CHAPTER
UNIT 204
4
INSTALLATION
AND
WIRING SYSTEMS
ENCLOSURES
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Chapter 4: Installation of wiring systems and enclosures
Type of screwdriver
Description and uses
Flat-blade
Older screws tend to have a slotted head. Flat-blade
screwdrivers are designed to fit into this type of screw head.
Available in all sizes from the small terminal driver type to
large heavy duty versions.
Phillips
Most fixing screws now have Phillips-type heads. Phillips
screwdrivers tend to be available in two sizes: smaller for
terminal screws and larger for fixing screws.
Posidrive
Similar to Phillips, posidrive screws are often used as terminal
screws. The posidrive’s star shape makes for a firmer grip
between the screwdriver and the screw itself.
Chapter
4 163
Unit
GH8
Table 4.1: Screwdriver tips
Safe working
Never point a ratchet screwdriver
towards your own, or anyone
else’s, face if the shaft is retracted
into the main body. The shaft will
spring out with a lot of force and
could cause a serious eye injury.
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Ratchet screwdrivers
Ratchet screwdrivers are fitted with mechanical gearing which means that
you can turn the screwdriver bit by either:
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• pumping the handle
• turning a handle which will only engage when rotated in one direction.
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Magnetic screwdrivers
Magnetic screwdrivers and gripping screwdrivers will hold a screw steady if it
is being inserted into an awkward position where you cannot grip the screw
with your fingers. Magnetic screwdrivers can also be used for picking up
screws that have dropped into small or difficult spaces.
Tool
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Electric screwdrivers
Electric screwdrivers are being used more and more. Although they can be
purchased as a specialist power tool, most modern electric drills will accept
screwdriver bits and are geared so that they can not only tighten fixing
screws, but also loosen them by being run in reverse.
General purpose
hand-held
screwdrivers
Ratchet
screwdrivers
Electric
screwdrivers
Check for:
Optimum performance
PPE to be worn when
using these tools
• Damage to handles
• Shaft loose in the handle
• Damage to insulation on handles
• Damage to insulation on screwdriver shaft
• Flat-headed – blade is
sharp and undamaged
• Phillips and posidrive –
end is intact and not worn
• Weakened catch that will not hold retracted shaft
Keep retractable shaft
lubricated
There is no PPE specific
to using screwdrivers.
The main method of
controlling risk is
careful use.
• Insulation is intact
• Shaft and tip is undamaged
• No sign of overheating
• On/off switch or trigger is working
• Lead and plug are undamaged (if plug-in type)
• Battery is fully charged if
battery type
• Tips are sharp with no
wear on edges
Table 4.2: Using screwdrivers safely
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Chapter 4: Installation of wiring systems and enclosures
Tool
Check for:
Optimum performance
PPE and other safety advice
Jig saw
• Damaged lead and plug
• Damaged insulation
• General damage
• Faulty on/off switch/trigger
• Loose blade clamping screws
• Do not use worn blades.
• Use the right blade for the material.
• If possible use a guide to keep the
saw on the cutting line.
• Eye protection
• Gloves
• Ear protectors
• Secure the workpiece
• Always cut away from yourself
Circular saw
• Damaged lead and plug
• Damaged insulation
• General damage
• Faulty on/off switch/trigger
• Check guard is in place and
working properly.
• Do not use worn blades.
• Use the right blade for the material.
• Use a guide to keep the saw on the
cutting line.
• Eye protection
• Gloves
• Ear protectors
• Secure the workpiece
• Always cut away from yourself
if using a hand-held version
Table 4.7: Using saws safely
Chapter
4 169
Unit
GH8
Progress check 4.2
1 Why is a retractable bladed
knife a safe option for the
electrician?
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Hammers
The hammer is probably the most basic item in the electrician’s toolbox and
is used for a wide variety of jobs, such as knocking in nails and driving a
chisel through masonry or wood. Hammers are generally graded according
to the weight of their head.
Use
Claw hammer
The claw hammer is two tools in one. The hammer face is
used for general work and the claw is used for removing
unwanted nails and other levering tasks. To remove a nail,
the head is gripped between the two blades of the claw and
the top of the hammer used as the fulcrum of a lever action.
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Ball pein hammer
3 What type of saw is used
for cutting holes in
plasterboard walls?
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Type of hammer
2 In which direction should
the teeth of a hacksaw
blade face?
Like the claw hammer, the ball pein is a combination tool
with a standard striking face and a rounded second face.
The ball pein was originally designed for driving in rivets.
Lump hammer
Lump hammers are a heavy, block-headed tool usually used
in combination with a cold chisel. This is a heavy tool so
make sure you select a weight that is comfortable. A large
two-handed version of the lump hammer is the sledge
hammer, used for breaking up concrete and for general
demolition type work.
Scutching hammer
Used by electricians for cutting chases, the scutching
hammer has replaceable blades or teeth that fit into each
end of its head.
