So you are looking to buy a new towel radiator and you have done your homework. Know exactly what size radiator you need and you have used our BTU Calculator to find out your heat requirements but the search is still on simply because you are confused!
You have seen a few heated towel rails from various online or high street retailers but you are puzzled with fact that same or very similar size radiators gives out different heat. You are asking yourself “How come these two same/similar size radiators gives out different heat?” While your search for the perfect towel radiator may be still on, you have at least come to the right place to get your answer for the question above.
A simple one word answer to your question would be Delta (a.k.a. Delta T). The heat output of a radiator depends on three temperatures; Flow (water entering the radiator), Return (water exiting the radiator) and Room/Ambiance temperature. To ensure that a sensible and accurate comparisons can be made between different products, all radiators are tested in controlled laboratory environment as per BS EN442 standards. From 1st July 1997 all radiators manufactured in the EU must comply with BS EN442 standards and all radiators must be tested using the following temperatures;
Flow = 75℃ (Water Temperature)
Return = 65℃ (Water Temperature)
Room/Ambiance = 20℃
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Flow ℃
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Return ℃
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MWT ℃
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Room Temp ℃
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Delta T
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75
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65
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70
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20
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50
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So the calculation would be;
75 + 65 = 140
140 / 2 = 70 (mean average water temperature)
70 – 20 = 50 (Delta50)
Once we know the heat output of a radiator in Delta50 we can easily convert it to Delta60 by multiplying this figure with “1.264″. Now lets explain where the differences is coming from. If a towel radiator is advertised as 1000 BTU’s in Delta50, it can also be advertised as 1264 BTU’s in Delta60. Radiator is the same and the heat output is fixed but different suppliers may display their towel radiator’s BTUs in different Delta T figures and this is why you may see same or similar size radiators have discrepancies in their heat outputs.
You may now ask yourself; If whole of Europe is using Delta50 and all radiators are tested to Delta50 standards, why here in the UK we are still using Delta60? Prior to July 1997 BS 3528 was used which was based on Delta60 and most plumbers and heat engineers here in the UK are still using Delta60.