🔧 Burner
The technician removes the burner, cleans the nozzle (spray), checks ignition electrodes, replaces the oil filter (if oil-fired), and adjusts combustion air. For gas boilers, they check gas pressure, flame ionisation and the safety chain.
Annual Boiler Service: The Only Way to Know What Your Home "Breathes"
Every winter, thousands of households in Greece fire up their boiler without knowing whether it produces carbon monoxide (CO) - an odourless, invisible gas that kills. The annual service is not a luxury - it is a legal obligation and a matter of life.
What exactly does the technician do? What does flue gas analysis measure? How much does neglect cost?
1. What a "Complete" Annual Service Includes
A proper service is not "a quick blow on the burner". It is a full medical examination of the boiler - inside and out. The procedure takes 45-90 minutes.
♨️ Heat exchanger
Using a special brush and vacuum, they remove soot deposits (dark layers of ash). Just 1 mm of soot on the exchanger reduces efficiency by 5-8%. After 3 years without cleaning, you lose 15-25% energy.
💧 Condensate trap
Condensing boilers produce acidic water (condensate) that must drain away. The technician checks the siphon is clear - otherwise the boiler shuts down or, worse, the acid eats the internals.
🔒 Gas safety
They check every gas joint with a leak detector or soapy water. A micro-leak may not smell but still poses a risk. They also inspect the flue: is the draught correct? Is there moisture? Do the flue gases exit or return into the house?
2. Flue Gas Analysis: The 4 Numbers That Reveal Everything
After cleaning, the technician connects the flue gas analyser to the chimney. A small instrument that "sniffs" the exhaust gases and delivers 4 critical readings.
🌡️ Flue gas temperature
How hot do the gases exit? Ideal: 80-160 °C (condensing) or 180-220 °C (conventional). If temperature is too high, the exchanger is dirty - heat is escaping up the chimney.
💨 O₂ (Oxygen)
How much oxygen remains in the flue gases? Ideal: 3-5%. Above 8%, the burner is taking too much air (poor adjustment) - wasting energy. Below 2%, air is lacking and CO increases.
☠️ CO (Carbon Monoxide)
The critical value. Ideal: below 50 ppm. Above 100 ppm = danger. Above 200 ppm = the boiler must be shut down immediately. The analyser literally "saves lives".
📊 Efficiency rating
The analyser calculates efficiency: how much energy transfers to the water vs how much is lost. Modern condensing: 93-98%. Old conventional: 80-88%. If efficiency drops below 85%, it is time for a replacement.
3. Carbon Monoxide (CO): The Silent Killer
Every winter, dozens of people in Greece die from CO poisoning. Hundreds more are hospitalised. CO is odourless, invisible, tasteless - you do not notice it until it is too late.
❌ When it is produced
When combustion is incomplete: too little air, dirty burner, blocked flue. Instead of CO₂ (harmless), CO (lethal) is produced. A dirty boiler in a sealed room = a lethal cocktail.
🏠 Early signs
Headache, dizziness, nausea - symptoms resemble "flu". Many people do not connect them to the boiler. If two or more family members feel ill simultaneously every morning, open windows immediately.
🔔 CO detector
A CO detector costs €20-40. Placed in the same room as the boiler, at 1.5 m height. It alarms at 50 ppm. It is the cheapest life insurance you can buy.
💀 Statistics
Across Europe, over 500 deaths/year from residential CO poisoning. In Greece, most cases involve old oil-fired boilers without proper ventilation or in basements without a detector.
4. Service Sheet & Legislation
The annual service is mandatory by law (Law 3661/2008, KENAK, Government Gazette 2202/2012). The law requires a signed service sheet from a licensed burner technician.
📋 What it records
Date, technician details (licence number), boiler type, flue gas readings (CO, O₂, temperature, efficiency), work carried out, owner details. The technician signs and stamps the document.
💰 Fines
If no service sheet is available during an inspection, fines range from €500 to €3,000. In apartment block boiler rooms, the responsibility falls on the building manager. In detached houses, on the owner.
⏰ When to schedule
The ideal time: September-October, before the heating season starts. A "last-minute" service in December means weeks of waiting - technicians are swamped. Book early.
💶 Cost
Annual gas boiler service: €80-120. Oil-fired: €100-150 (+ oil filter). With gasket/electrode replacement: +€20-50. Compared to breakdown costs (€500-2,000), the service is an investment with 10× return.
🔑 Do not wait for the boiler to "break" or, worse, for something to happen to your family. The annual service saves lives, money and energy. Book every September - and always request a service sheet.
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