Excerpts from CHAPTER 13
Modernizing Old Wiring
THE WIRING THAT WAS INSTALLED in a house many years earlier, or even as
recently as a decade ago, may not be adequate for the job it is called
upon to do today. A complete rewiring job is in order—or is it? Do not
jump to the conclusion that every outlet must be torn out and every
receptacle replaced. Many times a less expensive job will serve the
wiring does not include an equipment grounding conductor, either in the
form of a separate grounding conductor or a metallic raceway or cable
armor, as is often the case for wiring over forty years old, consider
completely rewiring all circuits.
equipment grounding conductor is present, is the wiring inadequate because
you are using too many lights? too many floor lamps? too many radios and
TVs? That is seldom the case. The wiring usually is inadequate because you
have added many electrical appliances that were not considered or perhaps
were not even on the market at the time of the original wiring job. The
installation does not provide enough circuits to operate a wide assortment
of small kitchen appliances, plus range, water heater, clothes dryer, room
air conditioners and other heavy appliances. Some of these operate on
240-volt circuits, which may not be available; others operate at 120 volts
but when plugged into existing circuits they overload those circuits. In
addition, the service entrance equipment may be just too small for the load.
To analyze the
problem of your particular house, ask yourself this: If you disconnected all
the appliances, would you have all the lighting circuits you
need? The answer is probably yes, which means that your rewiring job is
simplified. You will still have to rewire the house, but probably not as
completely as first appeared necessary. Proceed as if you were starting with
a house that had never been wired, but leave the existing lighting circuits
intact. (These lighting circuits, of course, will include many receptacles
used for small loads like a vacuum cleaner, radio, and TV, but not the
receptacles for kitchen or laundry appliances.) This chapter discusses the
overall plan for modernizing an existing installation, including upgrading
to a larger service and adding new circuits. It also offers problem-solving
approaches to the specific challenges you are likely to encounter.
Everything in previous chapters describes the wiring of buildings while they
are being built, which is called “new work.” This chapter describes “old
work,” which is the wiring of buildings after they have been completed.
Problems of "Old Work"
little difference between old and new work, except that in old work there
are a great many problems of carpentry. The problem is to cut an opening
where a fixture is to be installed, and another where a switch is to be
installed, and then to get the cable inside the wall from one opening to
the other with the least amount of work and without tearing up the walls
or ceilings more than necessary.
One house to be wired may be five years old, another a hundred years
old. Different builders use different methods of carpentry. Every job will
be unique. No book can possibly describe all the methods used and all the
problems you will meet. Watch buildings while they are being built to get
an idea of construction at various points. In old work, good common sense
is of more value than many pages of instruction.
In general, old work requires more material because it is often wise to
use ten extra feet of cable to avoid cutting extra openings in the walls
or to avoid cutting timbers. Many problems can be solved without cutting
any openings except the ones to be used for outlet boxes and switch boxes.
Others require temporary openings in the wall that must later be repaired.
Techniques are given in this chapter for running cable behind walls and
ceilings, and for installing boxes, switches, receptacles, and outlets in
both lath-and-plaster and drywall construction.
The rest of the chapter covers--
Installing new service and circuits
Installing boxes and running cable
Installing switches, switches, and outlets
Chapter 2. Planning Your Electrical Installation
Chapter 6. Circuit Diagrams
Chapter 19. Troubleshooting and Repairs
Park Publishing, Inc.
Softcover, 5 1/2 x 8 1/2 inches, 256 pages, 228 illustrations
45th edition, May 2017
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