The Gas Line BTU Demand Calculator estimates the minimum pipe diameter required for natural gas supply based on total appliance BTU/hr demand, pipe length, and diversity factor. Proper gas line sizing ensures adequate pressure at all appliances and compliance with fuel gas codes.
How It Works
Formula:
Design Demand (BTU/hr) = Total Connected BTU/hr × Diversity Factor (%)Step 1: Calculate Total Connected Load
Sum up (BTU/hr rating × quantity) for all gas-powered appliances.
Step 2: Apply Diversity Factor
Not all appliances run simultaneously. A diversity factor of 70% is typical (30% safety margin).
Step 3: Size Pipe Diameter
Using NFPA 54 / International Fuel Gas Code tables for low-pressure natural gas (0.5 in. w.c. pressure drop, 0.6 specific gravity):
| Pipe Diameter | Max Capacity at 100ft | Max Capacity at 200ft |
|---|---|---|
| 1/2″ | 150,000 BTU/hr | — |
| 3/4″ | 300,000 BTU/hr | 200,000 BTU/hr |
| 1″ | 600,000 BTU/hr | 450,000 BTU/hr |
| 1-1/4″ | 1,000,000 BTU/hr | 750,000 BTU/hr |
| 1-1/2″ | 1,500,000 BTU/hr | 1,100,000 BTU/hr |
| 2″ | 3,000,000 BTU/hr | 2,200,000 BTU/hr |
Formula:
Design Demand (BTU/hr) = Total Connected BTU/hr × Diversity Factor (%)Step 1: Calculate Total Connected Load
Sum up (BTU/hr rating × quantity) for all gas-powered appliances.
Step 2: Apply Diversity Factor
Not all appliances run simultaneously. A diversity factor of 70% is typical (30% safety margin).
Step 3: Size Pipe Diameter
Using NFPA 54 / International Fuel Gas Code tables for low-pressure natural gas (0.5 in. w.c. pressure drop, 0.6 specific gravity):
| Pipe Diameter | Max Capacity at 100ft | Max Capacity at 200ft |
|---|---|---|
| 1/2″ | 150,000 BTU/hr | — |
| 3/4″ | 300,000 BTU/hr | 200,000 BTU/hr |
| 1″ | 600,000 BTU/hr | 450,000 BTU/hr |
| 1-1/4″ | 1,000,000 BTU/hr | 750,000 BTU/hr |
| 1-1/2″ | 1,500,000 BTU/hr | 1,100,000 BTU/hr |
| 2″ | 3,000,000 BTU/hr | 2,200,000 BTU/hr |
| Appliance | Typical BTU/hr |
|---|---|
| Commercial Range (6-Burner) | 150,000 |
| Deep Fryer | 120,000 |
| Broiler | 80,000 – 120,000 |
| Griddle | 60,000 – 100,000 |
| Convection Oven | 60,000 – 100,000 |
| Steamer | 60,000 – 80,000 |
| Hot Water Heater | 50,000 – 200,000 |
FAQ
Q: What is a diversity factor and why is it important?
A: Diversity factor accounts for the fact that not all gas appliances run simultaneously. Using 70% is standard for commercial kitchens.
Q: Can I use this for propane instead of natural gas?
A: This calculator is designed for low-pressure natural gas. Propane has different BTU content and pressure requirements.
Q: What if my pipe run is longer than 200 feet?
A: Longer runs require larger diameter pipes. The calculator accounts for this with the pipe length input.
References
- NFPA 54: National Fuel Gas Code
- International Fuel Gas Code (IFGC)
- ASHRAE Handbook — HVAC Systems and Equipment