The Siemens 3RQ4128-2AB30 is a SIRIUS 3RQ4 coupling relay in the narrow 6.2 mm housing, designed for isolating and switching control signals in industrial panels. It carries a 24 V AC/DC coil and one changeover contact rated at 6 A thermal current, with an integrated H-0-A (Hand-Off-Auto) switch for local override during commissioning or maintenance. The 6.2 mm width saves rail space compared to conventional 14 mm or 17.5 mm relay sockets — useful when packing multiple signal isolators into a control cabinet.
RoHS compliance is confirmed effective 26 September 2024, and REACH candidate-list information is available from Siemens. No UL or CSA listing is stated in the product record, so verify site-specific approval requirements before specifying for a UL 508A panel.
Integration notes
The H-0-A switch protrudes slightly from the face; allow clearance for the switch lever when mounted next to other relays or terminal blocks. Packaged singly (1 piece per unit). Shipping dimensions are 95 x 93 x 65 mm — small enough for consolidated orders with other SIRIUS control gear.