Meaning of Delta 50 (75/65/20)
Delta 50° (75/65/20)  with Delta T of 50°C, means 75°C inlet water temperature, 65°C outlet water temperature and 20°C of room temperature. The average water temperature in this example is 70°C (i.e. 75° plus 65°, divided by 2). If we then take the 20°C room temperature we are left with a temperature differential of 50°C or Δt 50°.
Method 
Add the flow water temperature and the return temperature together
Divide the answer by 2
Subtract the room temperature from the answer this gives you the Delta T temperature
Select the closest Delta T valve from the table and multiply the corresponding factor by the output provided for the particular radiator to obtain the output for your calculated Delta T valve.
If we then take into account the reduced inlet temperature eg you will be getting a heat source pump.
If we replace this with inlet water at 4
5°C inlet water temperature, 35°C outlet water temperature and 20°C of room temperature. The average water temperature in this example is 40°C (i.e. 45° plus 35°, divided by 2). If we then take the 20°C room temperature we are left with a temperature differential of 20°C or Δt 20°.
The conversion rate from T50 to T20 is 0.3039.
Eg a radiator 1800 x 500 has 795 Watts at Delta T50 x 0.3039 is 241 Watts (this is the T20 figure).
If we use another Heat Source Pump, water temperature leaving our system will be 60 degrees returning at 50 and the Delta figure will be 35 degrees.
Eg at Delta 50 say the radiator has a BTU of 3,500.
To convert this to Delta 35  3,500 x 0.6290 is 2,202
If we have the figure of at Delta 35 and we want to convert to Delta 50
2,202 / 0.6290 is 3,500 BTU
Btu Value T50 
T50 to T35 (T50 x 0.6290) 
Equivalent T50 figure to give the required T35 is T50 / 0.6290 



3776 
2375 
6003 
3349 
2106 
5324 
3780 
2377 
6009 
5405 
3399 
8593 
2368 
1489 
3764 



4513 
2838 
7174 
4009 
2521 
6373 
5125 
3223 
8147 
2755 
1732 
4379 
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 endusers 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 input at Delta T 50°, alternatively, you can use the listed correction factors below, also based on Delta T 50°.
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.
Meaning of Delta 50 (75/65/20)
Meaning of Delta 50 (75/65/20)
Delta 50° (75/65/20)  with Delta T of 50°C, means 75°C inlet water temperature, 65°C outlet water temperature and 20°C of room temperature. The average water temperature in this example is 70°C (i.e. 75° plus 65°, divided by 2). If we then take the 20°C room temperature we are left with a temperature differential of 50°C or Δt 50°.
Method 
Add the flow water temperature and the return temperature together
Divide the answer by 2
Subtract the room temperature from the answer this gives you the Delta T temperature
Select the closest Delta T valve from the table and multiply the corresponding factor by the output provided for the particular radiator to obtain the output for your calculated Delta T valve.
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 endusers 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 input at Delta T 50°, alternatively, you can use the listed correction factors below, also based on Delta T 50°.
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.