What is the maximum voltage drop allowed in Canada?

CEC Rule 8-102 limits voltage drop to 3% in a feeder or branch circuit and 5% total from the supply side of the consumer's service (or the transformer secondary) to the point of utilization. Unlike the NEC, these are mandatory requirements.

Does the CEC require the load current or the breaker rating?

Rule 8-102(2) bases the calculation on the connected load of the circuit if known, otherwise 80% of the rating of the overcurrent device protecting it. If you don't know the load, enter 80% of the breaker size.

Can I enter lengths in metres?

Yes. Choose m beside the length field. The calculator converts to feet internally (1 m = 3.28084 ft) and uses the same resistance values.

Which voltages are common in Canada?

120/240 V single phase for homes, 120/208 V three phase for apartments and small commercial, and 347/600 V three phase for larger commercial and industrial buildings, with 347 V lighting.

Where do the resistance values come from?

They are DC resistance of uncoated stranded copper and aluminum at 75 °C, the same physical values as NEC Chapter 9 Table 8. The CEC's Table D3 distance tables are based on the same physics, so the results agree closely.

Voltage Drop Calculator Canada (CEC Rule 8-102)

Check voltage drop against CEC Rule 8-102. Enter lengths in metres or feet, at 120, 208, 240, 347 or 600 V, for copper or aluminum.

CEC data notice: CEC values were checked against public summaries of CSA C22.1:24, not the code book itself. Conduit and conductor areas use NEC Chapter 9 data, and some aluminum kcmil ampacities are unverified. Confirm against the CEC edition and provincial amendments adopted where you work.

CEC Rule 8-102 in brief

The Canadian Electrical Code, Part I (CSA C22.1), Rule 8-102 says voltage drop in an installation must not exceed:

5% from the supply side of the consumer's service (or the secondary of the transformer for a separately derived system) to the point of utilization, and
3% in a feeder or branch circuit.

The demand load used is the connected load if known, or 80% of the overcurrent device rating. Because these are code requirements in Canada, inspectors can and do check them on long runs, especially detached garages, shops and outdoor equipment.

The formula

Single phase: VD = 2 × I × R × L ÷ 1000
Three phase: VD = 1.732 × I × R × L ÷ 1000
L in feet = L in metres × 3.28084

R is the conductor resistance in ohms per 1000 ft. For example, 10 AWG copper is 1.21 Ω and 8 AWG is 0.764 Ω. Full values are in the wire gauge chart.

Worked examples

1. Detached garage subpanel, 240 V

A 30 A load at 240 V, 40 m from the house, on 10 AWG copper:

L = 40 × 3.28084 = 131.2 ft
VD = 2 × 30 × 1.21 × 131.2 ÷ 1000 = 9.53 V → 3.97%

That is over the 3% branch circuit limit. 8 AWG copper gives 6.01 V, or 2.51%, which complies. If you don't know the load, the code basis is 80% of a 30 A breaker, 24 A, which gives 3.18% on 10 AWG, still over the limit.

2. 347 V lighting circuit

20 A on a 347 V lighting circuit, 60 m, 10 AWG copper:

L = 196.9 ft
VD = 2 × 20 × 1.21 × 196.9 ÷ 1000 = 9.53 V → 2.75%

Within 3%. Higher voltage makes 347 V lighting efficient over long distances in warehouses and parking structures.

3. 600 V feeder

150 A over 91 m (300 ft) on 3/0 aluminum, three phase: VD = 1.732 × 150 × 0.126 × 300 ÷ 1000 = 9.82 V, or 1.64% of 600 V. See the 3 phase voltage drop calculator for more feeder examples.

Fixing excessive voltage drop

Upsize the conductors. Each two-gauge step cuts resistance by about 37%.
Use a higher voltage: run a 240 V circuit instead of 120 V where the equipment allows.
Move the panel or add a subpanel closer to the loads.
Split the load across more circuits.

When you upsize for voltage drop, check whether the bonding conductor and conduit size need to change too. Check the raceway with the Canadian conduit fill calculator.

Ampacity in Canada

Voltage drop is only one check. Conductors must also meet CEC Table 2 (copper) or Table 4 (aluminum) ampacity, with the Rule 4-006 termination temperature limits and Rule 14-104 small-conductor protection limits (14 AWG copper 15 A, 12 AWG 20 A, 10 AWG 30 A). The wire size calculator applies the equivalent NEC values, which are close for common sizes.

Voltage Drop Calculator (Canada, CEC)