How to choose the right breaker size?

Choosing the right breaker size depends on several factors defined in the Quebec Construction Code:

General rule: The breaker must be sized at 125% of the load's rated current for continuous loads (3 hours or more), and 100% for non-continuous loads.

Standard breaker sizes available: 15 A, 20 A, 25 A, 30 A, 35 A, 40 A, 45 A, 50 A, 60 A, 70 A, 80 A, 90 A, 100 A, 110 A, 125 A, 150 A, 175 A, 200 A.

Practical examples:

• Receptacle circuit (living room): 15 A, #14 AWG wire
• Kitchen receptacle circuit: 20 A, #12 AWG wire
• Electric dryer (5,000 W / 240 V = 20.8 A × 1.25 = 26 A) → 30 A, #10 AWG wire
• Wall heat pump (3,000 W / 240 V = 12.5 A × 1.25 = 15.6 A) → 20 A, #12 AWG wire

Never install a breaker rated higher than the conductor's capacity. For example, #14 AWG wire (15 A) must never be protected by a 20 A breaker, except as specifically allowed by the Code.