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When a boiler is not heating radiators but is heating water, it can be a cause for concern. Boilers are complex machines, and it can be difficult to diagnose the exact cause of the problem. However, there are a few common culprits that are worth checking before calling out a professional. In this article, we'll discuss how to identify and fix the problem when a boiler is not heating radiators but is heating water.

The first step is to check the pressure of the boiler. If the pressure is too low, then it could be the cause of the problem. The pressure of the boiler should be between 1.0 and 1.5 bar. If it is lower than this, then it could be that the pressure relief valve is faulty, or the pressure is too low due to a leak in the system. If the pressure is too high, then it could be that the filling loop is faulty, or the system is overfilled. In either case, the pressure should be adjusted to the correct level.

The next step is to check the thermostat. If the thermostat is not set to the correct temperature, then the boiler won't be able to heat the radiators. The thermostat should be set to the desired temperature and the boiler should be reset. If the thermostat is set to the correct temperature and the boiler is still not heating the radiators, then it could be that the thermostat is faulty and needs to be replaced.

The third step is to check the air vents. If the air vents are blocked or not working correctly, then the boiler won't be able to heat the radiators. The air vents should be checked to make sure they are open and not blocked. If the air vents are blocked, then they should be cleared to allow the boiler to heat the radiators.

The fourth step is to check the radiators. If the radiators are not heating up, then it could be that the valves are not working correctly. The valves should be checked to make sure they are open, and if they are closed, then they should be opened. If the radiators are still not heating up, then it could be that the radiators are blocked or the pipes are not connected correctly.

The fifth step is to check the pump. If the pump is not working correctly, then the boiler won't be able to circulate the hot water around the system. The pump should be checked to make sure it is working correctly, and if it is not, then it should be replaced. If the pump is working correctly, then it could be that the system needs to be bled to remove any air that is trapped in the system.

The sixth step is to check the system for leaks. If there are any leaks in the system, then the boiler won't be able to heat the radiators. The system should be checked for any leaks, and if there are any, then they should be repaired. If there are no leaks, then it could be that the system needs to be descaled to remove any scale that has built up over time.

The seventh step is to check the system for blockages. If there are any blockages in the system, then the boiler won't be able to heat the radiators. The system should be checked for any blockages, and if there are any, then they should be cleared. If there are no blockages, then it could be that the system needs to be flushed to remove any debris that has built up over time.

The eighth step is to check the system for corrosion. If there is any corrosion in the system, then the boiler won't be able to heat the radiators. The system should be checked for any corrosion, and if there is any, then it should be treated. If there is no corrosion, then it could be that the system needs to be serviced to ensure that it is working correctly.

These are just a few of the things that can be done to diagnose the problem when a boiler is not heating radiators but is heating water. If none of these solutions work, then it could be time to call out a professional. A qualified engineer will be able to identify the exact cause of the problem and advise on the best course of action.