large single or smaller double radiator better

[nyck]

My daughter just bought a house and the majority of the rads are very old . when replacing is a large single or smaller double radiator better.
Or is it the BTU rating is the BTU rating . Im thinking the more of the outside/window wall you can heat the better ie: a larger single ??

Also if a room comes to say 3000 BTU on the rad calculator ,how much do you over size or you dont have to ??

thanks

 

[StephenStephen]

I'm thinking that the answers might be helpful if we have an idea of why the radiators are being replaced....?

 

[fixitflav]

My daughter just bought a house and the majority of the rads are very old . when replacing is a large single
Or is it the BTU rating is the BTU rating . Im thinking the more of the outside/window wall you can heat the better ie: a larger single ??

Also if a room comes to say 3000 BTU on the rad calculator ,how much do you over size or you dont have to ??

thanks

In general the higher output (at a given water temperature) the better, as it means more condensation in the boiler or higher CoP if a heat pump is installed.
But it needs a bit of thought in each case.

 

[oldbuffer]

1. Provided the heating is adequate in each room, then replace Btu for Btu.
2. Otherwise do a heat loss calculation and install correct size.
3. If you go single to double or vice versa the new radiator:
3.1 Will have its pipe centres at different distances from the wall. Pipework changes likely to be required.
3.2 If a different width, pipework changes or radiator extensions will be required.
4. Rather than replace:
4.1 Look at each in turn. If no obvious leaks or serious paint flaking, clean and repaint.
4.2 Just take each one in turn off the wall and wash out outside to remove sludge.

 

[nyck]

I'm thinking that the answers might be helpful if we have an idea of why the radiators are being replaced....?

As i mentioned they are and look very old . Single rads with no fins and going by the Stelrad chart undersized for the room .

1. Provided the heating is adequate in each room, then replace Btu for Btu.
2. Otherwise do a heat loss calculation and install correct size.
3. If you go single to double or vice versa the new radiator:
3.1 Will have its pipe centres at different distances from the wall. Pipework changes likely to be required.
3.2 If a different width, pipework changes or radiator extensions will be required.
4. Rather than replace:
4.1 Look at each in turn. If no obvious leaks or serious paint flaking, clean and repaint.
4.2 Just take each one in turn off the wall and wash out outside to remove sludge.

1... Taking a rough guide from the stelrad chart they are under sized by about 400-800 BTU depending on which room
3... Adjusting the pipe work not a problem .. I have all of the gear and a bit of a idea
4..... As mentioned they are very old and having majority of the rooms re-plastered , new rads will look a lot better

thanks

 

[gas112]

Fit whatever looks the best in the space

 

[ericmark]

If the boiler can modulate to 6 kW, then we want to get rid of 6 kW if we can. So with a house full of programmable TRV's we want to be able to turn off radiators in rooms not being used, so we can reasonably expect only two rooms at a time to be used, so we want radiators able to sink at least 3 kW, maybe more. Otherwise, the boiler will start cycling.

We also want the response time to be fast, so the lighter the radiator and the less water it holds, the better.

Ideal would seem to be the fan assisted radiator, it is small for the output it has, and has a matrix (the bit which gets rid of the heat) which is more like a car radiator. But there is a problem, the control is by varying the fan speed, which does not really work when the radiators are plumbed in parallel, they work better when in series, so we are stuck with panel radiators.

They should be mat black, but that does not look good, so we have to consider more what they look like then how well they work. So single, double, or triple panel, more down to what they look like and where they will fit.