750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
2-11
2.7 — Additional Controls for Heavy Oil
2.7 — Additional Controls for Heavy Oil
The oil heater steam is provided to heat heavy oil to the point where it can be effectively atomized and burned.
Most heavy oil heaters utilize an electric heater to reduce the viscosity of the heavy oil until the point where either
steam or hot water is available. Heavy oil heaters operating with hot water will have additional controls not shown
in Figure 2-11.
FIGURE 2-11. Oil Heating Assembly (Steam)
Component Description
Heater Switch (not shown) Manually provides power to the oil heater system.
1. Oil Heater (Electric) Used for heating sufficient fuel oil for low-fire flow during cold starts before steam
or hot water is available for heating. The heater must be turned off during extended
boiler lay up, or at any time the fuel oil transfer pump is stopped.
2. Oil Heater Thermostat
(Steam)
Senses fuel oil temperature and controls the opening and closing of the steam
heater valve to maintain the required temperature of the fuel oil.
3. Oil Heater Thermostat (Elec-
tric)
Senses fuel oil temperature and energizes or de-energizes the electric oil heater to
maintain required temperature of the fuel oil.
4. Oil Heater Shell (Steam/Hot
Water)
Heats fuel oil through medium of steam or hot water. electric heater is housed in
the steam heater, but is housed separately on a hot water heater. Steam oil heaters
on 15 psi boilers operate at boiler pressure. Steam oil heaters furnished on high
pressure boilers are to be operated at less than 15 psi. Operation is accomplished
with a steam pressure regulator valve.
5. Oil Return to Tank Excess oil returned to the heavy oils supply tank.
6. Oil Inlet from Supply Tank Heavy oil inlet from the supply tank.
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