Capacities/specifications in the fo

Capacities/specifications in the following charts are based on natural gas (0.65 specific gravity and 1000 Btu/ft3 calorific value); #2 fuel oil (140,000 Btu/gal); and #6 heavy oil (150,000 Btu/gal). Other gaseous or distillate fuels such as propane, #1, kerosene and JP-4 may be used in all MULTIFIRE® Burners, but #4 or heavier oils may only be fired in 6" HO MULTIFIRE® Burner. Propane gas may be fired at approximately 40% of the differential gas pressure shown for natural gas. #6 heavy oil must be heated to maintain a viscosity of 90 SSU or less to the burner inlet of 6" HO MULTIFIRE® Burner. Air differential pressure readings are measured between burner inlet (or burner test port connection) and combustion chamber static pressure. MULTIFIRE® Burners are 3-pipe burners with gas and atomizing air flows using the same inlet connection. To achieve the on-ratio minimum capacities shown for gas firing, the differential combustion air pressure must not exceed 0.3" wc. In the oil firing chart (page 4505), operations with excess air at minimum firing rates provide the lower minimum capacities shown as absolute minimum.