Myson MPE 222 problem?

Barry1647

Hi Guys, looking for some advice. I have a Potterton gas heating system with 2 MPE 222 valves, one for CH, one for HW.
Potterton PTT100 external stat on HW cylinder.
Problem....no hot water.
If I adjust stat on cylinder the HW valve opens and orange light comes on but boiler does not fire.
If I adjust room stat the CH valve opens and that orange light comes on and boiler and pump fire up.
Wiring from HW actuator is all firmly connected at nearby connector panel BUT grey (SAT) wire from tank stat is not connected.
Any thoughts gratefully received.

keystone

Sounds like an S plan setup is that correct?

Cheers

Barry1647

No idea what an s plan is..

Barry1647

Just googled it..yes that looks like what we have.

keystone

Is there a balancing valve on the return from the cylinder? With both stats calling for heat open it half a turn. The pipework should get hot.

Also try running through the faultfinding section on S plan systems on pages 26 to 27 of THIS document

Cheers

Barry1647

The pipework gets hot with both stats calling for heat. Hot water heating up when both stats calling. As soon as I turn down room CH stat boiler shuts down but HW valve still open. System seems ok except for HW valve not calling for boiler to fire up.
What causes the HW valve to signal the boiler? Is it just the operation of the valve or is there another switch/mechanism/system in the actuator?

keystone

Sorry - as I refuse to contribute to the Murdoch Empire's profits if I can possibly help it I'm reduced to watching the Italian GP highlights on the Beeb. It sounds as though the valve is fine. It could be the tankstat not quite making the circuit correctly or it could be the programmer. Both of these can be checked using a continuity tester.

Cheers

PS If I disappear again its because I'm watching the box again.

Barry1647

Thanks for that, appreciate your time.

gas4you

Answered on another forum

southcoastrgi

gas4you wrote: »

Answered on another forum

what a helpful comment !!

southcoastrgi

does it have a lever on the hot water valve that you can move by hand ? if it does try moving that fully so the valve is open does the boiler fire ? if it does i would say either the mirco switch or the motor in the valve head.