Intro

On most jobs, electrical wiring makes or breaks your schedule. Done right, it’s clean, safe, and passes inspection the first time. Done wrong, it adds rework and delays. This guide explains electrical wiring from plan to handover. We’ll keep it simple: plan loads, size wires, rough-in clean, and test to code. You’ll see measurements that matter, common mistakes, and quick checks inspectors look for. Whether you’re leading a crew or coordinating trades, this will help you deliver safe, code‑compliant work without drama.

Quick Answer

Electrical wiring means planning loads, sizing conductors, installing cable and devices to the Canadian Electrical Code, and testing before handover. Use 14 AWG on 15A, 12 AWG on 20A, and support NMD90 every 1.5 m and within 300 mm of boxes. Bond metal enclosures, add GFCI/AFCI where required, and leave 150 mm free conductor in boxes.

Table of Contents

• Electrical Wiring Planning: Circuits and Loads
• Wire Sizes, Breakers, and Protection
• Electrical Wiring Rough-In: Step-by-Step
• Panels, Grounding, and Final Connections
• Code, Safety, and Testing
• Documentation and Handover

Key Takeaways

• Size conductors to breakers: 14 AWG/15A, 12 AWG/20A, 10 AWG/30A.
• Support NMD90 every 1.5 m and within 300 mm of boxes.
• Leave 150 mm free conductor in each box; strip 12–15 mm at devices.
• Use GFCI in wet areas and AFCI in most living spaces per CEC.
• Test continuity and polarity before trim; aim for clean results on first inspection.

Electrical Wiring Planning: Circuits and Loads

When you’re on site, start with the plan. Map loads before you pull a single cable.

• Walk the space. Mark lights, switches, receptacles, appliances.
• List loads: general receptacles, lighting, kitchen small-appliance, laundry, bath fans, HVAC.
• Separate circuits by use. Keep kitchens, bathrooms, and laundry on dedicated lines.
• Continuous loads (over 3 hours) should be at or below 80% of circuit rating.

Practical Layout Tips

• Switch height: commonly 1.1–1.2 m above finished floor (AFF).
• Receptacle height: often 300–450 mm AFF in living areas.
• Kitchen counters: 20A small-appliance circuits; space receptacles so no point is more than 900 mm from one.
• Lighting: group by area so one fault doesn’t blackout the whole floor.

Pro tip: Add allowances for future. Pull a spare 20A to a mechanical room or garage when it’s cheap to do so. If you’re also looking to streamline professional proposals, our guide on professional proposals pairs well with this planning step.

Wire Sizes, Breakers, and Protection

Match conductor size to breaker size and the environment. Keep it simple and safe.

• Cable: NMD90 is standard for dry indoor runs; use AC90/armoured or TECK90 where exposed or required.
• Colour code (Canada): black/red hot, white neutral, green/bare bond.
• Voltage: typical 120/240 V single-phase residential.

GFCI and AFCI

• GFCI: bathrooms, outdoor, garage, and near sinks (commonly within 1.5 m of a sink). Use 5 m extension cords? Don’t rely on that; install proper GFCI protection.
• AFCI: required on most 125 V, 15/20A dwelling circuits like bedrooms and living areas. Check your provincial amendments.

Cable Support and Protection

• Support NMD90 at least every 1.5 m and within 300 mm of boxes.
• Use nail plates where cables pass within 32 mm of stud faces.
• Avoid overfilling holes; keep at least 38 mm spacing between bored holes carrying multiple cables when heat could build up.

If you need to improve pricing accuracy, see our notes on pricing strategies and project timelines. Better planning equals fewer change orders.

Electrical Wiring Rough-In: Step-by-Step

Follow these steps for a clean, code-friendly rough‑in that passes inspection.

1. Mark Boxes
   • Set boxes flush to finished surface. Use depth rings for tile or paneling.
   • Keep device boxes plumb. It saves minutes on every trim-out.
2. Drill and Route
   • Drill centred holes in studs. Maintain 32 mm clearance from edges.
   • Group home runs neatly. Label each with a marker at both ends.
3. Pull Cable
   • Run NMD90 with smooth sweeps. Avoid tight bends (radius ≥ 5× cable diameter).
   • Leave 150 mm free conductor in each box.
4. Staple and Protect
   • Staple within 300 mm of every box and every 1.5 m along runs.
   • Add nail plates where needed. Protect drops in stud bays.
5. Make Up Boxes
   • Strip 12–15 mm of insulation at devices later; for now, cap neutrals and bond conductors.
   • Pigtail grounds in metal boxes. Bond bars to yokes as required.
6. Label at Panel End
   • Tag each cable with location and load (e.g., “Kitchen SABC #1”).
   • Keep a circuit schedule draft in your phone or notebook.
7. Inspector Walkthrough Prep
   • Clear insulation from boxes. Expose all staples and nail plates.
   • Coil conductors neatly in boxes; no sharp kinks.

