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3) Vacuum Switch
– This boiler is equipped with a vacuum switch that is designed to prevent burner operation if the
combustion fan does not operate properly or there is a blockage in the vent system. This switch “makes” (permits
burner operation) as the vacuum increases. Figure 40 shows the correct method of reading the switch vacuum. The
vacuums in Table 9 are the minimums required for reliable operation. After the boiler fires, the vacuum will drop for
several minutes before stabilizing. The vacuum shown under “Burners On” in Table 9 is the minimum reading which
should be observed after the vacuum has stabilized. The Table 9 readings correspond to sea level vacuum switch
settings. Consult your Crown representative for possible variations in settings at altitudes over 2000ft.
MODELS BURNERS ON
BWF061, BWF095 -0.57 -0.51
BWF128, BWF162 -0.96 -0.89
BWF195, BWF229 -1.21 -1.14
TABLE 9: MINIMUM. VACUUM SWITCH
READINGS (in. W.C.)
DURING
PREPURGE