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This instructional manual is only intended for use by a qualified service professional or authorized Noritz
Service Representative. Any unauthorized use of this manual may result in voiding the warranty.
Please contact Noritz Technical Support (866-766-7489) for additional support.
SKJ70NL
Rev. 10/13
NR501, NR662 Series Heat Exchanger
Replacement
NR501-OD, NR662-OD
Noritz America Corporation
11160 Grace Avenue, Fountain Valley, CA 92708
Phone 866-766-7489 Fax 714-241-1196
Page 1
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Summarization of Contents
Remove Front Cover and Initial Disconnections
Disconnect Electrical Power
Disconnect electrical power supply to the unit before proceeding with maintenance.
Turn Off Gas and Water Supply
Ensure gas and water supply valves are turned off before starting disassembly.
Remove Cover Screws and Drain Unit
Remove four screws and two drain valves to completely drain the unit.
Remove Circuit Board Cover
Carefully remove the cover protecting the circuit board.
Circuit Board and Wiring Harness Disconnection
Disconnect Circuit Board Connectors
Unplug all connectors from the main circuit board for safe removal.
Remove Ground Wires
Disconnect and remove the two ground wires attached to the unit.
Remove Circuit Board Assembly
Remove the circuit board, unscrewing it from its mounting point.
Unplug Ignition and Flame Rod Wires
Disconnect the Flame Rod and Ignition Plug wires from their connections.
Unplug Freeze Prevention Heater and Thermal Fuse
Loosen cable ties and unplug the freeze prevention heater and thermal fuse.
Unplug High Limit Switch and Thermistor
Disconnect the high limit switch and thermistor for the heat exchanger.
Unplug Remaining Harness Wires (Excluding Water Servo)
Unplug all wiring harness connections except for the main water servo.
Manifold Plate and Water Component Removal
Remove Manifold Plate Screws
Remove three large and two small silver screws securing the manifold plate.
Remove Manifold and Gas Solenoid Connectors
Remove the manifold plate and unplug connectors from the gas solenoid valves.
Disconnect Water Sensor Clamp
Remove the 'C' clamp securing the water flow sensor and water servo main.
Remove Water Flow Sensor
Carefully remove the water flow sensor from its connection.
Heat Exchanger Removal and Component Transfer
Remove Heat Exchanger Set Screws
Remove set screws from the bottom of the burner and the top of the case.
Extract Heat Exchanger Assembly
Remove the copper heat exchanger, burner, and fan as one section.
Separate Burner from Copper Heat Exchanger
Remove ten screws to separate the burner from the copper heat exchanger.
Replace Exhaust Box Gasket
Replace the gasket on the front of the exhaust box with a new one.
Transfer Freeze Prevention Heater
Move the freeze prevention heater from the front side to the new heat exchanger.
Transfer High Limit Switch and Thermistor
Transfer the high limit switch and thermistor from the left side to the new unit.
Replace Thermistor O-Ring
Ensure a new O-ring is fitted for the thermistor during transfer.
Install Freeze Prevention Heater and Route Wires
Attach Thermal Fuse and Clamps
Attach the thermal fuse and six clamps to the heat exchanger.
Route Thermal Fuse Correctly
Ensure the thermal fuse is routed correctly according to diagrams.
Install Thermal Fuse in Stopper
Insert the thermal fuse (White) inside the stopper.
Keep Thermal Fuse Straight
Ensure the thermal fuse is kept straight during installation.
Final Component Installation and Gasket Replacement
Install New Freeze Prevention Heater
Place the new freeze prevention heater and wrap it around the outlet pipe.
Route Wire Correctly
Make sure to route the wire as shown in the provided diagram.
Replace Burner Gasket
Remove the old burner gasket and replace it with a new one.
Install New O-Rings on CU HE
Place new O-rings on the inlet and outlet of the Copper Heat Exchanger (CU HE).
Reassembly of Heat Exchanger and Case
Reattach Burner and CU HE
Attach the burner and the CU HE using ten screws around their perimeter.
Secure Assembly in Case (Bottom)
Secure the assembly back into the case by fastening the bottom set screws.
Secure Assembly in Case (Top)
Secure the assembly back into the case by fastening the top set screws.
Reconnect High Limit, Thermal Fuse, and Freeze Prevention Heater
Ensure high limit switch, thermistor, thermal fuse, and freeze prevention heater are connected.
Reconnect Wiring Harness
Reconnect all wiring harness connections as shown in the diagrams.
Reconnect Water Pipes and Sensor
Connect outlet pipe to water servo, inlet pipe to water sensor, and attach clamps.
Final Component Reinstallation and Leak Checks
Reconnect Gas Solenoid Connectors
Plug the connector to the gas solenoid valves as shown in the diagram.
Confirm Manifold Plate O-Ring
Confirm that an O-ring is present before replacing the manifold plate.
Reattach Manifold Plate to Gas Valve
Replace the two smaller silver screws attaching the manifold plate to the gas valve.
Reattach Manifold Plate to Burner
Replace the three large silver screws attaching the manifold plate to the burner.
Hand Tighten Manifold Screws
Hand tighten all five manifold screws equally.
Replace Drain Valves
Install the two drain valves.
Check for Water Leaks
Turn on cold water slowly, check for leaks around clamps, and re-secure if necessary.
Wiring Harness Reconnection and Finalization
Plug Wiring Harness Connections
Plug all wires that attach to the wiring harness and the body of the water heater.
Route Wires with Cable Ties
Tie wires using cable ties as shown in the diagrams.
Position All Wires
Put all wires in the correct position as shown in diagram (4).
Secure Ground Wire
Secure the ground wire properly.
Circuit Board Reinstallation and Wire Management
Replace and Secure Circuit Board
Replace the circuit board, securing its screw and ground wire.
Reconnect Circuit Board Connectors
Reconnect all connectors to the circuit board.
Reconnect High Limit and Thermistor
Plug the high limit switch and the thermistor for the heat exchanger.
Reconnect Freeze Prevention Heater and Thermal Fuse
Plug the freeze prevention heater and thermal fuse, and tie wires with cable ties.
Reconnect Flame Rod and Ignition Plug
Plug the Flame Rod and Ignition Plug.
Final Wire Arrangement and Cover Replacement
Arrange All Wires as Diagram
Arrange all wires according to the specified diagrams for NR501-OD and NR662-OD.
Replace Circuit Board Cover
Replace the cover for the circuit board.
Perform Gas Leak Check
Turn on gas and check for leaks around manifold plate and joining areas.
Conduct Trial Operation
Turn on the unit and check for proper operation and leaks.
Secure Front Cover
Secure the front cover of the unit with four screws.
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