OMRON G7Z-4A High-Power Relay

Series: G7Z Multi-pole Power Relay (Compact Electromagnetic Contactor Type)

Model Definition:

G7Z: Series code, high-power double-break relay

-4A: 4-pole Normally-Open (4a, 4PST-NO), no normally-open main contacts

Complete part numbers: G7Z-4A DC12/ G7Z-4A DC24; suffix -R denotes revised version; -11Z-R indicates fitted with 1a1b auxiliary contact block

Core Electrical Specifications

Coil (DC driven)

Main Contacts (4-pole NO, double-break structure, Ag-alloy contacts)

Resistive load: 40A @ AC440V; max. AC480V

Inductive load (cosφ=0.3): 22A @ AC440V

DC load: 5A @ DC110V

Max. Switching Capacity: Resistive 17600 VA; Inductive 9680 VA

Terminals: Screw terminals; Mounting: DIN-rail mountable

Dimensions: 80×100×100 mm; Built-in operation indicator light, enclosed housing

Model Variants

1. G7Z-4A DC12 / DC24: Basic unit, 4 main NO contacts, no auxiliary contacts
2. G7Z-4A-11Z-R DC24: Main unit 4a + attached 1a1b auxiliary contact block for status feedback signals

Legacy G7Z-4A-□Z models are discontinued; replace with -R suffixed versions: G7Z-4A-□Z-R

Typical Applications

Switching high-power 3-phase 380-440 V loads (heaters, power supplies, fans)

DIN-rail installation inside control cabinets, alternative to small contactors; direct PLC DC-output drive

⚠️ Note: Coil power consumption 3.7 W; calculate current margin for PLC output modules. Derate contact current above 40 °C ambient: reduce 0.7 A per 1 °C rise.

Replacement Options

1. Omron same-series: G7Z-4A-xxZ-R (factory upgraded replacement)
2. Contactor alternative: 4-pole small AC contactor (40 A class, DC coil)
3. Domestic equivalent: 4-pole 40 A DC24 V coil DIN-rail power relay. Verify key specs: double-break, AC440 V rating, screw terminals, coil power consumption.

Common Troubleshooting Checkpoints

1. Verify coil supply voltage ≥75 % rated value; measure coil resistance to detect burnt-out coils
2. Main contact erosion: Service life drops sharply under 40 A inductive loads; use derated contactor sizing as preferred practice
3. Maintain adequate heat dissipation in high-temperature environments to avoid insufficient current derating.

OMRON G7Z-4A Mounting Instructions

The G7Z-4A supports DIN-rail mounting and panel screw-mounting. Mandatory mounting orientation: coil terminals facing upward. Never mount with terminals upside-down.

1. DIN-rail Mounting (Standard for Control Cabinets)

Compatible rail: Standard DIN EN50022, 35×7.5 mm (TR35-15Fe) steel rail

❗ Not compatible with over-thick heavy-duty rails from some manufacturers, risk of insecure latching.

Mount orientation: Horizontal installation with coil terminals upward. Vertical or inverted mounting is prohibited.

Installation procedure: Hook rear spring clip onto upper rail edge, press down until a “click” confirms full engagement.

Anti-vibration securing: For high-vibration environments, fit PFP-M rail end stops on both sides to prevent sliding or dislodging.

Removal: Pry down bottom spring clip with flat-blade screwdriver and lift the relay upwards.

2. Panel Screw-Mounting

Secure via two M4 screws through mounting holes on the housing. Tightening torque strictly 1.2-1.3 N·m. Avoid over-tightening (cracked housing) or under-tightening (looseness).

Keep coil terminals oriented upward.

Suitable for custom enclosures without standard DIN rail.

