As a heating system expert with years of experience in diagnosing and resolving issues related to home heating, I'd like to provide you with a comprehensive answer to your concern about having hot water but no heating.

Firstly, it's important to understand that central heating and hot water systems are interconnected but operate independently of each other. The central heating system is designed to distribute heat throughout your home, while the hot water system provides heated water for your taps and showers. If you have hot water but no heating, it suggests that there is a specific issue affecting the central heating circuit, while the hot water circuit remains unaffected.

Here are several reasons why this might be happening:


1. Faulty Thermostat: The thermostat controls the operation of your heating system. If it's not working properly, it might not be triggering the heating system to come on, even though it's allowing the hot water system to function.


2. Pilot Light Issue: Some boilers use a pilot light to ignite the gas for heating. If the pilot light is out or there's an issue with the ignition system, the heating might not work, but the hot water could still be supplied by an electric element.


3. Boiler Diverter Valve Problem: As you've mentioned, the boiler's motorised diverter valve plays a crucial role in switching the flow of water between the heating system and the hot water system. If this valve is broken or stuck, it could prevent the heating system from functioning correctly.


4. Circuit Breaker or Fuse: A tripped circuit breaker or a blown fuse related to the heating system could cut off power to the heating circuit, leaving the hot water system unaffected.


5. Air in the System: Air trapped in the heating system can prevent the circulation of hot water. This can be resolved by bleeding the radiators to release the trapped air.


6. Programming or Timer Issue: If your heating system is programmed to come on at specific times, it's possible that the timer is not set correctly, or the programming has been altered.

7.
Zone Valve Malfunction: In systems with zone valves, if one of these valves is not opening, it can prevent heat from being distributed to certain areas of the home.

8.
Heat Exchanger Issues: If the heat exchanger in your boiler is damaged, it can affect the heating system's ability to produce and distribute heat.

9.
Pressure Problems: Low pressure in the heating system can also prevent the circulation of hot water. This can be checked and adjusted using the boiler's pressure gauge.

10.
Gas Supply: Ensure that there is a continuous supply of gas to your boiler. A gas supply issue could affect the heating but not the hot water system, especially if the hot water is heated by an electric element.

To resolve the issue, you should:

- Check the thermostat and ensure it's set to the correct temperature and is functioning properly.
- Inspect the pilot light or ignition system if your boiler uses one.
- Examine the diverter valve for any signs of damage or malfunction.
- Check the circuit breakers and fuses related to the heating system.
- Bleed the radiators to remove any trapped air.
- Review the programming and timer settings for your heating system.
- Check the operation of zone valves if your system has them.
- Inspect the heat exchanger for any visible damage.
- Verify the pressure in the system and adjust if necessary.
- Confirm that there is a steady supply of gas to the boiler.

If you are not comfortable performing these checks yourself, it's advisable to contact a qualified heating engineer who can diagnose and fix the problem for you.

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If your boiler seems to be working and your hot water supply is still functioning, but your central heating is not working, then the problem is either down to the settings on your boiler and central heating system or because a component of the boiler -C almost certainly the motorised diverter valve -C is broken.read more >>