Skip to content 
If the boiler works well for hot water but fails to heat your radiator, it can be disappointing, especially in cold months. The problem can occur due to various causes, including the airlock, a deficient diverse valve, low boiler pressure, or mud structure in the heating system.
In this guide, we will run through possible causes and solutions to act as your heating system again. Whether you own a Warster residence boiler or any other brand, these steps will help you troubleshoot and solve the problem.
Why Is My Boiler Not Heating the Radiators but Heating Water?
If your combi boiler provides warm water but does not heat the radiator, one or more of the following problems may be:
1. Faulty Diverter Valve
The diverter valve is responsible for directing either losses or radiators to direct hot water. If stuck, hot water can only flow in the tap and rain, while the radiator remains cold.
2. Airlocks or Trapped Air in the System
The air trapped inside your radiators can prevent the hot water from circulating properly. This can keep some or all the rays cold while the boiler continues to function normally for the hot water supply.
3. Low Boiler Pressure
In order to work efficiently to the heating system, the pressure on the boiler must be at an optimal level. If the pressure falls too little, the radiator may not get enough hot water.
4. Sludge or Debris in the Pipes and Radiators
Over time, mud and debris can be produced in the central heating system, which can block the flow of hot water to your radiators. This problem is more common in chronic systems.
5. Thermostat Issues
If your thermostat is faulty or inaccurate, it may not signal the boiler to heat your home. As a result, the radiators won’t get warm.
Troubleshooting: How to Fix a Boiler That Is Not Heating Radiators
When you understand the possible causes, some step-by-step solutions go through solutions to solve the problem.
1. Check Your Boiler Pressure
A decrease in pressure can prevent your heating system from working efficiently. How to check and fix it:
- Find the pressure gauge on the boiler.
- The ideal pressure should be between 1 and 1.5 times when the system is cooled.
- If the pressure is low, follow the manufacturer’s instructions to suppress the system using the filling loop.
- If the pressure falls, you may have a leak in the system that requires professional attention.
2. Bleed Your Radiators to Remove Trapped Air
If the air is stuck in your radiator, the warm water does not circulate properly. Bleeding radiators can help:
- Turn off the heating system and allow it to cool.
- Use a radiator key to open the bleeding valve on top of the radiator.
- Listen to a hatred sound, which means the wind is survival.
- When the water starts to go out continuously, close the valve.
- Repeat the process for all radiators.
- Check the pressure on the boiler again after bleeding, as it may require topping.
3. Check and Fix the Diverter Valve
A fixed diverter valve is one of the most common causes of hot water, but no heating. You can check if it works properly:
- Turn on the heating and check if the kettle fires.
- If you hear that the kettle begins, but the beams remain cold, the diverse valve can be deficient.
- Some different valves can be released manually, but in most cases a professional plumber will have to change or repair the valve.
4. Flush the System to Remove Sludge and Debris
If some radiate are hot, while others remain cold, or if the system golds or makes noise, mud build-up can be a problem. A power flushing system can help clean:
- Close the pan and dry the system.
- Use a cleaning chemical designed for the heating system.
- Refill the system and transfer the cleaning agent for a few hours.
- Empty with fresh water and fill again.
- If the problem persists, consider hiring a professional for power flushing.
5. Check the Thermostat Settings
Make sure your thermostat is set to the correct temperature. If it is very low, the heating cannot be on. If your thermostat is old, it may be time to replace it with a new software or smart thermostat.
6. Inspect the Zone Valves
Some heating systems contain zone valves that control the flow of hot water in different areas. If a valve gets stuck or breaks, some radiators cannot get heat.
- Find the zone valve near the boiler.
- Check if it happens when the heating starts.
- If the valve is fixed, a professional may need to replace it.
Check Eligibilty For ECO4 Scheme
Get Free Heating System Installed Today at your Property Under ECO4!
When to Call a Professional
If you have tried the steps above and your kettle still does not heat the radiators, it is time to call an expert. Look for professional help if:
- The diverter valve is stuck or broken.
- The boiler has frequent pressure drops.
- Radiators remain cold after bleeding.
- There is strange noise from the kettle or pipe.
- A certified heating engineer can safely and effectively diagnose and repair the problem.
Conclusion
If the boiler heats the water, but not a radiator, do not panic. Begin by checking the pressure, bleeding the radiators and inspecting the latter valve.
In many cases, easy troubleshooting can restore your heating system. If the problem remains, a professional heating engineer can help diagnose and repair the problem.
By taking the right steps, you can ensure a warm and comfortable home for cold months.
FAQs
A faulty diverter valve is a common issue in Worcester Bosch boilers. It may be stuck in hot water mode, preventing heat from reaching the radiators. Other causes include low boiler pressure, trapped air, or sludge buildup.
Check the thermostat, discard bleed to the radiators, and make sure the pressure on the boiler is at the correct level. If the problem persists, inspect the liner valve and consider the system as flush.
Most boilers have a reset button. Press it for 10 seconds to restart the system. If the problem continues, check the error code or contact the user manual.
Your heating system may contain air, a broken diverse valve or mud build -up. Try to check the beams for bleeding and obstacles.
The cost depends on this problem. Bleeding radiators are free, while fixation of a dive valve can cost between £150 – £300. The price of a professional power flush can be between £300 – £600.
