What a commercial boiler service includes, step by step
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A commercial boiler service is a planned visit in which a Gas Safe registered engineer checks that the boiler is burning gas safely and efficiently, that its flue and air supply work, and that its safety controls respond as they should, then cleans what the manufacturer says to clean and records what was found. On a typical modern condensing boiler that means function checks, a gas rate check, a flue gas (combustion) analysis, cleaning or inspecting the burner, heat exchanger, sump and condensate trap, checking the flue terminal and seals, a gas soundness test and a written record. The exact steps come from the manufacturer's instructions for the model on your site. This guide walks through those steps in order, explains where SFG20 schedules and CIBSE Guide M fit, and lists the paperwork a duty holder should expect afterwards.
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What does a commercial boiler service include?
Why commercial boilers need a proper service
HSE's guidance for employers warns that if gas appliances such as boilers are not properly installed and maintained, there is a danger of fire, explosion, gas leaks and carbon monoxide (CO) poisoning. It gives the example of a primary school where 25 pupils and 2 members of staff were evacuated from a classroom after carbon monoxide from an inadequately maintained boiler leaked into the room above it. The employer had a maintenance system, but poor practices had crept in.
The legal duty sits with the duty holder. Regulation 35 of the Gas Safety (Installation and Use) Regulations 1998 says every employer or self-employed person must ensure that "any gas appliance, installation pipework or flue installed at any place of work under his control is maintained in a safe condition so as to prevent risk of injury to any person." HSE says employers should make sure gas appliances are maintained in a safe condition by a competent person "in line with manufacturers' instructions and appropriate standards".
In workplaces such as shops, restaurants, schools and hospitals, HSE says work on gas fittings must be carried out by a Gas Safe registered engineer who is qualified to do the work, that it is illegal for anyone else to do it, and that it is the employer's responsibility to check. In factories and agricultural premises the work must be done by a competent person, and any part of those premises used for sleeping or living accommodation needs a Gas Safe registered engineer.
How often: the manufacturer sets the interval
GSIUR does not set a fixed service interval, so the manufacturer's instructions are where the frequency usually comes from. As one example, Ideal's installation and servicing manual for its Evomax 2 commercial condensing boiler says the frequency of servicing "will depend upon the installation condition and usage but should be carried out at least annually". It also tells the installer to point out to the owner that the boiler "must have regular maintenance and cleaning, at least annually", and that this should preferably be done at the end of the heating season. Other makes and models have their own wording, so always go by the manual for the boilers you actually have.
A commercial boiler service, step by step
The servicing schedule in Ideal's Evomax 2 manual is a good illustration of what a service on a modern commercial condensing boiler involves. Your engineer will follow the instructions for your own make and model, which may differ.
| Step | What the engineer does |
|---|---|
| 1. Make safe | Ideal says to always turn off the gas supply at the gas service cock and switch off and disconnect the electricity supply to the appliance and any external controls before servicing or replacing components. |
| 2. Function checks | Light the boiler and carry out function checks, "noting any operational faults". |
| 3. Gas rate | Run the boiler for 5 minutes and check the gas consumption rate, with the burner forced to maximum rate. |
| 4. Combustion analysis | Connect a gas analyser to the sampling point in the flue adapter. For that boiler, Ideal says the CO/CO2 ratio of the flue gas should not be greater than 0.004 and the CO2 values should match the manufacturer's table. If they do, and the gas input is at least 90% of nominal, no further action is needed on the burner. |
| 5. Burner | If the readings are not right, remove and clean the burner. If the gas input is still not at least 90% of nominal after cleaning, Ideal says to contact the manufacturer. |
| 6. Heat exchanger, sump and condensate trap | Inspect the heat exchanger through the burner opening, clear deposits from the sump, and remove the condensate trap and flush it through. Ideal says removal and cleaning is recommended annually, and that the heat exchanger, sump and condensate trap must be inspected and cleaned after a maximum of 2 years' operation. |
| 7. Flue | Check that the flue terminal is unobstructed and that the flue system is sealed correctly. |
| 8. Final safety checks | After servicing or replacing components, Ideal says to always test for gas soundness, check the water system is correctly filled and free of air, examine water connections for soundness with the system hot, check the gas rate and measure CO/CO2 (the ratio should not exceed 0.004 and CO should not exceed 350ppm for that boiler), and carry out functional checks as appropriate. |
| 9. Record it | After servicing, complete the service section of the log book and return it to the owner or their representative. |
The law adds its own checklist. Regulation 26(9) of GSIUR says that where a person performs work on a gas appliance, they must immediately afterwards examine the effectiveness of any flue, the supply of combustion air, the appliance's operating pressure or heat input (or, where that isn't reasonably practicable, its combustion performance), and its operation "so as to ensure its safe functioning". They must then take all reasonably practicable steps to notify any defect to the responsible person and, where different, the owner of the premises.
