10.5 Unit 204 Practical Skills: Tools, Preparation & Installing Wiring Systems
Key Takeaways
The Unit 204 hand tools are rules, levels, gauges, plumb lines, cable cutters, screwdrivers, wire strippers, knives, files, reamers, wrenches, hammers and saws.
Before using a power tool, check that it is safe (condition and inspection), set the correct speed, fit and secure the correct attachment, check guards are in place, wear the right PPE and use sharp bits.
Install from drawings by taking off materials, setting a datum, marking out, fixing accessories level and to dimension, fitting supports at the correct spacing, and then installing and terminating cables.
Good terminations have no bare copper outside the terminal and no trapped insulation, are tightened to the correct torque, and have green-and-yellow sleeving on CPCs and brown sleeving on switched lines.
Main bonding uses BS 951 clamps on clean pipe with a 'Safety Electrical Connection - Do Not Remove' label, is typically 10 mm² copper for PME supplies, and is then continuity tested.
10.5 Unit 204 Practical Skills: Tools, Preparation & Installing Wiring Systems
Unit 204 (Installation of wiring systems and enclosures) carries 21 of the diploma's 49 credits and is assessed by a practical assignment. Its first four learning outcomes are about tools, preparing to install, installing wiring systems from drawings, and bonding mains services to the main earthing terminal (MET). Inspection and dead testing (learning outcomes 5 and 6) are covered in Chapter 14. The same knowledge also supports questions in the Unit 201 and 203 tests.
Hand Tools (Learning Outcome 1)
| Tool | Typical task |
|---|---|
| Rules (steel rule, tape measure) | Measuring and marking out from drawing dimensions |
| Levels (spirit level, laser level) | Setting boxes, conduit, trunking and tray horizontal or vertical |
| Gauges (wire gauge, depth gauge, thread gauge) | Checking sizes, depths and threads |
| Plumb line | Finding a true vertical over a height, such as a riser |
| Cable cutters | Making clean, square cuts in multicore and armoured cables (ratchet type for large sizes) |
| Screwdrivers (VDE-insulated) | Terminating and fixing; the tip must match the screw (slotted, Phillips or Pozidriv) |
| Wire strippers | Removing insulation without nicking the conductor |
| Knife (or cable sheath stripper) | Removing cable sheaths, always cutting away from the body |
| Files | Removing sharp edges from cut trunking and tray |
| Reamers | Removing burrs from inside cut conduit |
| Wrenches and spanners | Tightening glands, locknuts and couplers |
| Hammer (with bolster and chisels) | Fixings, cutting chases and lifting floorboards |
| Saws (hacksaw, junior hacksaw, floorboard saw, plasterboard saw) | Cutting conduit (32 tpi blade), trunking, armour, timber and board |
Power Tools and Their Safety Checks
The Unit 204 range lists the drill, hammer drill, pillar drill and electric screwdriver:
| Power tool | Typical use |
|---|---|
| Drill | Holes in timber, metal (high-speed steel bits) and enclosures |
| Hammer drill (SDS) | Holes in masonry and concrete for fixings and cable entries |
| Pillar drill | Accurate holes in the workshop, with the work clamped to the table |
| Electric (cordless) screwdriver | Driving screws and fixings quickly, with the torque clutch set to avoid stripping screws |
Before and during use, carry out the safety checks named in the range:
- Check it is safe to use: no damage to the casing, cable or plug, and an in-date inspection label where your company uses one; on site, use 110 V or battery tools.
- Correct speed setting: slower speeds for large holes and metal, hammer action only for masonry.
- Correct attachments: the right drill bit, hole saw, driver bit or chuck for the job.
- Attached correctly: the chuck tightened and the chuck key removed, or the SDS bit locked in.
- Guards in place: for example the chuck guard on a pillar drill.
- Correct PPE: eye protection, hearing protection and a dust mask where needed; no loose clothing, jewellery or gloves near a rotating chuck.
- Best performance: sharp bits and blades, because blunt ones overheat, wander and snatch.
Preparing to Install (Learning Outcome 2)
- Hazards: make sure circuits you could disturb are safely isolated (Section 3.1), follow safe working practices, and read the risk assessment and method statement. Use a cable and pipe detector and check the drawings before drilling or chasing.
- PPE: hard hat, safety glasses, safety shoes, gloves, ear defenders and protective workwear, chosen for the task.
