Commercial heating failures often become apparent in the first sustained cold spell of autumn, when plant that has done little since April is suddenly asked to run flat out. Controls are still on summer settings, a pump that sat idle for five months won't turn, and every heating engineer in the region is taking the same calls.
For a facilities manager, a heating failure at that point affects everything at once: occupant comfort, staff productivity, your legal duties and your budget. Most of those failures can be prevented, and a pre-season check costs far less than a winter breakdown once downtime and emergency rates are counted.
This checklist sets out what a proper pre-winter check should cover, the legal duties behind it, and when to book it so the work is done before demand peaks.
Why does commercial heating fail at the start of winter?
Heating plant deteriorates most while it isn't running. Over a summer of low or no demand:
- Pumps and valves seize. Circulating pumps that haven't turned for months can stick. Motorised and zone valves can jam in one position.
- System pressure drops. Small leaks and expansion vessels that have lost their charge let sealed-system pressure fall without anyone noticing, until the boiler locks out on low pressure.
- Marginal faults stay hidden. Ignition that is barely working, poor combustion or a partially blocked condensate trap may cause no symptoms at low load. At full load they cause lockouts.
- The load changes overnight. Going from idle to full heating demand in a single cold snap is the hardest test the system will face all year.
The last problem is outside your control: demand on contractors. When temperatures drop, reactive call-out times get longer across the whole region, just when you need a quick response. If you already have warning signs, our guide to 7 signs your commercial boiler needs repair covers what to look for.
What should a pre-winter heating check cover?
A pre-winter check is more than a boiler service. Commercial heating can include boilers, pumps, radiators, fan convectors, warm air heaters, radiant systems, controls and BMS. The check should cover the whole system: the plant that produces the heat, the gas supply and flues, the water circuit, the controls, and the equipment that delivers heat to the building. Use the sections below as a checklist with your engineer. Any work on gas appliances, pipework or flues must be carried out by a Gas Safe registered engineer.
Boilers and burners
- Full service, including a combustion analysis. Flue gas readings show whether each boiler is burning safely and efficiently. Poor readings are often the first sign of a fault developing.
- Burner, heat exchanger and ignition. Clean and inspect them, and confirm that ignition and flame supervision work reliably.
- Safety devices. Test the overheat thermostats, pressure switches and lockout functions. These are the parts you never want to find faulty when they're needed.
- Condensate trap and drain. On condensing boilers, check the trap is clean and the drain runs freely. External condensate pipes can freeze in cold weather and shut the boiler down, so check they are protected against frost.
Gas supply, flues and ventilation
- Tightness test on the gas installation. Confirm there are no leaks on the installation pipework serving the plant.
- Flue integrity. Inspect flue runs, joints and terminations for damage, corrosion or obstructions. Bird nests and debris often build up over summer.
- Plant room ventilation. Check that air vents and louvres are clear. Plant rooms are often used for storage over summer, and boxes stacked against a vent can cause combustion problems.
- Carbon monoxide detection. Where CO detection is fitted, confirm it is working and within its service life.
Water side and system pressure
- System pressure and pressurisation units. Check that pressures are correct and that the pressurisation unit is working as it should.
- Expansion vessels. Check the pre-charge. A vessel that has lost its charge causes pressure swings and repeated low-pressure lockouts.
- Pumps. Confirm they run, turn in the right direction and aren't unusually noisy. Test the duty/standby changeover where it's fitted.
- Water treatment. Check inhibitor levels, and take a water sample if one is due. Corrosion and sludge shorten the life of every component in the circuit.
- Leaks and air. Bleed air from the system and inspect valves, joints and pump unions for weeping.
Controls and BMS
- Time schedules. Update them for this winter's occupancy pattern, including holiday shutdowns and any changes to how the building is used.
- Frost protection. Test that it switches on at its set points. It protects the building when the heating is off, which is when nobody is watching.
- Sensors and zone valves. Check sensors read accurately and zone valves open and close when commanded. A faulty sensor can make a building too hot and too cold at the same time.
- Optimum start. Where your controls offer it, set optimum start properly so the building reaches temperature for occupancy without heating empty rooms for hours beforehand.
