taking priority over the heating.

[Gangsta]

My 3way valve is knackered, if we have a powercut the valve resets to 'water', the water heats, then the full system clicks off - it doesnt click over to 'heating' so I have to visit the attic and manually pull the little lever on it to change it over. once this is done the heating fires up. incidently when on heating it still provides more than enough heat to the hot water, but I have heard that the 3 way valves are never fully one way or the other, they always alow a small amount to pass?