OZ-SH-124L,294

FAQFrequently Asked Questions

• What is the minimum control voltage required to reliably operate the OZ-SH-124L,294 relay in a 24VDC system, and what happens if the supply voltage drops during operation? The OZ-SH-124L,294 must operate voltage is 18 VDC, meaning the relay will reliably pull in and maintain its contacts closed at any voltage from 18 VDC to 24 VDC. If your supply voltage drops below 18 VDC during operation, the OZ-SH-124L,294 contacts may drop out unexpectedly, even if they were already closed. In systems with marginal power supplies or long cable runs to the relay coil, voltage drop across wiring must be calculated to ensure the coil receives at least 18 VDC under worst-case load conditions. For critical applications, a regulated 24VDC supply with a minimum 10% margin is recommended.
• How should the OZ-SH-124L,294 be specified for applications requiring fast switching, and what are the actual transition times? The OZ-SH-124L,294 has an operate time of 20 milliseconds and a release time of 8 milliseconds. If your application requires contact switching within these timeframes—for example, sequencing power supplies or controlling motor circuits—the OZ-SH-124L,294 is suitable as long as your control logic accounts for these delays. For faster switching (sub-millisecond response), solid-state relays or semiconductor switches must be considered instead. The 20 ms operate time is typical for general-purpose electromechanical relays; if your system timing margin is less than 30 ms, verify that the OZ-SH-124L,294 switching speed will not cause missed cycles or race conditions.
• Can the OZ-SH-124L,294 be used to directly switch 240VAC loads at its maximum current rating? Yes, the OZ-SH-124L,294 contacts are rated for 240VAC at a maximum of 16 A. However, contact rating derating applies when switching AC loads compared to DC. The contact material on the OZ-SH-124L,294 is Silver Cadmium Oxide (AgCdO), which provides good AC switching characteristics but generates higher arc energy than pure silver contacts. For continuous operation at or near 16 A on 240VAC, thermal cycling and contact erosion occur over time, shortening relay life. For loads above 8 A on 240VAC, verify the expected duty cycle; if the application requires switching more than once per minute continuously, consider over-rating to a 20 A or 25 A relay to extend contact life, or use the OZ-SH-124L,294 for lower-duty infrequent switching.
• What is the coil power consumption of the OZ-SH-124L,294, and how should it be driven from a microcontroller or logic circuit? The OZ-SH-124L,294 coil draws 21.8 mA at 24 VDC and has a coil resistance of 1.1 kOhms. The coil power consumption is approximately 524 mW (24V × 21.8 mA). Most microcontroller I/O pins cannot source or sink 21.8 mA directly; the OZ-SH-124L,294 must be driven through a transistor interface (typically an NPN BJT or N-channel MOSFET) with a current-limiting resistor on the base or gate. A 1N4007 freewheeling diode must be placed across the OZ-SH-124L,294 coil to clamp the voltage spike when the coil de-energizes, protecting the transistor from destruction. For reliable operation in noisy industrial environments, include a 100 nF ceramic capacitor across the coil to suppress RF noise that could cause false relay actuation.
• How does the OZ-SH-124L,294 perform in high-temperature environments, and what derating should be applied? The OZ-SH-124L,294 is rated for operation from -30°C to 70°C. At temperatures above 55°C, the coil resistance increases, requiring slightly higher control voltage to maintain the must-operate specification. The contact material of the OZ-SH-124L,294 (Silver Cadmium Oxide) becomes more prone to oxidation and contact resistance increase at elevated temperatures. For applications in environments above 60°C, reduce the switching current by 10–15% and verify contact closure voltage drop remains below acceptable thresholds. The OZ-SH-124L,294 is not suitable for continuous operation above 70°C; if your application requires higher temperature operation, specify a relay with Class B (130°C) or Class F (155°C) insulation instead.
