On the dwelling, the three wires from the pole/inexperienced field transformer are related via a wattmeter after which enter a fundamental service panel that’s grounded to a protracted copper rod pushed into the bottom or to the metal in a house’s basis. The A-phase and B-phase wires that enter the primary panel are related via a fundamental disconnect breaker, whereas the impartial wire is related to a terminal known as the impartial bar or impartial bus. A floor bar additionally could also be current inside the primary service panel. The bottom bar is related to the grounding rod or to the muse’s metal helps. Inside fundamental service panels, the impartial bar and the bottom bar are related collectively (they act as one).
Nevertheless, inside subpanels (service panels that get their energy from the primary service panel however that are positioned a long way from the primary service panel), the impartial and floor bars will not be joined collectively. As a substitute, the subpanel’s floor bar receives a floor wire from the primary service panel. Usually the steel conduit that’s used to move the wires from the primary service panel to the subpanel is used because the “floor wire.” Nevertheless, for sure important purposes (e.g., pc and life-support methods), the bottom wire most likely can be included inside the conduit. Additionally, if a subpanel just isn’t positioned in the identical constructing as the primary panel, a brand new floor rod usually is used to floor the subpanel. Observe that completely different areas inside the US could use completely different wiring protocols.
Inside the primary service panel, there are usually two bus bars into which circuit breaker modules are inserted. One in all these bus bars is related to the A-phase wire; the opposite bus bar is related to the B-phase wire. To energy a bunch of 120-V hundreds (e.g., upstairs lights and 120-V retailers), you throw the primary breaker to the off place after which insert a single-pole breaker into one of many bus bars. (You may select both the A-phase bus bar or the B-phase bus bar. The selection of which bus bar you employ solely turns into essential with regards to balancing the general load-more on that in a second.) Subsequent, you are taking a 120-V three-wire cable and join the cable’s black (sizzling) wire to the breaker, join the cable’s white (impartial) wire to the impartial bar, and join the cable’s floor wire (inexperienced or naked) to the bottom bar. You then run the cable to the place the 120-V hundreds are positioned, join the recent and impartial wires throughout the load, and fasten the bottom wire to the case of the load (usually a floor screw is equipped on an outlet mounting or gentle determine for this function).
To energy different 120-V hundreds that use their very own breakers, you mainly do the identical factor you probably did within the final setup. Nevertheless, to maximise the capability of the primary panel (or subpanel) to produce as a lot present as doable with out overloading the primary circuit breaker within the course of, it is very important stability the variety of hundreds related to the A-phase breakers with the variety of hundreds related to the B-phase breakers.
That is known as balancing the load. Now, if you wish to provide energy to 240-V home equipment (e.g., ovens, washers, and so on.), you insert a double-pole breaker between the A-phase and B-phase bus bars in the primary panel (or subpanel). Subsequent, you are taking a 240-V three-wire cable and fasten one among its sizzling wires to the A-phase terminal of the breaker and fasten its different sizzling wire to the B-phase terminal of the breaker. The bottom wire (inexperienced or naked) is related to the bottom bar. You then run the cable to the place the 240-V hundreds are positioned and fasten the wires to the corresponding terminals of the load (usually inside a 240-V outlet). Additionally, 120-V/240-V home equipment are wired in an identical method, besides you employ a 4 wire cable that comprises an extra impartial (white) wire that’s joined on the impartial bar inside the primary panel (or subpanel). (As a sensible word, you might use a 4 wire 120-V/240-V cable as an alternative of a 240-V three-wire cable for 240-V applications- you’ll simply depart the impartial wire alone on this case.)
As a word of warning, don’t try dwelling wiring until you might be positive of your skills. If you happen to really feel that you’re succesful, simply be sure that to flip the primary breaker off earlier than you begin work inside the primary service panel. When engaged on lighting fixtures, switches, and retailers which can be related to a person breaker, tag that breaker with tape in order that you don’t mistakenly flip the mistaken breaker once you return to check your connections.