Size an atmospheric gas burner and its orifice/nozzle for a burner service or furnace/boiler application. Given gas type, desired burner BTU/hr, and supply pressure in inches of water column, compute required orifice diameter, gas flow in CFH, and a recommended regulator/nozzle. This is combustion sizing — distinct from HVAC space-load BTU sizing.
Gas flow in cubic feet per hour is derived from the burner firing rate and the heating value of the fuel: CFH = BTU/hr ÷ BTU/ft³. The orifice is then sized with the standard gas orifice flow equation CFH = 1658 × d² × K × √P, where d is the orifice diameter in inches, P is supply pressure in inches of water column, and K is a discharge coefficient. Solving for diameter: d = √(CFH / (1658 × K × √P)). This sizes a burner's orifice for a given firing rate — it is not HVAC space-load BTU sizing, which accounts for room heat loss.
| Fuel | Heating Value | Typical Supply P |
|---|---|---|
| Natural Gas | ~1,000 BTU/ft³ | 3.5–5" WC |
| LP / Propane | ~2,500 BTU/ft³ | 6–11" WC |
| Butane | ~3,200 BTU/ft³ | 6–11" WC |