Hi I have a Ferroli Optima 901 combi boiler and have recently been experiencing occasional problems with no hot water.
This has been noticed when running the bath, with it initially running warm and then running freezing cold.

I think I may have loft gremlins as when i get the step ladders out to access the loft, go into the loft, look at the boiler to check the pilot light and system pressure and then try the hot water again it seems to of rectified its self!!

I have in the past (6 mths ago) had problems with the ch side loosing pressure which was resolved with replacing the PRV.
The pressure in the boiler was repressurised to 1.5 bar (while cold). and rises to about 2.25bar when the CH is on, i assume that this is correct due to the expansion caused by the increased temperature.

The only thing I can think of is that the problem seems to happen when the CH is not on (or at least thats when ive noticed it) thus the CH system pressure is at its lowest. I know the Boiler shuts down at 0.5 bar, is it possible for this sensor/valve (or whatever) to be faulty? Or any other ideas?

Is it possible that it is the air pressure switch or is that purely there to monitor the operation of the fan?

Sorry for the ignorance, trying to understand whats going on and hopefully fix it - if it is an issue thats caused by the heating being off!

Thanks Chris

Chris, August 2006

hi to whom it may concern, i have been reading the problems that you have had with the boiler, regrading the fault with the hot water being intermintent. Reading through your letter, you say to replace two parts, which are 800310 (temperature sensor) and 801260 CH boiler thermostat. You quote the price around £25 please can you give me an email address where i can obtain these parts.

Many regardes

Norman Clarke, March 2010

Ferroli Optima 901 -occasional Hot water problem.
The most likely cause of this fault is the thermostat for the domestic H.W. system needs replacing, the part No is 800310,
locate this part on the hot water outlet pipe at the bottom of the boiler, for access remove the control panel, an other cause can be the C.H. thermostat part No 801260, located on the control panel, the thermostat comes complete with a plug, as you will see this plugs into the printed circuit board, 2 screws to remove from the plastic facing to gain access, I would fit both parts while you are in there, the parts should cost under £25 for both. hope this helps

James Redpath, March 2007