Timeframe: For a typical 3‑bedroom house, a two‑person crew often roughs in 2–4 days, depending on layout and complexity.

Panels, Grounding, and Final Connections

Panels are not the place to guess. If you’re not licensed for service work, bring in the right person.

Panel Setup

• Mount panel level with clear working space (at least 1 m clear in front).
• Keep home runs dressed on the sides; avoid crossing the neutral bar messily.
• Torque lugs to manufacturer specs. Don’t guess. Use a torque driver.

Bonding and Grounding

• Bond all metal boxes and enclosures using the green/bare conductor.
• In subpanels, isolate neutrals from grounds. One neutral‑ground bond only at the service.
• Use listed connectors for grounding conductors; no back‑of‑the‑box twists.

Final Device Connections

• Back‑wire only if the device is rated for it. Side‑terminate with properly formed hooks otherwise.
• Tighten screws to spec; over‑torque can crack devices.
• Maintain polarity: hot to brass, neutral to silver, ground to green.

This pairs well with understanding invoice templates that save time when you’re ready to bill after final.

Code, Safety, and Testing

The Canadian Electrical Code (CEC) is your rulebook. Local Authorities Having Jurisdiction (AHJ) may add amendments. Always check current requirements in your province.

Safety First

• Lockout/tagout when working near energized gear.
• Verify absence of voltage with a meter, not just a non‑contact tester.
• Keep box fill reasonable. As a rule, don’t cram more than makes sense—use larger boxes for 3+ splices.

Pre‑Cover Tests

• Continuity: grounds bonded end‑to‑end; low resistance path (< 1 Ω is a practical target on short runs).
• Polarity: hot/neutral correct using a plug‑in tester before trim.
• Insulation: if you megger, aim for ≥ 1 MΩ between conductors at 500 V on new dry runs.
• GFCI/AFCI: function test each device/breaker.

Common Fail Points (Avoid These)

• Staples missing within 300 mm of a box.
• No nail plates over stud‑face‑close bores.
• Neutral and ground tied together in subpanels.
• Not enough free conductor length (less than 150 mm) in boxes.
• Kitchen receptacles not on required 20A small‑appliance circuits.

If you track changes as they happen, clients sign off faster. Tools like Donizo help you capture voice notes and photos, then generate a clear proposal or change order for approval.

Documentation and Handover

Document as you go. It saves callbacks and speeds inspections.

• Circuit Directory: Keep a clean, legible panel schedule. Number breakers and note locations.
• Photos: Shoot walls before drywall. Capture stud bays and cable routes.
• Labels: Label junction boxes above ceilings and in mechanical rooms.
• Client Pack: Provide device locations, GFCI reset spots, and any special equipment notes.

Handover Checklist

• All plates on, devices straight.
• AFCI/GFCI tested and labelled.
• Panel schedule complete and accurate.
• Work area clean; no debris in boxes.

This documentation step connects well with client management. If you also need to tighten up estimates and approvals, platforms such as Donizo offer e‑signatures and one‑click invoice conversion after acceptance.

FAQ

How many receptacles can I put on a 15A circuit?

Rules vary by province and occupancy. In general homes, many electricians space general receptacles so no point along the wall is more than 1.8–3 m from one, and keep sensible loading. Always follow your AHJ. Kitchens and bathrooms have dedicated requirements and often need 20A circuits.

Do I need AFCI or GFCI on bedroom circuits?

Bedrooms typically require AFCI protection on 125 V, 15/20A circuits under the CEC, subject to local amendments. GFCI is for wet or damp areas like bathrooms, outdoors, and near sinks. Check provincial rules and use combination devices/breakers where required.

What’s the difference between 14/2 and 14/3 cable?

14/2 has hot, neutral, and ground. 14/3 adds a second hot (red), useful for three‑way switches or split receptacles where permitted. Match the cable to the design and breaker rating. Never down‑fuse to hide an undersized conductor.

How much wire should I leave in a box?

Leave at least 150 mm of free conductor measured from where it enters the box. This makes device connections easier and meets common inspector expectations. Also leave 12–15 mm stripped at devices when you trim.

Can I mix 12 AWG and 14 AWG on the same circuit?

Don’t do it. The smallest conductor sets the breaker size. Mixing can lead to overcurrent on smaller wires. Keep the entire circuit consistent with its breaker rating.

Conclusion

Electrical wiring is about planning loads, sizing conductors, installing cleanly, and testing to code. Do the basics well and you’ll pass first inspection, cut rework, and protect your margin. Next steps: 1) Walk your next job and map circuits, 2) Standardize heights, supports, and labels, 3) Add a pre‑cover test checklist. For faster client approvals and smoother billing, consider solutions like Donizo to turn site notes into signed proposals and invoices. Build safe, build clean, and keep projects moving.