Mallet
The mallet can be either wood or a nylon type head. Mallets
are used mainly in combination with wood chisels. The
softer versions are also used for dressing cables, particularly
mineral insulated, although they must be used with care
when carrying out this type of job because striking the
cable too hard could damage or misshape its outer sheath.
!
Safe working
Always remember the following
safety guidelines.
• Never use a hammer if the
head is loose.
• Do not use if the handle is
cracked or greasy.
• Check the impact face of a
hammer – if the edges are
cracked or curled back, do
not use.
• Wear gloves and eye
protection when using a
hammer – nails can break off or
fly out if mishit.
Table 4.8: Different types of hammer
169
Level 2 Electrical Installations (Buildings and Structures)
Chapter
4
Tool
Check for:
Optimum performance
PPE and other safety advice
Hammer
• Damaged handle
• Loose head
• Damaged head
• Use the right hammer for the job.
• Hold the hammer near the bottom of the handle –
let the weight of the hammer head do the work.
• If you are buying a hammer, check the different
weights and choose one that is comfortable.
• Gloves
• Eye protection
• Secure the workpiece
Table 4.9: Using hammers safely
Chisels
Hammers are often used in combination with chisels. There are three basic
types: wood chisels, cold chisels and bolsters.
Type of chisel
Use
Wood chisels
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These are very sharp and used for woodworking jobs.
They should be looked after so that their blades are
protected from damage and blunting.
Cold chisel
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These are used for masonry work such as knocking holes
into brick or block work. There are a number of cold chisel
types:
• flat chisel
• cross-cut
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• half-round
• diamond point
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Bolster chisel
This has a flared blade that can be used for cutting straight
edges into masonry, for example, the edges of a wall chase.
Bolsters are also used for levering up floorboards.
Table 4.10 Different types of chisel
Tool
Cold chisels
and bolsters
Wood chisel
Check for:
Optimum performance
PPE and other safety advice
• Broken, split, ragged impact
point at the top of the chisel
• Damaged hand-guard
• Use the right chisel for the job.
• Keep blades sharp.
• Gloves
• Eye protection
• Damaged handle
• Blade is loose in the handle
• Use the right chisel for the job.
• Keep blades sharp.
• Store in a chisel roll or other protective
covering. This prevents blunting of blades
and corrosion.
• Gloves
• Eye protection
Table 4.11: Using chisels safely
Progress check 4.3
1 Give two safety reasons not to use a hammer.
2 What are two uses for a claw hammer?
3 What is a bolster used for?
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Chapter 4: Installation of wiring systems and enclosures
Files
Available in different sizes and levels of coarseness, files are generally used
by the electrician for smoothing metal after cutting or drilling. Table 4.12
shows the main types of file.
Type of file
Chapter
4 171
Use
Flat file
Used for flat surfaces, tapers in thickness and width at
the front. A thinner version is known as a warding file
and is used for filing narrow slots.
Hand file
Has a safe edge with no teeth that can be used up to a
shoulder without marking it.
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GH8
Round file
Square file
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Used for opening up square holes.
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Sometimes called a rat-tail file for opening up holes or
filing internal radii.
Three square file
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Used for filing square corners, sometimes called a
triangular file.
Knife file
Half round file
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Used for tapered narrow slots and for very precise work.
Used to file the inside of curved surfaces.
Table 4.12: Files types and their uses
Using a file
When using a file to smooth metal, remember the following points:
1 The workpiece should be secure and at a comfortable height. If it is a
small workpiece, secure it in a vice.
2 Grip the file with two hands – one on the handle, one on the tip of the file.
3 Apply pressure on the forward stroke of the file. The file teeth face
forward and only cut when the file is moved in that direction.
4 Do not apply pressure on the return stroke. This is because it will have no
effect on the workpiece and can also damage the file.
5 If the piece to be filed requires a coarse file to correct, finish off with a
fine version.
Figure 4.4: Correct file use
171
Level 2 Electrical Installations (Buildings and Structures)
Pillar drill
Pillar drills are fixed drilling machines used mainly in workshops and
factories. The workpiece is secured in place using a vice which can be
adjusted so that the workpiece is in the exact drilling position. The drill is
then lowered onto the workpiece using either a handle or wheel. Modern
pillar drills are automated or even programmable so that they can carry out
repeated operations with the same degree of accuracy.
Chapter
4
Key term
A clear, see-through guard must be fitted to the drill to prevent eye injuries
from flying swarf and other debris thrown out from the drill area.
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Swarf – fine chips or filings
produced by machining.
Figure 4.10: A pillar drill
Figure 4.11: A centre punch
176
Drilling metal
Metal should be drilled at a slow speed using a twist bit. Make sure the
workpiece is secure before attempting to drill. A centre punch should be
used first to avoid skidding and to create a more accurate drill hole. The
pointed end of the centre punch is pressed against the centre of the drill
site. Some centre punches are then struck with a hammer to make a small
dent in the metal surface. Spring-loaded centre punches are also available.
