IC694MDL930 Relay Output Module: Specs and Applications

IC694MDL930: 8 Isolated Relay Outputs for Mixed AC and DC Loads

The IC694MDL930 solves a switching problem that solid-state output modules cannot: a single module that has to switch both AC and DC loads, and keep them galvanically separate from each other and from the PLC logic. Eight individually isolated Form A (normally open) relay outputs, each able to handle inductive and non-inductive loads across 5-250 VAC (50/60 Hz) and 5-30 VDC, is exactly the specification that a machine with mixed voltage loads ends up needing.

The isolation is the part worth being precise about. Because each relay output is individually isolated — and the module provides point-to-point isolation — a fault on one output circuit cannot propagate to the others, and the field wiring has no common return path into the controller. Field-to-backplane isolation and isolation to frame ground are both rated 250 VAC continuous and 1500 VAC for 1 minute. That is what allows the same module to switch a 240 VAC solenoid and a 24 VDC solenoid without either circuit touching the other reference.

IC694MDL930 Against the Other PACSystem RX3i Relay Modules

Two RX3i relay output modules cover most applications. The choice comes down to point count and load type:

IC694MDL660 RX3i 24 VDC discrete input is the matching input module for reading the limit switches that drive these outputs. Browse all GE parts · I/O Modules · PLC & I/O Modules

Where Relay Outputs Still Win Over Solid-State Outputs

A solid-state output is faster and cheaper, which is why it dominates most new designs. Relay outputs remain the correct answer in three situations: the load is highly inductive and the switching stress would degrade a transistor; the load switches at mains voltage and the isolation barrier has to be physical; or the switching frequency is low enough that relay life is not a constraint.

Solenoid valves, contactor coils, lamp banks and small motors fall into those categories. The 4.0 A per-point resistive rating covers coil loads directly, so no interposing relay is required — which removes a failure point and halves the panel depth for a bank of eight. The 20 A per-module UL limit is the figure to respect when all eight outputs are energised simultaneously, and the 10 mA minimum load per point is the other end of the range that has to be checked against LED indicator loads and small relay coils.

Wiring Practice for Form A Relay Outputs

Because the outputs are normally open, a field device energises only when the PLC output is driven — a useful property for fail-safe design, because a lost wire or a de-energised controller leaves the load off rather than on. Keep inductive loads on their own output circuits and do not share a neutral return between an AC and a DC output, since the isolation between outputs is what provides the separation and a shared external return defeats it outside the module.

Response Time, Inrush and Relay Life Budget

Response time is stated as 15 ms for the module with 10.0 ms also given on the specification sheet. Inrush rating is 5.0 A per point. On an application where a solenoid must respond quickly to a process event — a safety trip or a high-speed clamp — that response figure, not the 4 A switching capacity, is the number that decides whether the module fits.

Relay contact life is quoted between 50,000 and 1,000,000 operations depending on voltage and load type. The tenfold spread is not marketing conservatism; it reflects real load behaviour. A purely resistive load sits at the top of that range, while an inductive solenoid load pulls the contacts toward the lower end. For a machine where the outputs cycle continuously, sizing against the lower figure is what determines service interval.

Backplane Draw and Mixed Power Budgets

Backplane draw is 6.0 mA at 5 VDC with all outputs on, and 70 mA at 24 VDC from the backplane relay power with all outputs on. Those two figures matter when the RX3i rack power budget is already tight, because the relay power figure is fifteen times the logic figure — a rack full of relay output modules consumes far more 24 VDC relay power than 5 V logic power, which is exactly the opposite of what a rack full of input modules does.

Commissioning and Verification

Verify each output independently during commissioning: energise one output at a time and confirm the corresponding field device operates, rather than switching all eight together. On a Form A bank this catches mis-mapped output-to-device assignments, which are the most common commissioning error on relay output modules and which will otherwise surface as an intermittent machine fault when one device operates out of sequence.

Ordering Notes and Sourcing

Confirm the platform before ordering: IC694MDL930 is for PACSystem RX3i racks, while the mechanically and electrically similar IC200MDL930 is for VersaMax racks. The part numbers are close enough that this is a genuine substitution risk on a maintenance order.