A tandem breaker allows two individual 120-volt circuits to be controlled from one slot, effectively doubling the number of circuits the panel can accommodate. What size distribution box do you need for a house? How do you know which circuit breaker to use? Can you add more breakers later? Why do you need GFCI or AFCI breakers? Choosing the right size and setup for your distribution box keeps your electrical system safe and working well. While the outer cover typically has blank plates covering unused spots, removing the panel cover reveals the bus bars where breakers connect. The number of empty slots dictates the simplest. Example: Need a circuit for your 1,800W microwave? Calculator Tip: Tools like Desmos' scientific calculator make light work of conversions. Just plug in your wattage and voltage—let it handle the decimals. A distribution box is a low-voltage electrical enclosure that receives incoming power and distributes it safely to multiple outgoing circuits through protective and switching devices such as MCBs, RCDs, RCBOs, fuses, isolators, busbars, neutral bars, earth bars, and surge protective devices. These components, often referred to as tandem, twin, or half-size breakers, are designed to fit two separate circuits into a single one-inch slot on. Initially the three-phase distribution boards have four ways, accommodating a total of 12 single phase circuits, and the single-phase distribution boards four single phase ways, accommodating a total of 4 single phase circuits. To increase the number of ways, select a distribution board from the.