# DELTA T CONVERSION

BS-EN442

It is the legal responsibility of all radiator manufacturers, distributors, wholesalers, and resellers to ensure all hydronic radiators and towel rails conform to the European Standard BS-EN442.

A reseller could also be classified as a contractor, developer, architect, specifier or an M&E consultant and if supplied directly to a client, then technically they are responsible for ensuring the products have been legally tested and certified to BS-EN442 by an accredited laboratory.

Products that conform will have a CE mark (Conformité Européenne) but importantly B2-EN442 states by law, that all hydronic radiator and towel rail outputs are tested and presented at Delta T 50° or ΔT 50°.

What is Delta T?

Delta T, or ∆T, specifically relates to the difference in temperature between the water circulating in the central heating system and that of the ambient or room temperature. If the ambient or room temperature is 20ºC and the mean water temperature inside the radiators is 70ºC, the Delta T or ∆T value is calculated as 70 ºC - 20 ºC = 50º.

Delta T 50° is the UK standard for all domestic gas boilers and is set to allow professionals, end users and consumers alike, make a fair and reasonable comparison of hydronic radiator and towel rail outputs from various suppliers and across a mix of product types.

Delta T Correction Factors - Delta T 50°

###### Delta T Conversion

B2-EN442 states all hydronic radiator and towel rail outputs are tested and presented at Delta T 50° or ΔT 50°. To calculate the output at a different Delta T, enter your output at Δt 50°C and select your required Delta T conversion.

##### Your Calculation Result

Having input your output at ΔT 50°, your correction value output is shown below. For correction factors at Delta T 60°, please use the additional table supplied below.

##### Require Delta

###### Converted Delta

When comparing products ensure you are being quoted Delta T 50°, furthermore look for the MARC logo (Manufacturers Association of Radiators and Convectors) and be sure to request the Declaration of Performance, conducted by an accredited body.

A Delta T correction factor allows end users and professionals to find out the actual output of a radiator or towel rail in the range of Delta T variations, the above calculator has been designed to efficiently calculate this based on an input at Delta T 50°, alternatively, you can use the listed correction factors below, also based on Delta T 50°.

Delta T

Correction

Factors

75°

1.69

70°

1.55

65°

1.41

60°

1.27

55°

1.13

50°

1

45°

0.87

40°

0.75

35°

0.63

30°

0.51

25°

0.41

20°

0.3

15°

0.21

10°

0.12

5°

0.05

Example: Assuming a radiator or towel rail has a heat output of 1000 Watts at ΔT (Delta T) = 50°. At ΔT (Delta T) = 60°, the output would be 1000 x 1.27 (from the table above) equating to 1270 Watts. Alternatively, at ΔT (delta T) = 40°, the output would be 1000 x 0.75 equating to 750 Watts.

Delta T Correction Factors - Delta T 60°

Some older UK boiler systems operate at higher flow and return temperatures and therefore (albeit illegally) some suppliers/resellers may quote radiators and towel rail outputs at Delta T 60° only.

Where Delta T 60° is provided you can use the listed correction factors below, to find the actual output at Delta T 50° and below.

Delta T

Correction

Factors

60°

1

55°

0.906

50°

0.787

45°

0.705

40°

0.605

35°

0.519

30°

0.43

25°

0.344

20°

0.262

15°

0.185

Example: Assuming a radiator or towel rail has a heat output that gives 1000 Watts at ΔT (delta T) = 60°. At ΔT (delta T) = 50°, the output would be 1000 x 0.787 (from the table above) equating to 787 Watts.

At Clyde Radiators, we are proud of our MARC (Manufacturers Association of Radiators and Convectors) affiliation, and our accreditation to BS-EN442.