Dakota Demand Factors Residential Guide for Red Seal Exam (CEC 2024)

The Big Idea:

How much power does a house need?
We’re going to size the electrical service, wires, and panel by figuring out:

1. How big the house is
2. What’s inside the house
3. How much power all that stuff uses

‍

Step 1: How Big Is This Place?

You use CEC Rule 8-110 + 8-200 to calculate total "living area":

• 100% of ground floor
• 100% of anything above
• 75% of only those areas below the ground floor that exceed 1.8 m in height,

Mr. Winnipeg Chevrolet builds a mansion that has 30m by 30m dimensions:
30m × 30m = 900 m²/floor
2 floors + 75% of basement (it’s greater than 1.8m in height)
Total = 2,475 m²

Now use the basic load rule from 8-200:

• First 90 m² = 5,000 W
• Every 90 m² after that = +1,000 W

Let’s calculate the floor sizing:

• 30m x 30m = 900 m²
• First floor = 900m²
• Second Floor= 900m²
• Basement= 900m² * 75% = 675m²
• 900 + 900 + 675 = 2,475 m²

Now, to calculate the total load.

First 90 m² → 5,000 W

The amount leftover afterwards is 2,475 m² - 90 m² = 2,385 m²

• 2,385 m² / 90 m² = 26.5
• 26.5 round ups to 27
• 27 * 1000 W
• 27,000 W + 5000 W
• = 32,000 W basic load

‍

Step 2: What's Inside?

Time to list the appliances and equipment!

You’ll use different rules for each item, like:

• Fridge (1.5 kW) → Additional Load
  
• Freezer (2 kW) → Additional Load
  
• A Stove (14 kW) → 8-200(1)(a)(iv)
  
• Washer (800 W) and Dryer (2.3 kW) → Additional Load
  
• Microwave (1.2 kW) → Additional Load
  
• Dishwasher (1.5 kW) → Additional Load
  
• Furnace (2 kW) → 8-200(1)(a)(iii)
  
• Air-Conditioner (1.5 kW) → 8-200(1)(a)(iii)
  
• Hard-wired electric fireplace (3 kW) → Additional Load
  
• Hot Water Tank (1 kW) → 8-200(1)(a)(v)
  
• Hot Tub (2 kW) → 8-200(1)(a)(v)

The easy way to remember what is what:

• If it has a VERY specific rule (like the stove), go with that rule
• If it DOESN’T have a specific rule, AND it’s above 1.5kW, it’s an additional load.

‍

Step 3: Add It All Up!

Let’s total the demand:

‍

Step 4: Convert to Amps

I = P/E

I = 47,375 W / 240 V

I= 197.4A

We use 240V because it’s a residential dwelling!

‍

Step 5: Size the Conductors

Use Table 2, RW75. 75C Termination Temperature.
197.4A requires #3/0 AWG copper (rated for 200A)

As per usual, Rule 4-006 applies!

‍

Step 6: Size the Overcurrent Protection

Per CEC Rule 14-104:

• The O/C device can’t exceed the ampacity of the conductors
• But we can use Table 13 if the breaker matches load

Use a 200A breaker

‍

Final Cheat Sheet

"How to Math an Apt" in 8 Fun Steps:

1. Get the square footage
2. Add all major loads (stove, furnace, A/C, etc.)
3. Add minor additional loads (appliances >1500W at 25%)
4. Total demand in watts
5. Divide by 240V → get Amps
6. Choose conductor size (Table 2)
7. Choose panel size to match
8. Pick an appropriate breaker (Table 13)

‍

The VERY Specific Rules:

The Range (Stove)

We use 6000W towards the demand calculation plus:

40% of any amount more than 12kW

• 14W stove
• We use 6000W for the first 12kw.
• Anything OVER 12kW we take at 40%
• 14kW-12kW= 2 kW
• 6000W + 2000W = 8000W        

8000W is what we use to calculate the demand for ONE stove.

But……what if we have more than one stove? Like Mr. Winnipeg Chevrolet who loves to entertain and serve many hot appetizers.

Rule 8-200 1) a) vii)

Consider it an additional load!

‍

Hot Stuff

The rule to remember is: If it’s HOT, it uses A LOT.

So anything hot (furnace, AC, sauna, hot water tank) will be taken at 100%.

Except (because there’s always an ‘except’ with Code):

Furnace: 62-118 (3)

If the heat is individually controlled: the first 10 kW of connected heating load at 100% demand factor AND the rest of the connected heating load at 75% demand factor.

‍

Interlocks (Heating & AC)

Interlock is a fancy way of saying that you can’t have 2 or more things all going at the same time.

There are 3 types of Interlock:

• Mechanical (a physical ‘thing’ preventing 2 or more things from happening. Example: Car’s gearshift. It won’t allow you to put it into Forward and Reverse at the same time.
• Electrical (Uses Relays and contacts for control wiring)
• Logistical (PLC’s/Computer Programming)

Since Heating and Cooling are 2 sides to the same coin, Interlocking can apply here.

If Heating and AC are interlocked, that means you calculate the demand load for both, but ONLY USE THE HIGHEST ONE.

If Heating and AC are NOT interlocked, USE BOTH.

‍

Additional Loads:

If there isn’t a specific code, and it’s over 1500W, add it all up and take it at 25%.

See? Super easy. Kind of.