Hi I have a Ferroli Optima 901 combi boiler and have recently been experiencing intermittent problems with no hot water. Shortly after this started I lost all pressure in the CH side which turned out to be a faulty pressure relief valve. This was replaced and the system repressurised to 1.5 bar (while cold).

I noticed that this pressure rises to 2.25bar when the CH is on, i assume that this is correct due to the expansion caused by the increased temperature. the pressue with the CH off is 1.35 bar.

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?

Last time I posted this question someone was good enough to point me in the direction of the Diverter valve being the possible cause.
How do I locate the diverter valve and the associated micro switches? Anyone got any other ideas?
Sorry for the ignorance, trying to understand whats going on and hopefully fix it before summer - if it is an issue thats caused by the heating being off!

Chris, March 2006

off the top of my head I think your boiler has a diaphragm operated flow switch, this will usually be the disk shaped brass section with the microswitches housed on top. Now myself I would be just changing the diaphragm but I am a service engineer by trade.
To be honest if you have never worked on central heating boilers before and by the fact your asking the question I am guessing not, I would personally not reccomend doing the job yourself as it could potentially go very wrong and you could end up with a bigger problem than you started with.

HTH

Andy the gas man, March 2006