The drill bit is placed into the dent made by the punch.
Chapter 4: Installation of wiring systems and enclosures
A hole saw should be used for cutting large holes in metal. Hole saws, or
tank cutters as they are sometimes called, are metal cylinders with teeth cut
into the open end. The saw is then screwed onto a mandrill. The mandrill is
also fitted with a twist bit which drills a pilot hole into the workpiece and
which anchors the saw while cutting takes place.
Drilling wood
Wood can be drilled using a metal twist bit, but there are a range of
specialist wood bits available. These are spade-shaped with a sharp pilot
point. Care must be taken when using these types of drill bit because they
can become jammed and cause the drill itself to twist round.
4 177
Figure 4.12: Metal bit and hole saw
Unit
GH8
Figure 4.13: Wood bit
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If no power is available, a brace-and-bit is used for drilling wood.
This is shaped like a crank shaft and fitted with auger bits (much like
twist drills). A brace-and-bit is usually fitted with a ratchet handle so
that it can be used in a confined space where the crank cannot be
rotated fully.
Chapter
Check for:
Optimum performance
PPE and other safety
advice
Electric drill
• Damaged lead and plug
• Damaged insulation and casing on the drill
• Free movement of the chuck
• Chuck grips the drill bit securely
• For battery drills, keep batteries
fully charged and always keep a
spare charged battery.
• Only use sharp drill bits.
• Eye protection
• Gloves
• Ear protection
• Secure the workpiece.
Activity 4.1
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Table 4.17: Using electric drills safely
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Tool
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Carry out a visual safety inspection on a selection of tools. Demonstrate this to your
tutor. Explain what you are looking for, e.g. damaged handle, blunt edges, damaged
leads and plugs on power tools.
INSTALLING WIRING SYSTEMS
Progress check 4.6
1 What type of drill bit is used
for drilling a small hole in
metal?
2 What is a pilot drill?
3 What tool can be used for
drilling wood if no power is
available?
Select materials from drawings
The main diagram the electrician will work to is the scaled layout drawing,
often called a plan. From this the electrician can count up the amount of
accessories and items of equipment needed for the job. Cable lengths can also
be calculated using the scale and likely cable routes shown on the drawing.
Marking out
Before starting actual installation work, the job has to be marked out. The
drawing is used to show where all accessories and items of electrical equipment
are to be fitted. It is important to install all equipment in the correct position.
If a socket or switch is not placed where it should be it could end up hidden
behind a cupboard or radiator. When marking out, the position of accessories,
equipment and cable drops are drawn on to the wall with a pencil or chalk.
177
Level 2 Electrical Installations (Buildings and Structures)
Chapter
4
Progress check 4.12
Activity 4.5
1 Why should an electrical
installation be inspected and
tested?
1 Working in teams, construct a ring final circuit consisting of three 13 A sockets. These
do not have to be fixed to a board but wired together using singles cables (perhaps
even scrap cable).
2 What instrument is used
to test for continuity of
protective conductor?
2 Once complete, carry out the full set of ring final circuit dead tests: end-to-end,
r1 + rn and r1 + r2, and insulation resistance.
3 Introduce a fault into your circuit.
3 What is the minimum
acceptable reading for an
insulation resistance test?
4 Retest to see how the fault is shown up on your test instrument.
5 Swap your circuit with another team and try to find the fault by carrying out the full
set of ring final circuit tests on their circuit.
Knowledge check
circular saw
jig saw
wood saw
junior hacksaw
a
b
c
d
carborundum
aluminium
steel
iron
3 Why must extra low voltage tools be
used on construction sites?
To reduce risk of fire
To reduce risk of electric shock
To reduce risk of short circuit
To reduce risk of mechanical
damage
4 Which hammer is used with a cold
chisel for cutting masonry?
a
b
c
d
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6 Drawing the positions of equipment
and cable runs on walls before
starting the work is called:
a
b
c
d
a site survey
marking out
a quantity survey
laying out
7 The length of cable cores left at a
socket or switch box for connection
should be:
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a
b
c
d
Assembly drawing
Layout drawing
Blueprint
Block diagram
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2 The cutting wheel on a grinder is
made from:
a
b
c
d
Ball pein
Mallet
Scutching
Lump
a
b
c
d
1.5 times the width of the box
2 times the width of the box
2.5 times the width of the box
0.5 times the width of the box
8 Which of these cables is normally run
in conduit?
a
b
c
d
9 What colour is a crimp lug for a
2.5 mm conductor?
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a
b
c
d
5 Which type of diagram is used for
counting up amounts of materials
needed?
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1 A slot can be cut into metal trunking
using a:
Twin-and-earth
Mineral insulated
Main bonding conductor
Singles
e
f
g
h
Yellow
Red
Blue
Green
10 The main bonding conductor should
be connected:
a as far from the point of supply
as possible
b to E terminal in a 13 A socket
outlet
c as close to the point of supply
as possible
d the loop-in terminal in a
ceiling rose