Cv-boiler malfunction? How to fix it yourself

A properly working cv-boiler is essential for a comfortable and warm home, especially during cold periods. Malfunctions can be unexpected and annoying. This blog helps you step by step to recognize the most common malfunctions, provides useful tips, and includes a checklist to solve simple problems yourself.

What symptoms are most common in a cv-boiler malfunction?

There are various symptoms that occur more frequently than others. We have listed the most common cv-boiler malfunctions for you. You will also read when it is wise to call a technician.

1. Your radiator or underfloor heating does not get warm
   
   • Defective pump: if the pump does not work, the heating water does not circulate through the system. Have one of our technicians check if the pump is defective and replace it if necessary.
   • Air in the system: air bubbles can hinder water circulation. Bleed the system thoroughly to solve this problem.
   • Too low supply temperature: if the temperature of the supplied water is too low, the radiators or underfloor heating will not get warm enough. In this case, have a technician adjust the system supply temperature to the recommended level.
     
     
2. The water pressure drops constantly
   When the water pressure keeps dropping, it often indicates a leak in the system. In many cases, the cause is the expansion vessel. Have one of our technicians check and replace it if necessary.
   
   
3. One or more radiators make gurgling sounds
   • Air in the radiator: bleed the system regularly to remove trapped air from the pipes.
   • Radiator not aligned correctly: make sure the radiator is slightly tilted, with the bleeder valve slightly higher. This helps air to collect and escape through the bleeder.
     
     
4. Not all radiators get warm
   If some radiators work well while others remain cold, it is usually because the system is not properly balanced. Often, the hydraulic balancing is missing, preventing hot water from reaching all radiators. Have the system balanced so that all radiators distribute heat evenly.
   
   
5. Boiler fails due to flame fault
   A flame fault means the boiler cannot maintain or ignite a flame. Possible causes include:
   • Incorrect gas supply: check both static and dynamic gas pressure. Wrong gas pressure can hinder the boiler’s operation.
   • No grounding: the earth wire is attached to the metal housing of the boiler. It ensures that if something goes wrong, electricity safely flows to the ground. Without proper grounding, the boiler may malfunction or become unsafe.
     
     
6. Room thermostat has no contact with the boiler
   If the thermostat cannot connect to the cv-boiler, it is usually due to power supply or communication issues.
   • Thermostat power: check if the display works. If not, replace the batteries.
   • Communication protocol not matched: ensure both the thermostat and the boiler use the same protocol (e.g., on/off). If they do not match, no connection is possible.

Do you have a cv-boiler malfunction that won’t go away? Our technicians at HR Installatietechniek will resolve it safely and quickly.

Checklist for cv-boiler malfunction

If the cv-system is not functioning properly or there is no hot water, you can perform some basic checks yourself with the checklist below. By following these steps, you can often identify or even fix the problem.

1. Check if hot water comes out of taps in the house, such as the kitchen, bathroom, or outdoor faucet.
2. Ensure the boiler plug is firmly in the socket.
3. Check that the boiler is switched on correctly.
4. Verify that all fuses are intact and in the correct (up) position.
5. Ensure the residual current device (RCD) is on (up).
6. Check that the gas valve is fully open.
7. Set the thermostat to a temperature higher than the current room temperature.
8. Make sure at least one or two radiator valves are fully open (position 3 or higher).
9. Check that the water pressure in the boiler system is between 1.5 and 2 bar.
10. Make sure the boiler system is fully bled and contains no air.

Cv-boiler malfunction: fix it yourself

A malfunction in your boiler is annoying, but some problems are easily solved yourself. Below, we explain the steps you can take before calling a technician.

Refill your cv-boiler

Check the water pressure (1.5–2 bar). If it is below 1.5 bar, refill the boiler. Note that a leak in the expansion vessel may cause recurring pressure issues. Always start with a cooled system. Connect the filling hose to the tap and the boiler filling point. Open slowly until the pressure is above 1.5 bar. Close the tap and disconnect the hose.

Bleed Your Central Heating

Set the thermostat low and switch off the boiler. Start with the lowest radiator. Use a radiator key to release trapped air.
Wait until water flows, then close the valve. Check the water pressure and top up if necessary.

Reset your cv-boiler

Locate the reset button (refer to the manual if needed). Press the button for a few seconds and wait for the boiler to restart. Check if the fault is resolved. If not, contact HR Installatietechniek.

Turn off cv-boiler during malfunction

In the event of a malfunction, it may be necessary to turn off your boiler. This can help prevent further damage. It’s wise to follow the steps carefully and do it safely.

1. Use the on/off button: this is usually the safest way.
2. Unplug from the socket if the first step doesn’t work, and wait 30 seconds.
3. Close the gas valve in case of a gas leak or serious malfunction.
4. Call a technician immediately if you smell smoke, gas, or fire.

Cv-boiler makes noise

A boiler should operate silently. If your boiler makes noise, there can be various causes. Below are common sounds, what they mean, and what you can do. Recognizing these signals prevents bigger problems and unnecessary damage. When in doubt, always contact us.

Gurgling sound: often caused by air in the system; usually fixable by bleeding radiators.

Ticking sound: caused by expansion and contraction of metal pipes; usually harmless.

Rattling or humming: often due to vibrations from loose parts or poorly mounted boiler; may indicate wear.

Grinding sound: indicates worn or damaged moving parts such as pump, bearings, or fan; contact a technician promptly.

Frequently Asked Questions (FAQ)

Conclusion

Always check the basics first: power supply, gas valve, water pressure, and thermostat settings. Many problems can be solved by refilling, bleeding, or resetting the boiler. Regular maintenance and timely replacement of wear-prone parts ensure reliable operation.

If you want immediate assurance or to schedule a visit, contact HR Installatietechniek – we are happy to help.