Overview of Square D QO Circuit Breaker from Schneider Electric

When it comes to electrical circuit protection, the square D QO breakers have always been the best. The breaker protects appliances from overload and short circuits.

It also controls the flow of electricity and interrupts faulty currents that can threaten the safety of our homes.

Circuit breakers come in different types and sizes, but they do similar work, which is overload and short-circuit protection.

Whenever you intend to install or replace your breaker, make sure it is a Square D product.

Overview of Square D QO Miniature circuit breakers

Square D QO circuit breakers are a series of breakers from Schneider Electric, a leading company in circuit breaker and safety switch manufacturing.

The QO circuit breakers come with plug-on options and a range of amperage and interruptors to fit various panels. 

 The QO series is one of the most popular and widely used breakers in the market.

Here are some series of breakers from Square D that you can buy.

Square D QO Qwik-Gard 20 Amp Single-Pole GFCI Circuit Breaker

QO 100-Amp Two-Pole Circuit Breaker

Square D – 30-Amp, 120/240V, 2-Pole, GFCI, plugin mount

Schneider Electric QO260CP QO 60 Amp Two-Pole Circuit Breaker

Square D by Schneider Electric QO250CP QO 50 Amp Two-Pole Circuit Breaker

Square D QO Qwik-Gard Ground Fault Miniature Circuit Breaker; 40 Amp, 120/240 Volt AC, 2-Pole, Plug-On Mount

Square D Tandem Circuit Breaker 20/20 Amp Bulk

Importance of using Square D circuit breakers.

Using a high quality and reliable breaker is important because it enhances:

Safety: The primary role of a breaker is to protect the circuit and appliances from overload and short circuits.

High-quality breakers are built to stringent safety standards that can enable them to interrupt faulty currents and prevent electrical hazards.

Circuit protection: Breakers play a huge role in safeguarding electrical circuits. They can detect and quickly cut off the flow of abnormal currents to protect the circuit and appliances.

Durable and reliable: High quality breakers are built with robust materials and advanced technologies, which makes them strong and reliable.

Compatible: High quality breakers are built to meet residential and industrial standards, ensuring compatibility with various electrical systems and equipment.

They come in different sizes, current ratings, and trip characteristics, enhancing proper matching with specific load requirements.

How the Square D QO breakers work

The QO circuit breakers have a thermal-magnetic trip element calibrated at 40°C ambient temperature.

Whenever there is an over current in any of the poles, the trip mechanism opens, switching OFF the current.

Voltage rating

The voltage rating of the breaker must be higher, or equal to that of the system, for normal performance.

If the voltage rating is normal, the breaker can easily extinguish its arc whenever there is a faulty current.

The Qwik-Open “QO”and Qwik-Open-Bolted “QOB” breakers are rated for the following systems:

  • 120 Vac
  • 208/120 Vac
  • 120/240 Vac
  • 240 Vac
  • 48 Vdc (10–70 A for 1 and 2 pole circuit breakers, 10–60 A for 3 pole circuit breakers)
  • 120 Vac
  • 208/120 Vac
  • 120/240 Vac
  • 240 Vac
  • 48 Vdc (10–70 A for 1 and 2 pole circuit breakers, 10–60 A for 3 pole circuit breakers)

Key Features of square D QO Breakers

Plug-on design

The qo breakers come with a plug on design for easy installation or replacement. If you want to install the breaker, all you can do is to plug it into the load center or panel. No need for wiring.

Visi-trip indicator

Square D QO breakers come with a Visi-Trip indicator, a red window that displays a trip sign when the breaker is off. This feature helps to easily identify the breaker that has tripped off.

Dual function capability

Some models of the QO series combine both the features of a circuit breaker and a ground fault circuit interrupter (GFCI) or an arc fault circuit interrupter (AFCI) in a single device. This integration improves safety by providing protection against both ground faults and arc faults.

High quality and Reliable

Square D breakers are known for their superior quality and reliable. They are designed to provide safe and efficient circuit protection for both residential, commercial, and industrial applications.

Wide Range of Options

The QO series offers a wide range of circuit breakers to meet various needs. They are available in different ampere ratings, ranging from 15 to 125 amps, allowing for the protection of circuits with different power requirements.

Other circuit breakers from Square D

QOT Tandem Circuit Breaker

Tandem circuit breakers are known with different names such as duplex, half-height, half-inch, slimline, twin, double, and wafer breaker.

They usually look like a two-pole circuit breaker, but only connect to a single pole at the panelboard.

They are often used on residential applications with light or non-continuous circuit loading. QOT breakers are available in 15/15A, 15/20A and 20/20 ampere construction.

They are also available in standard versions for modern circuit total limiting (CTL) on load centres and non-compliant types for non-CTL load centres.

QO arc fault circuit interrupters (AFCI)

The arc fault circuit interrupters detect an arc fault and quickly opens the breaker to prevent fire outbreak.

Unlike the normal circuit breaker that detects only short circuits and overloads, AFCI detects overload, short circuit and arc-fault.

They come with a special microprocessor that differentiates true arcs from operational ones.

Once they detect the arc fault, they open the circuit.

They also come with Qwik-Open and visible trip indicator just like others.

QO Ground Fault Circuit Interruptor (GFCI)

The ground fault circuit interrupters offer protection against ground faults. They are usually installed in the bathroom, kitchen, and wet area where currents may easily come in contact with water.

The breaker shuts OFF power once it senses current leakage. They do that by comparing the inputs and output currents from electrical devices.

If there is variation between the input and output current even as little as 0.005 amps, the breaker will trip OFF.

Square D QO CAFI combination

This circuit breaker combines both AFCI and GFCI in one device there by protecting against arc and ground fault.

Before 2014, when the National Electrical Code (NEC) recommended the use of dual circuit breakers, AFCI and GFCI usually came separately. But after the invention, the two breakers became one providing dual functions.


What is the difference between a QO and QOB breakers?

The main difference between the two is that the QO breakers have a plug-on design that enables you to plug it into the load centre. While the QOB breakers have a bolt-on design for easy installation in the load center.

How do I know if I have a QO breaker?

You can know a QO breaker by looking at the label. The breaker usually has a QO letter on it. Secondly, it is usually smaller and equally has a small window where you can see if it is in on or trip position, unlike the Home line breakers.

How do I know which Square D breaker I need?

You can know the breaker you need by determining the type of load the breaker will be protecting. This may include cooker unit, air conditioning, lighting and other types of electrical appliances. Once you know the load type, you can then determine the current rating of the breaker based on the maximum current the load can draw. You should also consider the voltage rating and the number of poles (single or double) required for the device.  

What does QO on the circuit breaker mean?

The “QO” on the Square D circuit breakers means Qwik-Open. Meaning it is the fastest to open circuit breaker in use. The device opens after a full power cycle.

QO plug-on breakers come in 1-pole, two, and three pole terminals just to suit your requirements.

They are ideal for QO load centers, OEM mounting bases, NQ and NQOD panel boards, and others.

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About mariaelectricals

Hi, I am Emmanuel Nwankwo, a commercial electrician and the founder of mariaelectricals.com. I established this blog to share my seven years of work experience in electrical installations and repairs.