Checking Gas Appliance Input

Verifying Gas Input or Clocking the meter

1. Turn off gas supply to all appliances other than gas-fired boiler.
2. Note the rated manifold gas pressure listed on the boiler’s rating label.
3. Connect Manometer to manifold pressure tapping on Gas Valve (Figure F-1). to verifying input.
4. Light main burners by adjusting thermostat to highest setting.
5. If required, adjust gas manifold pressure to the rated setting by turning the gas valves adjustment screw clockwise to decrease manifold pressure or counterclockwise to increase manifold pressure (Figure F-2). Several turns may be required.
6. On models using more than one gas valve, turn off the gas valve not having pilot control and first adjust the gas valve with pilot control. Then, turn on both gas valves and adjust the gas valve without pilot control.
7. Clock gas meter for at least two (2) revolutions of the dial typically labeled ½ or 1 cubic foot per revolution on a residential gas meter.
8. Determine gas flow rate in Cubic Feet per Hour based on elapsed time for two revolutions. (Example: 70 Seconds for (2) Revolutions = 102.8 Cu. Ft.
9. When the clocked time falls between two table values (Table F-1), add the table values shown above and below your clocked reading and divide by 2 (Example:  68 Seconds for (2) Revolutions = (110.7+102.8) /2 = 106.7 Cu. Ft./Hr.).
10.Obtain gas-heating value (Btu per cubic (foot) from gas supplier or use nominal value of 1000 Btu per cubic foot.
11. Multiply gas flow rate by gas heating value. (Example: 70 Seconds for (2) Revolutions = 120.8 Cu. Ft./Hr. X 1027 Btu/Cu. Ft. = 124,061 Btu/ Hr.
12.Compare measured input rate to input rate stated on rating label. DO NOT EXCEED the boiler’s rated gas input.
13. If input is too high, reduce input rate by decreasing manifold pressure.

Alternate Calculation

1. Turn off all other appliances and pilot flames.
2. If gas meter has a 1 Cubic Foot Gauge
3. Divide 3600 by the number of seconds for the 1 cu ft scale to make one revolution.
4. Multiply the above result by btu of natural gas

40 seconds for 1 revolution
3600/40 = 90
90 * 1050 = 94,500

Disclaimer: The information found on this website is for informational purposes only. All preventive maintenance, service, installations should be reviewed on a per job situation. Any work performed on your heating system should be performed by qualified and experienced personnel only. Comfort-Calc or its personnel accepts no responsibility for improper information, application, damage to property or bodily injury from applied information found on this website as it should be reviewed by a professional.