750-96 (revised 2010)
Model CB Packaged Boiler Manual
5-23
5.19 — Oil Heater Thermostat: Series 300, 500, 800, 900
5.19 — Oil Heater Thermostat: Series 300, 500, 800, 900
The electric oil heater on a No. 4 or No. 5 oil fired burner has a built-in adjustable thermostat. The maximum tem-
perature setting is stamped on its dial. Desired temperature can be obtained by turning the adjusting screw using
the thermometer in the fuel oil controller as a guide.
A hot water burner burning No. 6 oil and equipped with a hot water oil heater also uses this type of electric heater
and thermostat. In this case, the thermostat should be set at a sufficiently lower temperature (approximately 15º)
than the hot water heater thermostat. This eliminates the electric heater from operation when the water heater is
functioning. The electric heater is sized to provide sufficient heated oil for low fire operation on cold starts before
hot water is available.
5.20 — Steam Oil Heater Thermostat: Steam, No. 6 Oil, Series 400, 600
The maximum temperature setting of the control is stamped on the dial. This is attained with the adjusting knob
turned to the “high” end of the scale. Lower settings are obtained by turning the adjusting knob clockwise using
the thermometer in the fuel oil controller as a guide.
The final setting of this thermostat should provide oil at a sufficient temperature for efficient combustion based on
flue gas analysis. There is no need to heat the oil in excess of this temperature.
A 0.005 MFD capacitor is wired in parallel with the thermostat lead connections to prevent contact bounce and
arcing. The control differential is non-adjustable.
5.21 — Hot Water Oil Heater Thermostat: Series 400, 600
To adjust, insert a screwdriver into the center slot in the control cover and turn the dial until the pointer is at the
desired temperature level. This control generally has a set differential and will close 5º F below the set point.
The thermostat contacts close to energize the booster water pump which pumps water from the boiler through the
heater. On cold starts it is normal practice to manually close the valve in the pump discharge line until boiler water
temperature exceeds the temperature of fuel oil entering the heater.
The electric oil heater on a hot water boiler burning No. 6 oil and equipped with a hot water oil heater has a built-in
adjustable thermostat. The maximum temperature setting is stamped on its dial. Desired temperature can be
obtained by turning the adjusting screw. The thermostat should be set at a sufficiently lower temperature (approxi-
mately 15º) than the hot water heater thermostat. This eliminates the electric heater from operation when the
water heater is functioning. The electric heater is sized to provide sufficient heated oil for low fire operation on
cold starts before hot water is available.
5.22 — Steam Heater Pressure Regulator: Steam, Series 400, 600
This regulator is provided on a boiler designed to operate at pressures above 15 psi for the purpose of reducing
boiler steam pressure to the level necessary for proper operation of the steam oil heater. This pressure should be
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