My Potterton Suprima 60 ( with new PCB 3 years ago ) has developed a fault where it stays on continuously even if the timer controller (Potterton EP2002) is in the OFF position.

I replaced the timer controller (cost £43.00) but it still comes on regardless. The only way to switch the boiler off completely is the internal temperature control ( OFF - MAX ).

Has anyone had a similar problem and what is the solution?

Mistry, December 2008

Thanks Collin,

The problem was a faulty motorised value, the internal spring was broken and luckily it was stuck in the open position hence causing the boiler to stay on - hence we had heating atleast.

Replaced the Potterton Myson ACT222 Actuator and all working OK now.

One problem - the replaced central heating controller i.e. Potterton EP2002 - the digital display is not as clear as my old one, I have had it replaced but still the same problem - for example you can only distinguish the number 3 and number 8 only when you view the display square on if you know what I mean.

Thanks for your advise.

Mistry, December 2008

If your boiler is running continuously i would suggest that you check the basics before spending anymore cash!
You bolier requires 2) 240v inlet live signals in order for it to light....

1) A 240v pemanant live, N & earth this will power the boilers PCB (printed circuit board) & allow for the internal pump over run stat to power the pump in order to circulate hot water thru the heat exchanger & allowing the appliance to cool down thus stopping it from going into overheat lockout mode inbetween cycles or ON/OFF peroids..... more commmon on high Kw rated boilers.

2) A 240v switched live, this is an external signal sent from an outside sorce in order to ignight the burners ie......

Timeclock via room stat (if fitted)

Cylinder stat

Motorized valve(s)

I would suggest you carry out the following checks, switch off all external controls just leave on the main boiler 240v supply.
Remove the right hand control panel on the boiler in order to expose the wiring strip! using a multi-meter check for 240v between the SWL (switch live) & a good earth, if your meter displays 240v then you have a switch live coming from a mororized valve this is because in most instances the micro switches fitted in motorized valves have 2 wires a 240v inlet normaly wired to a permanant sorce this wire is colour coded grey.
The micro switch also has a 240v outlet colour coded orange this is you SWL signal....... if you motorized valve is jammed in the fully opened position or the internal micro switch is jammed in the closed circuit mode then it will send a demand signal to the SWL on the appliance thus switching it on regardless.


Either that or there is a live looped between the perminant live & SWL but i guess you would have worked that out because the boiler would have always behaved in this mannar??

good luck mate!!

Collin, December 2008