Gas
Gas volume demand from heat input
- where
- gas volume demand (m³/s; the calculator shows m³/h)
- heat / power rate (W; any unit you pick is converted)
- calorific value at volume reference conditions (J/m³; any unit you pick is converted)
Explain this equation
Turns an appliance heat input into the gas volume it needs per hour. You use it when adding up appliance demands for pipe sizing tables or checking a meter can cope.
P is the heat input rate of the appliance. It must be the input, not the useful output, because the burner consumes gas to cover its losses as well. cv is the energy in each cubic metre of gas at the reference conditions the volume is measured at.
Energy per second divided by energy per cubic metre leaves cubic metres per second, which the calculator shows per hour. It is the gas-input equation turned around, with no correction factor.
Sense check: 24 kW at 39.5 MJ/m³ (about 11 kWh/m³) needs roughly 2.2 m³/h. A quick mental version is kW ÷ 11.
Watch out: this gives demand only. Summing appliances and choosing a pipe size must follow the applicable sizing method.
Enter your values to see the result.
Good to know
Use appliance heat INPUT, not useful output. Sum downstream appliance demands per the applicable sizing method; this does not select a pipe size.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.