Phoenix Contact PLC-RSC-24DC/21 Interface Relay Module

The Phoenix Contact PLC-RSC-24DC/21 is a 24 V DC coil DIN-rail interface relay module from the PLC-RSC (Relay Single-Pole Contact) series, providing galvanic isolation between a PLC digital output or DCS discrete output card and a field device, motor contactor, solenoid valve, or control circuit. The relay module contains a miniature electromechanical relay with a 6 A / 250 V AC single-pole changeover contact (SPDT: 1 NO + 1 NC) that is activated by a 24 V DC coil rated at 0.5 W power consumption. The DIN-rail mounted module includes a plug-in relay socket that allows relay replacement without tools and without disturbing the terminal wiring — an important feature in Saudi plant DCS rooms where relay replacement must be performed during plant operation without causing associated I/O point trip. The module incorporates a coil LED indicator (green when energised), a mechanical relay status flag, and a test button that allows manual relay actuation for commissioning verification without applying DCS output commands — useful during pre-startup instrument loop checks in ARAMCO and SABIC process facilities.

The galvanic isolation provided by the PLC-RSC interface relay is a safety and signal-integrity requirement on all ARAMCO DCS and ESD panel designs. Saudi Aramco's engineering standards require galvanic isolation between PLC/DCS electronic output circuits and field-device operating circuits (solenoid valve coils, motor starter coils, pilot lamp circuits) to prevent field-wiring earth faults or high-voltage transients from reaching the DCS I/O card bus, which could cause multiple I/O card failures and a widespread process upset. The PLC-RSC module's 4 kV impulse withstand between coil and contact sides (per IEC 60950-1 reinforced insulation) ensures that even a direct lightning transient entering via a solenoid valve field cable (a realistic scenario in Saudi open-desert installations) does not propagate to the PLC bus. Additionally, the contact side circuit can operate at 24 V DC to 250 V AC — allowing a single PLC-RSC module to interface a 24 V DC PLC output to either a 24 V DC solenoid coil or a 230 V AC motor contactor coil, depending on field device design, without changing the module.

The PLC-RSC-24DC/21 is a standard component in ARAMCO and SABIC DCS and ESD panel marshalling sections, used to interface DCS I/O cards to all field actuators where galvanic isolation is required — which in ARAMCO's design philosophy means virtually every DCS discrete output to a field device in Zone 1 or Zone 2 classified areas (where the isolation also forms part of the intrinsic safety or Ex e certification boundary), and all ESD solenoid valve outputs regardless of area classification. Saudi panel builders in Jubail and Yanbu stock PLC-RSC modules as a standard panel component, consuming thousands of units per year across ARAMCO EPC and SABIC expansion projects. The NEOM smart-city BMS panel system uses PLC-RSC interface relays to provide isolation between the Building Management System (BMS) controller outputs and the field-mounted actuators — electric damper actuators, fan motor starters, and valve solenoids in the smart-building HVAC and lighting control systems across Sharma, Sindalah, and OXAGON.

Razz Middle East maintains comprehensive PLC-RSC stock — 24 V DC coil, 120 V AC coil, and 230 V AC coil variants, both single-pole (SPDT) and double-pole (DPDT) contact options — in Riyadh and Jeddah, with same-day dispatch capability. We supply PLC-RSC modules with matched Phoenix Contact CLIPLINE UT 2.5 terminals and PTF 14-PE/24DC relay base sockets in pre-assembled strip configurations, reducing panel-build time for Saudi EPC panel fabricators. All PLC-RSC-24DC/21 supplies include Phoenix Contact CE declarations, IEC 61810-1 test reports, and SASO import conformity documentation.