Extension cords   Spliced wires

e.  Extension cords   Spliced wires:
Extension cords within houses are to be avoided and are especially hazardous if they extend through walls, (Fig. e1, Item A) floors, or under rugs (Fig. e1, Item B).  It is common for people to insert a thin extension cord into a receptacle and plug a large appliance into the extension cord.  Under these conditions, the thin wire will quickly heat up and may burn (Fig. e1, Item C).  A thin cord can heat up, burn and never trip a circuit breaker or blow a fuse.  Using such cords can negate the protective value of these devices.

Fig. e1

WARNING:  Extension cords that run under carpet are considered very dangerous.

PROPER CONNECTIONS ARE CRITICAL IN ELECTRIC SYSTEMS: There are approved ways of joining wires.  Ideally, connections will be accomplished using approved “wire nuts” or they will be soldered together and insulated with tape.  All splicing or joining of wire should be done within approved junction boxes.  Splicing wires may be done carefully and is quite safe however, wires are often loosely wound around each other and insulated with wrappings of tape.  Such loose connections may easily heat up and cause a fire.  Poorly spliced wire connections are to be avoided and are not to be depended upon.

What to:  How to:
If you must use an extension cord, make sure it is at least as thick in wire gage as the appliance cord it serves.  Never run extension cords through walls, floors or under carpeting. 

Wire connections should be made in junction boxes.  If you wish to correct an “open air” spliced connection, terminate one end of the wire in a junction box leaving about 6 to 8 inches of extra wire through the box.  Secure another junction box several inches away on the other wire leaving the same amount of excess wire through that box.  Now join the two wires with a third length of wire between the two junction boxes.  Normally the junction boxes will be about 12 to 18 inches apart.

Reference: E4, E5, E17, EX42