1734-OW2 — POINT I/O 2-Point Relay (Form A) Output Module

The 1734-OW2 is a two-point relay output module for the 1734 POINT I/O platform. Each point is a Form A (normally open) contact rated at 240V AC or 125V DC, 2A. The two contacts are isolated from each other and from the POINT I/O backplane — different circuit voltages, different supply references, no shared common between the two points.

Relay outputs sit in a specific niche in distributed I/O nodes. They're not as fast as transistor outputs, they wear out after enough operations, and they generate contact bounce. What they offer in exchange is voltage flexibility — the ability to switch any circuit up to 240V AC or 125V DC without needing the load to run at the same voltage as the control system. In a POINT I/O node that's otherwise 24V DC, adding a 1734-OW2 handles the one or two AC-voltage outputs without a separate relay panel or interposing relay.

Specifications

Parameter	Value
Part Number	1734-OW2
Platform	POINT I/O (1734)
Output Points	2
Contact Type	Form A (Normally Open)
Max Voltage (AC)	240V AC
Max Voltage (DC)	125V DC
Max Current (resistive)	2 A per point
Min Load	10 mA @ 5V DC
Isolation	Point-to-point and point-to-backplane isolated
Electrical Life (full load)	500,000 operations
Mechanical Life	10 million operations
Backplane Current (5V)	75 mA
Backplane Current (24V)	95 mA
Operating Temperature	−20°C to 55°C
Standards	UL 508, CE, IEC 61131-2

Two Isolated Points in One POINT I/O Slot

The full isolation between the two output points is worth emphasizing. Point 0 can switch a 120V AC solenoid valve on one circuit, while Point 1 simultaneously switches a 24V DC pilot light on a completely different supply — no shared common, no electrical relationship between the two circuits except that they both use the same module. This flexibility is what makes a two-point relay module more useful than its small point count might suggest.

Isolation to the backplane means neither contact circuit has any electrical connection back to the POINT I/O backplane power or signal lines. A wiring fault on the load side — say, a 240V AC wire shorts to the relay terminal — is contained within the output circuit and doesn't propagate to the POINT I/O backplane or the controller network.

Contact Life and Load Management

The 500,000 operation electrical life at 2A / 240V AC is the rated worst case. Actual contact life varies significantly with what the relay is switching:

Resistive loads — the mildest on contacts. Life tends to exceed the rated figure at loads below the maximum.
Inductive loads (solenoids, contactor coils) — the inductive arc on breaking degrades contacts faster than resistive loads. Always fit a suppressor: a MOV or RC snubber across AC inductive loads, a flyback diode across DC inductive loads. This extends contact life dramatically.
Lamp loads — incandescent bulbs draw high inrush current on closing (cold filament resistance is low). If switching incandescent lamps, derate the current rating to roughly 20% of resistive rating for closing inrush.
Motor loads — treated as inductive for sizing purposes. Use AC-3 duty ratings (not resistive ratings) when switching motor starter circuits.

The 1734-OW2 has Form A (NO only) contacts. There is no normally closed contact available on this module. If a normally closed output is required, either invert the output logic in the controller program and use the NO contact, or select a different module with Form C contacts.

FAQ

Q: Can the 1734-OW2 switch 277V AC circuits (common in North American lighting panels)?

No. The maximum rated voltage is 240V AC. For 277V AC switching, an external relay with appropriate ratings is needed outside the POINT I/O module.

Q: Is there a version with Form C (NO + NC) contacts for this module?

The 1734-OX2 is the Form C version, providing both a normally open and normally closed contact per point in the same POINT I/O form factor. If both contact states are needed from one output, the OX2 is the right choice.

Q: Can I replace a 1734-OW2 while the POINT I/O node is powered?

The 1734 terminal base stays mounted and wired in place when the module body is removed. Whether hot-swap is safe depends on the adapter module type and the controller configuration. Electrically, the load circuits connected to the relay terminals remain live when the module is removed — de-energize the load circuits before removing the module to avoid arc hazards at the terminal base contacts.

Q: The minimum load is listed as 10 mA @ 5V DC — what happens below this threshold?

Silver-alloy contacts can develop a thin resistive film at low current levels. Below the minimum load, this film may not be reliably cleared on each switching operation, causing intermittent contact resistance and unreliable switching. For very low-current signal switching, gold-plated contacts or a solid-state output are more appropriate.

Q: How are the two output points addressed in the controller program?

The two points map to individual output bits in the controller's I/O image — O.Data[0] and O.Data[1] for the two contacts. They are controlled independently; setting one output tag does not affect the other.

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