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Why Do Same Size Towel Radiators Give Out Different Heat – BTU

Different btu between Delta50 and Delta60 heat outputs and their calculations according to BS EN442 standards and formula to convert Delta50 btu to Delta60 btu

Understanding DeltaT50 vs DeltaT60

When comparing towel radiator heat outputs, you'll often see BTU ratings listed for both DeltaT50 and DeltaT60. These aren't different models - they refer to the mean water temperature differentials used in heat output testing. Here's what this really means:

What Are DeltaT50 and DeltaT60?

DeltaT (ΔT) represents the difference between:

  • The average water temperature inside the radiator

  • The ambient room temperature

The two standard testing scenarios are:

SpecificationWater Temp (Flow/Return)Room TempΔT Calculation
DeltaT5075°C/65°C20°C(75+65)/2 - 20 = 50°C
DeltaT6090°C/70°C20°C(90+70)/2 - 20 = 60°C

 

Why This Matters for Heat Output

  1. Higher ΔT = Higher BTU Rating

    • The same radiator will show 27% higher BTU at ΔT60 versus ΔT50

    • Example: A 600x1500mm large ladder towel rail might be:

      • 2540 BTU at ΔT50

      • 3225 BTU at ΔT60 (2540 x 1.27)

  2. Real-World Implications

    • UK central heating systems typically operate closer to ΔT50 conditions

    • Older systems or commercial applications may reach ΔT60

    • Heat Pump systems will never reach these levels. These are usually at around ΔT30

    • Always compare radiators using the same ΔT standard

How to Choose the Right BTU Rating

For most residential installations:

  • Focus on ΔT50 ratings - more representative of actual performance

  • Use ΔT60 figures only if:

    • You have an older high-temperature system

    • Your installer confirms your system runs at higher temps

  • Use ΔT30 figures if you have a heat pump system

Technical Note: Testing Standards

All reputable manufacturers test to:

  • BS EN 442 (European standard for radiator testing)

  • Uses controlled laboratory conditions

  • Requires specific temperature differentials

This ensures fair comparison between different models when evaluated at the same ΔT.


Key Takeaways:

✅ DeltaT refers to testing conditions, not radiator models
✅ Same radiator shows different BTU at ΔT50 vs ΔT60
✅ Most homes should reference ΔT50 ratings
✅ Always compare using the same ΔT standard