A boiler that refuses to turn off can be both frustrating and costly, especially during the colder months. This issue typically arises from a fault in the system, which might range from a simple thermostat problem to a more complex issue with internal components.
Below is our in-depth guide on potential causes and solutions.
Common Causes
1. Faulty Thermostat
The thermostat controls when the boiler heats water or activates the central heating. If it’s malfunctioning, it may fail to send the “off” signal to the boiler. Common thermostat issues include:- Batteries are running low
- Incorrect settings
- Old or broken thermostat devices
2. Malfunctioning Timer or Programmer
If the timer or programmer that controls heating schedules is faulty, the boiler may stay on indefinitely. Older mechanical timers are especially prone to failure.3. Diverter Valve Stuck Open
In combi boilers, the diverter valve directs hot water to either the taps or radiators. If stuck, it can cause the boiler to operate continuously.4. Wiring or Electrical Faults
Loose or damaged wires can interfere with the proper communication between the thermostat and the boiler, causing it to ignore commands to shut down.5. Pump or Motorized Valve Issues
A pump that fails to shut off or a stuck motorized valve may keep hot water circulating, tricking the boiler into staying on. Our Solutions For These Problems
1. Check the Thermostat
- Reset the thermostat: if it’s digital, try resetting it to factory settings
- Replace batteries: many modern thermostats run on batteries, and low power can lead to malfunctions
- Ensure the thermostat is not set to a temperature higher than the current room temperature
2. Inspect the Timer/Programmer
- Verify the set heating schedule. Some timers can default to “always on” if they’re reset or lose power
- Replace faulty timers if necessary, especially if it’s an older mechanical model
3. Test the Diverter Valve
- A diverter valve issue typically requires a professional engineer. If you notice hot water flowing to radiators even when the heating is off, this might be the culprit
4. Cut the Power
- If you’re unable to determine the problem, switch the boiler off using the isolation switch. This is a temporary solution until a professional assesses the system
Is it Time To Call in a Professional to Fix Your Boiler?
If troubleshooting doesn’t resolve the problem, it’s time to call a Gas Safe registered engineer. Persistent issues may stem from complex faults, such as:- Internal electrical components failing
- Wiring issues that need professional handling
- A complete breakdown of critical parts like the pump or diverter valve
Prevention Can Be Better Than a Fix
Regular Maintenance
- Annual servicing can prevent many boiler issues by identifying and fixing problems early
Upgrade Old Equipment
- Outdated thermostats, programmers, and even boilers may struggle to function efficiently. Modern smart thermostats and new boilers are more reliable and energy-efficient
Monitor Usage
- Pay attention to any unusual behaviours, such as heating running outside programmed times, and address them promptly
