A few years ago I saw an advert for a small fan+duct which blew air through the fins of a radiator. The idea was to get more heating power.
Has anyone used this system, and how well did it work?
I wonder if this idea would be useful for a heat pump installation; could it overcome the problem that the circulating water from a hear pump is at a lower temperature than from a gas boiler?
If you open up your car and have a look, it has an electric fan next to the cooling radiator.
Notice that in the car, there are a large number of fins. And the spacing between them is a lot tighter.
Ordinary room radiators are intended for convection transfer. The air moves very slowly. The aperture between elements is quite large, and this is to accommodate the convection powered air movement. Convection air will not go through a quarter inch hole.
If you wanted to switch to fan transfer, most of the fan "effort" is wasted on such crude radiators. Instead, you would want a car radiator, tight fin spacing, lots of fins, a powerful electric fan that can provide significant pressure to force the air through the fins. You then compare the surface area of the car radiator, to the lazy room radiator design.
Each design, is optimized for conditions, and does the best job possible... when designed a certain way.
You will also find various forms of window air conditioners, use noisy high pressure fans, tight fin spacing, lots of fins and so on. For the same reasons. To maximize the spreading of the cool air into the room. Nobody in the window air conditioner business would be using those loud fans, if they could possibly avoid it. Making a 10 foot by 10 foot conventional convection radiator is out of the question for them (too much metal material, too high a price).
On a "split unit" air conditioner, some of the noise should be outside the house, some of the "air noise" inside the house.
One way to get heat pump output into a room, is to make the floor into a giant convection radiator. Where my brother lives, that style of floor design is common. If we were to discuss that topic, my brother would have to resort to his collection of swear words :-) And he doesn't even swear (normally). He's a scientist after all, wears a suit and everything. But he spent a lot of money when his floor leaked. Money he did not have to waste.
Whatever you decide to do, it must be maintainable. This is why ordinary rads are so nice. They're out in the open, where a DIY person can tend to them. Any time equipment is hidden from view, all hell breaks loose. In my house, a favoured game is "what is that smell?" and "where is that smell coming from?". The perils of the things you cannot normally see.
Paul
I had fan assisted radiators in my house. They were noisy and they rattled and they were always getting blocked up by fluff.
As a branch of the question could we pump hot air through radiators instead of water? There'd have to be solid temperature control.
If you replace 15mm pipe with 50mm pipe,maybe , too much surface friction otherwise. See Dyson vaccuum cleaners, requiring non-compliant-EU excessive power to transfer air through the extra 10 foot of piping
I have got one (1970's vintage) in the fitted kitchen which was not well endowed with space for a radiator. Works fine but you do have fan noise.
Branding plate has long since fallen off but ISTR it was a Myson. It looks *very* 1970's with its fake veneer finish but still works fine. They built things to last back then!
Potentially yes although you won't get as hot air out of it. Try and find one to see if you can live with the fan noise though. It isn't a problem in a busy kitchen - it might be in a living/listening room.
Air doesn't carry anything like the amount heat, that the water can, so you would need much more airflow than the water flow for the same amount of heat. Which explains why all the heat needed for a room, can be passed through a 20mm pipe, but for the room to be heated by air, the air needs a large duct.
A couple of months ago I bought one of these:
It seems a reasonable option if you have a heat pump and want to boost the output of your radiators, but you have to put up with the noise. I posted some pics of it on this thread:
What I was trying to do was fan *cooling* with the ASHP, which it turns out doesn't work on radiators because of (lack of) convection. The fans didn't materially change that.
In general, it's better to have passive silent emitters than active ones. So I wouldn't want to use these as a full-time replacement for larger radiators but, possibly in spaces like kitchens where there isn't enough space for a full radiator, the fan system may be worth doing.
Theo
There's not much in them to fail anyway - just a pipe with fins, a thermoswitch and a motor with a fan on it. When the pipe gets hot, the thermoswitch turns on the motor and when it cools it turns it off.
I'd definitely not want one in a living-room or bedroom, but yes, they are fine in a kitchen.
I have custom made fan blown convectors Sort of 'kickspace' for walls.
Allegedly gets 2kw out of a car radiator sized radiator.
Yes they do work, but are a tad noisy
Yes, I would say that it could. But its still a radiator change, of sorts
Such things are called "fan convectors" and have fins and a tangential fan at the bottom and a thermostat. Other replies have mentioned them. I doubt that adding a fan to an existing radiator intended to heat by convection would be much good.
I've played with PC fans but not enough to offer a view.
You can see manufacturers' figures for the difference between their passive and fan-assisted output - including noise levels. Example in link (but NB the noise levels below are at 2m so not exactly a typical home).
A slow running desk fan would help move the heat from a standard radiator, into a room.
Agree useful in kitchens, installed in the kickspace, especially as kitchens often lack the wallspace for normal radiators. But even then the fan noise can be intrusive if you want to sit and read quietly after a meal ! There seems to be only 2 makes available in the UK, Mysons and Smiths; I reckoned that the Smiths was, on paper, quieter for the size I wanted.
Axial fans tend to be less annoying noise than axial, double bearings so none/less of that precession? rattle/clatter noise . Try a fan-heater on cold setting
less annoying noise than radial
Horrible noisy rattly things. I threw all mine out.
Bill
FWIW, This guy put me off doing the same
DIY radiator booster
It's a bit disappointing there are no pictures of the setup on his radiator. His fans look much bigger than most radiators, so I wonder if he's just sucking air past the back of the radiator rather than pulling it through the fins.
Any radiator of hot water already has convection driving air flow, so a fan needs to drive faster than the natural convection, and also transfer more heat from the radiator surface. It may be the surface area isn't enough.
That's useful for central cooling, but it's not very efficient for transferring heat. Hence you need large ducts and big fans. Our houses are smaller and older, and a 15mm pipe is an easier retrofit than an 8" duct.
Theo
But if you go for air to air or ground to air heat pumps you can cool and heat and you don't need huge amounts of ducting. The modern in-room units are quiet and heat the room quickly. My wife is really enamoured with mine. You start getting warm air within a couple of minutes.
It wasn't much more than the replacement boiler I had a few years ago and with the VAT reduction today it would be cheaper.
Somewhat regretting my original choice of retaining the hot water tank, should probably have gone for a combi...
Dave
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