Increasing the output of standard radiators

[mpooley]

Has anyone ever experimented with adding a fan to a normal rad ?

There are a couple of gadgets that promise this will save money by warming the room up quicker so the boiler turns off sooner!

I think this is nonsense as you need the same amount of heat input to attain a given temp in any particular room. (am I right?)

BUT i was wondering, that if you wanted to increase output from a normal rad so that you could use lower water temps for a heat pump system, maybe just maybe this could help?

what do you think?

Mike

[StationHouse]

Hmmmm.... I've heard of people talking about this before... Thing is the fans in fan convectors are long cylinder type things all ducted trhough oooo's of fins.

[dhaslam]

It would depend a lot on the existing radiator.   I suppose there aren't  many infinned  radiators now  so as long as there is a good big surface area  it should work.   For a plain radiator it would probably mean making up a box  with fins and fan that attaches to the back.  There is an Irish company that makes   radiators  with thermostatically controlled fans that  work from  30 degrees and produce about 100 watts per square foot of radiator so it should be possible to get  similar results.

[M]

There may be an argument for faster heat, or the illusion of heat.

Last year Wifey and I re-decorated the living room, and I decided to utilise the underfloor tails for a conservatory radiator (that we never got round to installing, and won't as it would waste too much heat) to put an additional radiator on the opposite wall.

We removed the existing 900mm double radiator, which didn't fit properly, put in an 800mm double, then fitted a new 600mm double in the opposite corner.

Can't fully account for it, but heating time (cold morning temp, to pleasant warm room) has dropped from approx 2hrs to about 15mins. I think the factors at play are that the original radiator faced a door left partially ajar for our 'clowder' of cats, so most of its effort was helping to heat a hallway.

But, the illusion part, whilst the room feels warm in 15 mins, it will cool back down fast, so I think it's the better distribution of heat that we are benefiting from. So the fan idea may have some legs. After all why heat the whole room and walls up to a comfortable temp, if you can just heat up the air. At night most of it will be lost anyway. I think?

Mart.

[johnrae]

Rather than blowing air over the radiator, how about placing a duct, say 6" or 8" diameter in the corner of the room, mounted on short legs, say 9", and extending to within say 6" from  the ceiling.  Within the duct fit an inline fan.  Then you can suck the hot air from the ceiling space and discharge it at room level.

Why heat the ceiling when it's your feet that are cold ?

[Baz]

The natural convection airflow is miserably small so a fan can increase it substantially increasing power transfer (if your boiler can cope with every rad on steroids). Quicker heating means later start if you are the type who expects 20C to be achieved at time x rather than turning on at time x and making do with what you get.
A later start means less time at full temp for heat loss through walls etc. So say one hour less for the evening taking 7hrs down to 6hrs ought to save 1/7th x factor to account for it being during temperature rise not at full temp. Aspects relating to thermal mass probably come into effect but I can see it being a significant help in lightweight timber frame construction.

[mpooley]

This is all very interestink!

I think i might do an experiment in our cold Kitchen.
The Rad is under a marble worksurface which soaks up the heat.
I might arrange it so that air is sucked in through a slot in the bottom of an MDF sheet and blown out into the room at the top.

I was thinking of a large fan at low speed but would maybe have to make the temperature switch up myself.

[acresswell]

If the worksurface is quite close to the top of the radiator, it's quite possible that it's reducing the convection current simply because the gap at the top isn't big enough. 

I used to have a house with radiator shelves.  The radiator output always seemed rubbish, even though the rads themselves were getting nicely hot. I took a rad shelf off during decorating, and the room suddenly got much warmer, so when I re-fixed the shelf I moved it up about 2cm... much improved heat output.

I recognise that you probably can't move the worksurface up, but could you sneak the radiator down?

[M]

If the worksurface is quite close to the top of the radiator, it's quite possible that it's reducing the convection current simply because the gap at the top isn't big enough. 

I used to have a house with radiator shelves.  The radiator output always seemed rubbish, even though the rads themselves were getting nicely hot. I took a rad shelf off during decorating, and the room suddenly got much warmer, so when I re-fixed the shelf I moved it up about 2cm... much improved heat output.

I recognise that you probably can't move the worksurface up, but could you sneak the radiator down?

That's interesting, we popped a shelf over the kitchen radiator this summer. Now when I walk past it I get a strong blast of heat on my hand and arm. It was quite a surprise the first time. Very nice result.

Just checked and the shelf is 90mm above the radiator, don't know what the ideal height is (assuming there is one)?

Mart.

[mpooley]

If the worksurface is quite close to the top of the radiator, it's quite possible that it's reducing the convection current simply because the gap at the top isn't big enough. 

I used to have a house with radiator shelves.  The radiator output always seemed rubbish, even though the rads themselves were getting nicely hot. I took a rad shelf off during decorating, and the room suddenly got much warmer, so when I re-fixed the shelf I moved it up about 2cm... much improved heat output.

I recognise that you probably can't move the worksurface up, but could you sneak the radiator down?

No the rad is to near the floor to do that.

I have been meaning to do something out with it so I think I will experiment with the fan idea as soon as I get a moment.


I was actually thinking about using one of those largeish tabletop fans set on as slow as possible.

I'm even wondering if i just sit it on the floor pointing inwards towards the rad(still under the worktop of course) would the increase flow of air  be enough to improve matters even though it was not going in underneath and out of the top?
as I intend to fit a grill over the space eventually it wouldnt matter what it looks like !
This is so easy to do it must be worth trying although I will  have to cough up for the fan.

Mike

[johnrae]

tie your dog to the floor in front of the radiator and give it a bowl of food.  The tail wagging will act as a fan !

[mpooley]

tie your dog to the floor in front of the radiator and give it a bowl of food.  The tail wagging will act as a fan !

I don't  know ?
I think his carbon footprint might be higher than the electric fan   

[acresswell]

The radiator shelf that restricted the heat output was only about 40-50mm above the radiator...  so it was about 70mm by the time I'd moved it up and I'm not surprised that Mart's 90mm is working OK.

Have you considered swapping the rad for a double that is 100mm shorter?

[mpooley]

No as its a double already

But I am considering a triple.

[dinitro]

I got a couple of 12v computer fans put them between the panels in a double convector.  They lie flat but for some reason move , causing a horrible grinding noise and then need to be repositioned.

I managed to find a thermocouple that switches on the fans if the pipework is more than 35? degrees.

The room seems to heat up faster but I believe this could be a placebo effect.

The only downside is the hum of the fans...

I have a 12v rail so a 12v power source was not a problem.  What I might do is put on a radiator shelf since the
radiator is below a window and I believe the curtains are deflecting the heat to the glass rather than the room.

dinitro