The Flow Switch is the link between the burner shutting down when the Trigger Gun is released. If the burner stays on, the steam-water pressure builds within the coils and will blow the inner coil out. Meaning a small hole will appear which cannot be repaired. When replacing an inner coil, the flow switch should be changed out as well or the same will occur again , blowing out a new coil. If you hear a loud bang, then the coil blew due to a faulty flow switch. This normally occurs when dirt/sand/debris is found flowing through the water of your input garden hose. No other type of flow switch should be substituted for this model switch.
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