How much heat is convected/radiated by a radiator?

[andyste]

Hi all

A little background: a couple of years ago a plumber fitted a rad in our garage conversion but for whatever reason he put it on the back wall. However it's the front half of the room that is coldest as it juts out from the house, and the walls in this 6 foot or so of the room are thinner than the other walls. Also, the window is I suspect too big for the size of the room (7 ft wide), and despite being uPVC the draught coming off it almost cuts your head off when sitting on the sofa under the window.

Anyway, I was thinking of removing the existing rad and putting a long (e.g. 2200mm) rad under the window. If we kept the sofa up against the rad, I was wondering how much it would affect the heat output of the radiator? i.e. how much heat is radiated from the front of the rad and how much convects up out of the top (assuming I go for a P+ or K2)?

And one last question: the pipes feeding the existing rad come straight down from the ceiling (it was plumbed in under the floor in the bedroom above). If I extend these pipes by another 15ft along the skirting of the garage conversion to the window wall, is it likely to affect the CH system in any way, e.g. flow or anything else?

Thanks in advance
Andy

 

[Agile]

You should KEEP the existing rad and ADD a new one. You can adjust the relative heat outputs with the valves ( and hopefully TRV ).

You might have to rebalance the rads after fitting an additional rad but that should not be any problem.

Allow about 200w/sq m if its reasonably well insulated. The front wall should be meeting the Building Regs for insulation. Or increase it with cavity insulation etc.

Most rads only radiate about 5% of their heat output ( more if painted matt black ).

You should not let a sofa touch any rad as the heat may damage the sofa. Leave a 100 mm gap!

Tony Glazier

 

[andyste]

Thanks for the reply. Just a quick follow-up question: the existing rad is connected by 10mm pipework which comes straight down the wall (connected somewhere under the floor above). If I was to extend this to the other end of the room (approx 18ft) using 10mm speedfit, and fit a rad of approx 8000btu, will the extended pipe run be able to cope, i.e. would the new radiator still get hot?

Thanks again
Andy

 

[gas112]

Have a look on myson /stelrad/ sites they should have info on how much heat is actually convected and radiated out,
And if you google how much heat can a 10mm pipe carry it should bring up the correct answer in kw and btu`s and distances

But dont tee into 10mm and try and run 2 rads it is not designed for that they need to be individual feeds unless very small rads