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APPENDIX F – ADJUSTING GAS INPUT RATE
Natural Gas Boilers:
1. Turn off gas supply to all appliances other
than gas-red 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).
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.
Do not force the adjustment screw.
6. On models using more than one gas valve,
turn “off” the gas valve not having pilot
control and rst 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 ow 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 ow 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. Do not
reduce more than 0.3” w.c. Instead, contact
Burnham for an orice replacement kit.
14. If input is below 98% of Rating Label input,
increase manifold gas pressure no more
than 0.3 inches w.c. If measured rate is still
less than 98% of rated input, replace or re-
drill existing main burner gas orices:
F-1
F-2