Radiators that do not heat up might become a major issue when the winter season approaches. The last thing you want to see in the wintertime is a cold house. So, what can you do if your radiators refuse to heat up?

Fortunately, you can take a few easy measures to diagnose the issue and get your radiators warming your house as quickly as possible.

To assist you in determining which concerns may apply to you, we've divided them into two sections:

  • One radiator not working

  • Multiple radiators not working



One radiator not working

When only one radiator is not working, there is either a stuck valve or trapped air. The thermostatic radiator valve (TRV) allows the flow of hot water to the radiator. However, sometimes it can get stuck or stop. That means it is unable to let the hot water flow when the heating is on. 

But not all radiators may have the same problem. So let us look at a few more potential problems that lead to one radiator not working.

Leak in the radiator: 

It might be annoying because it could indicate you'll have to change your radiator. On the other hand, external sealers and leak sealers may help based on the intensity of the problem.

Unfortunately, rust is the most common source of leaks. It indicates that your system requires cleaning and protection. However, this is the worst-case situation.

Another problem that you may come across with leaking is loosened nuts.

There are two ways that can tell you if the nuts have loosened.

  • a leak from the thermostatic radiator valve’s connection to a pipe or radiator

  • a leak from the pipe connection

However, just twisting it with a wrench could be enough to solve the problem.

Also, if you observe a large amount of water flowing from the piping, a leak is likely the root cause of the problem. For that, you should contact an expert.

Blockages (debris, sludge)

You may find that the radiator is cold at the base yet warm at the top on rare occasions. It indicates debris, a clog, or, more commonly, sludge accumulating in the radiator.

Because of all the accumulation at the base of the radiator, hot water cannot circulate.

Seeking expert assistance is the most effective and safest approach to cope with this issue. Most of the time, they will perform a power flushing service for you.

Power flushing is the act of eliminating dirt and waste from your central heating system. It removes the layers which have built up over time and is hindering it from working properly.

If certain rooms are cooler than the others, your heating system takes a long time to heat up. Likewise, your bleeding radiators may require a power flushing service. If you have restricted hot water, it might be a symptom of sludge accumulation. However, there are not one but many possible causes.

Problem with thermostatic radiator control valve

The reason may be that the thermostatic radiator control valve has been turned off after being programmed to a temperature. It's common for the valves to stop in a closed condition if you have selected a higher temperature.

That's something you can readily examine by removing the valve's top cover. The valve is generally secured by a knurled nut, which you may unscrew with your hand.

Be careful with this. You don't want to unscrew any of the other bolts on the valve. Otherwise, you'll have water spilling out all over the place!

After you've opened the valve's cover, make sure the central pine can freely move down and up a few millimetres.

If you are using a tado° smart thermostat that displays E1, E2, and E4 errors, you have run into some calibration problems.

An E1 error means the valve's closed state was not recognised. To fix this, uninstall the smart radiator thermostat. Double-check if the mounting bracket is securely attached to the valve body.

When there is no connection between the motor and the valve pin, an E2 error is shown. To fix this, check if the mounting bracket and adapter (if applicable) are correctly attached to the radiator.

When the distance measured between the open and closed positions of the valve is too little, an E4 fault is displayed. It might indicate that calcification has blocked the radiator valve. Kindly unmount the Smart Radiator Thermostat to fix this. To unclog the valve, use a wrench or a similar instrument to slide the pin in and out.

Air pockets in the radiator

If there are air pockets in the radiator, its top feels cold while the base is warm. It's an indication that the problem is just a buildup of air in the central heating. It happens when air fills the area intended for hot water, inhibiting proper radiator airflow.

These air bubbles could be caused if there is any problem with the pipes or a leakage.  

To repair this, you'll need to bleed the radiator. With the help of a radiator key, loosen the bleed screw till you hear air rushing out. Continue till you see water. Tighten the bleed screw as soon as you see water coming out.

Examine the pressure in the boiler system after the air has been evacuated to confirm it is within the limitations.

You can also save energy when you bleed your central heating system.

Multiple radiators not working

If one or more radiators aren't working, make sure your heating is turned on first! Yes, that may seem self-evident. But you'd be shocked how many people start panicking in such a situation. They think their radiators are damaged when all they had to do was flip a switch.

If everything seems fine, here are some of the reasons why multiple radiators are not working.

Central heating not working properly

Instead of the radiators, the issue might be a more significant problem with your central heating system.

It would help if you double-check that your central heating system is operational. For example, if all of your radiators aren't heating up, rather than just one or a few, it might be a sign of a larger problem.

Examine your central heating system to determine if there is anything unusual about it. Do you have access to hot water? Is there a strange noise coming from your boiler? If you've seen any of these indications, you should contact a professional heating specialist as quickly as possible. You have to act fast as there are chances of you getting Legionnaires' disease.

Legionnaires' disease is a kind of lung illness spread by contaminated water inhalation. Legionella bacteria are to blame for the ailment.

Legionella grows in water that has temperatures ranging from 20°C to 50°C. A setpoint temperature above 60°C must be scheduled in a domestic hot water system to minimise the risk of legionella growth. Anti-Legionella measures are standard on most boilers that are linked to a home hot water supply. Therefore, when you install tado°, you would least come across such issues.

