Picture of Upgrade hot-water radiator to convector
Hot-water radiators used in central heating systems use passive convection to distribute heat inside a room.
This is not very efficient, especially if they are mounted in the corner of the room.
For this reason, there are convector radiators that include a fan in order to improve the heat distribution and circulate higher volumes of air through the radiator blades.

In this alternative approach, standard radiators are upgraded to convector radiators using commercial off-the-shelf components (COTS) for 35€.
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Step 1: Assembling the fans

Picture of Assembling the fans
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These 4 fans are Brushless DC Cooling Fan 7 Blade 24V 120mm x 120mmx25mm.
This type of fan is very silent and about the same width as the hot-water radiator. By joining 4 fans together, they cover almost the entire radiator length.

Fan characteristics:
- 7 Plastic Blades
- Speed: 1600 RPM
- Airflow: 58 CFM
- Noise: 38 DBA
- Rating: DC 24V, 0.20A

These 4 fans were bought online for a total of 13.20€, plus 10.10€ for shipping.

The structural strength is given by the cable ties that pass through the holes in the corner of each fan, and join the fans together.

Step 2: Connecting the cables

Picture of Connecting the cables
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The fans use standard 2 pin connectors found in motherboards.
These hold quite well the tip of a coper cable.
It is also possible to merge 2 connectors with a small piece of cable, by plugging one to the back of another.
This minimises the number of cables reaching the power supply.

The power supply connected with a basic 2 wires AC cable on one side, and the DC cables from the fans on the other side.

Not shown in the pictures is a 1.5€ pass-through on/off switch and a basic AC plug (1.5€) at the end of the AC cable.

The power supply is a 24V Universal Regulated Switching 25W Power Supply.
Since the fans are 0.2A each and the power supply is rated at 1.0A, there is a margin in terms of the maximum current allowed.

Step 3: Testing the fans

Picture of Testing the fans
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Here are the fans working before installing under the radiator.
vicnur2 years ago
For a long time he lived and worked in the North of Russia 1990-2007, in the city of Novy Urengoy. The house used this design to increase the heat transfer. Applied fans on 220 v.Спасибо reminded.
Bartuss2 years ago
Does it reduced your bills? I have same heating system in my flat, and I have big problems with high costs of heating big rooms...
leto78 (author)  Bartuss2 years ago
Convectors are more efficient at transfering heat, so it would be faster to warm up a cold room. In principle, it would take the same amount of energy, it would just be faster.
However, there are some efficiency gains by creating a warm air barrier near cold surfaces, such as windows. This is why radiators are usually near or under the windows and not on the oposite side of the room. By circulating warm air with the convector, it should create this warm air barrier and provide some energy efficiency.
This is pretty clever. Great work, and great post!