Most Common Faults of Low-Temperature Boilers and How to Fix Them
Common Issues with Atmospheric Boilers and Practical Solutions
Atmospheric gas boilers, when well-maintained, can provide reliable heating for 15 to 20 years. However, as they age, problems tend to recur. These include issues like failure to ignite, pressure drops, strange noises, or weak hot water output. This guide outlines the most frequent problems, their likely causes, and what you can address yourself—before deciding whether to call a service professional. The aim is to help you identify the issue quickly and avoid unnecessary service calls.
1. The Boiler Fails to Ignite
Imagine trying to start your boiler in the middle of winter, only for it to remain silent. Before assuming the worst, verify the simplest factors first. Ensure the main gas shut-off valve is open and that the boiler’s gas supply tap is not closed. A quick test—using gas on another appliance like a stove—can confirm there’s no supply outage.
If the gas is fine but the boiler still won’t ignite, the issue might lie in the ignition or ionization electrode. A dirty or misaligned ignition electrode can prevent the spark that starts the flame. Similarly, a dirty ionization electrode may fail to confirm the presence of the flame, causing the boiler to shut down for safety. Another common cause is inadequate chimney draft, which some boilers detect via a pressure switch before allowing ignition.
Modern boilers often display error codes that can help narrow down the issue. But repairs to the electrodes or gas components should be handled by a qualified gas technician to ensure safety and compliance with regulations.
2. Pressure Drops in the System
After bleeding a radiator or letting the system run for a while, you notice the pressure gauge falling below the recommended range. This is a common occurrence and often nothing to worry about. Simply use the filling valve to restore pressure to between 1 and 2 bar, as indicated in the boiler’s manual.
However, if the pressure drops consistently and you have to top up frequently, this usually means there’s a leak in the system. The source could be a faulty expansion tank, a leaking radiator, or a worn joint. The expansion tank’s internal membrane can degrade over time, mimicking a leak by failing to manage pressure fluctuations.
While minor pressure drops are easy to fix, repeated issues should be left to a service technician. They can accurately locate and repair leaks and assess the condition of the expansion tank and other system components.
3. Bubbling and Unusual Noises
If your boiler starts making bubbling or gurgling noises, it could point to trapped air in the system. This is a common occurrence after refilling or following a long period of inactivity. The fix is straightforward: bleed the radiators using a bleed key, starting with the lowest ones and working upward. Keep an eye on the pressure gauge and add water as needed to maintain the correct level.
On the other hand, if the noise originates from the boiler itself—especially a deep, rumbling sound—it may indicate a buildup of limescale or sludge inside the heat exchanger. This restricts water flow, causing localized overheating and the characteristic boiling sound. Unlike air in the system, this issue requires professional cleaning, either chemical or mechanical, which should be performed by a qualified technician.
4. The Boiler Shuts Down During Operation
Consider this scenario: your boiler ignites normally, but after a few minutes, it suddenly shuts down and enters a fault mode. This could be due to a faulty or dirty temperature sensor, which prevents the boiler from accurately measuring the water temperature. Another common cause is a clogged heat exchanger, which restricts water flow and causes overheating, prompting the boiler to shut off as a safety measure.
Flue gas discharge issues can also lead to shutdowns, particularly if the boiler relies on a pressure switch to monitor flue gas flow. Changes in chimney conditions or duct blockages can disrupt this process. In most cases, the error code on the display will give you a clue. Refer to the boiler’s manual to decode the code before contacting a service technician. This helps speed up diagnosis and repair.
5. Weak Chimney Draft and Flue Gas Issues
Atmospheric boilers depend entirely on natural chimney draft for flue gas removal. This means any obstruction—like soot buildup, a chimney of incorrect size or height, or nearby structures—can compromise draft. The result may be slow or incomplete gas discharge, or worse, a backflow of flue gases into the boiler room.
Signs to watch for include a noticeable gas odor, soot or condensation near the chimney, frequent boiler shutdowns, or symptoms like headaches or dizziness among occupants. These could indicate carbon monoxide leakage. In such cases, do not attempt a DIY fix. Turn off the boiler, ventilate the area, and call a professional immediately. Atmospheric boilers pose a higher risk in these situations compared to turbo or condensing models, making prompt action essential.
