Sub-Panel vs Main Panel Upgrade: How to Decide
The decision starts with a load calculation under CEC Section 8. If your existing 100A or 200A main panel has capacity to spare and open breaker slots, a sub-panel is the right move. If you're already pushing the service limit — common when stacking an EV charger, hot tub, garage heater, and basement addition on a 100A service — we recommend a 200A main upgrade first, then the sub-panel. We do the math up front so you don't pay twice.
Detached Garage Feeders: Trenching for Frost
Detached garages — common in older Beacon Hill and Abasand lots and in newer Eagle Ridge builds with separate shops — need a buried feeder from the house. We run direct-burial copper or aluminum feeder inside Schedule 40 PVC conduit at the code-required depth (450 mm under landscaping, 600 mm under driveways). Sweep elbows at each building entry and sealed conduit ends keep spring melt and rodents out. A separate ground rod at the garage and a 4-wire feeder (CEC Section 10) provide proper bonding without parallel neutral paths.
Sizing the Sub-Panel
Right-sizing matters because re-pulling a feeder later is expensive. A typical heated detached garage with a 240V unit heater, an EV charger, lighting, and 120V receptacles needs 60A minimum, 100A comfortable. A finished basement with a wet bar, theatre, and electric fireplace usually fits inside a 60A sub-panel. A workshop with a welder, compressor, or large dust collector should start at 100A. We always leave 25% headroom for the next thing you'll add.
Bonding, Grounding & 4-Wire Feeders
The most common defect we see when fixing other contractors' sub-panels is improper neutral-ground bonding. In a sub-panel, the neutral and ground bus must be isolated — bonding only happens at the main service. We pull a dedicated equipment ground separately from the neutral, isolate the neutral bar, and (for detached buildings) drive a supplemental ground rod per CEC Section 10-700. Done right, this eliminates objectionable current on the ground path and keeps GFCI/AFCI breakers from nuisance-tripping.
RMWB Permits & Inspection
Sub-panel installations require an RMWB electrical permit and a pass inspection — there are no exceptions. We pull the permit, perform the work to CEC Sections 6 (Services and Service Equipment), 8 (Demand Factors), and 10 (Grounding and Bonding), and book the inspection. You receive copies of the permit and the inspection report for insurance and resale records.
