Hot Water & CH mix up?

[Crakkers]

Can anyone shed any light on the following?

Hardware: Eco tech 624 - System Boiler NOT combi with a pressurised HW tank.


What appears to be happening is;

When I have my boiler set to heat water only, it does so and appears to do so to the set temperature. I've messed about with the tank thermostat and the boiler cuts out at the right temperature.

When I have the CH on, it also appears to be heating the hot water, but to a much higher temperature and the tank thermostat has no input / effect.

Any ideas??

Thanks in advance,

C

 

[terryplumb]

Motorised valve sticking / not working properly.

 

[Crakkers]

Thanks for quick reply.

How do i diagnose / test this? I have all the covers off the pipe work at the moment and can see the two motorised valves.

 

[terryplumb]

On an unvented cylinder ,the motorised valves form part of the safety mechanisms . you should call in a G3 certificated engineer to check it all out.
Do not be tempted to work on any of it yourself.