Help please - radiator planning

18 May 2013
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United Kingdom
Hi all,

I am looking to put new radiators into my lounge in entirely different positions from the old ones (which lost too much wall space). This is a long, rectangular room (just over 8m x 4.3m) that was originally two rooms but has been knocked through. I know the required BTU for the room and I know where the rads will go. There will be three in total - one at each end of the room and one in the middle on the wall that runs the length of the whole space.

I have looked at various options to find combinations of 3 rads that a) fit in each of the three spaces and b) add up to the approximate total BTU required. I now need to decide which combination to go for and would appreciate some advice in making this decision.

The rads will be fitted with TRVs. My queries are:

1) Is it still cost effective to have a total higher possible BTU output than the room requires because the rads will still only heat to the room temp set? Just want to check I haven't misunderstood this. The combinations of rads that fit could exceed the required BTU by 500 up to 3500.

2) Should I consider the output of each of the rads in the 3 positions when deciding - what I mean is, one combination I could go for has a 6000 BTU at one end, 8000 in the middle, and 2500 at the other end. Does the fact that there is an imbalance in the heat output of the rads at the two opposite ends of the room have a big impact, or should the three in combination still heat the space adequately. Is it better to aim for equal BTU capabilities at each end?

I hope that makes sense
Many thanks :)
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I, personally, would go for 3 rads as similar in output as possible to try to keep an even as poss temp throughout the room.
Hi there. Please correct me if I'm wrong at any point, I'm still half asleep. Zzzzzzz... a british thermal unit is a measurement of heat output, much like a KW. So a radiator with a larger surface area will have a higher BTU so in retrospect it will heat a room quicker. You based your calculation on the heatloss of the room etc. And you've found that to heat that room efficiently you require X amount of BTU's. And you will be putting in a higher heat output to heat it.. Given the fact you have TRV's on the rads then providing you have each one set the same then you will not notice a difference in terms of heat in the room. And the theory of "its better to have too much than too little" comes into play. But its a waste of money. You've got the cost of buying the rads. Etc. Then you've got your boiler. If your boiler has been sized correctly for that heat output to heat your house you may put extra strain on it to heat 3 bigger rads etc etc.. so theoretically it is uneffcient. In answe to your second question I would guess the location of the rads would have to be considered I.e the larger one by the window as thats where you will get the most heatloss. And base the design like that.

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