Understanding radiator sizes

28 Jul 2013
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United Kingdom

I am looking at replacing all the radiators in my house with new ones. The house has very old radiators, but a new boiler, cavity wall insulation and good roof insulation.

My "concern" is that the radiator sizes seem very small when I do room size calculations, so I'm worried that I am doing it wrong.

So I've been using this calculator, which I found recommended on here, http://www.homesupply.co.uk/radiator_output_calculator.php

Putting in my living room size gives me a BTU of 5286. Then according to this for example http://www.plumbnation.co.uk/site/stelrad-elite-double-panel-double-convector-radiator/ I could get a 1100 * 450 to heat the living room.

This seems really small to heat a 5m * 4m space with a 3.2 sq meter window!

Does this sound right? I want to get the right rad, but I'm wary of over specing the system.

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Bear in mind that new radiators have convectors/fins which increase the surface area and therefore the heat output. This means smaller rads for the same heat output as your old rads, assuming they do not have convectors/fins.
If you require the accurate heat calculations, we could provide you with a heatloss calculator or be able to clarify the measurements over the phone in order for you to purchase the correct radiator.
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I have sent an email to you to say unfortunately we are unable to email you the calculator.

However if you can email me your address I will post a disc out in the post tonight.

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