No hot water

Hi all

I've got a ferroli optimax he31c combi boiler which i have had installed for nearly one year !
My problem is the hot water is not kicking in when requested although the heating is stil working fine just no hot water occasionally it will run for 5 mins or so and i can see on the display that its heating the water then the next time i turn the tap on nothing ... on the digital display its not showing that their is any fault with the boiler

Any help greatly appreciated

Cheers Phil/barc

Assuming the boiler is maintaining the necessary temperature for heating, it could be that the tempering valve has failed, and is mixing all cold in rather than tempering the hot to a safe value.

Another possibility (and there are probably many more I can't think of right off the top of my head) is that you may have a bad cartridge on a faucet somewhere that is providing a crossover between the hot and cold. With this type of water heating, there is usually a flow restrictor to prevent the water from going through the heat exchanger too fast and thus not getting hot enough. So, the flow and pressure would likely be higher on the cold lines, preventing the hot from getting where you want it if there was a crossover. Try turning any single handeled faucets in the house to full cold (thus blocking the hot), and see if you get any hot water where you want it. That would tell you you have a cartridge that needs to be replaced or repaired (maybe a new faucet with a different type!).

If the tempering valve is stuck, maybe try turning it a little - it might free up. Is hot getting to the tempering valve?