750-96 (revised 2010)
Model CB Packaged Boiler Manual
1-13
1.10 — Additional Controls for Heavy Oil (No. 4, 5, and 6)
1.10 — Additional Controls for Heavy Oil (No. 4, 5, and 6)
NOTE: Items 6 and 7 are applicable only on a hot water boiler. They may not be provided if other means are avail-
able to supply heated oil.
Control Description
1. Oil Heater Switch Manually provides power to oil heater system.
2. 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 layup,
or at any time the fuel oil transfer pump is stopped.
3. Oil Heater (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 will operate at boiler pressure. Steam oil heaters furnished on high pressure boil-
ers are also to be operated at less than 15 psi. This is accomplished with a steam pres-
sure regulator valve.
4. Electric Oil Heater
Thermostat
Senses fuel oil temperature and energizes or de-energizes the electric oil heater to main-
tain required temperature.
5. Steam Oil Heater
Thermostat
Senses fuel oil temperature and controls the opening and closing of the steam heater
valve to maintain the selected temperature.
6. Hot Water Oil Heater
Thermostat
This control is used on a hot water boiler to sense fuel oil temperature and control the
starting and stopping of the booster water pump to supply hot water to the pre-heating
assembly to maintain the selected temperature.
7. Booster Water Pump Started and stopped by the hot water thermostat to regulate the flow of hot water through
the hot water oil heater to maintain temperature of fuel oil.
8. Oil Heater Steam
Valve
A normally open solenoid valve opened by the steam oil heater thermostat to allow flow
of steam to the steam heater to maintain temperature of fuel oil.
9. Steam Heater Check
Valve
Prevents oil contamination of the waterside of pressure vessel should any leakage occur
in the oil heater.
10. Steam Heater Pres-
sure Regulator
Adjust to provide reduced (usually less than 15 psi) steam pressure to the heater to prop-
erly maintain the required fuel oil temperature. This regulator and the pressure gauge are
not furnished on 15 psi units.
11. Steam Trap Drains condensate and prevents loss of steam from the steam oil heater. Its discharge
must be piped to waste.
12. Check Valve (Steam
Heater Discharge)
Prevents air entry during shutdown periods when cooling action may create vacuum
within the steam heater.
13. Oil Supply Pressure
Gauge
Indicates fuel oil pressure in the oil heater and supply pressure to the fuel oil controller’s
pressure regulator.
14. Low Oil Temperature
Switch
Thermostatic switch that prevents burner from starting, or stops burner firing if fuel oil
temperature is lower than required for oil burner operation.
15. High Oil Tempera-
ture Switch (optional)
Switch contacts open when fuel oil temperature raises above a selected temperature.
Switch will interrupt the limit circuit in the event fuel oil temperature rises above the
selected point.
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