Electrical Module 26111-23: Residential Wiring - Sizing the Residential Electrical Service

Comprehensive practice flashcards for Electrical Module 26111-23 Residential Wiring, covering service load calculations, general lighting, appliance circuits, NEC code references, demand factors, and trade definitions.

In a residential occupancy, what type of electric service entrance does the utility company provide?

A $120/240\,\text{V}$, single-phase, three-wire service entrance with a solid neutral.

What is the very first step in calculating the residential electric service load?

To look at the floor plan.

How is the general lighting load for a residential dwelling computed according to NEC Section 220.41?

By determining the square footage of the living area and multiplying it by $3\,\text{VA/ft}^2$.

What specific outlets and receptacles are included within the general lighting load calculation?

General-use receptacles of $20\,\text{A}$ or less (including those in bathrooms and garages), outdoor receptacles, and lighting outlets in the dwelling.

What does NEC Section 210.11(C)(1) require regarding small-appliance circuits, and what is each circuit rated at for load calculations?

It requires at least two $120\,\text{V}$, $20\,\text{A}$ small-appliance branch circuits, with each circuit calculated at $1500\,\text{VA}$ per NEC Section 220.52(A).

What are the branch circuit and load requirements for the laundry area under NEC Section 210.11(C)(2) and NEC Section 220.52(B)?

One dedicated $20\,\text{A}$ branch circuit for the exclusive use of the laundry area, calculated at a load of $1500\,\text{VA}$.

How are demand factors applied to calculate the total general lighting load demand according to NEC Table 220.45?

The first $3000\,\text{VA}$ is calculated at $100\%$, and the remaining volt-amperes are multiplied by $35\%$.

Under NEC Section 220.53, what demand factors apply to residential fixed appliances?

A demand factor of $100\%$ applies if there are 3 or fewer fixed appliances, and a demand factor of $75\%$ applies if there are 4 or more fixed appliances.

Per NEC Section 430.24, what percentage of the largest motor must be added when calculating the service load?

$25\%$ of the largest motor load.

How is the required service size in amperes determined from the total volt-ampere load?

By dividing the total volt-amperes by the highest voltage in the service (e.g., $\frac{24{,}767\,\text{VA}}{240\,\text{V}} = 103\,\text{A}$).

What is the definition of a demand factor?

The maximum amount of volt-ampere load that you expect at any given time, compared to the total connected load of the circuit.

Which NEC code section covers standard feeder and service load calculations for electric cooking appliances in dwelling units?

NEC Section 220.55 (under NEC Article 220, Part III).

Which NEC code sections specify optional feeder and service load calculations for dwelling units and existing dwelling units?

NEC Section 220.82 for a dwelling unit and NEC Section 220.83 for an existing dwelling unit (both under NEC Article 220, Part IV).

How is the neutral conductor load for fixed-appliance loads calculated?

By totaling the $120\,\text{V}$ fixed-appliance loads.

What is the primary function of a Ground Fault Circuit Interrupter (GFCI)?

It protects personnel by de-energizing a circuit when a ground fault current exceeds the values established for a Class A device.

According to the provided floor plan and NEC Section 210.8(A), which eight residential locations require GFCI protection?

1. Bathrooms, 2. Garages, 3. Outdoors, 4. Basements, 5. Kitchens, 6. Sinks, 7. Bathtubs or Shower Stalls, and 8. Laundry Areas.

What code section requires dwelling unit services to be provided with a surge protective device (SPD)?

NEC Section 230.67(A) and (B).

What is the definition of a branch circuit?

The portion of a wiring system extending beyond the final overcurrent device protecting a circuit.

What is a feeder in a wiring system?

Any circuit conductor between the service equipment, the source of a separately derived system, or other power supply source and the final branch circuit overcurrent device.

What is the difference between a grounded conductor and a grounding electrode conductor?

A grounded conductor is intentionally grounded in the system or circuit, whereas a grounding electrode conductor connects the system grounded conductor or equipment to a grounding electrode or grounding electrode system.

What is a load center?

A type of panelboard normally located at the service entrance of a residential installation that distributes electricity to branch circuits and sometimes contains the main disconnect.

What are service-entrance conductors?

The conductors between the point of termination of the overhead service drop or underground service lateral and the main disconnecting device in the building.

A small residence has a floor area of $900\,\text{ft}^2$. What is its general lighting load?

$2{,}700\,\text{VA}$ (calculated as $900\,\text{ft}^2 \times 3\,\text{VA/ft}^2$).

If a dwelling has two kitchen areas, what is the total requirement for small-appliance branch circuits?

Four at $1{,}500\,\text{VA}$ each.

According to NEC Table 220.54, what demand factor applies to a household with two electric clothes dryers?

$100\%$.

What is the amperage of a lighting load of $2{,}700\,\text{VA}$ at $120\,\text{V}$?

$22.5\,\text{A}$ (calculated as $\frac{2{,}700\,\text{VA}}{120\,\text{V}}$).