Basics of Load Centers

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Why Use a Sub-panel?

You see, it would become quite costly to run each and every circuit that you need from one end of the house to the other and then into a garage. By placing a sub-panel in the area where a majority of the wiring exists, you’ll cut down on the overall expense of the project, and when a breaker trips, you won’t have to walk all the way to the other side of the world to reset it. See figure 5.


Figure 5

Sizing sub-panels to the need of your anticipated load can be tricky. You’ll need to consider the amount of available power load you’ll need and what the main service has to offer. For instance, If you have a 200-amp main service, you’ll have no problem adding a 100-amp sub-panel to feed a shed, garage, barn, etc… or a 60-amp sub-panel to power lighting and general-use outlets in another section of your home. But if you only have a 60-amp service to begin with and want to add a 60-amp sub-panel, you’ll have to upgrade your main panel first to allow such a distribution addition.

When adding a sub-panel, I suggest adding at least a 12-slot circuit breaker panel. This should provide ample room for lighting and general circuits. However, if you plan to add many 240-volt appliances like central air conditioning, baseboard heaters, water heaters, ovens, ranges, or 240-volt window air conditioners, then a circuit breaker panel with more opening may be required, as well as a circuit breaker panel with more openings and a larger main breaker rating.

What is a panel-board?

A panel-board is a type of enclosure for over current protection devices and the busses and connections that provide power to these devices and their associated circuits. So, A distribution board (or panel-board) is a component of an electricity supply system which divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit, in a common enclosure. Normally, a main switch, and in recent boards, one or more Residual-current devices (RCD) or Residual Current Breakers with Over-current protection (RCBO), will also be incorporated.

 Figure 6 illustrates a fairly standard American circuit breaker panel manufactured by General Electric and using interchangeable circuit breakers


Figure 6

Load Center Construction

Load centers are constructed of the following three parts: enclosure, interior, and trim. The enclosure is typically constructed of cold rolled steel (for indoor use) or galvanized steel (for outdoor use). Together with the trim, the enclosure is designed to provide component and personnel protection.
Knockouts are stamped into the enclosure to provide a convenient means of creating holes for use in routing electrical wiring.

Approved cable clamps or conduit hubs are used in the holes to secure and protect the cable and conductors.

NEMA Enclosures

The National Electrical Manufacturers Association (NEMA®) has established standards for electrical equipment enclosures. NEMA type 1 enclosure are intended for indoor use. NEMA type 3R enclosures are intended for outdoor use primarily to provide a degree of protection against rain, sleet and damage from external ice formation. Load center enclosures typically conform to one of these NEMA enclosure types.

What are branch circuits?

A home’s electrical system has feeder wires that supply power to the panel and branch circuits that leave the panel to power devices. As you may know, the service feeders connect to the main breaker, which supplies power to the electrical panel for distribution. It normally is connected to a 100- or 200-amp two-pole circuit breaker, This main breaker is the main disconnect for the power supply of the breaker box enclosure.

There are also many other breakers within this circuit breaker box enclosure. These breakers vary from the common 15- and 20-amp breakers to those breakers of 100 amps or more, depending on the size of the main breaker and the load requirements that are needed on each individual circuit. These breakers also come in single- (for 120-volt circuits) and double-pole (for 240-volt applications) styles. They are the current protection devices for the circuits that feed areas, devices such as appliances, and lighting throughout your home. These circuits are referred to as branch circuits, much like a branch on a tree is an extension of a tree. It is a part of the system and provides its individual protection of its circuit, but has ties to the main breaker. The main breaker could theoretically trips if the load across the individual branch circuit breaker became large enough due to the branch circuit’s failure to trip.

Branch Circuit Breakers plug directly onto the load center’s supply bus bars as shown in the following illustration.


Figure 6

What is a circuit directory?

Labeling circuit breakers and fuses is not only a good idea so that you know the location and devices they serve, nut also a National Electrical Code requirement. In article 408.4 it states the need for such a directory stating, “Every circuit and circuit modification shall be legibly identified as to be its clear, evident, and specific purpose or use.”

In article 110.22 it states, “Each disconnecting means shall be legibly marked to indicate its purpose unless located and arranged so the purpose is evident. The marking shall be of sufficient durability to withstand the environment involved.” A sharpie is a nice choice for permanent marking in this case.

But that’s not all. In fact, even spare breakers are to be labeled with a “SPARE” designation, even though there may be nothing connected to the circuit breaker. That way you will know what every breaker does or does not do.

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Key terms discussed on the download file:

Sub-panel, 12-slot circuit breaker panel, circuit breaker panel, main breaker rating, panel-board, over current protection, Residual-current devices (RCD) , standard, General Electric, Load Center Construction, Knockouts,  NEMA Enclosures, NEMA type 3R enclosures, Load center enclosures, NEMA enclosure types, feeder wires,) National Electrical Code requirement., sharpie, Load Center installation, Residential, current rating , current-carrying , RMS electric current, ambient temperature, excess current, short circuits, excessive load, ground fault, Fuses, circuit breakers, ground fault , Breaker Design, fuse , circuit Breaker Poles, Circuit Breaker Voltage Rating, Voltage Rating, Continuous Current Rating, current setting, maximum continuous current, Main Circuit Breaker , Branch Circuit Breakers, switches, QP Circuit Breaker, , QT Duplex Circuit Breakers, Ground Fault Protection, , circuit breaker, grounding conductor, defective cords, ground-fault circuit interrupter (GFCI) , GFCI, Arc Faults, Surge protection, surge protector (or surge suppressor), surge protection device (SPD), 1-Phase, 2-Wire System, single-phase electric power , Single-phase distribution (1-phase, 2-wore system), 1-Phase, 3-Wire System, split-phase, three-wire, single-phase, midpoint neutral , Three-phase electric power, 3-Phae, ES Series Load Centers, PL Features, ES Features, EQ load centers, sizing The Load Center, sub panels, Power Calculation , AC Disconnects, Commercial-duty low-voltage, switchboard, panel board , fused or non-fused disconnects, Low-voltage disconnect, ,maintenance, Feeder disconnects,  overcurrent protection , Disconnect switches,  shunt-trappable disconnect switch, ground fault monitor, sensor and relay,  low-voltage disconnect switches, medium-voltage disconnect switches, disconnect switches are UL Listed and CSA Certified and are designed to meet IEC 60947-3, VDE, DIN, BS and applicable NEMA requirements, Load Center Grounding, What is a residential utility metering device, An electricity meter or energy meter, Residential Meter Sockets, Single position socket, Meter Combos, SOLAR Ready, Temporary power outlet panels, temporary power panels, power outlet panels (POP),

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