6. Poor Hot Water Performance
If your boiler is heating well but the hot water from your tap is weak or lukewarm, the likely culprit is a clogged heat exchanger. This is especially common in areas with hard water, where limescale builds up over time and restricts heat transfer. The boiler may run normally, but the heat doesn’t reach the water efficiently.
Prevention is better than cure. Installing a water filter at the system inlet can reduce limescale buildup and extend the life of the heat exchanger. Once the exchanger is already clogged, though, it requires professional cleaning—either chemical or mechanical—by a qualified service technician. A filter, however, can be installed during a routine service check as a preventive measure.
When to Seek Professional Help
Certain issues are best left to the experts. If you suspect a problem with the burner, ignition or ionization electrode, gas valve, or heat exchanger, or if you notice a gas leak or flue gas leakage, it’s crucial to call a certified service technician immediately. These are not DIY tasks and involve serious safety risks.
If you detect the smell of gas, experience dizziness or headaches, or see soot around the boiler, turn off the unit, shut the gas supply, ventilate the area, and contact emergency services. Annual service and chimney inspections are also essential for preventing many of these issues and ensuring safe, efficient operation.
|
Pressure Expansion Tank IVAR.ER 12 (12 l) - if pressure in the system keeps dropping despite topping up and service rules out a visible leak, a worn membrane in the original expansion tank is often the hidden culprit. Replacing it with a new tank is a cheap and quick fix that can definitively solve the problem. Price from €47.73. |
|
NANO HOT 3/4" - 1" 500 mcr Water Filter - a brass filter installed at the water inlet to the boiler catches mechanical impurities and reduces the risk of the exchanger becoming clogged with deposits, especially in areas with harder water. Simple prevention instead of costly exchanger cleaning. Price from €65.50. |
Situations where you should not wait.
The first half of the six faults covered in this article.
The second half of the six faults covered in this article.
Distinguishing routine maintenance from professional intervention.
Choosing the Right Approach for Common Boiler Issues
When your boiler shows signs of trouble, knowing what to look for and when to call in a professional is crucial. Here are some key criteria to guide your actions:
- Monitor error codes: If your boiler frequently enters fault mode, check the display for error codes. These codes are specific to your boiler model and will help a service technician identify the issue quickly.
- Listen for bubbling sounds: This often indicates air in the system. Try bleeding the radiators starting from the lowest one. If it continues, the problem may be limescale or deposits in the heat exchanger — a job for a technician.
- Assess chimney draft: Poor draft is especially dangerous for atmospheric boilers. If you notice any unusual odors or hear rumbling, it’s best to shut the boiler off, ventilate the room, and contact a professional to inspect the chimney.
- Track water pressure changes: A need to top up the system frequently may point to a leak or a worn expansion tank membrane. Keep an eye on pressure fluctuations and don’t ignore recurring drops.
- Be cautious with gas components: Parts like the ignition or ionization electrode are part of the gas system. Attempting to replace them yourself is unsafe and may void your warranty. Always let a certified technician handle these tasks.
- Check water hardness in your area: Hard water increases the risk of limescale buildup in the heat exchanger. A water filter at the boiler’s inlet can help prevent this. If you already have buildup, professional cleaning is necessary.
Practical advice: Don’t try to diagnose or fix everything on your own. Regular maintenance by a qualified technician is the best way to ensure your boiler runs safely and efficiently. Keep your manual handy and act quickly when you notice changes in performance or unusual symptoms.
Explore Further on Low-Temperature Boiler Care and Installation
If you're seeking guidance on boiler maintenance, replacement timelines, or installation specifics, you’ll find helpful articles here. These resources cover essential aspects like spare parts, service routines, flue requirements, and common questions about gas boilers.
Guides for Homeowners and Installers
From understanding the lifespan of your boiler to choosing the correct flue system, these articles provide clear, actionable information. You’ll also find answers to frequently asked questions about low-temperature gas boilers, making it easier to maintain or upgrade your system efficiently.