EG4 ELECTRONICS Electrical Breakers Sizing Instruction Manual
- June 6, 2024
- EG4 ELECTRONICS
Table of Contents
EG4 ELECTRONICS Electrical Breakers Sizing
Product Information
Specifications
- Product Name: Electrical Breakers Sizing Guide
- Use: Properly sizing electrical breakers for inverters, batteries, and solar panels
- Components: PV DC Breakers, Charge Controller DC Breakers, Inverter AC Breakers
Product Usage Instructions
Overview
The guide provides technical information to help users determine the
correct breaker type and size for their electrical setup involving inverters,
batteries, and solar panels.
Breaker Use Cases
Select the appropriate breaker type for each component in your PV solar
system:
- PV DC Breakers: Protect solar panels from excess current.
- Charge Controller DC Breakers: Regulate battery charging.
- Inverter AC Breakers: Transform DC power to AC power.
How Do Breakers Work
Tripping Principles: Breakers trip to interrupt the circuit when excessive current flows, preventing damage or hazards.
Correctly Sizing Breakers
Ensure you size breakers correctly based on the device nameplate rating and
calculations.
-
Device Nameplate Rating
The device nameplate rating provides crucial information for selecting the right breaker size. -
Making the Calculations
Calculate the load on the circuit to determine the appropriate breaker size needed.
Types of Breakers
- Models: Different models of circuit breakers are available, such as single-pole, two-pole, three-pole, and four-pole circuit breakers.
- AC and DC Breakers: Use DC-rated breakers for direct current applications to ensure proper arc extinguishing measures.
FAQ (Frequently Asked Questions)
-
Q: How do I know which breaker size to choose for my system?
A: Refer to the device nameplate rating and perform the necessary calculations based on your circuit load to determine the correct breaker size. -
Q: Can I use an AC breaker for DC applications?
A: It is not recommended. Use DC-rated breakers for DC circuits as they are designed with specific arc extinguishing measures for direct current flow.
BREAKER SIZING
WHITE PAPER
This guide has been created to give the end-user a guide for properly sizing electrical breakers.
OVERVIEW
The goal of this guide is to provide technical information that will assist end users in determining the proper breaker type and size required to support the installation of inverters, batteries, and solar panels.
BREAKER USE CASES
Selecting the right type of breaker within a PV solar system is just like choosing the right tool for any job. Each component, whether it’s the PV solar feed, a charge controller, battery bank, or an inverter, requires a tailored solution. Let’s look at the key elements:
- PV DC Breakers: These are the gatekeepers of energy flow. They protect the solar panels, ensuring that excess current doesn’t flood the system during peak sun hours. Look for breakers with robust capacity and compatibility with direct current (DC) circuits.
- Charge Controller DC Breakers : Charge controllers regulate the battery charging process. Breakers here act to prevent overcharging or excessive discharging. For this application, consider breakers with the ability to handle both AC and DC currents.
- Inverter AC Breakers : Inverters transform DC power from solar panels into usable AC power. Breakers in this realm ensure smooth transitions, prevent overloads, and safeguard against faults. Look for options that align with your inverter’s specifications.
HOW TO BREAKERS WORK
Circuit breakers, also known as an Over Current Protection Device (OCPD),
protect electrical circuits by stopping the flow of electricity when they
detect too much current flow on the circuit. This “overcurrent” can be caused
by having too many devices plugged in or a sudden surge of electricity known
as a short circuit or ground fault.
When a breaker trips, it is known to have stopped the flow of electricity. A
breaker can be reset and used again, but only if you resolve the overcurrent
situation. If a breaker keeps tripping, investigate the circuit and or the
devices plugged into the circuit. If you’re not sure what’s causing the
breaker to trip, call a licensed electrician for help.
The ability to reset a breaker is a significant advantage over fuses, which
were common in homes before the introduction of circuit breakers. Fuses can
only be used once. If a fuse blows, it must be replaced.
TRIPPING PRINCIPLES
A circuit breaker has two different tripping principles to protect the
circuit. Thermal protection will lead to circuit interruption in case of
overheating. Electromagnet protection is designed to interrupt a circuit due
to a short circuit.
On the thermal-magnetic side of a circuit breaker, a bimetallic strip heats up
with the current. If the circuit’s current rises over a certain level, the
strip will bend moving the switch linkage breaking its connection to the
stationary contact, causing the circuit to break (open).
Electromagnetic protection comes from the copper coil. The electromagnet is
magnetized when electricity flows through the terminals. The larger the
current, the larger the electromagnetic force. When a current reaches unsafe
levels while traveling through this coil, the electromagnet becomes strong
enough to move a small spool inside it, which will also move the switch
linkage, the moving contact, therefore breaking (opening) the circuit.
CORRECTLY SIZING BREAKERS
Properly sizing breakers prevent unnecessary tripping or insufficient protection within the electrical system. Sizing breakers too low can result in frequent tripping during normal operation, such as when high-demand appliances like air conditioners or well pumps start. On the other hand, sizing breakers too high may fail to provide adequate protection in case of faults or overcurrent, risking damage to equipment and wiring. One key item to remember, the main job of the breaker is to protect the wire that connects the devices together. When you size a breaker, never install wire that supports less amperage than the installed breaker.
