750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
2-13
2.8 — Controls for Combination Burners Only
FIGURE 2-12. Heavy Oil Controller
2.8 — Controls for Combination Burners Only
Gas-Oil Switch: Burners equipped to burn either oil or gas include
equipment for each fuel. The selector switch engages the appropriate
interlocks and controls for gas or oil operation. Chapter 4 details the
required mechanical functions of each fuel system.
FIGURE 2-13. Control Panel with Gas-Oil Selector Switch
H. Orifice Oil Control Valve Valve may be opened prior to startup to aid in establishing fuel oil flow through the
controller. The valve must be closed prior to initial light off. Its disc has an orifice
to permit a continuous circulation of hot fuel oil through the controller.
I. Air Purge Valve Solenoid valve opens simultaneously with closing of oil solenoid valve at burner
shutdown, allowing compressed air to purge oil from the burner nozzle and adja-
cent piping. The oil is burned by the diminishing flame, which continues burning
for approximately 4 seconds after the oil solenoid valve closes.
J. Air Purge Orifice Nozzle Limits purging air to proper quantity for expelling unburned oil at normal delivery
rate.
K. Air Purge Orifice Nozzle Fil-
ter
Filters the purging air of any particles that might plug the air purge orifice nozzle.
L. Air Purge Check Valve Valve check prevents fuel oil from entering the atomizing air line.
M. Air Purge Relay When energized, controls operation of the air purge valve.
Component Description
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