CEC Ampacity Calculator
Size your conductors right the first time. CEC Tables 1-4 with temperature correction, conductor count derating, and terminal limits per CSA C22.1.
Switch to NEC1Load Information
Enter your load in amps. Continuous loads (3+ hours) are multiplied by 125% per CEC Rule 8-104.
Loads running 3+ hours
Intermittent loads
2Conductor Properties
Common CEC insulation types
3Installation Conditions
Using CEC Table 2
Standard: 30°C (Table 5A applies above 30°C)
CEC counts ALL conductors (Table 5C)
4Terminal Temperature
Per CEC Rule 4-006: 60°C for ≤100A OR ≤#1 AWG; 75°C for >100A OR larger than #1 AWG.
Enter load information to calculate ampacity
How We Calculate CEC Ampacity
This calculator applies derating factors in the correct order per CEC methodology. We start with Tables 1-4 ampacity (based on installation type), apply Table 5A ambient temperature correction and Table 5C conductor count adjustment, then verify against Rule 4-006 terminal limits.
Key CEC references:
- Rule 8-104 — 125% continuous load factor
- Rule 4-004 — Ampacity of wires and cables (which table to use)
- Tables 1-4 — Base ampacity values at 30°C ambient
- Table 5A — Ambient temperature correction factors
- Table 5C — Conductor count adjustment (4+ conductors)
- Rule 4-006 — Terminal temperature limitations
- • CEC uses separate tables for free air vs raceway (NEC combines)
- • CEC Table 5C ranges differ from NEC 310.15(C)(1)
- • CEC counts ALL conductors for derating (NEC only current-carrying)
- • CEC Rule 4-006 considers wire size (#1 AWG) for terminal rating
CEC Ampacity: What Canadian Electricians Should Know
How does CEC ampacity differ from NEC?
The Canadian Electrical Code (CEC) and NEC have several key differences in how they handle ampacity calculations:
- Separate tables for installation type: CEC uses Tables 1-4 based on material (copper/aluminum) AND installation (free air vs raceway). NEC combines these.
- Conductor count ranges: CEC Table 5C uses different ranges: 1-3, 4-6, 7-24, 25-42, 43+. NEC 310.15(C)(1) uses 4-6, 7-9, 10-20, 21-30, etc.
- Terminal rating rule: CEC Rule 4-006 considers BOTH amperage (100A threshold) AND wire size (#1 AWG threshold). NEC 110.14(C) primarily uses amperage.
- Conductor counting: CEC counts ALL conductors in raceway for derating. NEC only counts current-carrying conductors.
What is CEC Rule 4-004 about?
CEC Rule 4-004 is the primary rule governing ampacity of wires and cables in Canada. It specifies:
- Which ampacity table to use: Tables 1-4 based on conductor material and installation method
- When to apply correction factors: Table 5A for ambient temperature, Table 5C for conductor count
- Special installation conditions: Free air, ventilated cable trays, underground, rooftop, etc.
- Neutral conductor counting: When neutrals should or shouldn't be counted
It's the foundation rule—always start here when sizing Canadian conductors.
How does CEC Rule 4-006 terminal temperature work?
CEC Rule 4-006 establishes terminal temperature limits that often govern final ampacity. It uses a dual criteria approach:
This means even if you have 90°C wire, you may need to use the 60°C column ampacity value at the terminals. The "OR" is key—either condition triggers the lower rating.
What are CEC Tables 1, 2, 3, and 4?
CEC uses four main ampacity tables, each for a specific combination of material and installation:
All tables are based on 30°C ambient temperature. For raceway/cable (Tables 2 & 4) with more than 3 conductors, apply Table 5C factors.
How does CEC Table 5C conductor count derating work?
CEC Table 5C provides correction factors when more than 3 conductors are installed in a raceway or cable:
| Number of Conductors | Factor |
|---|---|
| 1-3 | 100% |
| 4-6 | 80% |
| 7-24 | 70% |
| 25-42 | 60% |
| 43 and up | 50% |
Important: CEC counts ALL conductors in the raceway, not just current-carrying conductors like NEC does. This is a common source of error when switching between codes.
What is CEC Rule 8-104 continuous load factor?
CEC Rule 8-104 requires conductors supplying continuous loads to have an ampacity of at least 125% of the continuous load:
A continuous load is defined as a load expected to operate for 3 hours or more continuously.
This is the same 125% factor used in NEC 210.20(A). It accounts for heat buildup in conductors during extended operation.
How do I use CEC Table 5A for temperature correction?
CEC Table 5A provides correction factors for ambient temperatures above 30°C. The base ampacity values in Tables 1-4 assume 30°C—if your installation environment is hotter, you must derate.
Steps to apply Table 5A:
- Determine actual ambient temperature at installation location
- Find the row matching your ambient temperature
- Find the column matching your insulation temperature rating
- Multiply base ampacity by the correction factor
Note: Where the table shows "—", that insulation type cannot be used at that ambient temperature.
Can I use 90°C wire ampacity for all installations?
No—even with 90°C insulated wire, terminal temperature limits often restrict your usable ampacity:
- Most equipment terminals are rated 60°C or 75°C
- Per CEC Rule 4-006, you must use the ampacity from the column matching the terminal rating
- 90°C ampacity is useful for derating calculations—you start with the higher value before applying factors
Example: #10 copper at 90°C = 40A (Table 2). If equipment terminals are 60°C rated, you can only use 30A at the connection points.