Gas tightness, ventilation and safety controls
A boiler service looks at more than the boiler casing. Three parts of the wider installation come up on most commercial visits:
- Gas soundness (tightness). Ideal's manual says to test for gas soundness after servicing, and that a complete installation must be tested for gas soundness and purged in line with the standards it lists, which include IGEM/UP/1, "Soundness testing and purging of industrial and commercial gas installation". Testing of the wider pipework is engineer-only work.
- Ventilation and flues. IGEM/UP/10 Edition 4 is the IGEM standard for installing flued gas appliances in industrial and commercial premises, covering hot water boilers of net heat input over 70 kW and up to 20 MW. Its contents include ventilation, chimneys, gas and fire detection, commissioning and handover, and servicing and maintenance. Where a design deviates from its prescribed ventilation or chimney requirements, IGEM says the calculations and conclusions must be kept with the plant records and a system design verification notice (SDVN) displayed to help anyone working on the installation. HSE's employer guidance also says rooms with gas appliances need adequate ventilation, and that air inlets must not be blocked and flues and chimneys must not be obstructed.
- Safety controls and interlocks. For industrial and commercial plant, HSE says to consider explosion relief and/or flame-failure protection as necessary, to make sure the gas supply is interlocked with the ventilation of the appliance, and to make sure there is enough ventilation to remove combustion products. Ideal's commissioning checks include proving the correct operation of any secondary system controls by operating each one separately and checking that the burner or pump responds. Ask your engineer to confirm on the report which controls and interlocks were checked.
Where SFG20 and CIBSE Guide M fit
Many facilities teams and maintenance contractors build their boiler servicing into a wider planned maintenance regime using two industry references:
- SFG20. Created by BESA (the Building Engineering Services Association), SFG20 describes itself as the industry standard for building maintenance specification. Its maintenance schedules are "structured task lists that define what needs maintaining, how often, and by whom", breaking each task into steps with priority, frequency, timings, skill level and safety notes. Tasks are colour-coded: red tasks are statutory and should be completed to achieve compliance, while amber tasks are not required by law but reduce the risk of unexpected failure. SFG20 says its library covers more than 1,500 schedules, including boilers.
- CIBSE Guide M. CIBSE's Guide M, Maintenance engineering and management (third edition, 2023), is intended to help building and property operators "become more aware of their responsibilities and duties". Its parts include operations and maintenance documentation, risk assessment and risk management, legislation, and training and competency.
Neither replaces the manufacturer's instructions for a specific boiler. They help you decide what goes into a planned preventive maintenance contract, how often each task happens and what skill level it needs.
A service is not a PSSR examination
Some commercial heating plant is also covered by the Pressure Systems Safety Regulations 2000 (PSSR). HSE's leaflet INDG178 explains that PSSR applies to systems containing a "relevant fluid", which includes pressurised hot water above 110°C and steam at any pressure; a steam boiler and its pipework and protective devices is one of HSE's examples. Where PSSR applies, the user or owner must have a suitable written scheme of examination in place before the system is operated, drawn up or certified by a competent person, and the system must actually be examined in line with that scheme. That examination is a separate duty from the annual boiler service, and the two should not be confused on a maintenance plan.
Where PSSR does not apply, as on many low-temperature hot water systems, relief valves, expansion vessels and pressurisation units should still be maintained by a competent engineer to the manufacturer's instructions. Our guide to written schemes of examination for heating plant explains when PSSR applies.
What paperwork to expect after a service
Ask for the record before the engineer leaves, and keep it with your plant records. A useful service record usually covers:
| Item | Why it matters |
|---|---|
| The boiler log book service section, completed | Ideal asks engineers to complete it after servicing and return it to the owner |
| Which appliances were serviced (make, model, location) and the date | Shows that each appliance under your control has been maintained (GSIUR regulation 35) |
| Combustion and gas rate readings | Gives a baseline the next engineer can compare against |
| Flue, air supply and safety checks carried out | Maps to the examinations GSIUR regulation 26(9) requires after work on a gas appliance |
| Any defects found and what was done or recommended | GSIUR regulation 26(9) requires defects to be notified to the responsible person and, where different, the owner |
| The engineer's name and Gas Safe registration number | HSE says it is the employer's responsibility to check the engineer is registered and qualified for the work |
HSE says you can check an engineer's registration and qualifications on the Gas Safe Register website or by phoning Gas Safe Register on 0800 408 5500. Do not use any appliance you know or suspect is unsafe.
