High Limit Switch - Navien NCB-180 Service Manual

4.9.2 High Limit Switch

Check Point
Function
Failure Event
Effects
Error Code
Diagnostic
Color/Number of wires
1. Overheat prevention switch.
2. If the unit detects extremely high temperatures, it will automatically trip and shut down the unit.
3. Excessively high water temperatures (more than 197.6 °F or 92 °C) in heat exchanger will activate
the high limit switch.
Unable to detect excessively high water temperature if switch fails.
Unable to shut down the boiler if the water temperature from the heat exchanger exceeds 197.6°F
(92°C).
E016, E046
1. Visual inspection: Connection and/or breakage of wires.
2. Resistance check: Check range of resistance shown below.
Resistance range : under 1.0 Ω
Check Point