-
DEVICE NAMEPLATE RATING
Always check the nameplate rating or the specifications sheet of the device to see what the amperage draw requirement is. The listed amperage rating determines the appropriate wire and breaker size. It is essential to ensure that the wires and breakers are sized correctly. Using an incorrect wire size or breaker can lead to inefficiencies, overheating, and safety hazards. The image below shows the nameplate ratings for the EG4® 6000XP. -
MAKING THE CALCULATIONS
Determining the appropriate size of circuit breaker for single phase supply depends on multiple factors like type of load, cable material and environment temperature etc. The general rule of thumb is that circuit breaker size should be rated 125% of the ampacity of circuit requirements.
For the calculation example, use the 6000XP nameplate sticker listed above. The max AC input is rated at 45A. To properly size the required breaker, take 45A x 1.25 (125%) which equals 56.25A. Since there is not a 56.25A available on the market for purchase, the next sized breaker would be used, a 60A. Also, remember to use properly sized wire rated for 60A.
TYPES OF BREAKERS
MODELS
There are several models of circuit breakers, such as the single-pole, two-
pole, three-pole, and even the four-pole circuit breakers. The numbers of
poles directly relate to the number of circuits (hot wires) the breaker can
support.
A single-pole breaker protects a single circuit in an electrical system. This
single circuit might power the lights in your living room or feed receptacles
in your kitchen. Single-pole breakers take up one slot in your home’s
electrical panel and typically protect 15-amp and 20-amp circuits.
Double-pole breakers work the same way as single-pole breakers, but they
protect circuits that support more amperage. For example, a 50-amp clothes
dryer uses two 120V circuits to deliver enough current for the appliance to
operate. Since both circuits need overcurrent protection, a double-pole
breaker is used that accepts two wires instead of one. These breakers are
larger than single-pole, so they take up two slots in your panel. If a double-
pole breaker trips, it has a handle that allows you to reset both hots
simultaneously.
AC AND DC BREAKERS
Understanding the difference between AC and DC breakers is essential in PV
solar systems. AC breakers are designed with internal contacts that separate,
opening the circuit when too much current flows. But because AC power
alternates between positive and negative voltage, there are two points in
every cycle where the voltage is zero. When the contacts separate and an arc
forms, the arc disappears within 1/120th of a second. AC breakers do not need
the arc extinguishing measures that are critical for DC breakers.
DC breakers are very focused, and specific to direct current applications.
Because DC voltage constantly flows in one direction, the breaker must have a
way to extinguish the arc. These arc extinguishing measures separate a DC
breaker from an AC breaker, so it is critical to use DC-rated breakers for DC
circuits.
When looking at AC breakers, they are labeled with a gentle tilde (~). The
symbol may or may not have a solid line above the tilde. DC breakers are
labeled with bold line resting above a dotted line (⎓).
WIRE CORE MATERIAL
When installing a breaker, ensure it’s rated for the wire core material that
is connected to the breaker terminals. Breakers are rated for copper wire
only, aluminum wire only, or for both. Using the incorrect wire material can
cause wire oxidation, overheating of the wire, and possible wire breakage at
the wire connection to the breaker. Breakers supporting copper only
connections are labeled as “Cu”. Breakers supporting only aluminum wire
connections are labeled “Al”. Breakers that support both are labeled with
both, Cu/Al.
POLARIZED BREAKERS AND INSTALLATION
When installing DC breakers, pay careful attention to the polarity (indicated
by a plus and/or minus sign) of each breaker to avoid compromising their
protective function. Incorrect installation, such as reversing positive and
negative connections, can lead to the loss of protection and potential damage
to the system. It is imperative to follow manufacturer instructions, examine
markings for polarity, and adhere to specifications to ensure proper
installation and functionality of polarized breakers.
THERMAL EXPANSION AND MAINTENANCE
Over time, breakers experience thermal expansion due to regular use, leading
to the loosening of connections and potential arcing. Proper torquing of
clamps during installation and regular maintenance checks are essential to
mitigate thermal expansion effects and maintain system stability. Using
quality breakers and following recommended maintenance practices contribute to
the long-term reliability and safety of PV solar systems.
An Ohm meter is recommended to check for resistance in breakers and assess
their performance. Low resistance indicates efficient operation, while high
resistance can lead to inefficiencies and overheating. Maintaining low
resistance in breakers ensures optimal performance and longevity of the
electrical components.
CONCLUSION
Sizing breakers accurately and using the correct type for each application is
critical to the overall performance and safety of PV solar systems. By
understanding the nameplate rating, conducting resistance checks, and
following best practices for installation and maintenance, solar manufacturers
and end users alike can ensure the efficiency and reliability of their systems
while meeting regulatory requirements.
CONTACT US
support@eg4electronics.com
903-609-1988
www.eg4electronics.com
References
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