Annual Boiler Service Keep It Safe, Keep It Efficient

A genuine annual service is a strip down and inspection, not a glance and a sticker. If nobody took the casing off and nobody produced a flue gas analyser, you did not have a service.

Before anything is touched. The engineer checks the boiler location, ventilation and clearances, looks at the flue route and where it terminates, and runs the appliance from cold, because a boiler start-up sequence tells an experienced engineer a great deal.

Gas soundness and supply. The gas installation is tested for tightness, and standing and working pressures are measured at the appliance. An undersized or partly obstructed gas supply causes intermittent faults that get wrongly blamed on the boiler.

Casing off. The burner is removed and inspected for damage, distortion and debris. The heat exchanger is inspected and cleaned. Sooting or scaling is recorded, because both are symptoms of something else rather than problems in isolation.

Electrodes and sensors. Ignition and flame sensing electrodes are cleaned or replaced and their gaps checked against the manufacturer figures. Worn electrodes are the most common cause of ignition lockouts on an otherwise healthy boiler.

Condensate trap. The trap is removed, cleaned and refilled. A trap that has silted up or dried out causes lockouts and, on some appliances, can let flue gases escape. The external condensate route is checked, which matters here in winter.

Seals and gaskets. Every seal disturbed during the service is inspected and replaced if it is not perfect. This is the step cheap servicing skips, and it matters more than anything else on the list, because those seals keep combustion products inside the appliance.

Flue gas analysis. Reassembled, the boiler is run at high and low fire and readings taken from the flue with a calibrated electronic analyser. The ratio of carbon dioxide to carbon monoxide shows whether combustion is clean and within the manufacturer tolerance. It is the most important safety test in the whole service and it cannot be faked.

Flue integrity. The flue is inspected along its accessible length, at the joints and at the terminal, for damage, correct fall, support and clearance from windows, doors and boundaries.

System side. Pressure, expansion vessel charge, pressure relief valve, pump and the condition of the system water. Any magnetic filter is emptied and cleaned. If the water is black or the filter comes out heavily loaded, we will tell you, because that is the start of a much more expensive problem.

Paperwork. A written record of what was checked, what was found, the readings taken, and anything needing attention now or before the next service.