- Access equipment: ladders, platforms (such as podium steps) and hop-ups, selected and checked as described in Section 4.2.
Installing Wiring Systems from Drawings (Learning Outcome 3)
Step 1: Select materials from the drawings
Read the drawing key and the specification, then take off the materials: sizes and lengths of conduit, trunking and tray (scaled from the drawing, with allowances for bends, drops and terminations), the number and type of boxes and accessories, and the cable types and sizes.
Step 2: Mark out
Establish a datum (for example a line set at a fixed height above finished floor level), then transfer the dimensions from the drawing using a tape and level. Mark box centres and route lines, and check them twice before cutting or drilling. Use the mounting heights given on the drawing (in new dwellings, switches and sockets are normally between 450 mm and 1200 mm above the floor).
Step 3: Fix accessories and supports
Fix boxes level, square and to the dimensions on the drawing, using fixings suited to the surface (Section 10.4). Space supports within the limits in the On-Site Guide (Appendix D): for example, sheathed cables up to 9 mm overall diameter need clips at no more than 250 mm horizontally and 400 mm vertically. Use supports that will not fail early in a fire (Regulation 521.10.202).
Step 4: Install the wiring systems
The Unit 204 range lists single-core and multicore thermoplastic cable, fire-resistant cable, data cable, multicore armoured cable, cable tray, steel and PVC conduit, and trunking:
- Draw cables into conduit and trunking without twisting or crossing them, using a draw tape and lubricant where needed, and keep within the conduit or trunking capacity (Sections 10.3 and 10.4).
- Respect the manufacturer's minimum bending radius, especially for armoured, fire-resistant and data cables.
- Keep data cables segregated from power cables, avoid kinks, and do not crush them with over-tightened ties; at terminations keep the pairs twisted as close to the connector as possible (no more than about 13 mm untwisted for Category 5e and 6).
- Fix fire-resistant cables with fire-rated metal clips.
- Gland armoured cables as described in Section 10.1, with a banjo tag and earth fly-lead.
Step 5: Terminate
- Strip to the right length so that no bare copper shows outside the terminal and no insulation is trapped under the screw.
- Tighten to the manufacturer's torque setting.
- Sleeve bare CPCs green-and-yellow and identify switched lines with brown sleeving.
- Leave neat, tidy cable loops, use grommets or glands at enclosure entries, and check polarity as you go.
Step 6: Work safely throughout
Keep the work area tidy, clear away offcuts, store tools safely, and use the JIB safe isolation procedure whenever you work on or near circuits that could be live (Section 3.1).
Bonding Mains Services to the MET (Learning Outcome 4)
- Identify cable sizes: main protective bonding conductors are typically 10 mm² copper for a PME supply with a neutral up to 35 mm², and at least 6 mm² for TN-S and TT supplies (Section 13.3).
- Terminate the cables: strip and terminate into the MET (or a crimped lug), and label each conductor.
- Connect the bonding clamps: clean the pipe to bright metal and fit a BS 951 clamp on the consumer's side of the service (for gas, within 600 mm of the meter outlet; for water, as near as practicable to the point of entry), before any branch pipework. Fix the label "Safety Electrical Connection - Do Not Remove".
- Test continuity with a low-resistance ohmmeter from the MET to the clamp; IET guidance expects about 0.05 Ω or less (Section 14.2).
Tip
In the practical assignment, assessors look for safe isolation, neat and accurate marking out, secure fixings at the correct spacing, correct terminations and identification, and complete, recorded dead test results.
Which hand tool is used to remove burrs from the inside of a cut length of steel conduit?
Plumb line
Reamer
Wire strippers
Spirit level
Which of these is a correct pre-use safety check on a pillar drill?
Remove the chuck guard so you can see the bit more clearly
Wear loose gloves to get a better grip on the work
Check that the guard is in place, the work is clamped and the correct speed is set
Use a blunt bit so it is less likely to snatch
When marking out an installation from a drawing, what should be established first?
A datum line or level from which the dimensions are measured
The insulation resistance results for each of the final circuits
The colour of the accessory faceplates
The client's invoice address
When bonding an incoming metallic gas pipe to the main earthing terminal, which label must be fixed at the clamp?
Danger 400 V
Isolate elsewhere before working
Test this RCD six-monthly
Safety Electrical Connection - Do Not Remove
Sections you finish are checked off in the contents.