Boiler Service

A modern boiler is often an electromechanical appliance with several moving parts and system components that can break down when you least expect. The checks below form a general maintenance schedule for boiler servicing.

In Europe, boilers may be maintained on hours-used (similar to cars) or on a time schedule — annual or biennially. In the UK we typically work to an annual maintenance schedule. Many manufacturers also invalidate extended warranties if the boiler is not serviced annually.

Checklist for modern condensing boilers

• Visual check externally to boiler.
• Checks on the flue integrity.
• Gas rating check of boiler in conjunction with FGA (Flue Gas Analysis) emissions check using a calibrated analyser.
• Checking safety devices.
• Boiler casing removed to check visually internal boiler condition of components — fan, pump, auto air vent.
• Checks and cleaning of internal heat exchanger dependent on emissions test and maintenance schedule (new seals may be required).
• Expansion vessel pressure if sealed system.
• Condense pump checked / cleaned.
• Boiler fired safely to identify any working faults.
• Boiler parts cleaned, if necessary.
• Check case seals form an effective seal.
• Fill in benchmark to note important checks carried out, or create a report.
• Check diverter valve condition.

Checklist for non-condensing boilers

• Visual check externally to boiler.
• Checks on the flue integrity.
• Burner pressure check of boiler in conjunction with FGA (Flue Gas Analysis) emissions check using a calibrated analyser (if flue gas testing is not possible, a full strip down and clean should be carried out).
• Checking safety devices.
• Boiler casing removed to check visually internal boiler condition of components — fan, pump, auto air vent.
• Checks and cleaning of internal heat exchanger dependent on emissions test and maintenance schedule (new seals may be required).
• Expansion vessel pressure if sealed system.
• Boiler fired safely to identify any working faults.
• Boiler parts cleaned, if necessary.
• Check case seals form an effective seal.
• Fill in benchmark to note important checks carried out, or create a report.

Combustion performance analysis / emissions testing

Most modern boilers require checking their combustion ratios using a flue gas analyser (FGA). Many older non-condensing boilers can also be checked using an FGA. Some older boilers in which you cannot measure combustion performance will require full strip down and servicing. The following CO/CO₂ ratio levels trigger actions:

Example calculation

Data: CO 10 PPM, CO₂ 9.0%

1. Convert CO₂ to PPM: 9.0 × 10,000 = 90,000 PPM
2. Ratio = 10 ÷ 90,000 = 0.0001

Key: PPM = parts per million.

Other information

There are other checks that are important and should be carried out by engineers. Checking the water quality of the heating system is crucial for a long-lasting system. Making sure correct levels of inhibitor / protector will help ensure the system does not corrode internally and cause premature breakdown of parts. Checking other parts of the system can indicate problems that may be caused by the boiler or to the boiler.

Information is guidance only; repairs require qualified professionals. Do your own due diligence; we accept no liability.