IDEC Relay Wiring Diagram: Node-by-Node RR2P Walkthrough

When you are staring at an IDEC relay wiring diagram for the first time, the standard 8-pin DPDT (Double Pole Double Throw) layout can look like a maze of intersecting lines. The direct answer for the most common industrial workhorse—the IDEC RR2P series plugged into an SH2B socket—is that pins 2 and 7 energize the coil, while pins 1/3/4 and 8/6/5 handle the two independent load poles.

Below, we will trace a standard 120VAC control and load circuit node-by-node, map the physical terminals, and show you exactly how to verify your connections with a multimeter before you energize the panel.

Decoding the IDEC Relay Wiring Diagram Symbols

Before tracing the wires, you need to read the schematic language. IDEC diagrams follow IEC and NEMA standard symbology. Here is what the specific symbols in this drawing mean:

• The Coil (Rectangle): Represented by a simple rectangle, often labeled with the pin numbers (2 and 7) or A1/A2. If it is a DC coil, a polarity mark (+) will be near pin 2.
• NO and NC Contacts: Normally Open (NO) contacts are drawn as two parallel lines with a gap, and a diagonal line representing the movable armature. Normally Closed (NC) contacts show the armature overlapping the stationary contact.
• Mechanical Link (Dashed Line): A dashed line connecting the coil to the switch arms indicates that the magnetic field of the coil physically moves those specific contacts.
• Flyback Diode: In DC diagrams, you will see a diode symbol in parallel with the coil (cathode to positive). This suppresses the inductive voltage spike when the coil de-energizes, protecting your PLC outputs or solid-state switches.

Terminal and Pin Mapping for the SH2B Socket

The physical IDEC RR2P relay mates with an SH2B (screw terminal) or SH2B-05 (PCB mount) socket. The relay base has a locking tab that aligns with a slot on the socket to prevent misalignment. Here is the exact terminal mapping you will see on the socket's printed legend:

Note: Always verify the pinout printed directly on your specific socket base, as older or specialized solid-state IDEC modules may deviate from the standard electromagnetic RR series layout.

Node-by-Node Wiring Trace: Source to Load

Let us trace a practical circuit: using a 120VAC IDEC RR2P relay to switch a 120VAC exhaust fan (Pole 1) and a 120VAC green pilot indicator light (Pole 2) simultaneously via a momentary pushbutton.

Safety Warning: This procedure involves 120VAC mains voltage. De-energize the panel, lock out the breaker, and verify the circuit is dead with a non-contact voltage tester and a multimeter before touching any terminals. NEC-style guidance requires proper overcurrent protection; always follow your local AHJ rules.

1. The Control Circuit (Coil Energization)

1. Source Hot (L1): 120VAC Black wire lands on the main panel breaker, routes to a 2A glass fuse holder, and exits to the momentary pushbutton (Normally Open contact).
2. Switch to Coil: The output of the pushbutton (White wire with Black tape, denoting a switched hot) lands on Socket Pin 2 (A1).
3. Coil Return: A Neutral (White) wire runs from Socket Pin 7 (A2) directly back to the panel's neutral bar.
4. Ground Path: The equipment grounding conductor (Bare/Green) does not connect to the relay coil or contacts. It routes directly to the metal exhaust fan housing and the metal pilot light bezel to ensure fault clearing.

2. The Load Circuit (Poles 1 and 2)

1. Load Source: A separate 120VAC Black wire from a 15A branch breaker lands on a terminal block, splitting into two jumper wires.
2. Pole 1 Feed: Jumper 1 lands on Socket Pin 1 (C1).
3. Pole 2 Feed: Jumper 2 lands on Socket Pin 8 (C2).
4. Pole 1 Output (Fan): A Black wire runs from Socket Pin 4 (NO1) to the Hot terminal of the exhaust fan motor.
5. Pole 2 Output (Light): A Black wire runs from Socket Pin 5 (NO2) to the Hot terminal of the green pilot light.
6. Load Neutrals: The Neutral wires from the fan and the pilot light tie together and return to the panel neutral bar.

When the pushbutton is pressed, pins 2 and 7 magnetize the coil. The armature pulls in, bridging Pin 1 to Pin 4, and Pin 8 to Pin 5. Both the fan and the light energize simultaneously.

Verifying Your Connections with a Multimeter

Do not rely on visual inspection alone. Relay sockets in industrial panels often suffer from loose screw terminals or cold solder joints on PCB variants. Use a digital multimeter (DMM) to verify the circuit before applying power.

1. Verify Coil Integrity (Ohms): With the relay unplugged, set your DMM to Ohms (Ω). Place probes on relay pins 2 and 7. A 120VAC IDEC RR2P coil should read between 3,500Ω and 4,500Ω. A 24VDC coil will read much lower, typically around 650Ω to 750Ω. If it reads OL (Open Line), the internal coil wire is broken.
2. Verify NC Contacts (Continuity): With the relay unplugged, set the DMM to continuity (beep mode). Probe Pin 1 and Pin 3. You should hear a beep (resistance < 0.1Ω). Repeat for Pin 8 and Pin 6.
3. Verify NO Contacts (Open): Probe Pin 1 and Pin 4. The meter must read OL. Repeat for Pin 8 and Pin 5.
4. Verify Socket Wiring (Voltage): With the relay unplugged and power restored to the panel, carefully measure AC voltage between Socket Pin 2 and Socket Pin 7 while pressing the pushbutton. You should read 114V to 126V. Measure between Pin 1 and Neutral, and Pin 8 and Neutral; both should read line voltage.

Frequently Asked Questions

How do I wire an IDEC relay for 24VDC instead of 120VAC?

The physical wiring topology remains identical, but you must swap the RR2P 120VAC relay for an RR2P 24VDC variant (e.g., RR2P-U DC24). On the control side, connect your 24VDC positive supply to Pin 2 and the 0VDC (ground) return to Pin 7. While AC coils are non-polarized, DC coils are polarized; reversing the polarity on a DC coil with an integrated flyback diode or LED indicator will cause the diode to short the supply or the LED to fail to illuminate. Always verify the '+' marking on the relay base.

Why is my IDEC RR2P relay buzzing loudly when energized?

A loud 60Hz hum or buzz from an AC electromagnetic relay indicates that the armature is not seating flush against the core. This is almost always caused by debris (metal shavings, dust, or wire clippings) lodged on the magnetic mating surfaces of the core. Unplug the relay, remove the dust cover, and wipe the top of the E-I core laminations with isopropyl alcohol and a lint-free swab. If the buzzing persists, the shading ring (a small copper loop embedded in the AC core to prevent zero-crossing chatter) may be cracked, requiring a relay replacement.

Can I use an IDEC SY4S relay in place of an RR2P?

No, they are not drop-in replacements despite both being DPDT. The IDEC SY4S is a smaller, lower-capacity relay (typically rated for 5A to 8A) that uses a completely different 8-pin footprint and mates with an SY socket. The RR2P is a heavy-duty 'ice cube' relay rated for 10A to 15A and uses the larger SH2B socket. If you need to upgrade from an SY4S to an RR2P for a higher inrush load (like a motor starter), you must also replace the socket base and ensure your branch circuit wiring can handle the higher current capacity.