What is the voltage limit for requiring an intrinsically safe device on control wiring and motor voltages? This is in regards to a sewage lift station. There is 24VDC normally going to the floats monitoring the wet well level and to control the pump operation. We also have a SCADA/BYPASS system (in the lift station control panel) that we can switch to in the event the PLC fails to control the pumps. This system, at present, would then use 120VAC or 24VAC (depending on the lift station) float voltage to monitor the wet well level and control the pump operation. Articles 501 & 504 is the sections I have been trying to use as a reference.