Electronic Controls; Theory Of Operation - Auto Modes - Norcold N611V SERIES Service Manual

Electronic Controls

A precise heat is applied to the boiler area of the cooling
unit causing a chemical reaction within the cooling unit that
ultimately results in the refrigerator cooling. The heat applied is
done so by means of:
• AC cartridge type heater positioned in heater wells
welded to the surface of the boiler
• LP Gas burner positioned below the boiler such
that the heat from the fl ame is directed across the
surface of the boiler
These heat sources are turned on/off via a factory preset
Auto mode. The unit will attempt to operate the heat source
requirements in the following order of priority:
• 1st Priority Choice - Auto AC Mode
While in the Auto AC Mode, the AC cartridge heater
is operated to provide heat to the boiler area of the
cooling unit.
• 2nd Priority Choice - LP Gas Mode
While in the Auto LP Gas Mode, the LP gas burner
is operated to provide heat to the boiler area of the
cooling unit.
A thermistor is mounted on the fi n assembly located inside the
fresh food compartment. The thermistor acts as a temperature
sensor, reporting the temperature sensed to the optical
display. The optical display then relays this information to
the power board that then turns on/off the appropriate heat
source accordingly. The optical display board, power board,
thermistor, and other components within the refrigerator are
interconnected via a wire harness.
Refrigerator Service Manual
Theory of Operation -
Auto Modes
AC voltage is applied to the power board via the AC power
cord at terminals L1 (Hot) and L2 (Neutral). This AC voltage
will pass through the AGC Series, 8A, Fast Acting, Glass Tube
Fuse (F2) where it is then measured. This measurement is
communicated to the optical display board which determines if
the applied voltage is below or above 85VAC. If the voltage is
above 85VAC the determination is that AC voltage is available
and the optical display board will request the power board to
operate via the Auto AC Mode. If the voltage is below 85VAC
the determination is that AC voltage is NOT available and the
optical display board will automatically default to the Auto LP
Gas Mode and request the power board to operate via the
Auto LP Gas Mode (see below). If the control is not able to
establish a fl ame while operating in the Auto LP Gas Mode the
optical display board will:
Automatically default back to the Auto AC mode and wait for
AC voltage to return, displaying the following fault code
• Solid RED power indicator light
Auto AC Mode
When operating in the Auto AC mode the power board
measures the thermistor value and communicates it to the
optical display board. The thermistor, a temperature device
whose internal resistance goes down as the temperature goes
up, is connected to the power board via terminals P2-1 and
P2-6. The optical display board compares the actual thermistor
value to preset cut-in and cut-out temperature values. Should
the thermistor value fall below the cut-in value it will request
the power board to turn ON the AC heater relay (K2). Should
the thermistor value go above the cut-out value it will request
the power board to turn OFF the AC heater relay.
Anytime relay K2 is turned ON, AC voltage is applied to
the AC heater via the now closed K2 contacts. Anytime AC
voltage is applied to the AC heater, AC current is produced.
This AC current is measured by the power board and its
value communicated to the optical display board. The optical
display board determines if the AC current is within specifi ed
limitations. If below the minimum specifi ed limit, the optical
display board will automatically default to the Auto LP Gas
Mode and request the power board to operate via the Auto
LP Gas Mode. AC related faults (Voltage or Current) are not
displayed while operating in the Auto Mode of operation.
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N611v, N811v Models