What's wrong with their hot water - any guesses?

[Madmog]

My Uncle and Auntie had a new Worcester Bosch combi installed in November and everything has been fine, up until the last couple of weeks. The central heating is working fine, but they're having problems with the water. It turns cold initially (which you would expect with cool water in the pipework), then runs warm before going cold again. Sometimes if they constantly run it, they can get the hot water to come back on.

Had the installers back twice (who are a bit known company) who haven't been able to solve it, so Worcester Bosch are coming out on Monday to look at it and hopefully sort! Just wondered if anyone has any ideas what could be wrong, as my Uncle and Auntie are elderly and it's worrying them.

Just bumping back up!

Lots of possible causes for this problem. On older boilers i would suspect a blockage of some type but given that you mentioned it only being installed in november i doubt it. Perhaps the diverter motor which switches the boiler between heat and hot water. Maybe a printed circuit board which controls everything the boiler does. It could be a thermistor which regulates the temperature of the hot water coming out of the boiler. All these parts will be free to replace if the boiler is new.

Its possible that there is a problem with the gas pressure due to a fault with the meter. The meter is designed to let more gas through when more is being used. Its fairly common for the pressure regulator to seize on the meter and since hot water requires the boiler to fire up on full rate, the heating may work fine while hot water fails. If they find this to be the problem then the gas provider will repair it free of charge.

The good thing about worcester coming out under warrenty is that the engineer will know the appliance inside out and normally carries all the spare parts with him so no second visit. Im sure they will have plenty of hot water by the end of Monday! The repair should be free although if Worcester find faults will the install they may refer you back to the original company.

Fill a bucket at the hot tap, time it, see how many litres per minute it delivers. It might be the flow switch. Does the bath tap have the same problem as the basin?

If you turn off the CH at the timer and wall stat first, and let the rads go cold before running the hot tap, see if there is any warmth going to the radiators when the hot tap is run.

If it is a new boiler fitted to old radiators, try to find out how long was spent cleaning out the old sludge and sediment before connecting the new boiler.

The installers should sort it but you can consult the makers if they fail.

...too slow!

But if the maker's agent is coming out I expect it will be sorted.