A.O. Smith XB-1000 Instruction Manual page 44

HIGH FIRING RATE SETTING
Set the boiler to the high firing rate by setting the High Firing Rate RPM as described below. Check combustion readings using a
combustion analyzer. If combustion readings are not in accordance with the chart below adjust the gas valve as follows: remove the
flat, round, blue plastic cap from the cover. Using a 3 mm (7/64") hex wrench, turn the adjustment screw counterclockwise to increase
or clockwise to decrease gas flow and achieve the desired CO
time delay between the adjustment and the response of the CO
allow the combustion readings to stabilize before readjusting. When desired adjustments are complete, reinstall the blue plastic cap
on the cover. Combustion samples should be taken in the stack within two feet of the boiler. The carbon monoxide (CO) values in
the combustion sample should not exceed 150 PPM under any circumstances. Contact OEM for any abnormal conditions leading to
excessive CO above 150 PPM.
(APPROXIMATE FACTORY SET)
MODELS (XB/XW)
NATURAL
1000 (920,000)
1300
1700
2000
2600
3400
LOW FIRING RATE SETTING
Set the boiler to the low firing rate by setting the Low Firing Rate RPM as described below. Check combustion readings using a
combustion analyzer. If combustion readings are not in accordance with the chart shown below adjust as follows: remove the cap
on the gas regulator using a slotted screwdriver. This will expose the offset adjustment screw. Using a TORX
wrench, carefully adjust the low fire gas setting to achieve the CO
Note: The rotation of the Low Fire adjustment is opposite of the High Fire as follows: Clockwise rotation increases gas flow,
counterclockwise rotation decreases gas flow.
Adjustments to the offset pressure regulators should not exceed 1/4 turn at a time before allowing the readings to respond and
stabilize.
After proper low fire offset adjustment is made, reinstall the slotted cap on the regulator.
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 lowest to highest fan speed).
Note: Make sure the Manual Mode is set back to Automatic Mode to each of the burners, once the required settings are
done. Turn off the individual burner before proceeding to the next burner settings.
(APPROXIMATE FACTORY SET)
MODELS (XB/XW)
1000 (920,000)
1300
1700
2000
2600
3400
* NOTE: Values listed in Table 19 and Table 20 are tested under laboratory conditions with minimum vent length. Values may slightly vary depending on
ambient conditions and field equipment accuracy.
TABLE 19. HIGH FIRE RATE
RPM
PROPANE
GAS
4450 4750
4850 5100
5700 5700
4700 4750
5700 5100
5700 5700
TABLE 20. LOW FIRE RATE
RPM
NATURAL PROPANE
GAS
1650 1540
1650 1600
1700 1700
1550 1540
1700 1600
1700 1700
level. Refer to the Table 19 for correct settings. There will be a slight
2
measuring instrument. Adjust the settings in small increments and
2
CO
2
NATURAL PROPANE
GAS
8.5 - 9.2% 9.3 - 10.2%
8.5 - 9.2% 9.3 - 10.2%
8.5 - 9.2% 9.3 - 10.2%
8.5 - 9.2% 9.3 - 10.2%
8.5 - 9.2% 9.3 - 10.2%
8.5 - 9.2% 9.3 - 10.2%
level prescribed in Table 20.
2
CO
2
NATURAL PROPANE
GAS
7.3 - 8.2% 8.4 - 8.8%
7.3 - 8.2% 8.4 - 8.8%
7.3 - 8.2% 8.4 - 8.8%
7.3 - 8.2% 8.4 - 8.8%
7.3 - 8.2% 8.4 - 8.8%
7.3 - 8.2% 8.4 - 8.8%
44
*MANIFOLD PRESSURE
INCHES W.C
NATURAL GAS PROPANE
-3.5 -4.7
-3.0 -3.6
-3.6 -4.4
-3.9 -4.9
-3.3 -3.6
-3.5 -4.4
T40 or a 5 mm hex
®
*MANIFOLD PRESSURE
INCHES W.C
NATURAL GAS PROPANE
-0.3 -0.25
-0.2 -0.14
-0.2 -0.23
-0.3 -0.31
-0.2 -0.14
-0.2 -0.23