Does Your Boiler Work But The Radiators Stay Cold? Here’s The Fix

If you have a functioning boiler, and the heating is on but there is still no central heating, your radiator may be the problem.

Your radiators might remain cold due to a few reasons. Often, you might not need to immediately call a professional or an engineer to check things up. Sometimes, a quick DIY fix should set you right back on track and have your radiators heating up again.

Here’s what you need to keep in mind and check before you move ahead towards fixing your radiators.

Reasons Your Radiator Is Staying Cold

There are several things you need to check in your boiler to help you determine the cause of the problem. The radiators could simply be filled with sludge or air pockets that might prevent it from getting hot. Or the damage could be of a more permanent nature.

The only way to find out would be to thoroughly check the important parts and see where the faults lie in the system.

Here’s a list of things that you need to check upon.

Check For Faults In Thermostat Or Timer

Your thermostat or timer may need to be replaced. Carefully check them to determine if they are damaged. If there is extensive and irreparable damage, you might need to call a Gas-Safe registered engineer to replace them.

Often faulty thermostats can point towards an air lock in the system.

Check For Air Pockets In The System

Air pockets in your radiator and heating system could prevent your heating from working. The radiators can go cold when air pockets are trapped in the system.

The water flow can be affected because of the trapped air, and that is why even when your heating is on, radiators remain cold to the touch. Often the top of the radiators will remain cold, which indicates air pocket blockages.

Check For Debris And Blockages In The System

Sometimes debris, sludge, and grime can cause a build-up of blockages that prevent the radiators from heating up properly. You can fix this simply by removing the debris and blockages.

The debris and sludge prevent proper circulation throughout your system, hence resulting in faulty central heating. In the case of sludge and grime build-up, the middle part of the radiator stays cold.

Both pressurized and open vent systems require different removal methods.

Check For Faults In Pumps

If there are blockages or damages to the pump, it could cause your radiators to stay cold even when your boilers are working. Often bleeding, the circulating pump is the solution. This would remove anything that could be preventing proper circulation in your pumps.

It is important to check if the heating pumps are making any strange noises or working properly. Depending on the severity of the issue, you may need to replace and change the pumps. Otherwise, sometimes other ways of fixing and bleeding them out work as well.

Ways To Fix Cold Radiator

There are several ways to fix your radiators. The fixes, however, depend upon the nature of the problem. There can be quite a few reasons for boilers to be heating while radiators remain cold. Some of the ways to fix the problems are as follows.

  • Checking and replacing the thermostat or timer
  • Bleeding out the air pockets
  • Removing blockages and debris
  • Bleeding out the pumps

Checking and replacing the thermostat or timer – Check the thermostat by turning on the boiler with the minimum setting on the timer. Make sure the boiler doesn’t fire up now. Then raise the temperature setting to maximum and see if it fires up. After that, turn it down again, and if the boiler doesn’t stop firing up, then the thermostat timer needs replacement. You can easily do this by calling a registered gas engineer.

Bleeding out the air pockets – The air pockets in the circulating system can prevent radiators from firing up. Clean the air pockets by bleeding out the radiators one at a time using a radiator key. Keep the radiator off when bleeding it and open the bleed valve to let any air or water escape.

Removing blockages and debris – The sludge and debris can easily be removed by cleaning out the radiators using power flushing. The accumulated grime could be preventing proper circulation. If you have accumulated contaminants, then the middle of your radiator will be cold. Check for that before cleaning the radiator.

Bleeding out the pumps – After locating the central heating pump, bleed it out using the head screw on the main pump or the separated bleed screw. You would just need to loosen it enough for any trapped air or water to trickle out. Clean it, and then tighten the screws again.

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Last Updated on December 26, 2021

Frequently Asked Questions

Why is the top of the radiator cold?

Air trapped inside can cause the top of the radiator to be cold, which you can fix by bleeding it out.

How long does it take for radiators to heat up?

It takes around 10-15 minutes, after which if it doesn’t heat, it may have some damage or blockages.

Are banging radiators dangerous?

Banging radiators aren’t dangerous in themselves but the banging could be a signal to bleed them out. It is important to be careful when bleeding it out, and best to consult a professional if you’re unsure.

David Thompson

Author: David Thompson

Dave has been involved in the UK building sector for over 3 decades and has developed a particular interest in energy efficiency in the home.

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