Application Scenarios

At a regional water-reclamation plant running an ABB AC500-based SCADA, the original I/O design used 32 transitor-output points plus 32 panel-mount ice-cube relays to drive duty/standby blower contactors, penstock solenoid banks, and local alarm horns. The relay panels alone consumed two full 800 mm subracks, and every summer thunderstorm brought at least one spurious trip traced to a sticky relay coil or a loose D-sub crimp on the interposing harness. During a phased MCC modernization, the integrator replaced the entire transistor + interposing-relay layer with four 3ASU21C110​ modules (two racks, 16 channels each). Because each channel on the 3ASU21C110​ carries an 8 A / 250 V AC SPST relay natively, the blower contactor coils (≈120 mA @ 230 VAC) and the 24 VDC solenoid groups (via a single channel-fed distribution fuse) were driven straight off the DO rack. Cabinet footprint shrank by 38 %, wiring terminations dropped from ~190 to ~60, and the operations team logged zero “interposing-relay” tickets across the next 18 months. The plant superintendent’s post-handover remark: “We didn’t just save panel space — we deleted an entire failure class.”

Parameters

Technical Principles and Innovative Values

• Innovation Point 1: True “Direct-Drive” 8 A Capability.​ Most AC500 digital output modules are transistor-type, capped at 0.5–2 A and requiring interposing relays for anything bigger than a pilot lamp. The 3ASU21C110​ flips that convention — each of its 16 SPST relays is rated 8 A / 250 V AC, meaning small motors (< 3 kW), contactor coils, solenoid manifolds, and heater bands can be switched straight from the rack. No ice-cube relays, no marshalling terminal doubling, no “one-more-point-of-failure.”
• Innovation Point 2: Dual-Layer Isolation for Harsh Cabinets.​ Every channel on the 3ASU21C110​ is optically coupled to the AC500 backplane and then physically isolated again by the relay armature gap. This two-stage barrier means a shorted solenoid coil or a 230 VAC inductive kick from a contactor won’t back-feed into the 24 VDC logic side — a common killer of transistor DO cards that the 3ASU21C110​ shrugs off.
• Innovation Point 3: Channel-Level LED + Software Diagnostics.​ Each of the 16 outputs has a front-facing LED (green = energized, off = de-energized; fault behavior varies by firmware), and the DCU30.7​ firmware exposes per-channel status bits to ABB Control Builder. During commissioning, an electrician can glance at the rack to see which solenoid didn’t fire, instead of toggling the PLC logic online to chase a dark output.

Application Cases and Industry Value

In a beverage-bottling line in Southern Europe, the capper turret, filler bowl, and conveyor starwheels were controlled by a mix of Siemens ET 200 and local ABB I/O. The capper alone needed 18 pneumatic valves (24 VDC solenoids, 1.2 A inrush) plus 4 motor-starter contactors. Originally specced with 2 A transistor DO modules plus interposing relays, the cabinet saw three relay failures in the first eight months — each failure cost ~45 minutes of line downtime (~€6 k/hour lost throughput). The integrator re-racked the capper I/O with two 3ASU21C110​ modules: 16 relays on the first card handled all 18 solenoids (two per channel, fused), the second card direct-drove the four contactors. Post-retrofit, the line ran 11 months without a single DO-related stoppage. The plant’s automation lead noted the LU6278​ (their internal storeroom code for the 3ASU21C110) had become their “default DO for anything over 1 amp” across the entire bottling hall.

Related Product Combination Solutions

The 3ASU21C110​ slots into a standard rack alongside these siblings and hosts:

• 3ASU21C109​ — 16-channel digital input module, the natural DI companion in the same mechanical footprint as the 3ASU21C110.
• 3AXM21C110​ — Analog output sibling (4–8 channels, ±10 V / 0–20 mA) often racked adjacent when the same machine needs both DO and AO.
• PM591 / PM595 / PM598​ — CPUs (entry to high-performance) that host the 3ASU21C110​ on the local I/O bus.
• S500 PS5600 / PS5610​ — rack power supplies (24 VDC in, 5 VDC backplane out); the 3ASU21C110​ draws its coil side from the backplane, but the relay-contact side switches field voltage, so a clean 24 VDC supply still matters for logic stability.
• CM588 / CM589​ — Communication modules (Profibus DP-V1, Profinet, Modbus TCP) that let the rack — and thus the 3ASU21C110​ outputs — sit as remote I/O drops on a Siemens/Rockwell DCS if needed.
• TU515 / TU516 / TU518​ — terminal units for S500 remote I/O cabinets; if the 3ASU21C110​ is deployed in a distributed S500 rack instead of local , these TUs provide the spring-cage terminations.
• 3ASU13C110​ — Lower-current 16-ch DO alternative (transistor) when your load truly is 24 VDC < 0.5 A and you want faster switching than the relay 3ASU21C110.