Radiator fans

Cirrus1

Hi,
I was wondering if anyone here has experience of these? Mine is the Dutch product which is supposed to go under the radiator and held there by magnets.
Do these fans work? The problem I am experiencing is that the fan
isn’t held in place between the oval tubes of my radiator. The magnets are in the wrong place for the radiator. I have emailed the firm and am waiting for a reply. The only YouTube I could find (plumberparts) had the guy attaching the fan onto a radiator with fins. He had no trouble, but then the radiator was a different design to mine.

I have the unit currently sitting on top of my radiator. Should the fan be parallel with the radiator (like it would have been if it was held properly) or 90 degrees to the top (the fans pointing to the room)?  Hoping some kindly engineer can help.
Trying various things to heat up the room faster, so will buy more if they work.

Reed_Richards

I don't know the specifics of your fans but the general principle is that they increase the output of your radiator.  Because of this your boiler will have to work harder and use more energy.  So you should get more heat but it will cost you more.

InvertedVee

Reed_Richards said:

I don't know the specifics of your fans but the general principle is that they increase the output of your radiator.  Because of this your boiler will have to work harder and use more energy.  So you should get more heat but it will cost you more.

Not quite. A fan increases the radiator output. It's the same effect as having a larger radiator. It's a way of getting more heat into the room. If that's what you're trying to do, they can help.

The increased heat output may actually allow a slightly lower flow temperature, which will help with efficiency. But as I said, these are devices to help to increase radiator output rather than to cut costs.

And, in case it's not obvious, there's no point putting on a radiator fan and turning down a TRV!

Reed_Richards

M0KBJ said:
Not quite.....

I don't see why "not quite".  You might be able to lower the flow temperature if you choose to and that might allow your boiler to operate with greater efficiency but the extra cost of running the fan-assisted radiator is very likely to outweigh this.  And if you lower the flow temperature you are boosting the temperature in the room with the fan-assisted radiator at the expense of the other rooms.  These rooms will either take longer to heat up or will a bit slightly colder.

Cirrus1

Thanks for the replies.
As I understand it, the fan is only to accelerate the movement of warm air to the room. The room is supposed to warm more quickly, the warm air better distributed and the thermostat turn off sooner. That’s the theory anyway. I’ve now placed the unit under the radiator on some cardboard (a bit Heath Robinson).
I can’t lower the boiler flow temperature because my house would never warm up in time with an outside temperature of -7 degrees.  It’s a low power fan (4W) and operated by a thermostat. It’s early days in my experiment.

Olly_J

What does your fan look like out of interest? All the ones I've seen all sit on top of the rad and suck warm air in the bottom of the fan and blow it out the front

chris_n

They can help with the output of a radiator if the size is marginal (there have been quite a few with this problem on here) but the only energy they will save is a small potential increase in efficiency if they allow you to lower the flow temp. I doubt that would be significant, may not even be measurable apart from in lab conditions. 

Cirrus1

Replying to Olly_J - it’s the SpeedComfort radiator fan. They only do one model. I can’t do links or photos yet.

Chris - The radiator the fan is on is not marginal in size. The purpose of the fan is to speed up the room getting warm. I wanted to find out what other people’s experience was of the item. It seems that they are a bit niche.
I will not be turning down the flow temperature of the boiler in these arctic conditions.

Rattusnorvegicus

I dont bother with the tiny fan things. I use a tower fan (Dimplex ion) (1metre of vertical grill) on medium speed 2metres/second 16m3/min airspeed (power is 24 watts) to blow air from the side across the radiator, or rotating over an oil radiator. Both heat the room(5x5x2 metres) to 20 deg c within an hour, even if the thermostat in the hallway says 16.

I dont have external wall insulation, the flats are generally D rated EPC.

My experience is i could spend all day trying to lift the thermostat 2 deg c without a fan, or raise it 4 in an hour using the fan.Its a no brainer. My heating cost including 2 tower fans comes in at 76p/day, but that only comes on when theres a frost, and the underfloor heating(from tenant below) isnt engaged.

Cirrus1

Thanks for sharing Rattus. It is really interesting that without the fan it takes so long to raise the room temperature and with it you can achieve 4 degrees in one hour. It spurred me on!
Yesterday we had -7 degrees for most of the day. It took 4.5 hours to achieve a rise of 1.5 degrees. I moved the fan to under a radiator closer to the thermostat and propped it up on some blocks. It has been in place since last night. Today we have -4 degrees and it has taken about 2 hours to get the same temperature rise!

The fan must be drawing the cold air into the bottom of the radiator and speeding up the convection process. I went around measuring the air temperature at various points and it seems more uniform than before. With the Hive thermostat showing 19 degrees, the air in the middle of the room, near the ceiling is in the range 20-22 degrees.

It is interesting that you are blowing across your radiator, whereas I am blowing up my radiator (like the manufacturer designed). Your stats are pretty impressive. Optimising radiator convection does not seem common.

Last year I was not bothered about improving heating efficiency. Gas was 1/3 of the current awful price and it took whatever was necessary to get lovely and warm. It’s a complete paradigm shift to live in a few warm rooms and be chilly everywhere else.

Effician

We don't have radiators , just one log burner but the principle is the same , air movement is all to us & if we relied on convection ( forced or natural) we'd have a very hot high lounge ceiling & the rest of the house would be freezing.

What works for us is a mix it up & spread it out approach with the aim to get each rooms bottom half & top half matched as close in temp as possible.

If you have a wide variation between floor & ceiling temps i guess a little rad fan will help a little but they're nothing like a ceiling fan or stand fan.