Conduit and Routing
How to route wiring safely through buildings — cable management principles, conduit installation techniques, and pulling wire through conduit.
Why This Matters
The difference between professional electrical work and amateur work is often visible in how cables are routed. Haphazard cable routing creates fire hazards (cables over heat sources, bundled too tightly), physical hazards (cables in walking paths), maintenance problems (can’t trace circuits, can’t add circuits), and damage risks (cables nailed against wood that will eventually be cut into).
Proper routing with conduit adds mechanical protection, enables future changes (pull out old wire, pull in new), provides a grounding path (metal conduit), and creates a system that’s readable and understandable by any competent electrician decades later.
In rebuilding scenarios where electrical skills are scarce, readable wiring that can be traced and repaired by a non-expert is a safety asset.
Conduit vs. Direct-Wired Cable
Conduit system: Conduit (a hollow tube) is installed first; wire is pulled through afterward. Changes and additions are easy — just pull new wire. More protection for wire. Higher initial labor.
Direct-wired cable: Cable with its own outer jacket (NM cable, armored cable) is routed without conduit. Faster to install. Harder to modify later. Less protection in exposed areas.
When to use conduit:
- Any exposed wiring (visible on walls, ceilings, in garages, barns, workshops)
- Any wiring subject to physical damage (near machines, tools, vehicles)
- Any wiring in damp or wet locations (conduit can be sealed)
- Any wiring that may need future replacement or upgrade
- Any wiring in high-temperature locations (industrial, near furnaces)
When direct cable is acceptable:
- Concealed wiring inside closed wall and ceiling cavities (in construction with insulation)
- Short runs in accessible areas with low damage risk
- Temporary or low-priority installations
Conduit Types and Selection
Rigid metal conduit (RMC/GRS): Heavy-wall steel or aluminum tube with threaded fittings. Maximum protection. Used in industrial, outdoor, and embedded-in-concrete applications. Heavy, requires threading tools.
Intermediate metal conduit (IMC): Thinner-wall steel. Lighter than RMC, still quite protective. Most common for commercial/industrial use where maximum protection is needed.
Electrical metallic tubing (EMT): Thin-wall steel, no threads — uses set-screw or compression fittings. Lighter, easier to work with. For indoor, protected locations. Not suitable for concrete burial without additional protection.
PVC conduit: Lightweight, corrosion resistant, cheap, electrically non-conductive. Good for outdoor and underground runs. Cannot be bent by hand (needs heat bending) or cut with standard tools (requires PVC saw or conduit cutter). Does not provide equipment grounding — must add separate ground wire.
Flexible conduit: Metal or plastic flexible tubing for connections to equipment that vibrates or moves (motors, equipment panels). Not for long runs — too much friction to pull wire through.
Conduit Sizing
Conduit must be large enough to pull wire through without excessive friction or damage. Fill rules limit how much wire can go in one conduit.
Fill limits (percentage of conduit cross-section that wire may occupy):
- 1 conductor: 53%
- 2 conductors: 31%
- 3+ conductors: 40%
Practical sizing table (mm conduit for copper wire):
| Wire size | 1 wire | 2 wires | 3 wires | 4+ wires |
|---|---|---|---|---|
| 2.5mm² | 16mm | 16mm | 16mm | 20mm |
| 4mm² | 16mm | 16mm | 20mm | 20mm |
| 6mm² | 16mm | 20mm | 25mm | 25mm |
| 10mm² | 20mm | 25mm | 32mm | 32mm |
| 16mm² | 25mm | 32mm | 32mm | 40mm |
When in doubt, go one size larger — pulling wire through a larger conduit is much easier.
Bending Conduit
Metal conduit must be bent to change direction. Three methods:
Conduit bender (hand bender): A purpose-made tool with a calibrated shoe that bends conduit to standard angles (30°, 45°, 60°, 90°) at consistent radii. Most common tool; provides accurate bends without kinking.
Mechanical bender (hickey): For small conduit bends in confined spaces. A lever tool; more effort, usable without a full bender.
Heat bending (for PVC): Heat the conduit with a heat gun or hot sand, bend to shape, hold while cooling. Difficult to get precise angles; use a bending form or template for accuracy.
Bending rules:
- Minimum bend radius: 6× conduit inside diameter for most conduit types
- Maximum 360° total bends between pull points (where wire can be pulled from); break up long runs with junction boxes or pull boxes
- 90° bends: use the dedicated mark on conduit benders for accurate placement
- Avoid reverse bends (saddles over obstacles): they add huge friction when pulling wire
Offsets and saddles: An offset is a pair of bends that moves the conduit laterally to go around an obstacle or into a box at an angle. Standard offsets are made with two equal bends of 10°, 22°, 30°, or 45°, calculated with trigonometry or conduit bender marks.
Pulling Wire Through Conduit
Before pulling:
- Verify conduit is secure and free of obstructions
- Count total bends (less than 360° recommended)
- Estimate length (measure conduit + add 300mm at each end for terminations)
- Prepare wire: cut all conductors for one circuit to length, tape ends together, attach pull string
Fish tape and pull string:
- Steel fish tape: a coiled flat steel strip that pushes through conduit. Feed from one end until it emerges at the other.
- Nylon pull string (fish line): lighter than fish tape; used for pulling wire after fish tape establishes the path
- Attach wire bundle to fish tape or pull string with electrician’s tape — smooth, streamlined, no protruding ends to snag
Wire pulling lubricant: Cable pulling compound (wire lube) dramatically reduces friction. Without it, wire may bind on bends. Improvised lubricants: petroleum jelly, liquid soap, white grease. Avoid oil-based lubricants that attack wire insulation.
Pulling technique:
- Pull steadily; jerking can damage insulation or break the pull string
- Have one person feed wire from one end while another pulls from the other
- If wire binds: don’t force — back up slightly, add more lubricant, try again
- Very long or complex runs may need a power wire puller (rented tool) for large cable
Raceway Systems: Surface-Mounted Alternatives
When conduit installation inside walls isn’t practical, surface-mounted raceways channel cables along walls and ceilings:
Wireway (surface raceway): A metal or plastic trough with a removable cover. Cables laid inside, cover clips on. Accessible at any point by lifting the cover. Good for workshops, warehouses, temporary installations.
Cable tray: An open trough of metal rungs or perforated sheet. Cables laid in without a cover. Used in large industrial/commercial settings. Provides maximum cooling and accessibility.
Conduit on surface: Conduit installed on the wall surface with clamps. Less elegant than wireway but more protective and familiar to most electricians.
All these systems should be installed horizontally or vertically, at consistent heights, with labels indicating circuit contents. A surface-mounted system that’s properly laid out and labeled is often easier to maintain than concealed wiring.
Separation Requirements
Different types of circuits should be separated to prevent interference and safety hazards:
- Power circuits (high voltage) should be at least 150mm from low-voltage signal circuits
- AC power should not run parallel to DC control circuits for extended distances (induced AC noise in DC circuits)
- Emergency and normal circuits should be in separate conduits or raceways — if normal power fails, emergency circuits shouldn’t be damaged by the same fault
- Telecommunication cables should be separated from AC power by at least 75mm or in separate conduit
Proper routing, protected by conduit where needed, is what separates installations that work safely for decades from ones that degrade, present hazards, and require constant repair.