Posted by: @deltona

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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.

Thats true, but having tried (and succeeded) in constructing a DiY version with computer fans, I can still appreciate the good design of the speedcomfort product.  Its surprisingly difficult to make by DiY an assembly that is neat and fixes reliably, and the speedcomfort product takes all this hassle (which most people wouldnt bother with) away.  Thus I can definitely see the value.  

I wanted to hijack this thread slightly to ask what may be a stupid question. Is there any tangible difference in effectiveness between having fans at the bottom of the radiator blowing air into the fins vs having fans at the top of the radiator sucking warm air out from the fins?

I would say ( not from experience) that any difference would be minimal Mars ?..

And the likely hood of SHSBO being impressed with them being in plain site is another topic in itself!.

It's not a hijack, it's a good question. Without testing it's impossible to be accurate and very difficult to test and be accurate.

The heat performance difference will be minimal.

You may well find it's better, but it won't be a lot and as said, difficult to test for.

The sound will appear louder though due to being closer to your ears and without any possible barriers.

The longevity of the fans will be less due to the heat.

Posted by: @nursethescreens

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I would say ( not from experience) that any difference would be minimal Mars ?..

And the likely hood of SHSBO being impressed with them being in plain site is another topic in itself!.

That was my initial expectation but I definitely wanted to canvass opinions.

Given I can get a bundle of four USB fans, a USB splitter and a few nuts and bolts for just under a tenner, and I have access to a friend's 3D printer, suddenly making a home version of the Speedcomfort product - notwithstanding @jamespa's proviso - seems very attractive. The biggest issue is method of fixing, and if the whole thing can sit on top of a radiator and be just as effective as if it were below then that simplifies things a lot more.

In addition, at least one of the radiators I have in my sights at home sits under something. If a top-mounted design could be just as good, the 3D printed housing for these fans could be designed to redirect the airflow horizontally into the room so it doesn't just warm the coats/shelf/curtains above the radiator.

Posted by: @majordennisbloodnok

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housing for these fans could be designed to redirect the airflow horizontally into the room so it doesn't just warm the coats/shelf/curtains above the radiator.

You've been able to buy that design for years now.

Posted by: @majordennisbloodnok

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I wanted to hijack this thread slightly to ask what may be a stupid question. Is there any tangible difference in effectiveness between having fans at the bottom of the radiator blowing air into the fins vs having fans at the top of the radiator sucking warm air out from the fins?

I suspect this depends on the fans.  The radiator side has more resistance and I'm guessing that fan fin design is quite sophisticated, so may well take into account resistance.

Posted by: @deltona

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Posted by: @majordennisbloodnok

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housing for these fans could be designed to redirect the airflow horizontally into the room so it doesn't just warm the coats/shelf/curtains above the radiator.

You've been able to buy that design for years now.

Agreed, but, in line with a point @editor made in the video, all the ready made radiator fans seem to have a thermostatic setting that only starts the fans at around 35degC. Right at the moment, my heat pump's flow temperature is hovering between 32 and 35, so that would largely disable the benefit of a radiator fan for me at any OAT temperatures above about 10 degrees. If I make one myself I can control the radiator fans centrally (integrated into Home Assistant, as it happens) and turn them on or off based on more intelligent criteria, even at low flow temperatures.

Posted by: @majordennisbloodnok

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Posted by: @deltona

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Posted by: @majordennisbloodnok

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housing for these fans could be designed to redirect the airflow horizontally into the room so it doesn't just warm the coats/shelf/curtains above the radiator.

You've been able to buy that design for years now.

Agreed, but, in line with a point @editor made in the video, all the ready made radiator fans seem to have a thermostatic setting that only starts the fans at around 35degC. Right at the moment, my heat pump's flow temperature is hovering between 32 and 35, so that would largely disable the benefit of a radiator fan for me at any OAT temperatures above about 10 degrees. If I make one myself I can control the radiator fans centrally (integrated into Home Assistant, as it happens) and turn them on or off based on more intelligent criteria, even at low flow temperatures.

 

What I mean is you may be able to pick one up cheap and use the housings.

Good idea, @deltona. I'll have a look around.

Posted by: @majordennisbloodnok

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Given I can get a bundle of four USB fans, a USB splitter and a few nuts and bolts for just under a tenner, and I have access to a friend's 3D printer, suddenly making a home version of the Speedcomfort product - notwithstanding @jamespa's proviso - seems very attractive.

In case it helps Andrew Kuhne on openenergy monitor has developed an 8 way (I think) fan controller which he sells at cost.  I used a commercial one with a manual speed control (a physical knob) for my "homebrew.".  With a 3d printer making up some sort of support would be much easier!