Wow, I feel like I’m being pranked. My review of these is going up on Sunday morning with a perspective of how they work with heat pumps.

My take on Speedcomfort radiator fans:

If anyone wants to give Speedcomfort's radiator fans a go, we have a 10% discount available. Use code RHH10 at checkout here: https://www.speedcomfort.com/en/shop

Hi Mars. By coincidence, I ordered one of these a week ago and it has just arrived.

I can see from the instructions that they only supply the "automatic" thermostat for the UK market. According to their instructions:

The Automatic Sensor (E) is suitable for all radiators and convectors in combination with systems that heat at higher water temperatures (> 55 °C), such as central heating systems, boilers, or oil-fired systems.

For the European market they also supply a "Control Sensor": 

The Control Sensor (F) automatically switches the SpeedComfort (A) on and off according to these settings. By adjusting the start temperature, the SpeedComfort is also suitable for use with low-temperature heating systems (< 55 °C), such as (hybrid) heat pump systems.

So from that I would gather that for us heat pumpers the correct sensor would be the Control Sensor.

I assume that you tested the "Automatic sensor".

How did you get on with the temperature limitations which are essentially for high temperature radiators from central heating boilers? 

&mars SpeedComfort have confirmed my understanding that the automatic thermostat is more suitable for high temperature systems and that they currently do not offer the "Control Sensor" for lower temperature systems in the UK.

Posted by: @richard24738

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How did you get on with the temperature limitations which are essentially for high temperature radiators from central heating boilers? 

I had the 32/33C sensor, so the fans only kicked in when the rads got quite warm... 

I watched the video to see whether they'd potentially be an alternative to installing fan coil radiators if looking to use the heat pump for cooling, but the narrative on operating temperature restrictions pretty much ruled that out.

I had to laugh at the 6-7 reference in the teaser too, as we've been living in that particular world for weeks via our two teenage daughters.

@mars I think you say somewhere in the video that fans dont increase rad output.  I think they do.  By blowing more air over the fins/panels the heat transfer from metal to air increases relative to that due to natural convection (which, as you say, is weak at low temperatures).  That's the principle of fancoils/fan radiators.

I wouldn't like to speculate how much the increase is, particularly if you use only one unit on a fairly long radiator, but Im certain there will be an increase.

I have one, otherwise marginal, radiator where I have fitted a bunch of computer fans underneath to do the same, and another for which I have just completed an assembly of 8 computer fans for use in summer, hopefully to enable it to cool.  Andrew Kuhne on openenergymonitor has reported good results with adding computer fans to radiators for cooling.  Mine aren't as well engineered as the Speedcomfort ones though!

Posted by: @sheriff-fatman

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watched the video to see whether they'd potentially be an alternative to installing fan coil radiators if looking to use the heat pump for cooling, but the narrative on operating temperature restrictions pretty much ruled that out.

This is a problem with the Mitsubishi fancoil I have.  Its otherwise absolutely brilliant and I wish I had bought a couple more but, for some unfathomable reason, has a fixed 30C threshold for switching on when heating, whereas my minimum FT is 28C.  I have installed a resistor in series with the temperature sensor in order to 'fool' it, but I also intend to try using it for cooling in summer so will need to remove the resistor then because otherwise it wont switch on at all for cooling!  What a pain!

I wonder why they aren't letting us have the correct type for ASHP? 

I also ponder what the ROI is on them, a whole house full would be quite a cost.

Posted by: @deltona

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I wonder why they aren't letting us have the correct type for ASHP? 

I also ponder what the ROI is on them, a whole house full would be quite a cost.

Too expensive IMHO for a whole house, at this point do the job properly and fit fancoils (also expensive!) or larger radiators.  Best IMHO used in 'marginal' situations where only a marginal increase in output needed to make an existing rad viable, or where the upgrades have been done but one rad is just a bit too small because of the inevitable calculation uncertainty.

Bear in mind that ROI isnt everything.  I have one (expensive) fancoil because the alternative (to get the required output) is a whopping type 33 rad that barely fits in, and would totally dominate, the available space.  All the other rads in the house are a sensible size.  I suppose I could have increased the design FT, but for one otherwise awkward rad in a room where the rapid reheat feature of fan radiators is particularly valuable, this just didn't seem a sensible trade off.  Horses for courses!

As to the answer to your first question, no idea, seems madness, if we were still in the EU you would just get them from someone elsewhere where they do supply the relevant control.

Posted by: @jamespa

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Too expensive IMHO for a whole house

I have to agree. Given, on Amazon, I can find a pack of four 60mm fans with USB plugs and a four-way USB hub for a tenner (and only needing a couple of bits of thin board to make a fan sandwich and some magnets or other fixings to make much the same contraption), that’s quite a cost difference. I’d say a DIY equivalent could easily be done for under £20 whilst moving more air just as quietly. I’m sure a low temperature sensor could be found for less than the remaining £35…

But how long is it going to take to recoup your £80 at the advertised (22%?) saving? 

In their defence they are very well designed, but the thing is, you only need that great design once when it's fitted, after that you'll (hopefully) never see then again.

One thing I found when having a new ASHP system planned was the amount of rads everywhere, we were going to lose a lot of wall space and these would counteract that.

Two other vids on them which someone erased for some reason:

This Simple Add-On Gets Heat Into the Room Faster - YouTube

Do Radiator Fans Work? WE TEST THE CLAIMS! - YouTube