In our last issue (part one of "What's in your home") we
attempted to explain in simple terms how to determine whether or not
there is enough power and adequate service size for any given home. This
was primarily dealt with by discussing "volts" and ‘amps".
This issue will describe some types of the electrical
wiring and conditions found in homes of various ages.
CIRCUIT PANEL
The first component of the electrical system
in the home is the circuit panel. In some homes built from the early
1960’s and before, you may find panels with fuses. Homes built from
the early 1960’ to today, and older homes that have had their system
upgraded will have circuit breakers.
FUSES: Fuses are no longer used in
new installations. Breakers are consider a safer device. Fuses can
become unsafe when they are loose or contacts are corroded.
Most fuse
systems are smaller with fewer circuits
because they are older. The demands of modern families can often
overload a circuit causing the fuse to blow. Fire hazards are created
when home owners install oversized fuses to prevent the fuse from
blowing. Upgrading to breakers is typically done when the service size
is too small or during major renovations. Just having fuses does not
require an upgrade.
 BREAKERS:
Breakers are a more permanently installed device with better connection
mechanisms then fuse and are therefore safer under normal circumstances.
Breakers should be tested periodically (see our issue on electrical
safety in our technical archive). Anything mechanical can fail. Moisture
from a damp basement or rain water following the service line into the
panel can cause rust and corrosion preventing the breaker from tripping.
A fuse panel in good condition is safer than then a breaker panel with
breakers that won’t trip due to lack of maintenance.
below you will see the different types of fuses. Cartage fuses are
not visible in a fuse panel, they are contained in a fuse block
in the panel. These lager type fuses in a fuse block come in pairs and service
larger items like the main shut off, a range or a cloths dryer. To
change them, the block must be pulled out of the panel. Plug fuses are
visible and screw into a socket.
In a breaker panel, the counter part to a cartridge fuse block is a
double pole breaker. Single pole beakers compare to the plug fuses.
With few exceptions, when a breaker trips, it trips to a position
between on and off. To reset the breaker it must then be pushed to
the off
position, then back to the on position.
|
|
WIRING
Wiring methods and materials have changed over
time. Obviously modern methods and materials are safer if installed
properly. Whether or not older systems are safe, have more to do with
their condition rather then the fact that they are older systems.
The images to the right show , romex wire, BX wire,
and knob and tube wiring. After the use of knob and tube wire and before modern romex and
BX, a wiring was used that appears much like romex; however, rather then
plastic insulation, it had a cloth and varnish insulation.
It should be understood, that while some wiring is considered safer,
it does not mean that other types are necessarily unsafe. Condition and
renovations typically dictate upgrades.
KNOB AND TUBE WIRING
Knob and Tube wiring was used from about the turn of the century
into the 1930’s (some may even be found as late as the 1940’s).
Unlike modern wiring where the hot, neutral, and ground wire are
enclosed in a single insulated cable, knob and tube does not have a
ground wire and the hot and neutral wire are individually insulated
and run
through the home separated by several inches (see diagram).
Knob and tube passes through framing in ceramic tubes and runs along
framing on ceramic stand-offs (knobs). When in good condition, knob and
tube wiring is still considered a satisfactory wiring system.
COMMON REASONS TO UPGRADE FROM KNOB AND TUBE:
- Insulation is typically the part of this system that wears out.
Areas with poor or damaged insulation should be upgraded.
- Poor or damaged connections should be replaced
- When renovations are being performed in the home that affect the
wiring, upgrades are recommended and often required.
- Some fixtures have exposed connections, these types of fixtures
should be replaced to prevent shock.
- With certain types of financing such as FHA or CFHA, upgrades may
be required in any areas that knob and tube wiring is visible.
- It is not common; however some insurance companies will also
require upgrades.
- If new wire is being tied in, and the entire length of the circuit
is exposed, it is better to replace that length rather than join the
two different wires together.
|
ROMEX WIRE
BX WIRE
KNOB & TUBE WIRING
Always hire a professional to do
your electrical repairs and upgrades
|
|
BX & ROMEX - Before modern BX and Romex
wire which contains a ground wire, there was a BX wire used that did not
have a ground wire. There was also a wire used similar to Romex, but the
insulation was not plastic, it had a cloth and varnish insulation and
did not have a ground wire. The obvious drawbacks of both is the missing
ground wire. This is easily worked around with the older BX because the
metal insulation can most often be use as the ground. Other methods such
as running a separate ground wire are need for the older Romex type wire
if grounding is necessary. It is sometimes easier to use
GFCI
outlets then to run a ground wire in many cases.
An exception to the GFCI substitute for a grounded outlet would be
for items like computers. A GFCI may trip when you don’t want it to
and damage the computer or loose unsaved data. If you must connect a
computer to a GFCI, a back-up battery is recommended. If you loose power
it will give you time to save your work and shut down the computer until
the power is restored.
Other concerns with the older wiring is the insulation. Older BX
should be checked for rusting and corrosion and replaced if found in
poor condition. The older cloth insulation tends to get brittle compared
to the plastic insulation on modern Romex and should also be replaced if
found in poor condition. The information
contained on this page is not exhaustive and is meant to be only an
overview. For complete documentation on this subject please contact
local or State heath officials.
|
