Small electrical installations normally have only one distribution board, connected directly to the main network, and the devices are powered by branch circuits protected by circuit breakers. However, powering all loads from the same distribution board is impractical in larger installations as the amount of cabling required would be excessive. In these cases, the secondary load centers are powered from the main distribution board and, in turn, these load centers supply electricity to individual appliances.
Feeder circuits connect the main distribution board to secondary load centers. As these circuit power load centers use large conductors and can become very expensive. For this reason, it makes sense to minimize the number of feeder circuits and their length.
In some cases, load centers must be installed close to each other. For example, this may occur in a construction area where many appliances require individual branch circuits and a load center does not provide enough space. When load centers are equipped with secondary supply terminals or feed through loops a single feeder circuit can supply two or more of them.
Optimize the design of your electrical installation and reduce costs.
How do secondary power terminals work?
The secondary power terminals have two connection spaces: one for the incoming power circuit and another to extend the connection to another load center. The secondary power terminals are located on the top of a load center, just like the main terminals, meaning the input and output connection are on the same side.
This configuration is only available for main terminal panels and not for main breaker panels, which means an external main breaker is required. However, as the external circuit breaker is located upstream of the first panel any secondary panels connected via sub-supply terminals will also be protected.
It is important to note that subfeed terminals add height to the load centers, but allow additional panels to be connected to the same power circuit. Any potential space lost due to secondary power handles is offset by space gained with additional load centers.
How does the power supply through the terminals work?
The power loops perform the same function as the subfeed loops, but the connection layout is different:
- The feeder circuit is typically connected to the top of the first load center using main terminals or a main circuit breaker.
- The power terminals are located at the bottom of the first load center and the second is powered from there.
- When the main terminals above are supplied with voltage, the supply terminals below are automatically energized because they connect to the same busbars.
This configuration is available for main terminal panels and main circuit breaker panels. Any main circuit breaker that protects the first load center also protects the second, since the connection is downstream.
If panels are installed side by side and power terminals are used, the wiring between them will be longer compared to a connection using secondary power terminals. This is because the wiring must run from the bottom of the first panel to the top of the second, while it must only run horizontally between the top of both panels with subfeed loops.
Alternative Configuration: Sub Feed Circuit Breaker
The layout is very similar to a load center with power straps, where the connection to the second panel is at the bottom of the first. However, in this case there is a circuit breaker built into the first panel, providing not only a connection point but also protection against failures.
This configuration is available for both the main terminal and main circuit breaker panels, as well as the power terminals. If the first panel has a main circuit breaker, the secondary panel will be protected by both the main circuit breaker and the secondary power circuit breaker.
Final Recommendation
To ensure your electrical installation has an optimal layout, the best recommendation is to work with qualified design professionals . In many cases, dramatic savings can be achieved with smart design decisions without compromising performance. Ideally, your installation should consolidate electrical cabling as much as possible – long, redundant power circuits represent a considerable waste of capital in a large installation.
