Groen capcold DH/INA/2-100, Руководство оператора

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OM-DH/INA/2-100 21
Sequence of Operation
The following “action-reaction” outline is provided to help service personnel understand
how the unit functions for systematic troubleshooting and fault isolation.
When the operator turns the heat to “ON”, electric power at 120V is supplied to the
thermostat. The automatic gas control is then energized. Simultaneously, an electric
arc is established at the spark gap, and the automatic valve for the pilot burner opens.
When the electric spark ignites gas flowing from the pilot burner, a pilot flame probe
detects the flame. The probe sends a control signal that causes the spark to shut off and
a circuit to close for 24 V power.
The 24 V provides power for the heating indicator light and the main automatic valve.
Gas flowing from the main burner is ignited by the pilot flame. If a pilot flame is not
sensed within 60 seconds after the spark, a timer shuts down the whole operation.
As heat from the main burner brings the temperature of steam in the jacket up to
the thermostat setting, the thermostat switch opens. With electric power cut off, the
main burner valve closes and turns off the burner. When jacket steam cools below the
thermostat set point, the thermostat switch closes and begins another heating cycle.
On-off cycling continues to maintain the kettle at the desired temperature.
The thermostat controls heating by alternately calling for flames at the full capacity of
the main burner or signaling the control to shut the burner completely off. Because the
control works in this “all or nothing” way, the kettle will heat as fast as it can until it
reaches the set temperature, no matter what that temperature is.Turning the thermostat
dial to a higher setting will cause heating to continue longer, until the kettle reaches the
higher temperature, but it cannot make the unit heat any faster.
The unit is equipped with a Pressure Limit Switch, Low Water Cut-Off and a Safety
Valve. These safety features operate as follows:
1. Pressure limit switch: If jacket steam pressure exceeds 43 PSI, the switch opens and
breaks the electrical circuit to the main gas valve solenoid coil. The valve closes and
stays closed until jacket pressure decreases to 44 PSI. The pressure limit switch
then closes, energizes the gas valve coil, and allows operation to resume.
2. Low-water cutoff: As long as steam jacket water touches the cutoff electrode, kettle
operation can continue. If the water falls below the end of the electrode, an electrical
control circuit is broken, and the main gas valve closes. Jacket water must be
restored to a safe operating level before the kettle can be heated again.
3. Safety valve: If steam pressure in the jacket reaches 50 PSI, the valve will open and
relieve the excess pressure.