1. What is a Combi Boiler Size Calculator?

Definition: This calculator estimates the required size of a combi boiler in kilowatts (kW) based on the heat output in British Thermal Units per hour (BTU/h).

Purpose: It helps homeowners and heating professionals determine the appropriate boiler size for efficient heating and hot water production.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P_{kW} \) — Boiler size in kilowatts (kW)
• \( Q_{btu} \) — Heat output in British Thermal Units per hour (BTU/h)

Explanation: The formula converts BTU/h to kW using the conversion factor 3412 BTU/h = 1 kW.

3. Importance of Proper Boiler Sizing

Details: Correct boiler sizing ensures energy efficiency, adequate heating capacity, and prevents short cycling or insufficient heating.

4. Using the Calculator

Tips: Enter the heat output in BTU/h (typically calculated based on property size, insulation, and climate). The value must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is 3412 the conversion factor?
A: 1 kW is equivalent to 3412.142 BTU/h, which is the standard conversion factor between these units.

Q2: How do I find my heat output in BTU/h?
A: Calculate based on your home's square footage (typically 30-60 BTU/sq ft) or use a heat loss calculation.

Q3: What's a typical combi boiler size for a home?
A: Most UK homes need 24-35 kW combi boilers, while larger homes may need up to 42 kW.

Q4: Should I round up the calculated boiler size?
A: Yes, it's common practice to round up to the nearest standard boiler size for safety margins.

Q5: Does this account for hot water demand?
A: Combi boilers must meet both heating and hot water needs - this calculation assumes the heat output includes both requirements.