Radiators hot when heating off combi boiler

Inadequate heat or haters that do not work properly are often blamed for any kind of heating problems. But have you ever wondered what would happen if you are not able to turn the heating off. We have at times come across people who complain about radiators being hot while the heating is off in combi boilers.

Combi Boilers

The combi boilers are systems, designed to operate by using water directly from the mains and serve you with heat on demand. As the name says ‘Combi’, these boilers combine the functions of a conventional boiler, hot water cylinder and a cold water storage tank. The Combi boilers have come being really popular systems that are compact in size and are easy to install.

The combi boilers operates by using the water from the main supply that results in stronger water pressure and ensures that you would never be lacking on hot water again. The modern highly efficient units come, being a stainless steel condensing boiler with an inbuilt heat exchanger that operates in order to serve the customers with hot water immediately.

There are two main reasons behind the combi boilers great and powerful efficiency i.e. these units have high operating efficiency and low internal water volume. This means when in summer days you don’t need space heating you are only paying to heat water which is domestically required.

Radiators hot when heating off combi boiler

Radiators commonly have two basic reasons of being heated while the central heating is off. Let’s have a look.

1. Malfunctioning check value- The older types of heating systems operate to keep the water hot all the time. Hot water from the boiler rises and flows by natural convection up to the radiators. As soon as the heating is turned on, the water from the boiler is pumped up to the radiators. A check valve is built in the system in order to keep the natural convection from allowing hot water to circulate to the radiators when the pump is off. A weight is made to keep the check valve closed and stop the natural convection from occurring. If in case the check valve fails because of a broken spring or some scrap, the radiators would be hot from the natural convection, even if the heat is off.
2. Diverter problems- These problems arise in case of the modern heating systems. Most of the modern heating systems have temperature sensitive switches in the form of thermostats that operate to turn the boiler on when heat is required in any form. Either the room thermostat or the water cylinder thermostat calls for heat when the boiler turns on. The diverter valve then directs the hot water to the radiator or the water cylinder as needed. And if in case both the thermostats call for heat at the same time, the diverter holds itself into a mid-position that allows the hot water to flow to both the water tanks and the radiators.

If in case the diverter fails or gets blocked anyhow, the hot water intended for the hot water circuit would move to the radiator circuit and this would probably happen to keep the radiators hot even when the heating is off.

Note- In both the cases, we would recommend you to fall for a professional help in order to solve the issue with causing any harm.