i have a Ariston EuroCombi A/23 which had a problem with the diverter valve. I was only getting hot water when the heating was on. This was repaired by having a new diaphragm installed. (the old one had a large split in it) This certainly fixed the problem and i now get hot water when required.
Unfortunatley this seems to have given me a new problem. When hot water is called for the rads become warm. They also heat up every time the boiler turns on to maintain the temperature of the water. I assume the boiler does this to allow you constant hot water when called for.
Do you think the plumber has possibly installed the diaphragm incorrectly? or is there another issue?
Are you certain that you didn't have this problem before?
I'm assuming you told the engineer what the boiler fault symptoms were when he arrived, and without much testing, other than operating your hot tap and testing the flow switch, he decided to change the diaphragm in the water section of the diverter valve. As this has fixed your hot water problem, it was obviously the right diagnosis.
Looking at how the new diaphragm would have been installed, I'd say it's unlikely that the engineer making the repair would have caused your latest fault, it's more a case of the fault has only become apparent now your hot water is functioning correctly.
If I were you, I'd contact your engineer and have a chat and see what he says.
Don't be surprised if he now tells you that a new diverter valve is required, which will include the part he's just changed. At least you'll have a spare for next time.
From reading up i thought as much. Just wondering is it possible the valve has just seized and can be fixed or do you think its better just to buy a replacement? Also any recomeneded websites where i could purchase a new valve.
You may be able to buy diverter valve service kits, stripping, cleaning and replacing all moving parts would solve the problem - but you have to weigh up the time/labour of stripping cleaning and re-assembling against the price of a new diverter valve.