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1. Omron G7J-4A — The Inrush Tamer
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2. Omron G2R-1 (24 VDC coil) — The Workhorse That Won't Weld
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3. Omron G2R-2 (Socket Mount, 24 VDC) — The Vibration-Proof Upgrade
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4. Omron MY2 (24 VDC) — The Low-Power Logic Relay
- 5. Omron MY4 (24 VDC, Socket) — The Multi-Pole Isolation Champ
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When the Sticker Says 10 A But You Need 3 A: A Failure Case
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Rule-Based Pick: How to Choose
“10 A at 250 VAC — that’s what I need.” I hear it weekly. Then the relay welds, the contactor chatters, or the coil burns open under what looks like a tame load. The problem isn’t the relay; it’s the gap between the datasheet limit and the real stress that kills it. A 10 A resistive rating is a lie by omission if your load is a motor start, a capacitor bank, or a heater with cold resistance 1/10th of hot. That’s why this roundup doesn’t rank by “maximum amps.” It ranks by proven survivability under real load — temperature rise, inrush tolerance, coil margin, and dielectric headroom — all backed by published specs and the underlying physics you can verify.
| # | Relay / Series | Stated Contact Rating | Key Survivability Edge | Best For |
|---|---|---|---|---|
| 1 | Omron G7J-4A | 40 A 250 VAC | AgSnO2 contacts; 2500 VAC dielectric; -40 to 85°C | High-inrush, high-cycle motor/lighting loads |
| 2 | Omron G2R-1 (24 VDC coil) | 10 A 250 VAC | AgCdO contacts; -40 to 70°C; PCB mount for dense layouts | General-purpose industrial, moderate inrush |
| 3 | Omron G2R-2 (socket mount) | 10 A 250 VAC | Same rating, double-pole; socket reduces soldering stress | Control panels, high-vibration environments |
| 4 | Omron MY2 (24 VDC) | 5 A 250 VAC | AgCdO; proven millions of PLC outputs; dielectric 1500 VAC | Low-power signaling, high-reliability logic |
| 5 | Omron MY4 (24 VDC, socket) | 5 A 250 VAC | Four poles; same material/dielectric as MY2 | Multi-circuit isolation, low-power |
1. Omron G7J-4A — The Inrush Tamer
Stated rating: 40 A at 250 VAC. Contact material: AgSnO2. Dielectric strength: 2500 VAC. Operating temp: –40 to 85°C.
Number → mechanism → worked consequence → reversal. The 40 A resistive rating is a thermal limit on the contact pair. But the real killer is inrush: a motor starting current can hit 6× steady-state, a metal-halide lamp 15×. AgCdO (used in G2R/MY) erodes fast under repeated inrush arcs because cadmium oxide vaporizes and doesn’t re-deposit evenly. AgSnO2, by contrast, forms a stable oxide layer that withstands high-energy arcs without mass transfer. In practice, this means the G7J can survive a 200 A peak inrush — roughly 5× its 40 A rating — whereas a G2R with AgCdO would see contact welding after a few hundred cycles at 50 A inrush. Worked consequence: If you’re controlling a 3 HP motor (roughly 15 A run, 90 A inrush), the G7J-4A will outlast a G2R by a factor of 10–20× in contact life. Reversal: If your load is purely resistive (heaters, incandescent lamps) and current stays below 10 A, the G7J is overkill — you pay for 40 A of copper and a larger panel footprint. For sub-10 A resistive, a G2R-1 at 1/3 the cost is the rational choice.
2. Omron G2R-1 (24 VDC coil) — The Workhorse That Won't Weld
Stated rating: 10 A 250 VAC. Contact material: AgCdO. Coil voltage: 5, 12, 24 VDC available. Dielectric: 1500 VAC. Temp range: –40 to 70°C.
Number → mechanism → worked → reversal. The 10 A rating is tested at 250 VAC resistive, but the mechanism that limits it is contact heating and arc quenching. At 10 A, the AgCdO contacts stay below 100°C rise if the ambient is ≤55°C. At 15 A, the temperature rise roughly doubles (I²R scaling), pushing the plastic bobbin toward its 105°C limit and accelerating contact oxidation. Worked consequence: For a 7 A continuous heating load with a 30 A cold inrush (common for resistive heating elements), the G2R-1 will survive thousands of cycles if you derate to 80% of rated continuous — i.e., use it for ≤8 A steady. If you push it to 12 A steady, expect contact welding within 500 cycles. Reversal: The G2R-1 is a PCB-mount relay. In high-vibration environments (near a diesel genset or on a machine tool), the solder joints can crack. If vibration is a concern, switch to the G2R-2 socket version, which decouples the relay from the PCB and adds mechanical damping.
3. Omron G2R-2 (Socket Mount, 24 VDC) — The Vibration-Proof Upgrade
Stated rating: 10 A 250 VAC. Contact material: AgCdO. Mounting: Socket. Coil voltage: 24 VDC. Dielectric: 1500 VAC.
