750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
8-35
8.22 — Combustion
The hot water oil heater contains a heat transfer solution. Oil flows through an inner tube while boiler water sur-
rounds the outer tube. The space between the two tubes is filed with the heat transfer solution and is connected to
an expansion chamber on the rear of the heater. A visual indicator on the chamber reveals the presence of any oil if
an oil leak occurs.
FIGURE 8-38. Circuit Layout for Hot Water Oil Heater
A 50/50 solution of permanent antifreeze and water is generally used as the heat transfer solution. If there is no
danger of freezing, plain water may be used as a replenishment if necessary to refill.
Evidence of oil in either the steam heater condensate or in the water heater indicator demands prompt repairs.
8.22 — Combustion
The frequency of burner adjustments depends upon several factors, including:
• Type of burner.
• Type of fuel.
• Load conditions.
• Ambient temperature.
• Climatic variables.
• General maintenance practices.
The air-fuel ratio should be checked monthly in order to alert the operator to losses in efficiency, which do not pro-
duce visible flame change. Any time maintenance is performed on the burner linkage, the air-fuel ratio should be
checked.
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