There is nothing nicer than waking up or coming home to a nice warm house when the weather outside is cold and crisp. However, if you have been running your heating and discovered that your radiator stays cold, you may well find yourself needing help. As well as leaving you shivering in winter weather, radiators that fail to heat up can also indicate more significant problems such as debris in the system causing blockages or poor system set up. 

If you have found yourself asking why your radiator is cold, here is what to do:

Check that your boiler is working

Check your boiler is in order

The first thing to do if your radiator stays cold when you are expecting it to be warm is to check your heating system to make sure that it is on the right setting and working properly. If you have a combi-boiler, check that it is set for both hot water and heating, is not in summer mode and that there is no fault code displaying. 

Whilst the first two can be adjusted with a simple adjustment, a fault code may be a little more complicated to deal with.

If you have a Viessmann boiler, check our Fault Code Page to find out more about the fault code that is being displayed. Alternatively, consult your boiler’s user manual for more information.

Whilst some fault codes can be rectified by the user, others may require the help of a Gas Safe certified professional. Always follow the user instructions and do not attempt to do anything yourself if you are unsure.

Check your heat pump is working

If your heating system has a heat pump, the next step in identifying why your radiator is cold is to ensure that this is working. If the pump has stopped working, it will no longer be heating the water required to keep radiators warm and will result in all of the radiators losing their temperature.

The simplest way to check if your heat pump is working is to check if it is making any noise. One easy way to do this is to take a screwdriver and place it between your ear and the housing. If the heat pump is running, you should be able to detect noise or vibrations.

Check the system

Check for air in the system

If you find that one or more radiators in your home are cold, this may be also a sign that there is air in the system. Air in the heating system tends to gather at higher points and prevents the correct distribution of heating water. Luckily, this particular problem is usually quite simple and straightforward to resolve with the following steps:

  1. Fully open all radiator thermostats and run the heating at full temperature for 10-15 minutes with all radiators on
  2. Turn the circulation pump off and wait until radiators are cool - usually 30-60 minutes
  3. Bleed the radiator nearest the boiler using a bleed key or screwdriver until water comes out
  4. Repeat this for each radiator
  5. Turn on the boiler and check the water pressure

If you are unsure about bleeding the system or encounter difficulties at any point, it is advisable to contact a professional at the earliest instance.

Check if valves are stuck

Another common cause for a cold radiator is a stuck valve. This is often the case if the problem is with an individual radiator. The thermostatic valve, usually a white control directly beside the base of the radiator, controls the flow of hot water to the radiator, but from time to time can become seized - often simply due to age.

To check if this is the case, remove the rotatable head to reveal a raised pin beneath it. It should be possible to depress the pin with your finger. It should then rise up again when you release the pressure. If the pin is already depressed or does not move freely, it may have become stuck. 

Try to free up the pin using some pliers and grease until it is able to move in and out with ease. Do not apply excessive pressure as this may damage the pin.

If you are not sure about doing this or are not able to get the pin moving, then it is advised that you seek help from a professional.

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Check the water pressure

If your boiler and/or heat pump appear to be working correctly, the next thing to check is your water pressure. This is shown on a small display known as a ‘Manometer’, usually located directly where the water supply is connected to your boiler. For a residential gas boiler, the correct water pressure is usually around 1.0 bar, often indicated on the gauge by coloured markings. If the pressure is lower than this, we recommend following the steps in our article about boiler losing pressure to solve the problem.

Balance your system

Your cold radiators can also be caused if there is a problem with the balance in your system. Hot water will tend to rise upwards in a system, so one clue that this may be the cause of your problem is if you find that upstairs radiators are working well whilst those downstairs remain cool.

If this is the case, go to the radiators upstairs and close the lockshield - the smaller valve at the opposite end to the thermostat then open the lockshields a quarter turn. This should not cause any reduction in the effectiveness of the upstairs radiators, but will encourage more heat to flow to those downstairs.

Balancing your system is recommended as it helps to ensure that your heating is as efficient and economical as possible and can help you to use less energy and spend less money in the long term.

It may be advisable to invest in having your system hydraulically balanced by a specialist for best effects.

Get peace of mind with regular maintenance

The best way to avoid problems with your radiators staying cold is to have your heating system regularly maintained by a qualified professional to help ensure it is always in the best possible working order.

As well as helping to prevent problems and ensure your safety, this can also help to keep the system running as efficiently as possible, helping you to keep your home warm and comfortable whilst saving money on your fuel bill.

Get a free consultation on a new heating system.

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