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:
| Specification | Water Temp (Flow/Return) | Room Temp | ΔT Calculation |
|---|---|---|---|
| DeltaT50 | 75°C/65°C | 20°C | (75+65)/2 - 20 = 50°C |
| DeltaT60 | 90°C/70°C | 20°C | (90+70)/2 - 20 = 60°C |
Why This Matters for Heat Output
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)
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
