DIY Radiator Booster

Central heating is a great invention and radiators generally do a good job of pumping out heat into a room. Sometimes however due to the layout of the room or positioning of the radiator it doesn’t quite work as well as it could. I have a room like this and decided to go for a bit of a DIY solution.

Booster in place

My kitchen and dining room are one and also open to the stairs and landing. With only one big raditor in the whole space most of the heat tends to rise and go up the stairs rather than circulating in the rooms, meaning it always feels chilly. There are various commercial radiator boosters available but some reviews say they are noisy and they all sit on top of the radiator which would mean moving it everytime I closed the curtains. So I decided to design and build my own.

The Idea

Take a standard quick PC fan, mount it to the bottom of the radiator, create a duct to direct the air across the floor and build a circuit to turn it on automatically when the radiator gets warm.

The Fan

Rather conveniently the gap between the front and back panels of the double radiator is just over 80mm meaning a standard PC fan will fit nicely. I bought a Be Quiet Silentwings Pure 80mm fan like this one from ebuyer which turned out to be pretty much silent when running.

The Circuit

I needed a circuit that would switch on the 12V fan when the radiator warmed up and turn it off again when it cooled down. I could have gone down the microcontroller route to do this, but it seemed like a fairly simple circuit with a temperature sensor and a relay should be able to do the job. After some time googling I found exactly what I needed. This site has done an excellent job of describing how to make a temperature controlled relay using a few basic electronics componets. There are kits for sale, but I chose to just buy the components and assemble them on some strip board.


The Ducting

Initially I was planning on using some thin plywood or something similar for the ducting. However a few members of the hackspace have 3D printers and kindly offered to print something for me. So following on from a talk given at the hackspace some months ago about how to use openscad I decided to try and design a 3D printable enclosure.


It took a couple of attempts to get something that was printable, but with the help and advice of other members I managed to design a nice curved duct with some fins and small box to mount the electronics in. The design is available on thingiverse.

Putting it all together

With all the parts made and colder weather fast approaching I assembled everything and wired it up using and old 12V power supply I had lying around. Tuning the temperature at which the fan comes on is as simple as adjusting the potentiometer on the circuit board. The fan doesn’t blast hot air out like a fan heater does, but it does produce a gentle breeze of warm air across the floor. Whether it has made a huge difference is hard to tell so far but I don’t think it can hurt.


3 thoughts on “DIY Radiator Booster

  • Is there not a danger that the fan will give you problems pulling warm air through it rather than pushing the air up ?

    • For example, I am currently sitting 30 cm from a radiator, with the central heating on and with my feet dressed in three warm layers. But my feet are so cold! So a fan that sucks air down and outwards would be ideal. Reluctant to use polluting plastics, so wondering if I could make one out of strong cardboard, preferably two or three fans long.

  • But wouldn’t that be ideal, to have the hot air pulled into the room low down, before it naturally rises towards the ceiling? Not only warming air low down, but maybe also reducing the cold draughts caused by cold air rushing in to replace the hot air rising from the radiator.

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