750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
6-27
6.28 — Steam Oil Heater Thermostat: No. 6 Oil, 400 and 600 Series (Steam)
The final setting of this thermostat should be at a temperature approximately 15º F lower than the steam heater
thermostat. This eliminates the electric heater operation when the steam heater is functioning. The electric heater is
sized to provide sufficient heated oil for low-fire operation on cold starts before steam is available.
6.28 — Steam Oil Heater Thermostat: No. 6 Oil, 400 and 600 Series (Steam)
The maximum temperature setting of the control is stamped on the dial. The maximum temperature setting 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 the 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 the temperature required for proper flow.
6.29 — Hot Water Oil Heater Thermostat: 400 and 600 Series
To adjust the thermostat, insert a screwdriver into the center slot in the control cover and turn the dial until the
pointer is at the desired temperature level. The control generally has a set differential, and will close 5º F below the
setpoint.
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 the 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. The desired temperature can be
obtained by turning the adjusting screw. The thermostat should be set at a temperature approximately 15 degrees
lower than the hot water heater thermostat. Such a temperature prevents 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.
To Next Page
Loading...
