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Before the water heater will operate:
1. The control system must be connected to a 110/120 power supply. This
control system has an overall rating of 12 amps or less. The water heater
must be securely and adequately grounded in accordance with the local
codes or, in the absence of local codes, with the current edition of the
National Electrical Code, ANSI/NFPA 70. The water heater must be
electrically "grounded" by the installer. The unit will not operate unless it is
properly grounded. This should be accomplished by using a grounded
conductor from the service panel to the ground lug located in the junction
box of the water heater
2. The ON/OFF toggle switch, located on the junction box must be in the "ON"
position for the electrical control system of the water heater to operate.
3. The gas knob, located on the gas control valve must be turned to the
"ON" position for gas to be able to flow.
4. The manual shut-off valve between the gas control valve and the burner
assembly must be in the "ON" position.
5. The manual hi-limits must be in the closed position, see "Venting Manual
Reset Switch" in the "For Your Information" section and "Compensating
Thermostat with Manual E.C.O." in the "Temperature Regulation" section.
OPERATIONAL SEQUENCE-
NATURAL GAS MODELS ONLY
When the thermostat calls for heat, a circuit is completed to the blower. When the
blower has achieved sufficient venting, the air pressure switch will close. A 24
volt circuit will be completed through the venting manual reset switch and on to
the ignition module.
The ignition module will then complete a circuit simultaneously to
the spark ignitor, and to the gas pilot valve solenoid. The spark
ignitor will begin sparking and the gas pilot solenoid will open,
allowing gas to pass to the pilot. When a pilot flame has been
established, the flame sensor in the pilot burner assembly will
signal the ignition module, shutting off the spark ignitor. The ignition
module will now complete a circuit to the gas control valve solenoid,
which will open, and allow gas to pass to the burner. Once the
thermostat has been satisfied, the electrical circuits will open and
the burners and blower will shut off.
SAFETY SEQUENCE-
NATURAL GAS MODELS ONLY
During a period when the thermostat is calling for heat and there was an
interruption of the pilot flame, the gas valve solenoid will close instantly shutting
off the supply of gas to the burner. The pilot valve solenoid will remain open
allowing gas to flow to the pilot. The ignition module will complete a circuit to the
spark ignitor, which will begin sparking, and the blower stays on.
1. If the pilot flame is reestablished the gas valve solenoid will open allowing
gas to the burner, and the water heater will resume operation.
2. If the pilot flame is not reestablished the gas valve solenoid will remain
closed. The blower will continue to run. The pilot valve solenoid will
remain open allowing gas to pass to the pilot. The spark ignitor will
continue sparking until the pilot flame is reestablished, or the water
heater is re-sequenced by turning the ON/OFF toggle switch "OFF"
and then "ON".
ROBERTSHAW CONTROL SYSTEM - NATURAL GAS
22
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