Direct burial depths, at a glance (CEC / OESC Rule 12-012 & Table 53)
Every one of these needs an ESA permit before you dig. Under the Canadian Electrical Code (CEC Part I) and Ontario Electrical Safety Code (OESC), direct burial requires NMWU (Non-Metallic Wet Underground) or TECK90 cable. Note: US UF-B cable is not CEC approved in Canada.
1. Single Branch Circuit vs. Subpanel Feeder
Before buying wire or digging a trench, decide how much electrical power your detached garage or shed will require:
- Single 120V Branch Circuit (15A or 20A): Ideal for simple shed lighting and 1 or 2 outlets for light power tools. Requires 14/2 NMWU (15A) or 12/2 NMWU (20A). No subpanel required, but a local disconnect switch (like a single-pole wall switch) at the shed door is required by CEC.
- Subpanel Feeder (30A to 100A, 120/240V): Required if you plan to run an air compressor, EV charger, 240V heater, or multiple power tools simultaneously. Requires a 4-conductor feeder (e.g. 8/3, 6/3, or 2/2/2/4 NMWU/TECK90) back to a dedicated double-pole breaker in the main home panel.
2. Main Disconnect Means at the Detached Building
CEC Section 6 and 26 require a single main disconnect means at any outbuilding fed by a subpanel or feeder. This allows anyone inside the garage or shed to shut off all power instantly in an emergency. This can be a main breaker inside the subpanel or an external weatherproof disconnect switch near the entry door.
3. Crucial 4-Wire Subpanel Rule: Separating Neutral & Ground
One of the most common ESA inspection failures for DIY garage wiring is improperly bonding the neutral bar inside a subpanel. Under Canadian Electrical Code:
- 4 Conductors Required: Hot 1 (Red), Hot 2 (Black), Neutral (White), and Ground (Bare/Green).
- Remove the Bonding Screw: The green neutral bonding strap/screw included with new panels MUST BE REMOVED in a subpanel. Neutral and ground buses must remain floating and isolated.
- Grounding Plate / Ground Rods: Detached structures fed by a subpanel must have their own ground electrode system (typically 2 ground plates or ground rods spaced at least 2 metres apart per CEC Rule 10-102) connected to the subpanel ground bus.
4. Protecting Wire From Frost Heave (Expansion Sleeves)
In Canadian climates (Ontario / GTA), freezing ground expands and moves vertically (frost heave). Rigid PVC conduit coming out of the ground into a building or main house wall must be fitted with an approved PVC Expansion Joint / Sleeve (CEC Rule 12-012). Without an expansion joint, winter ground movement will crack the conduit or rip the panel box right off the wall.
5. Interior Wiring Rules Inside Garages & Sheds
- Physical Protection: Romex / NMD90 wire running on unfinished garage walls below 1.5m (5 ft) off the floor must be protected from mechanical damage inside EMT conduit or PVC.
- GFCI Protection: Outlets in unfinished garages, sheds, or outdoors must have GFCI protection (CEC Rule 26-704).
- Weatherproof Covers: Outdoor receptacles must be equipped with "Extra-Duty" while-in-use wet location covers.
6. ESA Inspection Process in Ontario
When installing power to a detached garage or shed, the Electrical Safety Authority (ESA) requires a 2-stage inspection process:
- Rough-In & Trench Inspection: Must occur while the trench is wide open (bedding sand + cable + warning tape visible) and before any drywall/insulation covers subpanel wiring.
- Final Inspection: Conducted after all fixtures, receptacles, panel breakers, covers, and disconnect switches are fully trimmed out.
Why pool equipment is different
Pool and hot tub wiring sits in its own category — bonding requirements around water are stricter (CEC Section 68), and the depth and method depend heavily on the specific run and equipment. This is one of the few jobs on this list we'd say don't DIY any part of, not even the trench.