Help calculating size of new rad..........

[Hallsy]

After dumping an old rad in the summer our living room has only one radiator fitted, and now as the temps are coming down it is starting to get pretty cold!!
I used the B&Q BTU calculator and it said that for my room size I would need 9500 BTU/hour. The living room is pretty much the only heated room downstairs as the kitchen only has the boiler to heat it and hallway/downstair toilet have nor radiators. We have a large double glazed window and patio door, we also have laminate flooring so from this I decided that I would prob need more like 10 or 11000 BTU to keep the room warm enough.
The trouble I have is that I don't know what the output of the the existing radiator is. Can I guess it's output based on similar sized radiators, or as it is older will it be a lot more inefficient?
The existing rad is a double panel, double convector under the window 70" x 16". As an example I looked at a Stelrad double panel, double convector at 450mm x 1600mm so similar in size and that had an output of 7485BTU so would I right to assume my existing rad has an output of around 7000BTU and so I would need say another one of 4000 BTU to keep my room warm enough?

 

[JPC]

its not an exact science...but sounds good. always oversize and fit a TRV to control the room temp and job done...

 

[anjme]

Unless you have a small boiler and it may not take a large radiator or you are very, very energy conscious why not err on the safe side and put a large rad back in with a good quality thermostat valve. Look at the wattage output to gauge how hot the new rad would be, most gas fires sold are about 3 kw output for living rooms and its not often you see a gas fire on full all the time. A larger radiator is not going to be prohibitively expensive so try a large rad.
Yes its not what the green party want to hear but where were they last month when the multi millionaire flew into space in a rocket just for the hell of it. How much energy did that use? Was it really cost efficient?

 

[Hallsy]

Not worried about energy consumption at all, the boiler is very old but I reckon it is up to the job.
I'm really just going for one that fits between the pipework that is left from where the second rad was, and will get a double panel, double convector for extra oomph.

Thing is distance between fittings at the mo is 56" so 1422mm, but most new rads are 1400mm std width so what would I need to do to take up the slack? Set the pipes a little or can I use some sort of extension?

I'll either be adding a 6500 BTU one at 1400x450 or a 8200BTU one at 1400x600.

Can't remmeber what was there but think it was around 600 high, maybe even taller but a single panel so would make sense to get a shorter one but double panel.

 

[anjme]

its possible to purchase radiator tail extensions of various sizes. ask at your local merchant.

 

[MANDATE]

In Wickes last week I saw a pair of valves of the ball type. These were to screw into each end of the radiator between the rad and the existing valves. The idea being to turn off all four valves before removing radiator and having no spillage. The fitting of these may help make up the distance and worth considering.