Supply Air Boiler Room
Reference data and engineering information about supply air boiler room for hvac systems applications.
Overview
Engineering reference data for Supply Air Boiler Room in HVAC systems.
Key Formulas
Sensible Heat
Heat causing temperature change.
Latent Heat
Heat causing moisture change.
COP (Cooling)
Coefficient of performance.
Variables
| Symbol | Description | Unit |
|---|---|---|
| Heat transfer | W | |
| Mass flow rate | kg/s | |
| Specific heat of air | J/(kg·K) | |
| Temperature difference | K |
Code Requirements Comparison
Below is a consolidated comparison of air supply requirements from the major referenced codes and standards.
Code / Standard | Fuel Type | Outdoor Opening | Vertical Ducts | Horizontal Ducts | Min. Duct Dim. (in) | Wood Louver Free Area | Metal Louver Free Area | Damper Interlocked |
|---|---|---|---|---|---|---|---|---|
| NFPA 54 | Gas | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 2,000 Btu/h | 3 | 20-25% | 60-75% | Yes |
| NFPA 31 | Oil | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 2,000 Btu/h | 3 | 20-25% | 60-75% | Yes |
| BOCA | All | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 2,000 Btu/h | 3 | 25% | 75% | Yes |
| SBCCI | Gas/Oil | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 4,000 Btu/h | 1 sq. in. per 2,000 Btu/h | 3 | - | - | - |
| SBCCI | Solid | 2 sq. in. per 1,000 Btu/h | - | - | 3 | - | - | - |
Source: Extracted from engineeringtoolbox.com
Critical Safety Note
The ASME rule of 1 square inch of free area per 2,000 Btu/hr of total burner input is a widely accepted, practical starting point for sizing boiler room air intakes. Always round up to the next standard opening size.
Important: Temporary air sources (e.g., open windows, doors) are unreliable and dangerous. Occupants may close them in cold weather, leading to incomplete combustion, carbon monoxide generation, and a severe risk of furnace explosion from re-ignition of accumulated fuel. Permanent, unobstructed, and code-compliant air supply openings are essential for safety.