to rest the back of the clamp against a structural member.
In checking a suspected conductor for either an open
Be careful not to pinch wires in the cable clamp.
or a short, you may have to apply a slight pressure to the
conductor or simulate vibration. Shorts are often caused
LACING AND KNOTTING TECHNIQUES
by moisture, foreign particles, or a defective solder
FOR WIRE BUNDLES OR GROUPS. W i r e
connection at the plug terminals. Therefore, be sure to
groups and bundles should be laced or tied with cord
check the connectors carefully before replacing the
t o provide ease of installation, maintenance, and
cable.
inspection. This precaution keeps the cables neatly
s e c u r e d in groups and bundles and helps avoid
Repair and Replacement Procedures
possible damage from chafing or equipment
operation. A wire group is two or more wires tied or
In support equipment, conduit is eliminated
laced together to give identity to an individual system.
w h e r e v e r possible. Its elimination eases cable
A wire bundle is two or more wires or groups tied or
installation and maintenance. In replacing a cable, take
laced together to ease maintenance. A typical example
particular care to replace it in the exact position in which
of wire bundles is shown in figure 5-13.
it was installed originally. Do not try to reduce the length
Materials.-- Use cotton, nylon, or fiberglass cord for
of the cable by taking what might seem to be a logical
lacing or tying wire bundles. Make sure the cotton cord
shortcut.
is waxed to make it moisture and fungus resistant. Nylon
When installing or replacing wire or wire bundles,
and fiberglass cords are moisture and fungus resistant
make sure there is no excessive slack along the run.
and usually will not need waxing. Use
Normally, slack should not exceed a 1/2-inch deflection
pressure-sensitive vinyl electrical tape only where the
with normal hand pressure. Provide enough slack at
use of tape is specifically permitted.
each end to allow for the following:
The following sections describe some proper lacing
1. Easy removal and connection of plugs
and tying techniques. Refer to figures 5-14 through 5-16
2. Replacement of terminals two times
as you read these sections.
3. Prevention of mechanical strain on the wires
Precautions.-- When lacing or tying wire bundles,
observe the following precautions:
4. Free movement of shock and vibration-mounted
equipment
1. Lace or tie the bundles tightly enough to prevent
slipping, but not so tight that the cord cuts into or
5. Shifting of equipment during maintenance
deforms the insulation.
Bends in individual wires should normally be
2. Do not place ties on that part of a wire group or
limited to a minimum bend radius of 10 times the
diameter of the bundles. However, where the wire is
bundle that is located inside a conduit.
suitably supported at each end of the bend, a radius of
3 . Lace wire groups or bundles only inside
three times the diameter of the bundles is acceptable.
enclosures, such as junction boxes. Use double cordon
Wires passing through a bulkhead or structural
groups or bundles larger than 1 inch in diameter. Use
member must be supported at the hole by a cable clamp.
single or double cord for groups or bundles 1 inch or less
If the clearance between the wire and the edge of the
in diameter.
hole is less than 1/4 inch, use an approved supporting
Single Cord Procedure.-- To lace a wire group or
grommet in the hole.
bundle with a single cord (fig. 5-14), use the following
M a i n t a i n a clearance between wiring and any
steps:
movable control. If this cannot be done, install guards
1. Start the lacing at the thick end of the wire group
to prevent contact of the wiring with the control. When
or bundle with a knot consisting of a clove hitch with an
routing the wiring parallel to plumbing that is carrying
extra loop.
flammable fluids, maintain as much separation as
possible. Never support any wire or wire bundle from a
2. At regular intervals along
the wire group or
plumbing line that is carrying combustible liquids.
bundle (and at each point where a
wire or wire group
branches off), continue the lacing
with half hitches.
Install cable clamps so the mounting screws are
Space half hitches so the group or
bundle is neat and
above the wire bundle. (Otherwise the weight of the
securely held.
cable may bend and break the clamp.) If practical, try
5-12
