1. Introduction
The Leviton 51120-1 Panel Protector is a 120/240 Volt, 4-mode surge protective device designed for light commercial and residential electrical panels. Housed in a NEMA 1 enclosure, this unit provides protection against voltage transients, safeguarding sensitive electronic equipment from potential damage caused by power surges. It is listed to UL 1449 Standards, ensuring compliance with safety and performance requirements.
2. Important Safety Information
WARNING: Installation of this device involves working with high voltage electricity. Improper installation can result in serious injury, death, or property damage. It is strongly recommended that installation be performed by a qualified, licensed electrician in accordance with all national and local electrical codes.
- Always turn off power at the main circuit breaker before beginning any electrical work.
- Verify that the power is off using a voltage tester before touching any wires.
- Ensure all connections are secure and properly insulated.
- Do not install this device in wet or damp locations unless specifically rated for such environments.
- This device is designed for permanent installation in an electrical panel.

3. Product Features
- Voltage Rating: 120/240V Single Phase.
- Protection Modes: 4-Mode Protection.
- Max Surge Current Rating: 50kA.
- Enclosure Type: NEMA 1 Enclosure.
- Certification: UL 1449 4th Edition Type 2.
- Diagnostic Indicator: Real-time diagnostic visual indicator shows power and suppression status for each protected phase.
- Installation: Standard J-Box enclosure with pre-punched knock-outs for easy surface mounting.
- Low VPR: Ensures protection of sensitive electronic devices.
4. Specifications
| Attribute | Value |
|---|---|
| Model Number | 51120-1 |
| Voltage Rating | 120/240 VAC |
| Frequency Rating | 50/60 Hz |
| Connection Type | 12 AWG Lead Wire |
| Enclosure Type | NEMA 1 |
| Mounting | Panel Mount |
| Product Dimensions | 7" W x 4.06" D x 7" H (approx. 8.25 x 4.75 x 8.25 inches overall) |
| Item Weight | 4.29 pounds |
| Material | Metal |
| Approval | UL (Canada and US) |

5. Setup and Installation
Installation of the Leviton 51120-1 Panel Protector requires careful attention to electrical safety and adherence to wiring codes. Professional installation by a licensed electrician is highly recommended.
5.1 Pre-Installation Steps
- Power Disconnection: Locate the main circuit breaker for your electrical panel and turn it OFF. Confirm power is off using a voltage tester.
- Location Selection: Choose a suitable location near your main electrical panel for mounting the surge protector. The NEMA 1 enclosure is designed for indoor use.
- Gather Materials: You will need appropriate gauge wire (e.g., #10 copper wire for a 30-amp breaker), a two-pole circuit breaker (20-amp or 30-amp recommended), conduit (if required by local codes or for enhanced grounding), lock nuts, bushings, and mounting hardware.
5.2 Mounting the Device
- Prepare Knock-outs: The device features pre-punched standard knock-outs. Select the appropriate knock-out(s) on the surge protector and the electrical panel for conduit or wire entry.
- Mount Enclosure: Securely mount the Leviton 51120-1 enclosure to a wall stud or other stable surface adjacent to the electrical panel. Ensure proper alignment if using conduit between the two enclosures.

5.3 Wiring Connections
- Breaker Installation: Install a two-pole 20-amp or 30-amp circuit breaker into your main electrical panel.
- Wire Connections: Connect the lead wires from the surge protector to the appropriate terminals in the main panel:
- Connect the two black wires (L1 & L2) to the two poles of the newly installed circuit breaker.
- Connect the white wire to the neutral bus bar.
- Connect the green wire to the ground bus bar.
- Secure Wiring: Ensure all wire connections are tight and properly routed.
5.4 Post-Installation
- Close Panel: Replace the covers on both the surge protector and the main electrical panel.
- Restore Power: Turn the main circuit breaker back ON.
6. Operation
Once properly installed and power is restored, the Leviton 51120-1 Panel Protector operates automatically. The device features real-time diagnostic visual indicators (typically green LEDs) that show the power and suppression status for each protected phase.
- Green Indicator Lights ON: This indicates that the unit is powered and actively providing surge protection.
- Indicator Lights OFF: If one or both indicator lights are off, it signifies that the surge protection module for that phase may have been compromised due to a significant surge event or a power issue. Refer to the Troubleshooting section.
7. Maintenance
The Leviton 51120-1 Panel Protector requires minimal maintenance. Regular visual inspection is recommended to ensure proper operation.
- Monthly Check: Periodically check the diagnostic indicator lights on the front of the unit. Ensure both green lights are illuminated.
- Cleaning: If necessary, gently wipe the exterior of the enclosure with a dry, soft cloth. Do not use abrasive cleaners or solvents.
- No User-Serviceable Parts: The internal components are not user-serviceable. Do not attempt to open or repair the unit.
8. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| One or both green indicator lights are OFF. | The surge protection module for that phase has been compromised due to a significant surge event, or there is no power to the unit. |
|
| Device is warm to the touch. | Normal operation may involve slight warmth. Excessive heat could indicate an issue. | If the device feels excessively hot, immediately turn off power at the circuit breaker and contact a qualified electrician. |
9. Warranty and Support
For warranty information, technical support, or service inquiries regarding your Leviton 51120-1 Panel Protector, please refer to the official Leviton website or contact Leviton customer service directly. Keep your purchase receipt as proof of purchase.
Leviton Contact Information:
Visit www.leviton.com for product support, FAQs, and contact details.