Heat emitters and distribution
- Radiators, fan convectors, warm air heaters and radiant heaters. Clean, inspect and test them. Fan-driven units collect dust over summer, which reduces output and can create a fire risk.
- System balancing. If some areas were cold last winter while others overheated, rebalance the system now rather than dealing with complaints in December.
Records and documentation
- Gas safety and service records. Keep them up to date and easy to find for inspectors, insurers or auditors.
- Written schemes of examination. Some commercial heating installations, such as steam systems and certain pressure vessels, come under the Pressure Systems Safety Regulations 2000. If yours does, make sure the scheme is current and the examinations are up to date.
- Defect log. Record what was found, what was fixed and what is still outstanding. That record will matter if anything goes wrong later.
What are your legal obligations for workplace heating?
Several sets of regulations apply to commercial heating. Knowing which ones apply to you makes it easier to justify maintenance spending internally.
Gas safety. Under regulation 35 of the Gas Safety (Installation and Use) Regulations 1998, employers must ensure that gas appliances, installation pipework and flues at a place of work they control are maintained in a safe condition. HSE guidance for employers makes clear that this requires regular maintenance by a Gas Safe registered engineer or other competent person, and that appliances known or suspected to be unsafe should not be used.
Workplace temperature. The Workplace (Health, Safety and Welfare) Regulations 1992 require employers to keep indoor workplaces at a reasonable temperature. The HSE's temperature guidance says indoor workplaces should normally be at least 16°C, or 13°C where much of the work involves rigorous physical effort. These are guidance figures that describe what "reasonable" normally means, not an absolute legal limit. Even so, a heating failure that leaves an office at 12°C for a week is exactly the situation they exist to prevent.
Legionella control. Where your heating plant also produces domestic hot water, legionella control is part of the maintenance picture. HSE guidance for hot and cold water systems says hot water should normally be stored at 60°C or above, and distributed so that it reaches at least 50°C at outlets within one minute (55°C in healthcare premises). These controls apply to the hot-water system rather than space heating itself.
How often should commercial boilers be serviced?
For most commercial sites, the baseline is at least one full service a year. That reflects manufacturer servicing requirements, insurer expectations and the ongoing safety duty under the gas regulations. Many manufacturers make warranty cover conditional on annual servicing by a competent engineer, and some insurers ask to see service records after a claim.
Some sites need more than an annual visit:
- Healthcare, care and education settings, where vulnerable occupants depend on the heating.
- Buildings in use around the clock, where the plant runs far more hours than in a typical office.
- Older or heavily loaded plant, where interim checks catch problems before they become breakdowns.
This is the difference between a one-off annual service and a planned maintenance schedule. An annual service checks the plant once. A planned schedule sets the right frequency for each asset, includes the controls and water treatment, and makes sure nothing is missed from one year to the next. Our comparison of planned maintenance and reactive repairs explains the difference in more detail.
Is a PPM contract worth it for your heating?
A planned preventive maintenance (PPM) contract replaces separate call-outs with a fixed schedule. Each item of plant is serviced at the right frequency, the checks in this article are carried out every year as standard, and the results are recorded in one place. For heating, that usually means the pre-winter check is already in the diary. You don't have to remember to book it in August.
A PPM contract tends to make sense when:
- You manage several sites or several boilers. The more plant you have, the harder it is to keep track of service dates, certificates and defects across one-off visits.
- Downtime is costly. In schools, healthcare settings, offices with a lot of people in them and production floors, a heating failure costs far more than the maintenance that would have prevented it.
- Compliance evidence matters. Tender questionnaires, insurers and auditors often expect a documented maintenance regime rather than a collection of individual invoices.
- You keep facing the same problems every autumn. If the pre-winter scramble happens every year, the regime is reactive, however often engineers are on site.
It matters less for a small building with a single boiler, where an annual service booked at the right time may be enough.
If you do look at contracts, compare what's actually included. Check whether the contract covers the controls and water treatment as well as the boilers, what response times are guaranteed for breakdowns, and how defects found during visits are reported and priced. Our guide to what a commercial HVAC maintenance contract should include goes through each of these. For an overview of how planned maintenance works for heating and cooling plant, see our PPM contracts page.
