Distribution Board Breaker Arrangement Inside An American Panel

Breakers are usually arranged in two columns. In a US-style board, breaker positions are numbered left-to-right, along each row from top to bottom, as shown below:

Phase	Breakers
X	1	2
Y	3	4
Z	5	6
X	7	8
Y	9	10
Z	11	12

These breakers cycle through two or three phases, labelled as X, Y, and Z in the above diagram. This numbering system is universal across various competing manufacturers of breaker panels.

In a UK-style board, breaker positions are numbered top to bottom in the left hand column, then top to bottom in the right column. Each number is used to label one position on each phase, as below. It remains to be seen how the new wiring colours recently introduced in the UK will affect this labelling.

In both labelling styles the reason for the alternating pattern of phases is to allow for common trip breakers to have one pole on each phase. Ideally the number of rows is a multiple of 3, so there are the same number of breakers on each leg of the three-phase supply, but this is not always the case; some three-phase panels have 40 or 50 breaker slots, rather than 42 and 48.

2 Inside an American panel

Phase	Breakers
Red	R1	R4
Yellow	Y1	Y4
Blue	B1	B4
Red	R2	R5
Yellow	Y2	Y5
Blue	B2	B5
Red	R3	R6
Yellow	Y3	Y6
Blue	B3	B6

Inside a typical American breaker panel, located in a front living room. The three lugs at the bottom are the three "hot" ("live") wires. A fourth white (neutral) wire (not shown) comes in at the top of the panel to a neutral bar. This breaker panel has 12 positions, the bottom six of which (shown in the picture) are taken up by two three-pole breakers (position 7, 9, 11 at left, and 8, 10, 12 at right) that each supply a separate three-phase circuit. It can be seen that American breaker panels have a lot of exposed live parts when open. This is in sharp contrast with British distribution boards where live parts are usually confined to IP20 even with the cover off.

3 Inside a UK distribution board

Inside a typical 12-position UK distribution panel. The three incoming phase wires connect to the busbars via an isolator switch in the centre of the panel. The incoming neutral connects to the neutral busbar at the centre right of the board, which is in turn connected to the neutral busbar at the top left side of the board. The incoming earth wire connects to the earth busbar at the centre left side of the panel, which is in turn connected to the earth busbar at the top right of the board. The cover has been removed from the neutral bar at the right of the board; the neutral bar on the left side has its cover in place.

Down the left side of the phase busbars are two two-pole RCBOs and two single-pole breakers, one unused. Down the right side of the busbars are a single-pole breaker, a two-pole RCBO and a three-pole breaker.

The two-pole RCBOs in the picture are not connected across two phases, but have supply-side neutral connections exiting behind the phase busbars.

It is likely that the manufacturer produces 18- and 24-position versions of this panel using the same chassis which explains why there appears to be so much unused space.

4 Manufacturer differences

Most of the time, the panel and the breakers inserted into it must both be from the same company. Each company has one or more "systems", or kinds of breaker panels, that only accept breakers of that type. In Europe this is still the case despite the adoption of a standard DIN rail for mounting and a standard cut-out shape as the positions of the busbar connections are not standardised.

It is commonly known in North America that Siemens and Cutler Hammer panels and breakers of the type shown in the above and below picture illustrations are interchangeable. Therefore, these two types of breaker panels have gained widespread acceptance as a "standard". The two panels shown (one Siemens, and the other Cutler Hammer) seem to fit GOULD Type QP, ITE type QT, Cutler Hammer Type BR, and Siemens breakers.

5 Location

For reasons of aesthetics and security, circuit breaker panels are often placed in out-of-the-way closets, attics, garages, or basements, but sometimes they are also featured as part of the aesthetic elements of a building (as an art installation, for example) or where they can be easily accessed.

Larger buildings or facilities with high electric powerLund, Sweden Electric power often known as power or electricity involves the production and delivery of electrical energy in sufficient quantities to operate domestic appliances, office equipment, industrial machinery and provide sufficient energy for bot demand may have multiple circuit breaker panels. In this case, the panels are often indicated by letters of the alphabet. One case is The Decon Gallery, a modern building in downtown Toronto, which has 11 breaker panels designated "A", "B", "C", "D", and so on. A backstage outlet is therefore labeled "C27". In many such buildings, each outlet is on its own circuit breaker, and the outlets are labelled in the above specified manner to facilitate easy location of which breaker to shut off for servicing, rewiring, or the like.

American-style panels have the unusual practice of wiring large heating equipment line-to-line, thus taking two slots in the panel (two-pole). Large motors, air conditioners, subpanels, etc., are typically three-phase (three-pole breakers), and thus take three slots in the breaker panel.

Distribution boards may be surface-mounted on a wall or may be sunk in to the wall. The former arrangement allows for easier alteration or addition to wiring at a later date, but the latter arrangement may look neater, particularly in a residential situation. The other problem with recessing a distribution board into a wall is that if the wall is solid a lot of brick or block may need to be removed - for this reason recessed boards are generally only fitted on new-build projects when the required space can be built in to the wall.

6 Mobile operation

Portable American breaker panel having a cord with an L21-30Industrial power plug is used here to refer to those power connectors that, unlike mains power plugs, are not used for the average domestic appliance but rather for more heavy-duty applications such as arc welders, cranes, cinemas, large cooking ranges et plug, and featuring four three-phase circuits: three 15- ampereIn physics, the ampere (symbol: A often informally abbreviated to amp is the SI base unit used to measure electrical currents. The present definition, adopted by the 9th CGPM in 1948 is: "one ampere is that constant current which, if maintained in two str circuits; and one 20A circuit. The 15A circuits each go to a triplex-box, whereas the 20A circuit goes to an L21-20 receptacle, and one leg of it goes to a 20A duplex receptacle shown at the upper left. The neon nightlights on the upper right triplex box are to show the phase sequence.

Sometimes it is desired to have a portable breaker panel, e.g. for special events. In this case, a breaker panel is mounted to a board, together with various sockets. These are common in the movie industry, and are sometimes referred to as "Dief boxes" because John Diefenbaker tripped over one when they began to go into widespread use.

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1 Breaker arrangement