Radiator under window sill

[Harry Bloomfield]

If you look at Eric's diagram of heat circulation it exactly represents what happens in our lounge, the radiator is behind our seating position, although we do not have a sofa tight up to the radiator. The heat goes up from the radiator, across the ceiling, down the far wall and then cool air at low level flows back towards the radiator. That cool air hits our legs when sitting on the sofa and feels like a cold draft even though there is no draft. When the radiator goes off because the room is up to temperature the cold draft ceases.

You can combat that issue, to a large extent, by using a slow turning ceiling fan, to push the heat down.

 

[JohnW2]

You can combat that issue, to a large extent, by using a slow turning ceiling fan, to push the heat down.

Indeed ...

... If one does experience the issue you describe, and perceives it as a problem, I imagine that it could probably be addressed with a ceiling fan or suchlike?

 

[Agile]

I've been doing a bit of experimenting with fan heaters. Admittedly, the current ambient temp is not that low (about 11-12 °C) but a 2kW fan hear is a lot more than enough to heat the room - and that's with none of the adjacent rooms heated.

Kind Regards, John

You should measure the room temp and then run the fan heater for an hour and measure the new temperature.

With -1 C outside you need to be able to raise the temperature by 22 C to give you 21 C inside.

But generally fit the largest rad that you can get to fit in the space so presumably a 500 high and double panel.

An 1800 x 500 double panel T21 will give about 2.5 kW but I would recommend a T22 double panel with double fins as that is about 3.2 kW and give a bit of extra output for very cold weather and increase the boiler efficiency a little. You only fit the radiator once.

I find the Kudox brand good for looks and reasonable prices and generally well available including from Toolstation.

 

[JohnW2]

You should measure the room temp and then run the fan heater for an hour and measure the new temperature.

Thanks. That's exactly what I am currently doing.

With -1 C outside you need to be able to raise the temperature by 22 C to give you 21 C inside.

Indeed. As I observed, my current fan heater experiments are being undertaken in the context of an outside temp of 11-12 °C, so it could be far worse.

However, extrapolation from the empirical observations is far from straightforward. With 11 °C outside and 21 °C inside,the heating has has tyo raise the temp by 10 degrees. If it were, say +1 °C outside, it would have to raise the temp by double that (i.e. 20 °C). However, the amount of power required to do that will not be double. Certainly in the house in question, no room has more than one outside wall, and that one outside wall is often quite small, with all other walls (and also floors and ceilings in some cases) having fairly modest temperature differences (if any) across them. Dramatic increase in temp difference across that one small wall therefore dose not necessarily have a massive effect on the overall heat loss from the room.

But generally fit the largest rad that you can get to fit in the space so presumably a 500 high and double panel.

Indeed.

An 1800 x 500 double panel T21 will give about 2.5 kW but I would recommend a T22 double panel with double fins as that is about 3.2 kW and give a bit of extra output for very cold weather and increase the boiler efficiency a little. You only fit the radiator once.

Again agreed. I would generally always use T22s, unless there were some good reason not to. The slightly deeper profile does not usually worry me.

I find the Kudox brand good for looks and reasonable prices and generally well available including from Toolstation.

Yes, I've used them in the past. Mind yiou, I'm not sure that there is much difference between any of the makes, in price or anything else. It's interesting that, I presume because of 'larger markets', some sizes of radiators are usually appreciably cheaper than one would expect by looking at other sizes - sometimes to the extent that such an (PPrently) 'preferred size' is appreciably cheaper than smaller ones!

Kind Regards, John