All oil boiler manufacturers insist that the boiler be serviced annually to maintain your warranty with them.  This is in fact misleading since in most cases your boiler warranty itself expires after 2 years anyway.  That said, it is a good idea to have it serviced annually as worn components can cause your boiler to run out of tune which in turn can lead to a major sooting up.  A service is also a chance to check some of the components for deterioration and an imformed decision can be made whether to replace the part and pre-empt a potential failure or to wait until the failure actually occurs, if ever.

The boiler is first checked to make sure it’s working on arrival.  The burner is then removed and disassembled and cleaned thoroughly.  It is fully inspected for signs of wear or damage and non-service items are replaced as per discussion with the home owner.  The pressure jet (aka nozzle) is replaced and the burner is reassembled.  Flexible oil lines are checked for existing and potential leaks due to cracking and replaced as necessary.  The Primary heat exchanger is opened and the baffles removed for cleaning as is the heat exchanger itself.  On a condensing boiler the secondary heat exchanger receives the same treatment and the condensate trap is cleaned and refilled with clean water.  The boiler is then reassembled and the flue is inspected as far as is practicable.  The oil supply is checked for leaks and other damage and oil filters checked and replaced as necessary.  Oil valves and safety devices are checked for correct operation.  The oil tank is inspected for damage and corrosion and water removed from the oil if necessary.  The boiler is fired up and tuned for optimum efficiency and combustion gases.  Your boiler service is complete.

This depends on the type of boiler you have and how easy it is to access. It can take as little as 45 minutes or as long as 2 hours but in general an hour and 30 minutes is adequate.

It’s rare that a boiler has broken down due to not being serviced.  In extreme cases it does happen but usually a breakdown is due to a failure of a non-service item i.e. a motor or oil pump etc.  As such, servicing the boiler as described above is unlikely to resolve the problem.  Best practice is to fix the problem and then service a working boiler.  Every rule has it’s exceptions though and if the boiler simply hasn’t been serviced for several years then it could just be the pressure jet/nozzle which has caused the failure and although replacing it may be enough, a thorough service would be recommended.

ABSOLUTELY NOT! Sorry if the sounds rude but to work on gas appliances of any kind, one must be GASSAFE (formerly CORGI) registered. I specialize in oil boilers and so have never needed GASSAFE/CORGI registration. I can and do however, repair systems which have gas boilers but where the fault is not with the boiler itself i.e. a faulty circulation pump or control system.