Open Vent system problems hot water

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Hi
I have an open vented system with ideal boiler. When there is demand for hot water the central heating comes on (although there is no demand for heating).

Am I right in saying that its the mid position valve that needs replacing and not the actuator head or will it be both?

It was working before....

 

[gasmanrob]

Depends the actuator may have been knocked and locked its self in manual mode. Equally Drayton actuators for example have a small piece of plastic that retains a spring that sometimes snaps.

Systems do get mucky and cause the mid position valve to not fully close.

For the cost difference just replace the whole valve actuator and all. You'll know it's all brand fine new then.

Don't forget to add inhibitor if your draining down

 

[Ad_stoke]

Am I right in thinking its defo not the HEX passing thru? What are the symptons for that? Just for reference. Dont want to change the diverter valve and actuator and still not work.......

 

[gasmanrob]

Unless it's a combi boiler then it's the same heat exchanger that does both.

Boiler fires, heats water, pump circulates, diverter valve diverts, water returns to boiler.

Unless it's an old ideal classic with a 4 pipe set up in which you'll have gravity hot water and pumped heating in which case anti gravity valve is jammed open.

There is a remote possibility that the cylinder return has been teed in incorrectly and causing back flow but that would have surfaced years ago

 

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Cheers Rob