750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
2-9
2.6 — Controls Common to Oil-Fired Boilers (Including Combination)
FIGURE 2-9. Fuel Oil Controller and Relief Valve & Terminal Block
6. Oil Relief Valve Maintains a constant oil supply pressure to the fuel oil controller by bypassing
excess fuel oil.
7. Terminal Block Provides connections for fuel oil supply piping.
8. Fuel Oil Strainer Prevents foreign matter from entering the burner system.
9. Gas Pilot See Section 2.5 for description of the various components.
10. Light Oil Pilot Valve When a light oil pilot is furnished, a solenoid valve is provided to control flow of
fuel to the pilot nozzle. It is energized through programmer contacts. It is de-ener-
gized to shut off pilot fuel flow after the main flame is ignited and established.
11. Back Pressure Orifice A restriction located in the oil return line immediately downstream of the fuel oil
controller to create back pressure (100 and 200 series only).
12. Low Oil Pressure Switch
(optional)
Switch contacts open when the fuel oil pressure drops below selected pressure.
Switch will interrupt the limit circuit upon loss of sufficient fuel oil pressure for
correct combustion.
13. Fuel Oil Pump Transfers fuel oil from the storage tank and delivers it under pressure to the burner
system.
Component/Control Description
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