If your boiler is not coming on then, before you call an engineer, take a look and see if there is anything that you can do yourself. There are many reasons why your boiler does not come on when it is needed but these are some of the most common:
PILOT LIGHT ON BOILER HAS GONE OUT - if there is no visible flame then you can follow the instructions that should be visible on your boiler. However, if you smell gas do not try and relight it. If the pilot light often goes out then you should book a Gas Safe heating engineer to take a look.
THERE IS A RED LIGHT VISIBLE ON MY BOILER - A reset might be all that the boiler needs and you should be able to find the reset button somewhere on the control panel. If the reset button is not visible then have a look at the boiler instruction manual or search online for it if you cant find your own. Still not working? Like any good appliance, try and switch it off and switch it back on again. If you have to keep resetting it then call a Gas Safe engineer to check it.
CHECK YOUR THERMOSTAT - Double check the thermostat! It sounds silly but sometimes it is those simple things that we over look. If there has been a power cut, if the clocks have gone forward/backward or if someone has accidenatlly changed the settings, then your boiler will not switch on. Check the set temperature is not too low and without stating the obvious, If there is nothing displaying on the thermostat, it might just need a new battery.
THE PRESSURE ON THE BOILER HAS DROPPED - If the pressure guage on your boiler has dropped below 1 bar then, carefully, use the valve to increase the pressure to 1 - 1.5 bar. If you don't have the instructions to hand then check online as most companies have handy instructional videos just for these little jobs. You may need to reset the boiler again after you have adjusted the pressure.
LIKE ALWAYS, IF YOU ARE UNSURE THEN CALL A GAS SAFE ENGINEER TO PAY YOU A VISIT. VISIT THE GAS SAFE REGISTER HERE.