Replacing single radiators with double convectors

[kitchenlights]

We are getting the single radiator in the kids room replaced as it's a tiny single one heating a huge room which is always freezing.

There are 7 others, how worthwhile is it to replace all of them bearing in mind cost of a plumber?

Two are in small warm bathrooms, one in cold hallway, one in another bedroom and one in our room. Our room also has a single bay radiator which would be hugely expensive to replace so I'm minded to leave that one and should probably leave the other to match? Or not?

Is it more efficient to have a double convector in small room and just keep it turned down, than a single?

What would you do? Especially piglet John..

be sure you get a thermostatic radiator valve fitted, then you will not waste energy overheating the room, but it will warm up quicker.

A long low radiator heats the room more evenly than a short tall one, but if your rad is fairly modern, you may be able to get a double of exactly the same length, and it will fit the old pipes, which is less work than repositioning them. If your pipes come out of a concrete floor, it is very wearisome to move them.

If you have TRVs, you don't need to "turn the radiators down," they will automatically shut themselves when the room reaches your chosen temperature. The room will be more comfortable with a large radiator, warm, than a small one, very hot. The bigger radiators will also be capable of keeping the room warm on those exceptionally cold nights that are colder than the nominal standard winter temperature in the builders' ready-reckoners.

Housebuilders in particular like to fit the smallest possible radiators, because they are cheaper than big ones.

Modern boilers, especially combis, usually have ample power. In the very unlikely event that the output of all your radiators added together total more power than the boiler can supply, they will just run cooler until some of the rooms warm up and the heat demand drops.

Most of mine are about double the calculated size, because it warms the house faster from cold and I used to be away a lot. I changed them as and when each room got decorated.

Yes bigger radiators are just generally better, actually I am changing the one radiator in our lounge to 3 very short but long ones. This gives an even great but also we can run the boiler on a very low setting. Boilers run a lot more efficiently I'd you turn then down to a low water temperature. So definitely do it if you have the space.

We've just done this ready for winter as we were so cold last year!
We figured for the cost of gas chewing on trying to get the house warm (old stone house, not many doors!) with the small, undersized, badly placed rads it would pay for itself by putting doubles/larger ones in

Thank you we have trvs although a lot of them don't seem to work, so labour wise probably worth probably worth replacing radiator too once that's being done. Drayton trv4 per piglet John recommendation.

New rads would be same size and shape, agree about moving pipes

TRVs do sometimes fail, though the Drayton is a very good one.

If other brands, you can try easing the pin with a soupspoon and a tenth of a drop of WD40. If the thermohead has failed from age you might be able to get a new one to fit (doubtful with budget brands).

The other TRV I am very fond of is the RAS C2 by Danfoss which is also a more reasonable price.

I'm replacing three single radiators with modern double convector ones and TRVs as am having the rooms replastered so seemed like a minima additional cost once you've paid for the labour to take them off and on.

Thanks for the TRV link PigletJohn.

Where do you get unusual sized rads from? Height is flexible but I have widths of 715, 550, 930 and I can only find whole numbers of metres.

It's possible that your old ones were feet-and-inches sizes.

Here are some off-the shelf sizes from a FMCG dealer:

Height
300 mm(34)
400 mm(42)
500 mm(88)
600 mm(92)
700 mm(42)
1400 mm(1)

Width
400 mm(12)
500 mm(15)
600 mm(32)
700 mm(24)
800 mm(32)
900 mm(24)

And here from a manufacturer www.kudox.com/Files/Website%20Technical/2014%2004%2009%20Kudox%20Steel%20Panel%20Radiators%20Technical%20Data.pdf

You can make small adjustments in fitting width by adjusting the pipes and valve tails.

You may be able to order other sizes, but will need to consult either a local plumbers merchant, or ask a manufacturer.