Between services: what site staff can do
Trained site staff can help the engineer by keeping up visual and gauge checks: walking the plant room, keeping ventilation openings clear, keeping combustibles away from boilers, logging pressure gauge readings against the range the engineer has set, and reporting anything abnormal. They should not adjust burners, controls or relief valves, and they should not keep resetting a boiler that has locked out; note the time, the fault code and what else was running, then call an engineer. Our commercial plant room safety checklist and our guide to reading a commercial heating pressure gauge cover those checks, and our frost protection guide covers the settings worth confirming at the autumn service.
If you suspect a gas leak, HSE says to turn off the supply and phone the National Gas Emergency Service on 0800 111 999 (for LPG, your LPG supplier), and not to turn the gas back on until the leak has been dealt with by a competent person.
Where Fast Commercial Boiler Help fits
Our Gas Safe registered engineers carry out commercial boiler servicing to the manufacturer's instructions for the plant on your site, and can set up servicing on a planned preventive maintenance schedule. We also carry out commercial gas safety inspections and plant room repairs when a service turns up a fault. Where oil-fired plant is fitted, our engineers who work on oil are OFTEC trained.
Safety note
Under the Gas Safety (Installation and Use) Regulations 1998, gas work must be carried out by a Gas Safe registered engineer, and we apply that rule on every site. Don't attempt DIY work on gas appliances, burners, flues or safety devices. On pressure systems, trained site staff should stick to visual and gauge checks, log the readings and report anything abnormal. Never adjust, cap, plug or test-lift a relief valve yourself.
Talk to a Gas Safe commercial engineer
Fast Commercial Boiler Help is a Gas Safe registered (985448) commercial heating business based at 4 Market Hill, Clare, Sudbury, Suffolk CO10 8NN. Our team of over 10 local engineers covers East Anglia and East London, working on commercial boilers, plant rooms, water heaters, and warm air, radiant and unit heaters. We work on commercial premises only.
Call or WhatsApp 07947 578332 (a photo of the appliance data plate or the fault display helps) · Email [email protected]
Frequently asked questions
What does a commercial boiler service include?
It depends on the make and model, but on a typical modern commercial condensing boiler it includes making the boiler safe, function checks, a gas rate check, a flue gas (combustion) analysis, cleaning or inspecting the burner, heat exchanger, sump and condensate trap, checking the flue terminal and seals, a gas soundness test, final functional checks and a completed log book entry. Ideal's Evomax 2 manual sets out steps like these. GSIUR regulation 26(9) also requires the engineer to examine the flue, combustion air supply, operating pressure or heat input and safe functioning after working on a gas appliance.
How often should a commercial boiler be serviced?
GSIUR 1998 does not set a fixed interval. Regulation 35 requires employers to keep gas appliances, pipework and flues at places of work under their control in a safe condition, and HSE says appliances should be maintained by a competent person in line with manufacturers' instructions and appropriate standards. Many manufacturers specify at least once a year; Ideal's Evomax 2 manual, for example, says servicing should be carried out at least annually.
Who can service a commercial gas boiler?
In workplaces such as shops, restaurants, schools and hospitals, HSE says work on gas fittings must be carried out by a Gas Safe registered engineer who is qualified to do the work, and that it is the employer's responsibility to check. You can check registration on the Gas Safe Register website or by calling Gas Safe Register on 0800 408 5500. In factories and agricultural premises a competent person must do the work.
What paperwork should I get after a commercial boiler service?
Expect a completed log book service section, the appliances serviced, combustion and gas rate readings, the flue, air supply and safety checks carried out, any defects found with what was done or recommended, and the engineer's name and Gas Safe number. GSIUR regulation 26(9) requires defects to be notified to the responsible person and, where different, the owner of the premises. Keep the records with your plant records.
Is a boiler service the same as a PSSR examination?
No. Where the Pressure Systems Safety Regulations 2000 apply, for example to steam boilers or pressurised hot water above 110°C, the user or owner needs a written scheme of examination drawn up or certified by a competent person, and the system must be examined in line with it (HSE INDG178). That is a separate duty from the annual boiler service. Where PSSR does not apply, relief valves and pressure equipment are maintained by a competent engineer to the manufacturer's instructions.
Sources and further reading
- Ideal Evomax 2 commercial condensing boiler: installation and servicing manual (UIN 219458)
- Gas Safety (Installation and Use) Regulations 1998, regulation 35 (legislation.gov.uk)
- Gas Safety (Installation and Use) Regulations 1998, regulation 26: gas appliances, safety precautions (legislation.gov.uk)
- HSE: Gas safety for employers
- IGEM/UP/10 Edition 4: Installation of flued gas appliances in industrial and commercial premises
- BESA SFG20: What is SFG20?
- CIBSE Guide M: Maintenance engineering and management
- HSE INDG178: Written schemes of examination
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