|Residential Electric Service|
If you have any reservations doing the job yourself PLEASE get an electrician.
For Residential Electric Service the
power companies are required to provide residential customers a
SPLIT-PHASE 240 volt (+/- 5%) feed. These are two 120-volt 180-degree out
of phase legs. This service is called by many names 120-volt, 110-volt,
240-volt 220-volt but they are all the same.
On this discussion we are not talking about Industrial applications. There are 208-volt 240-volt and 480-volt 3-phase services. The 240-volt Residential is different from a 240-volt 3-phase service.
are four wires involved with supplying the main panel in your
house with power. Three of them will come from the utility pole, and a
fourth (bare) wire comes from elsewhere. The bare wire is connected to one
or more long metal bars pounded into the ground, or to a wire buried in
the foundation, or sometimes to the water supply pipe (has to be metal,
continuous to where the main water pipe enters the house) This wire
normally carries no current. (Click
on Photos to Enlarge)
One of the other wires will be white (or black with white or yellow stripes, or sometimes simply black). It is the neutral wire. It is connected to the "center tap"
The other two wires will usually be black, and are the "hot" wires. They are attached to the distribution transformer as well.
According the NEC, the "grounding" conductor is for the safety ground the green or bare or green with a yellow stripe wire. The word "neutral" is reserved for the white when you have a circuit with more than one "hot" wire. Since the white wire is connected to neutral and the grounding conductor inside the panel, the proper term is "grounded conductor". However, the potential confusion between "grounded conductor" and "grounding conductor" can lead to potentially lethal mistakes - you should never use the bare wire as a "grounded conductor" or white wire as the "grounding conductor", even though they are connected together in the panel.
The codes for residential installation requires a ground wire for many years on 120-volt plugs.
Watts, Volts and Amps
Watts are the standard unit of measurement of electrical power. One watt is one ampere of current flowing at one volt
Watts = Amps x Volts
Volt = Watts / Amps
Amps = Watts / Volts