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Natural Gas Flow

Gas flow measurement involves measuring the volume flow rate and/or total volume over time of fuel gasses (e.g., natural gas or propane), to determine the energy consumption of an appliance or system.

Table—Gas Flow Monitoring Methods
Measurement MethodApproximate Labor Cost @ $100/hrApproximate Equipment Cost
Gas consumption rate by “meter clocking”$100$0
Gas flow gas valve monitoring$150$175
Gas flow using pulse-output meter$500\$500 to $1,000

These costs are approximate costs for installation only. Data retrieval, maintenance, and removal are not included.

To understand combustion appliance in-use efficiency, it is important to properly measure natural gas flow rate into the appliance. Gas volumes vary with pressure and temperature, it is common to have a gas meter with temperature compensation features. Many times, long term monitoring is required to determine installed efficiency for furnaces and boilers or gas water heaters, so robust and reliable gas meters are required.  To properly calculate the amount of heat delivered to the combustion appliance, local heating value must be adjusted properly.

Utility Gas Meter

A utility gas meter is a common type of gas meter used in Building America field tests. A utility gas meter is a diaphragm/bellows type meter and is rugged and reliable for indoor or outdoor use. It’s generally installed downstream of the house utility gas meter in Building America field tests. No upstream or downstream piping clearance is required. Utility gas meters normally come with a temperature compensation feature that adjusts gas volume flow rate reading accordingly.

Indirect Natural Gas Flow Measurement

Directly measuring natural gas consumption of water heaters and furnaces and other natural gas appliances can be expensive and will always require hiring a professional. However, it may be possible to approximate gas flow consumption without the additional cost. When the fuel input rate of an appliance such as a furnace or water heater is fixed (e.g., the appliance does not have a modulating burner), obtain a one-time measurement of the fuel input rate. Once the gas input rate is known, that can be combined with monitoring of the time the gas valve is open to obtain total fuel use over time.

Thermal Mass Gas Flow Meter

One type of gas flow meter that's often used in laboratory and occasionally used in field tests is a thermal mass gas flow meter. This technology works on a constant temperature differential principle. The gas meter uses electronic sensor to maintain a constant delta T between a heated element and the gas temperature. Thus the amount of removed heat from the heated element or the power delivered to the heated element becomes directly proportional to the gas mass flow rate.

Gas Line Pressure

Pressure measurement in fuel gas systems may be of value in estimating flow rates through pilot light orifices or other components, or in validating adequate pressure during operation.