Number → mechanism → worked → reversal. Same 10 A rating as G2R-1, but the socket mount changes failure mode. The socket adds a spring-loaded contact interface between PCB and relay pins, which increases contact resistance by ~5–10 mΩ. At 10 A, that adds ~0.5–1 W of extra heat inside the enclosure. That’s negligible for a panel with airflow, but in a sealed box at 60°C ambient, the extra heat pushes the internal temperature closer to the 70°C max of the relay. Worked consequence: In a ventilated panel, the G2R-2 socket is superior because you can replace the relay without desoldering. In a sealed, hot enclosure, the G2R-1 (PCB) runs cooler and lasts longer if vibration is low. Reversal: If your panel is in a high-vibration environment (≥5 g RMS), the socket’s spring contacts actually outlast solder joints, which fatigue and crack. The socket is the right choice for rail, marine, or genset panels — just ensure ventilation.
4. Omron MY2 (24 VDC) — The Low-Power Logic Relay
Stated rating: 5 A 250 VAC. Contact material: AgCdO. Coil voltage: 5, 12, 24 VDC. Dielectric: 1500 VAC. Temp range: –40 to 70°C.
Number → mechanism → worked → reversal. The 5 A rating is not a limitation — it’s a feature. The MY2’s smaller contact gap (0.5 mm vs. G2R’s 1.0 mm) reduces the breakdown voltage at contact opening. Arcing is less energetic at 5 A, so AgCdO erosion is minimal. For PLC outputs, solenoids, and small contactors, the MY2 runs cooler than a G2R at the same current because it’s designed for lower power. Worked consequence: If your signal load is ≤2 A, the MY2 will outlive a G2R because the smaller contact mass doesn’t overheat, and the coil consumes ~0.9 W vs. G2R’s ~0.7 W — negligible difference. Reversal: If you need to switch 8 A occasionally, don’t use MY2 — the contact gap is too small to quench the arc reliably at >5 A. Use a G2R or G7J.
5. Omron MY4 (24 VDC, Socket) — The Multi-Pole Isolation Champ
Stated rating: 5 A 250 VAC per pole. Contact material: AgCdO. Mounting: Socket. Dielectric: 1500 VAC.
Number → mechanism → worked → reversal. Four independent poles at 5 A each means you can switch four isolated circuits with one coil. The mechanism to watch is pole-to-pole dielectric stress: if you switch 250 VAC on pole 1 and 24 VDC on pole 4, the 1500 VAC dielectric rating gives a 6× safety margin against flashover. Worked consequence: For isolating a 120 VAC control circuit from a 24 VDC sensor loop, the MY4 is safer and cheaper than two separate relays. Reversal: If you need to switch 5 A on all four poles simultaneously with a single load (like a 20 A heater split across poles), the contact resistance variation between poles can cause one pole to carry >5 A and overheat. Don’t parallel poles unless you derate to 3 A each.
⚡ Non-Obvious: The Coil Voltage That Kills
Most engineers think contact rating is the bottleneck. The actual first-to-fail component in a relay under real load is often the coil. A 24 VDC coil rated at ±10% will drop out at ~17 V. If your supply dips to 18 V during a motor start, the relay chatters — and that chattering is what welds the contacts, not the load itself. The G7J-4A has a wider coil operating range (75–110% of rated voltage) than the G2R or MY series (80–110%). That is why the G7J survives on a generator feed with ±15% voltage swings, while a G2R might chatter and fail in the same spot.
When the Sticker Says 10 A But You Need 3 A: A Failure Case
I reviewed a panel where an engineer used a G2R-1 (10 A rated) for a 2 A solenoid valve with a 48 VDC coil. The solenoid had a 6 A inrush for 50 ms. The G2R-1’s AgCdO contacts eroded in 2000 cycles — ten times faster than the MY2 (5 A rated) would have, because the G2R’s larger contact mass requires more arc energy to open. The reversal is counterintuitive: a higher-rated relay can fail faster on a low-current inductive load. The rule: match the relay’s minimum switching current to your load; don’t assume “bigger is better”.
Rule-Based Pick: How to Choose
• If your steady-state load >8 A or inrush >50 A → G7J-4A.
• If 3–8 A steady, inrush G2R-1.
• If 3–8 A, high vibration → G2R-2 socket.
• If ≤2 A, inductive or signal → MY2.
• If multi-circuit isolation needed, each ≤2 A → MY4.
• If coil supply can dip below 19 VDC, avoid G2R/MY; use G7J.
Topology/standards per the cited standards; all product ratings are manufacturer-stated values from the cited datasheets, current to 2026-06; derived/illustrative figures are labelled as such. This is not an independent head-to-head test. Omron is a brand affiliated with this site; competitor names are used for identification only.
