ICOS-HE12 Boiler

27 Jan 2010
Reaction score
United Kingdom
Can anyone help or would someone pass me onto someone please who can.

I have a Myson Digital Water and Central Heating Timer with an ICOS Boiler, The Thermostat for the house is a manual dial situated in the main stairwell of my house. The timer is set to come on obviously at different times throughout the morning, day and night, But presently my central heating seems to be on when the boiler is actually Off, i.e. no red light on the Timer stating that the heating is actually on. The ICOS Boiler does show the Burner Light Flashing and the digital status indicator shows [ or something that looks like straight printed letter C.

If you could provide any information to what might actually be the fault with my heating system at present it would be greatly appreciated.

Your Kindly
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IIRC, c means there is a demand and the flashing burner neon means the boiler is up to temperature. Your problem is possibly the CH valve stuck in the on/open position.
Next to the HW cylinder more often than not.

Try turning the power off to the boiler then on again. Sometimes this can clear a pcb glitch.
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Thanks for help, I will try that, I tried my luck with the developers as the hoose out of the 2 year warranty and they stated they will check it on Friday as well. Thanks for your help again.

Next to the HW cylinder more often than not.

Try turning the power off to the boiler then on again. Sometimes this can clear a pcb glitch.
i work alot on icos boilers, if a stray voltage above 6volts to the appliance wild make it fire up for central heating on earlier types of pcb.

I would also check for a stuck control
Think we have sussed out the cheap MYSON Plastic Valve not returning to auto, Been advised t change to the honeywell motorized silver box valve which i have u all know is connected there for my hot water already new, any opions appreciated
Mitch ;)
Some of the newer myson valves have heads you can remove either by screws you see them one either side or a clip you release via a button.

This will allow the valve to close on the motor head if it does then all you need to do is locate the spindle on the valve body using a light touch with a spanner or pliers turn the spindle slightly to free it, reconnect and go and arrange a replacement asap.

If the valve motor dont return, turn power off it may need a lack of power to turn off as they often hold them selfs open till another voltage is detected on ch off / hw on ect.

if the head cant be removed, you can use the stat on front of your boiler setting that to the lowest setting should help keep the boiler off a bit longer and make it cooler, but if the valve motor cant be removed and controls are off and still open for Central heating (if its not in the "auto" positon its probably in CH mode) you will need a engineer visit advise him of the problem and what you may need and he will sort you out for a nice honeywell metal valve not the myson plastic :)
The Honeywell valves are more expensive, but IMHO you get what you pay for, they are superior quality to the cheaper alternatives.
Well the Myson the levers break the bits inside the head break and generaly fail more then i have had on honeywell.

Honeywell all that i every realy need to worry about is the motor going.

Both valves suffer from sludge build up on the valves seating and stoping them closing and letting by but i find Honeywell last longer.

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