Navien NPE-180A Service Manual page 161

10.2.1 Basic Principles
The following diagram shows the basic operation of an
NPE-180A/240A water heater system with the H2Air+
controller.
System Diagram
WARNING
A mixing valve must be installed in the system in order to limit
the DHW output temperature and prevent scalding. Setting
the mixing valve to 115–120°F is recommended.
NOTE
Install a spring check valve for vertical pipe runs. Do not use
●
a swing check valve with vertical piping.
Install either a spring check valve or a swing check valve in a
●
horizontal pipe run.
An outdoor sensor and a flow switch are supplied with the
●
product.
Use 18 AWG cables for thermostat wiring.
●
Install NSF certified mixing valves and expansion tanks ONLY.
●
160 NPE Service Manual
10.2.2 Installing the Device in an
add-on
+
Follow the instructions to install the Navien H2Air+
NPE-180A/240A water heater.
1. Turn off the power supply to the water heater.
2. Remove the water heater's front cover by loosening the four
screws securing it to the case.
3. Remove the two screws holding the PCB tray in place and pull
out the PCB tray from the unit.
4. Verify the current PCB version of the NPE water heater.
For OLD PCB Version KDC-330-5M P12: The PCB must be
●
replaced with an updated version. Remove all the cables and
connectors from the PCB and replace with the latest PCB
version that is compatible with the H2Air+
the cables and connectors to the PCB. Proceed to the next
step.
For NEW PCB Version KDC-330-5M P20: The existing PCB
●
can be used. Pull out the PCB from the tray but do NOT
disconnect any cables or wires. Proceed directly to the next
step.
NPE-180A/240A Water Heater
in an
+
kit. Reconnect all
+
Version 2.21