Icos HE24 rapid cycling problem - SOLVED

[bandad]

Our Ideal icos boiler is continuously cycling. It fires up for about 45 seconds and then stops for a while (perhaps three mins) before restarting.
There are no fault codes.

The valve is operational (2 valve system) and the pump appears to be working too. Hot water gets around enough for radiators to be luke warm. However, the main return back to the boiler is quite cool.

I have tried draining off at the two low level drain points to clear any air locks in the system. I have also checked the rads - no air found there. The pump has water and is clearly pushing the hot water beyond that point.

The system is a traditional vented system with header feed and expansion tank.

The control unit is not brilliant (slider switches are a bit iffy) but I have it switched to constant and the lights are on. There is a clear demand from the room thermostat.

Is the problem in the PCB?
What else can I do - other than emigrate to a warmer climate!

Help!

 

[bandad]

OK, so no one brave enough to guess what is wrong?
Good news it is fixed.

Answer: circulation pump needed replacing.

It is not immediately obvious that the pump was shot - it sounded ok, made the right noises, and even went round. However, the lack of circulation resulted in the boiler overheating. New pump has worked wonders.

 

[MJN]

Thanks for posting back bandad, and well done on the self-diagnosis and fix - particularly given the current weather!

Mathew