• Can the OZ-SH-124L,294 replace an existing relay in a legacy PCB, and what compatibility checks are required? The OZ-SH-124L,294 is a through-hole mounted SPDT relay with PC pin termination, so physical fit on the PCB depends on the hole spacing and pin pitch of your existing socket or footprint. Before specifying the OZ-SH-124L,294 as a drop-in replacement, verify: (1) coil voltage matches (24VDC required for OZ-SH-124L,294); (2) contact current rating is adequate for your load; (3) switching voltage is compatible with your application (240VAC maximum for OZ-SH-124L,294); (4) mounting height does not interfere with surrounding components; (5) PCB hole diameter and spacing exactly match the OZ-SH-124L,294 pin configuration. Relays from different manufacturers or series (such as Omron MYS or Schneider Telemecanique) may have different pin arrangements despite similar specifications; always cross-reference pinout diagrams before soldering.
• What is the release voltage of the OZ-SH-124L,294, and could this cause contact chatter during power-down or in unstable supply conditions? The OZ-SH-124L,294 release voltage (dropout voltage) is 1.2 VDC. When the coil is de-energized and the supply voltage drops to 1.2 VDC or below, the contacts will reliably release and return to their open state. In systems where supply voltage ramps down slowly or is subject to ripple, the voltage could hover near 1.2 VDC, causing the OZ-SH-124L,294 contacts to chatter (open and close repeatedly) before fully releasing. This chatter can damage downstream equipment or corrupt data in control systems. To prevent this, add a bulk capacitor (typically 1000 µF or larger) on the relay power supply to smooth voltage transients, or implement a soft-start circuit that ramps the relay supply voltage monotonically to avoid the unstable region near the 1.2 VDC release threshold.
• Is the OZ-SH-124L,294 suitable for signal switching applications, or is it only rated for power switching? The OZ-SH-124L,294 is designed as a general-purpose relay suitable for both power and signal switching. For low-signal applications (switching milliamp-level currents at low voltage), the OZ-SH-124L,294 performs reliably without special considerations. However, the OZ-SH-124L,294 contact material (Silver Cadmium Oxide) is optimized for AC and resistive loads; for switching sensitive analog signals or high-impedance circuits, the contact resistance variability of the OZ-SH-124L,294 may introduce noise or measurement error. If your application requires ultra-low contact resistance or minimal voltage offset across the relay contacts, consult the detailed contact resistance specifications or consider a specialized signal-level relay with gold-plated contacts instead of the OZ-SH-124L,294.
• What environmental sealing does the OZ-SH-124L,294 provide, and is it suitable for humid or corrosive industrial settings? The OZ-SH-124L,294 is rated as "Sealed – Fully," meaning the relay case provides a protective enclosure against moisture ingress and contaminants. The Moisture Sensitivity Level (MSL) is 1 (Unlimited), indicating the OZ-SH-124L,294 can be stored and handled without special drying procedures and is not subject to moisture bake-out requirements before soldering. For industrial environments with condensation, salt spray, or chemical vapors, the sealed construction of the OZ-SH-124L,294 provides baseline protection. However, the PC pin termination is not potted or conformal-coated; for harsh corrosive environments (marine salt spray, chemical plants), additional conformal coating of the PCB and surrounding circuitry is necessary. The OZ-SH-124L,294 itself does not require additional environmental protection beyond standard PCB-level measures.
• What is the hold-in current required for the OZ-SH-124L,294 once the contacts are closed, and can the coil current be reduced after actuation? The OZ-SH-124L,294 coil current is specified as 21.8 mA at 24 VDC to achieve pull-in. Once the contacts close, the holding current for the OZ-SH-124L,294 is typically lower than the pull-in current (approximately 15–18 mA), due to the reduced air gap in the magnetic circuit. In energy-conscious designs, some control circuits implement a "soft-drive" approach: apply full 24 VDC and 21.8 mA to pull in the OZ-SH-124L,294 relay, then reduce the coil voltage or switch to a current-limiting resistor to reduce holding current. This technique reduces power dissipation but must account for the minimum hold voltage of the OZ-SH-124L,294 (approximately 12–15 VDC) to avoid unintended dropout. Consult the relay's detailed switching diagram or contact TE Connectivity for precise hold-in current specifications if your application requires power optimization.