Too low boiler pressure

Your boiler will not supply enough hot water to warm your home if it is not adequately pressurised

You may visually check the pressure by checking at the top of the cylinder, usually found in the airing cupboard or the front of the boiler. Combi boilers are pressurised between about one and two bars and operate on a closed-loop circuit. 

If you notice that the pressure is too low, adjust the top-up valve to raise the water pressure. It will allow the appropriate amount of water to enter. You must be cautious, though, since you do not want too much water to enter the system!

If pairing fails the following installation, your tado° device will display an E0 error message.

Problem with central heating controls

Your boiler may be operating well, and the pressure is within safe levels, but the radiators are still not turning on due to control problems. It's possible that there's a problem with the electronic control panel. 

This is the panel that controls your central heating and transmits signals to your boiler. Although this is an uncommon occurrence, it is possible. 

Verify that the timing control is set appropriately to determine whether this is the issue. To ensure that your radiators are heated, select the 'on' demand option.

It is not recommended to modify the control panel settings. You may have to face multiple issues if there is any slight modification to the basic settings. However, if you do, you risk making the problem worse and increasing its cost. Rather, call an expert who has the necessary experience to solve the problem.

With tado°, you can control all the different types of heating systems. This heating system decides how tado° can control the system. tado° usually connects directly to the boiler, or replaces the existing radiator or room thermostats.

Fault in diverter valve

A diverter valve may malfunction if the controls aren't operating properly and the pressure is adequate, but there's still no flow.

The diverter valve is a motorized valve in the boiler that regulates the flow of hot water to your heaters or taps. It will direct hot water to your taps initially. So, if you turn on your heating and need hot water from your tap, the valve will direct the supply to the tap first.

The diverter valve may be stuck if you have hot water at your taps, not at your radiators. That's not something you should attempt to repair on your own. Take the help of a professional.

The Need For Smart Radiator Thermostats For Your Radiators

All rooms that you wish to regulate intelligently should have a smart radiator thermostat. Smart Radiator Thermostats are best used in places where you are spending most of your time, like the living room, kitchen, and dining room. This way, you may have the most comfortable home while also saving the most money.

If you don't use Smart Radiator Thermostats, you'll have to adjust all radiators manually. Your traditional radiator thermostat will heat up anytime the boiler is turned on when left open.

Starter Kit - Smart Radiator Thermostat V3+

Make your radiators smart. Save energy and maximise comfort. Available with vertical or horizontal mounting.

Learn more

How does a radiator work?

Radiators function by drawing heat from steam or hot water and using it to warm the air around them. They may be used to heat a space in this manner successfully.

They're built out of metal since it's a great heat conductor. The outside fins of the radiator automatically heat up when hot water or steam passes through it. As the fins warm up, the air around them warms up as well.

Radiators are among the most traditional and efficient ways to warm a home. They are still employed in buildings all throughout the world, and only some more effective choices are available. Because of their practicality and capability to heat an area uniformly and comfortably, they remain popular.

The smart and economical way to control a radiator is using a wireless smart thermostat.

smart thermostats have advanced features and innovative capabilities to connect with WiFi. You can connect them to other devices for remote monitoring. Many smart thermostats have different features such as scheduling, and geofencing.

When the smart thermostat is connected to the internet, it can trigger a range of alerts. For instance:

  • Low battery on the thermostat

  • Humidity outside the set levels

  • Temperature outside the set levels

  • Loss of electricity

  • Water leaks

On the other hand, you can use the smart thermostat without configuring it for WiFi settings. In such cases, it will work like a traditional thermostat. However, when the WiFi connection is cut out, the thermostat will still work. It will consider the set temperature to regulate. It will continue to work in its regular way even when there is no internet connectivity.

How to take preventive care of the heating system with tado°?

tado° has different ways to take care of your heating system. Let's have a detailed look at each of the ways.

1. The Auto-Assist Skill / tado˚ auto assist automates the regulation of your heating system. Further, it eliminates the need for human changes.

The following enhancements to your tado° system will be available with Auto-Assist:

  • When you enable geolocation, tado° will regulate your temperature when the last person goes or the first person returns.

  • When an open window is identified, tado° will immediately regulate your temperature.

  • You have access to improved Care & Protect capabilities, such as 

  • Self-Fix Guides - These allow you to address issues independently, resulting in cost savings and time.                                           

  • Get access to your Heating Activity data - It provides daily, weekly, monthly, and annual heating usage.                            

  • Services - You may also make a comparison with data from the preceding period.

2. Care & Protect puts focus on the health of your heating system. It keeps you informed about your consumption and assists you in identifying problems if they develop.

If a problem is discovered, you will have the choice of repairing it yourself. You can also refer it to a professional, depending on the nature of the problem.

To begin, grab some information about your heating system. You can get more personalized responses if you mention what you have, such as underfloor heating and a boiler.

3. Through frost protection, tado° keeps your heating system safe as the weather becomes colder.

Pipes may freeze or even break in cold conditions, damaging your heating system. To avoid this, tado° guarantees that even when the heating is turned off through tado°, the temperature does not fall below 5°C.


It is necessary to take care of your radiators and have a regular keep-up of your radiators. It will prevent the unexpected breakdown of your radiators. With the tado˚ app, you can control and manage your radiators and water underfloor heating. Moreover, it is advisable to take the help of a professional to avoid the chances of any mishaps.