Myson MPE322

[rubble2]

Just moved into a new house last Friday and found that hot water from boiler is not working so have had to use immersion.

Investigating further today and I think the problem lies with the 3 way valve (model as above).

Could someone confirm that I am heading in the right direction please?

I have taken the actuator off the valve and the valve shaft is easily turned by hand so I think that mechanically all is well. The actuator itself is very hot even though the heating has been off all day and the manual/auto lever is just flopping around with no resistance. Can I therefore deduce that the actuator is shot?

I can get hold of and fit a new actuator if someone could confirm that I am on the right lines, but in the meantime is it possible to get the HW to work by manually turning the valve shaft? and if so in which direction? ( or do I just turn it until I get hot water?)

Thanks for any advice.

 

[polesapart]

in the meantime is it possible to get the HW to work by manually turning the valve shaft? and if so in which direction? ( or do I just turn it until I get hot water?)

1 yes

2 you can trace the hot water from the boiler flow by feeling the pipes
try for mid-position over the (short) range of shaft rotation

 

[stem]

From what you describe, it sounds to me like the valve is working OK. The good signs are:

1. "The valve shaft is easily turned by hand". Good, so it's not seized in the heating only position
2. "The manual/auto lever is just flopping around with no resistance". Also, good. it means the motor is working OK and has moved the valve to the heating position
3. "The actuator itself is very hot". Perfectly normal for a working valve.

It is very unusual for a motorised valve to fail and not provide any hot water. The valve is wound to the heating position by a motor when the heating is required, but when unpowered it is pulled by a spring back to the hot water position, which is where they normally sit when they go faulty. So, normally the hot water works, but the heating doesn't.

When the lever is floppy that shows the motor is working OK as it has wound the valve to the heating position, when the heating is off, that is when the resistance can be felt as you are pulling against the spring.

Often the motorised valve gets the blame for a fault, and in theory it is possible for it to have jammed in the heating position, so that the spring doesn't pull it to the hot water position, but it would be a very rare occurrence. Even less likely if you can move it easily. But there are other items that could cause the problem, such as the hot water cylinder thermostat, or programmer, or even an airlock or blockage in the pipes.

You haven't posted anything that would suggest to me that there is anything wrong with the 3-Port Valve.

 

[ollski]

Turn mains power off to the heating system and see if the valve actuator returns to hot water position so there is resistance on the lever again, if it does then it's ok