1. Product Overview
The Murray MP120 is a 20-Amp Single Pole Type MP-T Circuit Breaker designed for overload and short-circuit protection within your home's electrical system. This thermal-magnetic circuit breaker is a critical component for safeguarding wiring from excessive current and high temperatures.
Figure 1: Front view of the Murray MP120 Circuit Breaker, showing the 20-Amp rating and toggle switch.
Key Features:
- Single pole, 20 Amp, 120V type MP-T Circuit Breaker.
- Features a 10,000 AIC interrupting rating.
- Designed for easy plug-in connections in Murray enclosures with the time-saving Insta-Wire feature.
- Compatible with Murray Rock Solid load centers.
- Provides essential overload and short-circuit protection for electrical systems.
2. Important Safety Information
WARNING: Risk of Electric Shock or Fire.
Installation and servicing of electrical equipment should only be performed by qualified, licensed electricians. Always disconnect power at the main service panel before working on circuit breakers or any electrical wiring.
- Do not use "used" circuit breakers. Murray strongly recommends against the use of "used" breakers. The installation of used breakers in a Murray panel will void the warranty on the panel.
- Ensure the circuit breaker's rating matches the requirements of the circuit it protects.
- Always follow local electrical codes and regulations.
- Never attempt to bypass or tamper with the circuit breaker's protective mechanisms.
3. Installation Instructions
The Murray MP120 circuit breaker is designed for plug-in installation in Murray load centers or meter combinations. Proper installation is crucial for safe and reliable operation.
Pre-Installation Steps:
- Verify Compatibility: Ensure your load center is a Murray brand and compatible with Type MP-T circuit breakers. Using non-Murray breakers in a Murray panel may void the panel's warranty.
- Power Disconnection: Locate the main service panel and turn off the main breaker to completely de-energize the electrical system before beginning any work. Verify power is off using a voltage tester.
- Gather Tools: You will need basic electrical tools such as a screwdriver, wire strippers, and a voltage tester.
Installation Procedure:
- Identify Slot: Locate an available slot in the Murray load center. The MP120 is a single-pole breaker and requires one slot.
- Connect Wire: Strip approximately 1/2 inch of insulation from the circuit wire (typically 14-10 AWG for 20-Amp circuits). Insert the bare end of the wire into the terminal screw of the circuit breaker. Tighten the screw firmly to ensure a secure connection (refer to torque specifications if available, typically 25 in-lbs for 14-10 AWG).
- Plug-In Installation: Align the circuit breaker's clip with the bus bar in the load center. Press the breaker firmly into place until it clicks, ensuring it is fully seated on the bus bar.
- Secure Cover: Once all breakers are installed, replace the load center cover.
- Restore Power: Turn the main breaker back on at the service panel.
- Test Circuit: Test the newly installed circuit by turning on the breaker and verifying power to the connected circuit.
Figure 2: Example wiring diagrams for single-pole circuit breakers, illustrating connection to line and load.
Figure 3: Side view of the Murray MP120 Circuit Breaker, showing product labeling and UPC (040892518894).
4. Operating Instructions
The Murray MP120 circuit breaker operates automatically to protect your electrical circuits from overloads and short circuits. It also allows for manual control of power to a specific circuit.
Normal Operation:
- When the circuit breaker is in the "ON" position, power is supplied to the connected circuit.
- In the event of an overload (too much current flowing through the circuit) or a short circuit, the breaker will automatically "trip" to the "OFF" or center position, interrupting the power flow to prevent damage or fire.
Resetting a Tripped Breaker:
- Identify Tripped Breaker: A tripped breaker will typically be in a position between "ON" and "OFF", or fully "OFF".
- Address the Cause: Before resetting, identify and correct the cause of the trip. This usually involves unplugging overloaded appliances or addressing a short circuit.
- Fully OFF: Push the breaker handle firmly to the full "OFF" position. You may hear a click.
- Turn ON: Push the breaker handle firmly to the full "ON" position.
- If the breaker immediately trips again, do not attempt to reset it repeatedly. There is a persistent electrical issue that requires professional attention.
5. Maintenance
Murray circuit breakers are designed for long-term, maintenance-free operation under normal conditions. However, periodic inspection by a qualified electrician is recommended to ensure the continued safety and reliability of your electrical system.
- Visual Inspection: Periodically inspect the circuit breaker for any signs of physical damage, discoloration, or loose connections.
- Dust and Debris: Ensure the load center interior is free from dust, debris, or moisture, which can interfere with proper operation.
- Professional Check: Consider having a qualified electrician inspect your electrical panel and circuit breakers every few years, especially if you experience frequent tripping or other electrical issues.
Do not attempt to lubricate or modify the circuit breaker in any way. If a breaker appears faulty or damaged, it should be replaced by a qualified professional.
6. Troubleshooting
This section provides guidance for common issues you might encounter with your circuit breaker.
| Problem | Possible Cause | Solution |
|---|---|---|
| Breaker trips frequently. | Overloaded circuit (too many devices on one circuit), short circuit, ground fault, or faulty appliance. | Unplug some devices from the circuit. Inspect appliances for faults. If problem persists, consult a qualified electrician. |
| Breaker will not reset. | Persistent overload or short circuit, internal breaker fault. | Ensure all devices are unplugged from the circuit. If it still won't reset, do not force it. Contact a qualified electrician. |
| No power to circuit, but breaker is ON. | Loose wire connection, faulty outlet/switch, or internal wiring issue. | Check connections at the breaker and outlets. If unsure, contact a qualified electrician. |
For any electrical issues that you are not comfortable addressing, always consult a qualified and licensed electrician.
7. Specifications
| Attribute | Detail |
|---|---|
| Brand | Murray |
| Model Number | MP120 |
| Current Rating | 20 Amps |
| Voltage | 120 Volts |
| Number of Poles | 1 |
| Circuit Breaker Type | Standard, Thermal-Magnetic |
| Mounting Type | Plug-In Mount |
| Interrupting Rating (AIC) | 10,000 |
| Material | Copper |
| Finish | Black |
| Item Weight | 3.84 ounces |
| Product Dimensions (L x W x H) | 1 x 3.6 x 3.6 inches |
| UPC | 040892518894 |
8. Warranty and Support
For warranty information and technical support regarding your Murray MP120 Circuit Breaker, please refer to the official Murray documentation provided with your product or visit the manufacturer's website.
Important Warranty Note: Murray strongly recommends against the use of "used" breakers. The installation of used breakers in a Murray panel will void the warranty on the panel. Murray does not sell used breakers and has not approved any 3rd party sellers to do so.
For further assistance, contact a qualified electrician or Murray customer support.
