Vaillaint Ecotec 637 - HW but no CH

[rossyl]

Hi all

We've got an old Vaillaint Ecotec 637. There's a header tank and an old copper HW cylinder.

If we turn on the CH the boiler does not fire up.

If we turn on the HW the boiler does fire up.

If we have the HW and CH in at the same time, the boiler heats the water and one rad, but turning the HW off and leaving the CH still on, the boiler shuts off.

Any thoughts?

Thanks

 

[Harry Bloomfield]

Your 3-port valve actuator is faulty, or the 2-port serving the CH is faulty.