Navien NFC-175, Service Manual

Page: 65 / 138

NFC Service Manual 65 Version 1.0
4.12.14 3-Way Valve
Part Check Point
Function
Divert the water from the space heating system to the DHW plate heat exchanger and back based
on input from DHW flow sensor and PCB.
Failure Event
1. No hot water in the space heating mode.
2. No domestic hot water in the DHW mode.
Effects
In the case that the temperature of space heating is lower than the set temperature, the water
flow path for domestic hot water will start blocking so that heating water can flow through space
heating pipes.
Error Code E016
Diagnostic
1. Visual inspection: Check the 3-Way Valve connection wire.
2. Voltage check: Check range of voltage shown below.
Color/Number of wires
Black(1)-Blue(2) : ON 102-138 V, OFF 0V
* Confirm voltage as the 3-Way Valve operating