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Central Heating Radiator

A radiator is one of the basic items in a central heating system, i.e. a system containing a boiler that produces heat and distributes it throughout a home or building. The heat is transferred into each room through central heating radiators, also called hot-water radiators.

Known for delivering consistent heat to rooms, hot-water radiators provide good thermal comfort in the location they're installed. A central heating radiator can have a variety of materials, designs and methods of operation, which affect the degree of comfort, the heating system's performances and the energy consumption.

How does a central heating radiator work?

The way a central heating radiator works is simple: a boiler (gas, wood, oil or electric, or a heat pump) produces hot water at a temperature of between 30°C and 70°C. The liquid is then distributed through a network of pipes to the various radiators in a home.

A radiator is made from a heat-conducting material (cast iron, steel or die-cast aluminium) and features a large surface area for heating a room. The heat transfer between the warmth of the water circulating in the radiator and the ambient air happens in two ways: by convection through the movement of hot water and by radiation, as the surface of the radiator, once heated, also heats the room. In this way, a hot-water radiator gently and consistently disseminates heat and provides a very pleasant level of comfort.

How to choose a central heating radiator

In a home fitted with central heating, the performance of the chosen radiators determines the comfort and the energy consumption. It's also important to carefully consider which central heating radiator is suited to your needs.
  • What power?
A radiator's power is usually rated in watts. When choosing the power of your radiators you'll need to take into account the surface area being heated, as well as the height of the room and the quality of your home's insulation. You can also fit several radiators per room to achieve the desired heating power.
  • Which material should I choose for a central heating radiator?
Hot-water radiators are available in a variety of materials: cast iron, die-cast aluminium and steel. Each one has a different level of performance, benefits and drawbacks.

-Cast iron hot-water radiators: cast iron has a high inertia. This means that a cast iron radiator retains and transfers heat for a long time, even after the heating has been switched off. This makes it particularly suitable for maintaining a pleasant temperature in poorly insulated rooms that tend to cool down quickly. Another benefit is that cast iron radiators last a very long time. Nevertheless, they also have a few drawbacks: they're heavy, large, expensive and take a long time to heat up.

-Steel hot-water radiators: this type of radiator has lower inertia than cast iron radiators. A steel radiator therefore heats up more quickly, although its temperature also falls rapidly. Steel is therefore a good solution for backup heating in a room that isn't used much or in well-insulated rooms where the heat escapes less quickly. Nevertheless, steel hot-water radiators also have some advantages: because they're light and take up less space, they're easier to install and are available in a wide variety of models (size, design, etc.). Steel radiators are also significantly less expensive than cast iron radiators.

-Die-cast aluminium hot-water radiators: this type of product is a good compromise between a cast iron central heating radiator and a steel model. Die-cast aluminium has good inertia and retains heat for a fairly long time, and is also a lighter material than traditional cast-iron. Like a steel radiator, the temperature rises quickly when switched on and the cost is more affordable than a cast iron radiator. The only major drawback is that there's a risk of corrosion, which means regular maintenance is required.

It's up to you to choose which type of radiator is best depending on your budget, the insulation of your rooms and the performance you want. However, note that it's best to use the same type of radiator throughout your home.
  • Which design should I choose for a central heating radiator?
Hot-water radiators come in a variety of shapes and designs to ensure they fit the style of your rooms. You can camouflage your radiator so it can't be seen or showcase it with an elegant design. Traditionally, radiators only had a functional purpose and there wasn't much interest in their design. Today, manufacturers are continually striving to come up with more attractive products from a design viewpoint.

The most common shapes include horizontal and vertical hot-water radiators, as well as more discreet extra-flat radiators. Baseboard radiators don't take up much space and can easily fit underneath a window. Whether you're looking for a cast iron, steel or die-cast aluminium hot-water radiator, the variety of each type of product means you'll have no problem finding a radiator that will look good in your home. You can now buy coloured radiators, square models for small rooms such as the bathroom and radiators with a flat or grooved front. You can even create a tailor-made product that fits the constraints of your room (sloping ceiling, obstacle, etc.).

For even more practicality, why not choose a bathroom radiator that you can dry your towels on? These towel radiators, which are often vertical and don't take up much space, feature accessories or horizontal bars that you can put your towels on. This means you'll have warm towels when you get out of the bath or shower, and your bath linen will dry more quickly.
  • Which method of operation is best?
There are two categories of central heating hot-water radiators: firstly, traditional high-temperature radiators that heat the water to a temperature of 70 to 90°C; secondly, low-temperature radiators that heat the water to a temperature of 45 to 50°C. While high-temperature radiators are more affordable, low-temperature radiators are more energy-efficient.

Low-temperature radiators - which are more affordable, available in cast iron, steel or die-cast aluminium and are compatible with low-temperature condensing boilers or low-temperature heat pumps - have many advantages. However, they're more expensive than traditional radiators and the low-temperature models are often larger and have a bulkier design. Discover all our products

Installing a central heating radiator

A hot-water radiator works with a central heating system. This means it needs to be connected to a hydraulic circuit so that the water can circulate between the central heating installation and the radiators in each room. If your home has already been fitted with this type of radiator, then installation is simple. However, if you're replacing one type of heating system with another and no pipes are in place, some alterations will be required for installing your radiators. In a new home, installing a central heating system with radiators won't pose any particular problems.

As far as the position of your radiators concerned, a few rules need to be followed. This will determine how effective your heating system is, so it's worth considering more than the decorative aspect of a radiator.
  • It's best to install a radiator underneath a window and in all cases on an external wall to offset the cold transferred by these walls.
  • Don't put large objects or furniture in front of a radiator, as this will affect the proper circulation of heat through radiation.
  • Leave a space around your radiator: to heat a space effectively, you need to leave 15 cm on each side, 10 to 15 cm between the radiator and the floor, and 50 cm above.
  • In a large room it's better to have two medium-sized radiators than one larger one, even if it's powerful. This will distribute heat in the room more effectively. Ideally, they should be placed opposite each other.
  • In a bedroom, avoid placing the bed too nearby the radiator, as a heat source that's too close at night affects sleep.
  • In a corridor, position the radiator in the largest area, where it will be less of an obstacle.
  • In a bathroom, one compact radiator is enough to heat the entire room. A towel radiator is perfect and saves space.

How can I save energy with a central heating radiator?

To save energy while also enjoying optimal thermal comfort, it's important to choose a model that has the NF marking, which guarantees that the appliance complies with standards and ensures that the stated performances are accurate.

For optimal running of your hot-water radiator, remember to bleed the system every year. This gets rid of any air in the pipes and ensures that the hot water circulates properly in the radiators. To save energy and cut your bill, you can buy a low-temperature radiator, which uses the boiler less.

You can also fit your hot-water radiator with thermostatic valves to regulate the temperature in a room and therefore your energy consumption. This allows you to adjust the temperature based on how occupied your home is and to have the heating on less while you're away, while also enjoying optimal comfort when you're at home. Smart radiator valves even allow you to adjust the temperature remotely, meaning you can only heat your home when necessary and save money without having to over-think things.

The cost of a central heating radiator

The prices of central heating radiators vary depending on which type you choose: cast iron, steel or die-cast aluminium. Although the first option is more expensive, they last longer than a steel radiator in particular. Prices usually range from €50 to €1,000 depending on the radiator's power and design. The more design-oriented models are more expensive, particularly if the manufacturer used a well-known designer. Although low-temperature radiators are expensive, they allow you to offset the cost of purchase by saving energy.

Remember to factor in the cost of installation if you're completely renovating your system, as well as the cost of the energy consumed, which also depends on the type of radiator you choose.

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