If you are looking at an 8 pin ice cube relay wiring diagram for a standard DPDT (Double Pole Double Throw) relay like the ubiquitous Omron MY2N or Schneider RXM2AB, here is the direct answer: Pins 2 and 7 are the coil. Pins 1 and 8 are the common poles. Pins 4 and 6 are Normally Closed (NC), and Pins 3 and 5 are Normally Open (NO). In practical panel building, you will almost never wire directly to the relay pins; instead, you will terminate your wires into a matching DIN-rail or panel-mount socket (like the Omron PYF08A), which mirrors this exact pinout on its screw terminals.
Terminal Mapping and Diagram Symbols
Before tracing the circuit, you need to map the physical device to the schematic. Schematic diagrams use standardized IEC/NEMA symbols that can confuse beginners. The coil is drawn as a rectangle (sometimes with parallel lines inside). The contacts are drawn as switches: a gap indicates Normally Open (NO), and a diagonal slash across the switch indicates Normally Closed (NC). The moving 'wiper' of the switch represents the Common terminal.
| Pin Number | Function | Socket Terminal Label | Schematic Symbol |
|---|---|---|---|
| 2 & 7 | Electromagnetic Coil | 2 & 7 (or A1 & A2) | Rectangle / Inductor |
| 8 | Pole 1 (Common Wiper) | 8 (or 11) | Switch pivot point |
| 6 | Pole 1 (Normally Closed) | 6 (or 12) | Switch with diagonal slash |
| 5 | Pole 1 (Normally Open) | 5 (or 14) | Switch with open gap |
| 1 | Pole 2 (Common Wiper) | 1 (or 21) | Switch pivot point |
| 4 | Pole 2 (Normally Closed) | 4 (or 22) | Switch with diagonal slash |
| 3 | Pole 2 (Normally Open) | 3 (or 24) | Switch with open gap |
Pro-Tip on Socket Labels: Some manufacturers use IEC 60947 numbering on their sockets instead of the raw pin numbers. If your socket says 11/12/14 and 21/22/24, treat 11 and 21 as your Commons (Pins 8 and 1), 12/22 as NC (Pins 6 and 4), and 14/24 as NO (Pins 5 and 3). The coil will still be marked A1 and A2.
Node-by-Node Wiring Trace: From Source to Load
Let's trace a complete, real-world control circuit. We will use a 24VDC control circuit to energize the coil, which will in turn switch a 120VAC load. We are using the NO contacts for this example.
1. The Control Circuit (Coil Energization)
- Source: 24VDC positive leaves the power supply's +V terminal.
- Switching Device: The +V wire lands on a momentary pushbutton or PLC output transistor.
- Coil Input: The switched 24VDC wire lands on Socket Terminal 2 (Relay Pin 2).
- Coil Output: The current passes through the internal copper windings and exits at Socket Terminal 7 (Relay Pin 7).
- Ground/Return Path: From Terminal 7, the wire returns to the 24VDC power supply's 0V (negative) terminal. Note: In DC control circuits, this 0V reference is your ground path for the control logic, which should be bonded to the cabinet's earth ground bus at the power supply to prevent floating voltage hazards.
2. The Load Circuit (Switching the Device)
- Line Voltage Source: 120VAC Hot (Black wire) from the branch circuit breaker lands on Socket Terminal 8 (Pole 1 Common).
- Internal Routing: When the coil energizes, the magnetic field pulls the armature down. The internal wiper breaks contact with Pin 6 (NC) and makes contact with Pin 5 (NO).
- Load Feed: The 120VAC Hot exits the relay at Socket Terminal 5 and travels to the load (e.g., a contactor coil, a solenoid valve, or an indicator light).
- Load Return: The load's Neutral (White wire) returns directly to the panel's neutral bus bar, completing the AC circuit. The equipment grounding conductor (Bare/Green) is bonded directly to the load's chassis, bypassing the relay entirely.
Bench Verification: Testing Connections with a Multimeter
Never install a relay without bench-testing it first. Grab a multimeter (like a Fluke 117) and verify the internal paths. According to Fluke's relay testing guidelines, checking coil resistance and contact continuity catches dead-on-arrival components before they cause machine downtime.
- Test the Coil (Pins 2 & 7): Set your meter to Resistance (Ohms). Place probes on pins 2 and 7. A standard 24VDC Omron MY2N coil should read roughly 650 Ω. A 120VAC coil will read much higher (around 10,000 Ω). If it reads OL (Open Loop), the coil is burned out. If it reads 0.0 Ω, it is shorted.
- Test NC Contacts (Pins 8-6 and 1-4): Set your meter to Continuity (the diode/beep setting). With the relay unpowered and out of the socket, place probes on 8 and 6. You should hear a beep (near 0.0 Ω). Repeat for 1 and 4.
- Test NO Contacts (Pins 8-5 and 1-3): Still in continuity mode, place probes on 8 and 5. The meter should read OL. Repeat for 1 and 3.
- Verify Actuation: If you have a bench power supply, apply the rated coil voltage to pins 2 and 7. You should hear a distinct 'click'. While energized, re-test the NO pins (8-5 and 1-3) for continuity, and verify the NC pins (8-6 and 1-4) now read OL.
Frequently Asked Questions
How do I wire an 8 pin ice cube relay to a 120V AC control circuit?
The wiring topology (node-by-node trace) remains exactly the same as the DC example above, but you must use a relay with a 120VAC coil (e.g., Omron MY2N-AC110/120). Connect your 120VAC Hot to the switch, then to Pin 2. Connect Pin 7 to the 120VAC Neutral. Safety Warning: Because both your control circuit and load circuit are now at line voltage, ensure your socket is rated for 300V+ and that you are using properly rated ferrules and torqueing the socket screws to the manufacturer's spec (usually 0.5 to 0.8 Nm) to prevent arcing.
What happens if I reverse the polarity on a DC 8 pin relay coil?
For a standard, bare-bones DC relay, polarity does not matter; the electromagnet will pull the armature regardless of which way the current flows. However, if you are using a relay with built-in diagnostics—like the Omron MY2N-D2, which includes a flyback diode and an LED indicator—reversing the polarity will cause the diode to block the coil current (the relay will not pull in), and the LED will not illuminate. Always wire Pin 2 to Positive and Pin 7 to Negative on diode-equipped DC relays.
Why is my 8 pin AC relay buzzing loudly when energized?
A loud 60Hz buzz from an AC ice cube relay almost always points to a failed shading ring. As explained in All About Circuits' relay theory guides, AC relays have a copper shading coil embedded in the armature face to prevent the magnetic field from dropping to zero during the AC sine wave's zero-crossing. If this ring cracks, or if there is metallic dust/debris on the mating face of the armature, the relay will chatter violently. Clean the armature face with isopropyl alcohol; if the buzz persists, replace the relay immediately before the chatter welds the contacts shut.
