Noritz NR501-OD Service Manual page 26

<NRC661 (-DV/-OD)>
Circuit Board Block Diagram
HOT
FREEZE PREVENTION
HEATER
DC140V
DC12V
PRIMARY
SECONDARY
DC15V
15V POWER CIRCUIT
GND
HIGH LIMIT
SWITCH
SOLENOID VALVE 0
VARISTOR
RELAY 1
DC140V
POWER
COMBUSTION FAN
CONTROLLER
RELAY 2
WATER FLOW SENSOR
C A
WATER SERVO - MAIN
B
RELAY 1
GAS PROPORTIONING VALVE
POWER CONTROL CIRCUIT
RELAY 2
FLAME DETECTING CIRCUIT
WATER LEVEL ELECTRODE DETECTION CIRCUIT
THERMAL FUSE
GAS SOLENOID VALVE
DRIVING CIRCUIT
SOLENOID VALVE 1
SOLENOID VALVE 2
SOLENOID VALVE 3
NEUTRAL
10A(FUSE)
VARISTOR
VARISTOR ARRESTER
EARTH
IGNITER E
IG
GND
D
FLAME ROD EARTH
5V POWER CIRCUIT
26
Minimum Manifold Pressure Set Button
FAN CONTROL
FAN
OUTPUT
A
PULSE
CONTROL
B
FAN ROTATION
CIRCUIT
SPEED INPUT
C
FAN CURRENT
VALUE INPUT
D
Sub-CPU
E
SUB
CONTROL
UNIT
THERMISTOR
- AIR
THERMISTOR
- HOT WATER
THERMISTOR
- COLD WATER
THERMISTOR
- HEAT EXCHANGER
THERMISTOR
- EXHAUST
< -DV MODEL ONLY >
GND
Y