Radiator Sizing Calculator UK Stelrad

Radiator Output Formula:

\[ Output = nominal \times \left(\frac{\Delta T}{50}\right)^{1.3} \]

Actual Output (W):

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1. What is a Radiator Sizing Calculator (Stelrad UK)?

Definition: This calculator determines the actual heat output of a radiator based on Stelrad's UK formula, using nominal output and temperature difference.

Purpose: It helps heating engineers and homeowners correctly size radiators for efficient room heating.

2. How Does the Calculator Work?

The calculator uses Stelrad's formula:

\[ Output = nominal \times \left(\frac{\Delta T}{50}\right)^{1.3} \]

Where:

\( Output \) — Actual radiator output (Watts)
\( nominal \) — Manufacturer's nominal output at ΔT50 (Watts)
\( \Delta T \) — Temperature difference between mean water temp and room temp (Kelvin)

Explanation: The formula adjusts the nominal output based on your system's actual operating temperature difference.

3. Importance of Correct Radiator Sizing

Details: Proper sizing ensures efficient heating, prevents under/over heating, and optimizes energy consumption.

4. Using the Calculator

Tips: Enter the radiator's nominal output (from manufacturer specs) and your system's ΔT (typically 30K-60K for UK systems).

5. Frequently Asked Questions (FAQ)

Q1: What is ΔT in radiator calculations?
A: ΔT is the difference between mean water temperature ((flow + return)/2) and desired room temperature.

Q2: Why is the exponent 1.3 used?
A: The 1.3 exponent accounts for non-linear heat output characteristics of radiators at different temperatures.

Q3: What's a typical ΔT for UK systems?
A: Traditional systems run at ΔT≈50K, modern condensing boilers often use ΔT≈30K-40K for higher efficiency.

Q4: Where do I find nominal output?
A: This is provided in radiator manufacturer specifications (output at ΔT50 standard conditions).

Q5: How does this affect radiator sizing?
A: Lower ΔT requires larger radiators to deliver the same heat output as at higher ΔT.