4.9.2 High Limit Switch
Part Check Point
Function
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.
Failure Event Unable to detect excessively high water temperature if switch fails.
Effects
Unable to shut down the boiler if the water temperature from the heat exchanger exceeds
230 °F (110 °C).
Error Code E016, E046
Diagnostic
1. Visual inspection: Check wire connections are secure.
2. Resistance check: Check range of resistance shown below.
Testing/inspection
information
Resistance range: < 1.0 Ω
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