Worcester Bosch 28CDi RSF Combi problem

Their web site is

In article , richard snipped-for-privacy@yahoo.co.uk writes

How strange! My Worcester 28Cdi RSF had similar problems a few weeks back too...

I had excessive changes in pressure, lack of hot water and water appearing from the pressure relief valve.

Check Ed Siretts FAQ - it will answer everything!

Sealed CH FAQ

Lack of hot ware could be the diverter valve. Take the flow switches off, by removing the C clip and take a look at the plunger pin. It should come out when the hot tap goes on. If not, you need a new valve.

We used an Ariston (i think) diaphragm instead of buying a whole new valve.

The install manual is available on the net, it has a fault finding chart which may help.

God, I didn't even know what a combi boiler was last month.....!

TTFN

Worester Bosch were very good. responded to my email within half an hour (I was most surprised - I usually despair when I have to rely on organisations replying to emails, particularly urgent ones ...).

I managed to book a next day "tiered price" appointment - ie one price if it just needs service, another if it needs any parts, and a third price if the heat exchanger needs replacing. Not unreasonable, particularly when it's being serviced by trained Bosch people, and nice to know the cost is capped.

He sorted out a long standing problem which I posted about a few years back - when the central heating temperature dial is close to the actual temperature, for low settings, the boiler repeatedly fires up then shuts down instantly, over and over again. For the benefit of anyone else who has this problem, he replaced the main controller board.

He also replaced the heat exchanger plate, which was the source of the leak.

However, in terms of hot water not firing up, he said the boiler seemed fine and that he thought the problem was cross-flow in a mixer valve, presumably high pressure cold water leaking through a mixer into the hot water inlet.

Now, I know that my shower does have this problem, but am not sure why the boiler is suddenyl unable to cope with it after five years. Alternatively, it could be a new mixer fault elsewhere.

Does anyone have any ideas on how to easily diagnose the source of such a mixer problem - I have four sets of mixers - without physically disconnecting each pair of taps in turn and trying the hot water until it works?

Would I be right in thinking that the more modern taps, such as a

Hope all this helps someone in the future ... Thanks, Richard

Having isolated put a stop end in the hot water pipe out of the boiler, so that only a single (washing machine) outlet is in the run, the hot water problem remains.

The tap needs to be turned fully on to get the boiler to fire up. This is a much greater flow than used to be necessary for hot water, and the kitchen sink and shower are unable to trigger it.

I am therefore sure the problem is within the boiler itself. All other problems have been fixed. Bosch will be back in a week to take another look, but in the meantime does anyone have any ideas on where the problem might lie, eg the hot water diverter valve / flow switch sensor thingy?

Thanks, Richard

The web site is down ATM so I can't check the precise means by which the boiler senses water flow. However the symptom of insensitivity to HW flow is very likely to indicate a split diaphragm of some sort. This part will likely not exceed £40 (whole valve) or £10 a replacement diaphragm.

Valves are £75 plus vat and you can't get the diaphragm as a spare part!

Take a look at the B E S Website and see if your valve is among those they sell. Most of the Worcester valves are made by Giannoni which is what BES sell