MACH® Gas-Fired Boiler
Page 36
High Fire Setting
Set boiler to the “BNR ON TEST HI”, as described above, to achieve maximum firing rate of the boiler. Check
combustion readings using a combustion analyzer. If combustion readings are not in accordance with Table of
Combustion Exhaust Settings, adjust as follows:
Remove the flat, round, plastic cap from the gas valve. Using a 3mm (7/64”) hex wrench, adjust the high fire screw
(see the figure below) on each of the gas control valves by turning clockwise or counterclockwise to achieve the
desired CO
2
or O
2
level; see Table 3-1 for correct settings. (There will be a time delay between the adjustment and
the response of the CO
2
/O
2
combustion analyzer). Adjust the settings in small increments. When desired adjustments
are complete, reinstall the blue plastic cap on the gas valve. Clockwise rotation decreases gas flow.
Counterclockwise rotation increases gas flow.
Low Fire Setting
Set boiler to the “BNR ON TEST LOW”, as described above, to achieve minimum firing rate of the boiler. Check
combustion readings using a combustion analyzer. If combustion readings are not in accordance with Table of
Combustion Exhaust Settings, adjust as follows:
Remove the gray cap on the gas regulator using a slotted screwdriver. This will expose the low fire adjustment screw.
Using a TORX® T40 or a 5 mm hex wrench, adjust the low fire screw on the pressure regulator (see the figure above)
to achieve the correct CO
2
/O
2
level. Adjustments to low fire should not exceed ¼ turn at a time before allowing the
readings to respond and stabilize. Clockwise rotation increases gas flow. Counterclockwise rotation decreases gas
flow. After the low fire adjustment is made, reinstall the slotted cap on the regulator.
NOTICE! The rotation of the Low Fire adjustment screw is opposite to the High Fire adjustment screw.
Following all gas valve adjustments, check for proper light-off and verify correct fuel/air mix and combustion quality
throughout the entire firing range (from low fire to high fire).
3.11.3 Checking Flame Signal
Using the control panel, enter the information mode and scroll down to FLAME SIGNAL. When the boiler is firing, the
FLAME SIGNAL will be displayed in units of µA.