Loss of pressure
Combination and system boilers must be at the correct operating pressure (between 1 -2 bar) for your system to work properly. Typically, if your system pressure falls below 1 bar your boiler will implement a safety lockout feature to prevent it from firing until re-pressurised. This is to protect the boiler components from damage caused by operating under the incorrect operating pressure.
Re-pressurising your boiler is straightforward enough and can usually be carried out by the user with reference to the manufacturer’s instructions, but frequent pressure loss usually means there is a fault within your heating system.
Your boiler could be losing pressure for several reasons. Pressure loss is most commonly caused by a leak in the heating system, typically from a radiator valve or boiler component. Another common cause is a faulty expansion vessel and pressure relief valve. The expansion vessel, typically located inside the boiler, contains air as well as water from the heating system. When the water in the heating system heats up and expands, the air pocket compresses to take up the expansion. If the air pocket depletes or the diaphragm in the vessel becomes perforated, the pressure in your heating system will fluctuate extensively, often triggering the pressure relief valve. Typically, both parts are replaced at the same time.
PCB and Ignition failure
The PCB (Printed Circuit Board) is essentially the brain of your boiler, telling it when to turn on the pump, when to ignite and how much gas to use. If the PCB fails, the boiler will usually start behaving peculiarly or displaying several fault codes relating to ignition failure. Unfortunately, PCB failures are quite common, but are usually straightforward to diagnose.
Another common cause of ignition failure is faulty spark generators and electrodes. These parts are responsible for creating the spark required to fire up the boiler. If they fail, the boiler will be unable to ignite and will display a fault code. Gas valves, which regulate the gas supply to your boiler, can also fail but this occurrence is less common.
Boilers will typically lockout if they overheat, accompanied by high display temperatures and strange banging noises. The most common causes of boilers overheating are pump failure, sludge build up, air in the system, or faulty thermostats.
If you suspect your boiler is overheating, it may be a good idea to try to bleed your radiators to check for air in the system. If this is unsuccessful, it is unwise to attempt any further repairs on your own and you should contact ASP Plumbing and Heating Services straight away.