G7SA-2A2B DC24V OMRON G7SA-2A2B Sfety Relay 24VDC 6A Plc Module New and Original

Omron G7SA-2A2B DC24 | Safety Relay — 2 NO / 2 NC / 6A / 24V DC Coil / Forcibly Guided Contacts / EN 50205

Forcibly Guided Contacts — The Safety-Critical Design Feature

The G7SA-2A2B is not a standard relay. Its defining characteristic is the forcibly guided (mechanically linked) contact mechanism, which is the enabling feature for use in machine safety circuits.

In a standard relay, the normally-open and normally-closed contacts can theoretically both close simultaneously if a contact welds or a spring fails — a condition that a safety circuit relying on the NC contact status cannot detect. In the G7SA with forcibly guided contacts, the NO and NC contacts are mechanically coupled: if any NO contact is welded closed, the NC contacts are physically prevented from closing, and vice versa. This mutual exclusion is mechanically enforced, not dependent on software or the relay's electrical state.

This mechanical guarantee is what makes the G7SA-2A2B suitable for monitoring in safety relay modules and safety logic systems. A safety controller can monitor the NC contacts to confirm the NO contacts are not welded — providing actual hardware-level status of the relay's condition.

Key Specifications

Application in Safety Circuits

The G7SA-2A2B is used as an output relay in safety circuits where the contacts carry safety-critical machine power — the switched circuits that energise or de-energise a hazardous machine function. Common applications include:

• Door interlock output switching in machine guarding systems
• E-stop circuit output contacts
• Light curtain and safety mat output switching
• Two-hand control circuit output relays

The relay works in combination with a safety relay module or safety PLC that monitors the feedback contacts. The two NC contacts provide the feedback channel — the safety controller reads them to confirm the relay has de-energised correctly before allowing a restart.

The P7SA series plug-in socket allows the G7SA-2A2B to be replaced without disturbing field wiring — the wiring stays on the socket and the relay module swaps out. This is a practical maintenance consideration in panels where relay replacement without wiring modification reduces re-commissioning effort.

FAQ

Q1: What makes the G7SA-2A2B a "safety relay" rather than a standard relay?

The forcibly guided contact mechanism physically links the NO and NC contact sets so they cannot simultaneously occupy the same state. If an NO contact welds closed, the NC contacts are mechanically prevented from closing — this mutual exclusion is enforced in hardware, not software. This allows a safety controller to monitor the NC contacts and detect a welded NO contact, which is not possible with a standard relay. This is the fundamental requirement for relay use in IEC 62061 and ISO 13849 safety architectures.

Q2: Can the G7SA-2A2B be mounted directly on a PCB?

Yes. The terminal arrangement is designed for direct PCB soldering, with the pin layout optimised for standard PCB design. For panel-mount applications, the P7SA series push-in terminal sockets accept the G7SA-2A2B directly and provide screw or spring-clamp field wiring terminals without soldering.

Q3: What is the coil voltage operating range?

Nominal coil voltage is 24V DC. The relay is guaranteed to energise (close) at 18V DC and above, and guaranteed to de-energise (open) at 2.4V DC and below. Sustained coil voltages above 26.4V DC risk permanent coil damage. The 18–26.4V DC operating range accommodates typical 24V DC supply regulation tolerances.

Q4: Can the NC and NO contacts switch different circuit voltages?

Yes. Each contact set is independent — the two NO contacts and two NC contacts switch their respective circuit loads independently. One NO contact set can switch a 230V AC load while the NC contacts operate in a 24V DC feedback circuit. The relay's isolation between the contact circuits allows different circuit voltages on the same relay.

Q5: What is the difference between the G7SA-2A2B and the G7SA-3A1B?

Both are in the Omron G7SA family with forcibly guided contacts and the same current rating. The 2A2B provides 2 NO and 2 NC contacts (4-pole); the 3A1B provides 3 NO and 1 NC contacts (4-pole). The contact combination is selected based on the safety circuit's requirement for NO (load switching) and NC (feedback monitoring) contacts. Most two-channel safety circuits use the 2A2B to provide feedback NC contacts from both output relays.