I had a new boiler fitted in April this year. Last eve it stopped working, showing f 11. We have not been using the central heating, only hot water, for several months. In May it showed F25, but we bled the radiators and reset boiler and it has provided hot water ever since - but we have not used the central heating system since. Please advise what is wrong and can I reset it, or should I call out the fitter?

K Venn, August 2016

If combo boiler heater check the gauge on the dashboard it must read 1.5-2.0, underneath the heater/boiler there will be a thin copper pipe with a tap at each end, open both taps inline with the pipes and watch the gauge till it reaches at least 1.5 then turn them both off, your machine should then work,
It is a safety measure to stop the pipes being burnt out through lack of water in the system.

Rick, August 2016

Superficial research suggests flow/return thermistor issues

Probably best to call in a specialist

Good Luck..., August 2016