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Cold radiators? What to check

Hands on a radiator that is cold at the top

Cold radiators are a common problem in many households. While they could be a result of a more serious problem with your central heating system or boiler, there are a number of smaller faults that should be ruled out first.

When you first discover a cold patch on your radiator, check if the:

  • Thermostat is set too low
  • Timer isn’t working
  • Radiator valve is closed

If none of the above apply, your radiator might be cold if there are:

  • Air pockets in the system
  • Blockages within the system
  • Circulation fault

Table of contents

  1. Why are some of my radiators not working?
  2. Why is the top of the radiator cold?
  3. Why is the middle of the radiator cold?
  4. Why is my radiator hot at the top and cold at the bottom?
  5. Why is my radiator still cold, even after bleeding it?
  6. Radiator still cold? What to do next

Why are some of my radiators not working?

If none of your radiators are heating up properly, there could be a problem with your central heating system or boiler. However, if some of your radiators are heating up while others aren’t, this could be one of a number of issues. Run through our quick fix checklist below to find out more.

Issue 1: Cold radiators in some parts of the home

If a radiator in your home isn’t getting hot, it may be due to a problem with one of the zones in your central heating system.

Central heating systems work by pumping a continuous flow of hot-water from the boiler to the radiators, then back to the boiler to pick up more heat. Within this system, you could create ‘ zones.’ This means that you can control the temperature in separate areas of your home, depending on your heating requirements in each room. If you find that radiators are cold in one area, it could indicate that there is a problem with a particular zone.

Issue 2: One radiator not working

If one radiator within your home stays cold, ensure that the valves on the sides of the radiator are open. If the valves are open but the radiator is still cold, it’s possible that the valves are blocked. A suitable system cleanse conducted by a Gas Safe Registered engineer will usually do the trick.

Issue 3: Cold radiators upstairs

If the upstairs radiators in your home are cold, it’s an indication that the feed and expansion tank in your loft has run dry. This usually points to a larger problem. However, it’s also possible that the ball valve in the tank isn’t working correctly; it may be blocked or jammed.

Try the following:

  • The cistern is usually found in the loft
  • Clear any obstructions to the ball valve
  • Refill the cistern, making sure there is enough room for the water to expand when the system heats up
  • Refill the cistern so that there is just enough water to float the ballcock
  • When the system is cold there should be just enough water to make the ball float and switch off the water coming in

It’s highly recommended that you seek the skills of a Gas Safe registered engineer when you have major heating or boiler problems. Remember that a competent engineer should regularly check and service all boilers and heating systems.

With a full cistern, the upstairs radiators should start heating, but it’s a good idea to get a professional plumber in to work out why the cistern ran dry in the first place.

Issue 4: Cold radiators downstairs

If your downstairs radiators are failing to heat up, there could be a problem with your pump. If this is the case, it won’t be producing enough power to push the water around the heating system.

Pumps can get warm, but if it is hot or making a grating sound, then it might be about to break down, in which case it will need replacing. One of HomeServe’s Gas Safe registered engineers can provide help and advice to rectify this issue.

Why is the top of the radiator cold?

cold radiators - person touching a radiator that is cold at the top

If the top of your radiator is cold, it’s possible that air is trapped within the system. Bleeding the radiator will release any trapped air, vastly improving the efficiency of your entire heating system.

Why is the middle of the radiator cold?

If the middle of your radiator is cold, there may be a build-up of debris or sludge which is obstructing parts of the bottom of the radiator. You’ll need to clean it out and remove all unwanted substances that are blocking the bottom length of the radiator.

If you have an open-vent system

  1. Buy a heating system sludge remover at your local DIY store and use it as per the manufacturer’s instructions
  2. Add the liquid to the feed and expansion tank
  3. After a few days, you will need to empty and refill the system.

If you have a pressurised system

  • You’ll need a plumber or heating engineer to help you
  • They will remove the radiator and flush it out to clean it
  • In some cases, your radiator will need replacing

Why is my radiator hot at the top and cold at the bottom?

If your radiator is hot at the top but cold at the bottom, there may be a build-up of scale, rust, or sludge which is obstructing the flow of water.

As with the middle of the radiator, if you have an open-vent system which is unpressurised and tank fed, you’ll be able to use a sludge remover to flush your radiator. However, if you have a pressurised system, you’ll need the assistance of a Gas Safe registered engineer.

Why is my radiator still cold, even after bleeding it?

If after you bleed your radiators they still aren’t getting hot, you might have a problem with your thermostatic radiator valve (TRV). This issue is usually caused by a stuck pin in the valve. Thankfully, this is easy to check yourself, with no need to call for a professional.

If the issue isn’t your TRV there might be blockages in the system. Unfortunately, this is less easy to fix yourself and we recommend calling in an engineer to flush the system for you.

Radiator still cold? What to do next

If you’ve managed to diagnose the problem with your cold radiator(s), the next step is to fix cold radiators in your home.

However, if you’re still stumped as to why your radiators aren’t working, our expert repairs team will get things working again in no time.

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About the author

Chris became a fully qualified Gas Engineer in 2009 and has been with HomeServe since 2016. Chris hung up his tool bag in 2018 to concentrate on ways to use technology to help Customers.

He currently heads up the Self Fix team who are able to get Customers back up and running over the phone without the need for an Engineer.

He is kept busy looking after his two daughters and is a lover of all things CrossFit, Yoga and Ice Baths!

“I chose to work at HomeServe after running a small business. I wanted to be able to help people on a greater scale and HomeServe has helped me achieve that.”

Qualifications

Gas Safe registered, CCN1, CPA1, CENWAT, CKR1, HTR1, NVQ Level 3 Plumbing & Heating

Years qualified

Since 2009
Read more

Share this post

About the author

Chris became a fully qualified Gas Engineer in 2009 and has been with HomeServe since 2016. Chris hung up his tool bag in 2018 to concentrate on ways to use technology to help Customers.

He currently heads up the Self Fix team who are able to get Customers back up and running over the phone without the need for an Engineer.

He is kept busy looking after his two daughters and is a lover of all things CrossFit, Yoga and Ice Baths!

“I chose to work at HomeServe after running a small business. I wanted to be able to help people on a greater scale and HomeServe has helped me achieve that.”

Qualifications

Gas Safe registered, CCN1, CPA1, CENWAT, CKR1, HTR1, NVQ Level 3 Plumbing & Heating

Years qualified

Since 2009
Read more

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