Hello, I own a Myson Midas Si combi boiler (no I'm not proud!). From reading other posts I realise these aren't the best boilers in the world, but I can't afford a new one! Anyway, with HW off CH on everythings fine. HW on CH off, fine. HW on CH on, overheats water to about 80c then cuts off. comes back on hourish later then does the same. PLEASE help!
Myson Midas overheating
- Thread starter mradam
- Start date
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it's the fact that you can have one or the other that's strange. have you had a pump changed recently?
No, it has been fine since we moved in year before last. Started going a few months ago. But has been happening with more and more regularity.
Seems as though it is trying to heat the hot water when it's set to both. If I turn HW switch off it starts the CH pump again and i'ts fine, If I switch HW back on it starts to overheat again. Read on another post about turning the tap on and off several times to free the diverter valve, but this hasn't helped.
Seems as though it is trying to heat the hot water when it's set to both. If I turn HW switch off it starts the CH pump again and i'ts fine, If I switch HW back on it starts to overheat again. Read on another post about turning the tap on and off several times to free the diverter valve, but this hasn't helped.
it sounds like its the dhw preheat stat (i think myson call it a dhw safety stat on the si) if it fails it can keep the boiler in a constant state of dhw preheat stopping it from switching over to ch. by switching the dhw off you're stopping the demand for dhw so it goes back to ch. there is no diverter valve on that boiler.
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look underneath the boiler
do you have 2 sensors on 2 seperate pipes entering the dhw heat exchanger? one red, one blue.
do you have 2 sensors on 2 seperate pipes entering the dhw heat exchanger? one red, one blue.
the blue one is the preheat sensor, the red conrols the heat of the water as it's running.
readily available, bit expensive for what they are. i actually carry them as van stock because of the amount of midas' still installed in the ne
they are wet pocket sensors so remember to turn off the cold water feed to the boiler.
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