High Limit Switch - Navien NCB-150E Service Manual

4.9.2 High Limit Switch

Part
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 230 °F or 110 °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: Check wire connections are secure.
2. Resistance check: Check range of resistance shown below.
Resistance range: under 1.0 Ω
Check Point
System Details 65