|
Should the receptacle ground prong be on top, or on the bottom? |
 |
 |
|
Written by Tony
|
|
Saturday, 19 July 2008 21:02 |
|
Makes no difference. Like all questions that make no difference, this one generates tremendous argument. Simply your life: ignore it.
There are two (obviously) widely- and fiercely-held arguments on this subject, and here they are:
|
|
Last Updated ( Sunday, 20 July 2008 19:27 )
|
|
Read more...
|
|
Are 20-ampere outlets better than 15-ampere outlets? |
|
|
|
Written by Tony
|
|
Saturday, 19 July 2008 21:00 |
Not necessarily. The rating of 15- and 20-ampere receptacles has to do with the rating of the load that may be connected, and may not reflect upon the quality or capacity of the device itself.
The parts of the NEC that deal with outlet ratings (2002 NEC 210.21) treat 15- and 20-ampere receptacles a little differently from higher-current receptacles. A 40a receptacle, for example, must be protected by a 40a breaker, but most 15a receptacles are rated such that they can be protected by either a 15a or a 20a breaker. A 20a receptacle can be used only on a 20a circuit. It is most common for all the receptacles in a home to be 15-ampere receptacles, while the branch circuits that supply them can be either 15-ampere or 20-ampere circuits. Certain circuits, such as the required small-appliance circuits and bathroom outlet circuits, are required to be 20-ampere circuits, but they usually supply 15-ampere outlets.
|
|
Last Updated ( Saturday, 19 July 2008 21:12 )
|
|
Read more...
|
|
If the two hot wires are out of phase, why is it called single phase? |
|
|
|
Written by Tony
|
|
Saturday, 19 July 2008 20:57 |
|
The two hot wires are not connected to different electrical phases, but to opposite poles of a single phase source. The neutral wire is connected to the center tap of that single phase source.
In ordinary electrical power work, there are three phasing conventions worth knowing about. They are: single phase, two-phase, and three-phase.
|
|
Last Updated ( Saturday, 19 July 2008 21:13 )
|
|
Read more...
|
|
What is the meaning of the wire colors? |
|
|
|
Written by Tony
|
|
Saturday, 19 July 2008 20:53 |
white or gray
green or bare
any other color | — the neutral wire
— the ground wire
— the "hot" wires |
|
|
Last Updated ( Saturday, 19 July 2008 21:16 )
|
|
Read more...
|
|
Can two circuits share one neutral? |
|
|
|
Written by Tony
|
|
Saturday, 19 July 2008 20:44 |
Yes, if it is done right.
Consider a three-conductor cable (red, black, and white) that originates at two circuit breakers which are connected to opposite poles, and at the neutral buss bar. One can connect a 120-volt load between the red and white wires, placing that load on one of the circuit breakers, and one can connect another 120-volt load to the black and white wires to place it on the other circuit breaker. The breakers, of course, are sized appropriately to protect the wiring. But what about the current in the white wire? The white wire is the return for both loads. Won't it be carrying more than its rated current?
|
|
Last Updated ( Saturday, 19 July 2008 21:16 )
|
|
Read more...
|
|
Is it permitted to make a splice in the breaker panel? |
|
|
|
Written by Tony
|
|
Saturday, 19 July 2008 20:34 |
Yes, usually.
This subject is covered in paragraph 312.8 of the 2002 NEC, as follows:
312.8 "Enclosures for Switches or Overcurrent Devices. Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space."
|
|
Last Updated ( Saturday, 19 July 2008 21:17 )
|
|
Read more...
|
|
|
|
|