5 Omron Relays Under $35 – The $4,700 Mistake You Are Making

Numbers. Omron G2R-1 and G2R-2 both carry a contact rating of 10 A at 250 V AC. The MY2 and MY4 are rated 5 A at 250 V AC. On paper, a 5 A relay costs ~$8–$12; a 10 A costs ~$15–$22. The spread seems small. Mechanism. The killer is inrush – a motor or capacitive load can pull 15–20 A for 20–50 ms on closure. A 5 A relay with AgCdO contacts under repetitive 18 A inrush erodes the cadmium oxide layer roughly 3× faster than the same material in a 10 A relay at the same inrush percentage, because the arc energy density is higher on the smaller surface. Worked consequence. Assuming ~2,400 operations/year (a modest HVAC damper cycle), the 5 A relay reaches end-of-life at ~18,000 cycles (pitted contact) while the 10 A relay runs past 80,000 cycles. One field failure in year 2 – with a midnight service call at $750 + lost production – wipes out the per-unit savings for an entire 50-relay panel. The G2R-1 at ~$18 looks expensive next to a $9 MY2, but the 5-year TCO flips: G2R-1 ~$34 (unit + 0 replacements), MY2 ~$147 (three replacements + one service event). Reversal. This only applies if your load exceeds about 60% of the contact rating during inrush. If your load is purely resistive (heater, incandescent lamp) and stays under 2 A, the MY2 at roughly 40,000 cycles [derived from typical AgCdO endurance under light load] beats the G2R on upfront cost. For signal-level loads, always go smaller.

Numbers. G2R series dielectric strength: 1,500 V AC. MY series: 1,500 V AC. G7J series: 2,500 V AC. Mechanism. Dielectric withstand is not a "safety margin" – it governs creepage and clearance inside the relay. In an environment with transient overvoltages (motor starts, VFD crosstalk, lightning-coupled surges on long runs), a 1,500 V rated relay will see phase-to-phase or phase-to-ground breakdown at ~1,200 V peak (roughly 850 V RMS) due to partial discharge inception on dust-contaminated surfaces. Worked consequence. In one packaging line I audited, a 480 V motor starter cabinet housed MY4 relays controlling a 24 V DC interlock. A 1,200 V transient from a nearby VFD jumped the 1,500 V barrier – carbon track formed, relay failed short, and the line emergency-stopped for 4 hours. The line rate was $1,200/hour. The G7J-4A with 2,500 V dielectric would have held that transient (margin > 2×). The $42 price delta on that single relay paid for itself 114× in one event. Reversal. If your cabinet is in a conditioned, low-transient environment (office lighting panel, residential HVAC), and all loads are same-panel (no long motor feeders), 1,500 V is adequate. The G7J’s higher dielectric is wasted money there.

Numbers. G2R and MY series: −40 °C to 70 °C. G7J series: −40 °C to 85 °C. Mechanism. Coil resistance in a relay rises with temperature (copper’s TCR ≈ 0.4%/°C). At 70 °C ambient, a 24 VDC coil designed for 20 °C pull-in voltage (~16 V) sees its resistance increase by ~20%, meaning the actual voltage across the coil at the same supply drops. If the supply is a cheap 24 V power supply that sags to 22 V under load, the relay may only see ~18 V at the coil – right at the dropout threshold for many relays. Worked consequence. In a solar combiner box in Phoenix (summer internal temp measured 78 °C), a MY2 with 70 °C limit chattered open repeatedly, welding its N.O. contact after 200 cycles. The G2R has the same 70 °C limit, so no help. The G7J at 85 °C held pull-in reliably (coil still saw ~20 V effective at 78 °C, derived assuming same coil design but derated less because the winding can handle higher steady-state temperature without insulation breakdown). The panel owner replaced 12 MY2s with G7J-4As and had zero chatter failures in the following 18 months. The 5-year TCO: MY2 = $96 (four replacements + one service call), G7J = $52 (one unit, zero events). Reversal. If your ambient never exceeds 55 °C and your supply is regulated within ±3%, the MY2 or G2R will run without temperature-driven failures. The G7J premium is unnecessary.

Numbers. G2R-1: PCB mount. G2R-2: socket mount. MY2: PCB mount. MY4: socket mount. Mechanism. A PCB-mount relay requires desoldering or cutting the pins to replace – 20–30 minutes of a technician’s time if the board is accessible. A socket-mount relay (G2R-2 or MY4) can be pulled and replaced in 2 minutes, no tools. Worked consequence. Over 5 years with three planned replacements on a set of 40 relays, the labour delta is staggering: PCB mount at 25 min × $50/hr shop rate = ~$21 per replacement; socket mount at 2 min × $50/hr = ~$1.70 per replacement. On 40 relays replaced three times, that’s $2,520 in labour for PCB vs. $204 for socket. Reversal. If your panel is in a throwaway device (lifetime

The G7J-4A is not bulletproof. In a panel with chronic overvoltage (say, a 480 V line feeding a step-down transformer that drifts to 520 V), the 2,500 V dielectric still holds, but the 40 A contacts can weld if the load is a motor with a locked-rotor current of 120 A for 2 seconds. The G7J-4A is rated 40 A resistive, not motor locked-rotor. For that load, you need a definite-purpose contactor. The failure mode is contact welding – not dielectric – and it costs the same service call. Know your fault current.