When should you book your pre-winter service?
Ideally in September or early October, before the first sustained cold weather. Booking early gives you:
- Your choice of dates, rather than whatever slot is left once demand rises.
- Time to fix what the check finds. A fault found in September can be repaired with parts ordered at normal lead times. The same fault found in November is an emergency.
- A better planned warm-up. Controls can be set up and the system run under load before occupants rely on it.
Different sectors have their own best timing:
- Schools: October half-term is the natural window for anything intrusive, but the check itself should come earlier so repairs can be scheduled into it.
- Offices and retail: book around occupancy, with early-morning or weekend visits where needed.
- Manufacturing and industrial sites: align the work with planned production downtime, especially for warm air and radiant heating serving the production floor.
What if the check turns up problems?
Deal with safety first. Under the Gas Industry Unsafe Situations Procedure, engineers classify dangerous defects as either Immediately Dangerous or At Risk. Anything given either classification takes priority over efficiency improvements or comfort complaints.
After that, sort the findings into three groups:
- Fix now: anything likely to cause a breakdown or compliance failure this winter.
- Monitor through the season: defects that are safe to run with but need watching.
- Plan for replacement: plant that is nearing the end of its life, where continued repairs no longer make sense.
If your check raises the question of whether a boiler is worth repairing at all, our guide to commercial boiler repair or replacement sets out how to decide.
Look for patterns too. If the same problems come up every autumn, and every pre-winter check turns into a rush, the heating is being maintained reactively. That is a sign the maintenance regime needs reviewing, and a PPM contract is usually the fix, because the checks happen on schedule whether or not anyone remembers to book them.
The pre-winter checklist in summary
Before the heating season starts:
- Service the boilers with a combustion analysis.
- Test the gas installation, flues and plant room ventilation.
- Check system pressure, expansion vessels, pumps and water treatment.
- Update the controls, time schedules and frost protection.
- Clean and balance the heat emitters.
- Bring all records up to date.
Book the work early enough that the repairs it finds can be completed before the cold weather arrives, and keep the paperwork, because it provides evidence of the maintenance and checks carried out. If the checklist feels like a lot to organise every year, that is the case for putting it on a planned maintenance schedule.
This article is general guidance and not legal advice. For your specific obligations, refer to HSE guidance and your own risk assessments.
Frequently asked questions
September or early October, before the first sustained cold spell. Booking then gives you a choice of dates and time to complete any repairs the check identifies before the heating is needed. Leave it until November and any fault that is found becomes urgent, at the point when engineers are busiest.
Not quite. A boiler service focuses on the boiler itself: combustion, burner, heat exchanger and safety devices. A pre-winter check covers the whole system, including gas pipework, flues, plant room ventilation, system pressure, pumps, water treatment, controls and heat emitters. Many heating failures start outside the boiler, so a check that stops at the boiler can miss them.
HSE guidance says indoor workplaces should normally be at least 16°C, or 13°C where much of the work involves rigorous physical effort. These figures describe what a reasonable temperature normally means under the Workplace (Health, Safety and Welfare) Regulations 1992, rather than an absolute legal limit. Even so, a heating failure that leaves staff working below them should be treated as urgent.
Site staff can usefully monitor the things that don't involve opening up equipment: reading the system pressure gauge, keeping plant room vents and louvres clear, noting fault codes or lockouts, checking that radiators and heaters aren't blocked by furniture or stock, and reporting cold spots. Any work on gas appliances, pipework or flues must be carried out by a Gas Safe registered engineer.
The engineer will classify it under the Gas Industry Unsafe Situations Procedure. An appliance classed as Immediately Dangerous will normally be disconnected, with the responsible person's permission. An At Risk appliance will normally be turned off, again with permission. In both cases you should receive a written warning notice, and the appliance should stay out of use until the fault has been put right.
Condensing boilers produce water as part of normal operation, which drains away through a condensate pipe. Where that pipe runs outside or through an unheated space, it can freeze in very cold weather, blocking the drain and causing the boiler to lock out. Checking that condensate pipes are correctly routed and protected is a simple part of a pre-winter check that prevents a common cold-weather breakdown.