3. Auxiliary Contact Block (G73Z-□Z-R) Assembly & Removal

Auxiliary contact blocks provide status feedback for G7Z-4A base unit:

1. Insert block claws into the recesses of the relay main body;
2. Press inward until latched with audible click;
3. Removal: Slide auxiliary block to disengage hooks and claws. Do not pry plastic hooks forcibly.
4. Mounting Clearance & Thermal Requirements (Critical for Current Derating)
5. Maintain minimum 5 mm clearance between relay housing and cabinet metal ground surfaces on all sides;
6. Multiple G7Z-4A side-by-side: Maintain minimum 30 mm spacing between units. Close adjacent mounting causes excessive self-heating and mandatory contact derating;
7. Keep upper area well-ventilated; avoid stacking heat-generating components directly above;
8. Derate contact current for ambient temperatures exceeding 40 °C.
9. Terminal Tightening Torque

Loose terminals cause overheating and burnout under high load; torque wrench usage is recommended.

6. Strict Prohibitions
7. ❗ Do NOT mount upside-down (terminals facing down): risk of abnormal mechanical operation and shortened service life.
8. ❗ Do NOT mount rotated 90° on side.
9. ❗ Do NOT use non-standard over-thick DIN rails.
10. ❗ Do NOT touch live terminals while powered; fit terminal safety covers for shock hazard protection.
11. Post-installation Checks
12. Relay secured firmly without wobble (rail clip or mounting screws fully tightened);
13. Auxiliary contact block is securely latched;
14. All terminals torqued to specified values;
15. Thermal clearances met; no obstructions surrounding the unit.

OMRON G7Z-4A Ambient Temperature Specifications

Operating Ambient Temperature

-25 °C ~ +60 °C, no icing, no condensation.

40 A rated contact current applies at ambient ≤45 °C.

High-Temperature Current Derating Rule (Critical)

For ambient temperature ＞45 °C up to 60 °C: reduce continuous allowable current by 0.7 A per 1 °C rise.

Example @50 °C: Max continuous current = 40-(50-45)×0.7 = 36.5 A

Example @60 °C limit: Max continuous current = 40-(60-45)×0.7 = 29.5 A

Same derating applies when G73Z-□Z-R auxiliary contact block is fitted.

Ambient Humidity

5 % ~ 85 % RH, non-condensing.

Storage Temperature (Unpowered unit)

Not explicitly listed on datasheet; industrial practice: -40 °C ~ +70 °C, no icing or condensation.

Design Notes

1. Operation at -25 °C is permitted; prevent cabinet condensation; dehumidify cabinet before cold startup.
2. Closely-mounted multiple units add self-heating; actual component temperature is higher than cabinet air-sensor reading. Adequate thermal spacing is mandatory.
3. Coil resistance increases with temperature. Verify coil supply voltage maintains ≥75 % rated value under high-temperature conditions to prevent unreliable pull-in.
4. Do not operate above 60 °C ambient: accelerates contact erosion and coil aging.

OMRON G7Z-4A Contact Configuration

Main unit main contacts: 4a (4PST-NO), four-pole normally-open; no main normally-closed contacts

Model code explanation: 4A = 4-pole-All-NO. All contacts open when coil de-energized; all four poles close simultaneously upon coil energization.

Contact mechanism: Double-break. Two separate break points per pole, enhanced arc-extinguishing capability for high-voltage AC440 V heavy-load switching.

Contact material: Ag-alloy.

Main Contact Ratings (per pole)

Resistive load: 40 A @ AC440 V

Inductive load (cosφ=0.3): 22 A @ AC440 V

DC load: 5 A @ DC110 V

Auxiliary Contacts (Separate G73Z-□Z-R block required; not built-in)

Auxiliary contacts use single-break construction, max rated current 1 A. For status feedback signals only. NOT suitable for carrying main power loads.

Cross-reference for related series models (for selection reference)

1. G7Z-4A：4a (4-pole NO)
2. G7Z-3A1B：3a1b (3-pole NO +1-pole NC)
3. G7Z-2A2B：2a2b (2-pole NO +2-pole NC)

Design Key Points

1. G7Z-4A base unit has no main NC contacts. Select G7Z-3A1B / G7Z-2A2B if main normally-closed contacts are required.
2. Double-break design provides high inter-phase withstand voltage; well-suited for switching 3-phase heaters and 3-phase fans.
3. Auxiliary blocks are strictly for feedback signals; never use for power-carrying circuits.