22.5 mm DIN-rail fit for level sensing
The RM4LG01B is a liquid level control relay from the Schneider Harmony RM4-L series, occupying 2.5 pitches of 9 mm on a DIN rail — that's a 22.5 mm footprint, so it slots into a standard panel without crowding adjacent control relays or terminal blocks. It detects liquid level through resistive probes, with a sensitivity scale adjustable from 5 to 100 kOhm, covering most conductive liquids from demineralised water to process chemicals.
Output and switching specs for pump control
A single changeover (1 C/O) contact with 90/10 silver-nickel alloy switches up to 250 V AC at 10 mA minimum, and the maximum switching voltage is 440 V AC. The 1.9 VA AC coil draw is light enough that a 24 V control transformer can drive several of these without derating. The electrode circuit is limited to 1 mA at 24 V AC — that's intentionally low to avoid electrolytic corrosion of the probe tips in conductive liquids.
Lifecycle and compliance for BOM planning
Pollution degree 3 per IEC 60664-1 and overvoltage category III mean it's rated for fixed industrial installations where transient overvoltages from the mains supply are expected — typical for a panel-mounted level relay.