Whole-House Fan Symbol
Definition: The Whole-House Fan symbol represents a large ceiling-mounted ventilation fan used in residential wiring diagrams to denote a motor-driven unit installed in an attic floor or hallway ceiling that exhausts interior air to the attic and draws in cooler outdoor air through open windows, typically rated 2,000–6,000 CFM at 120 V or 240 V, 15–30 A.
Also known as: whole house fan, attic fan (whole-house type), whole-home fan, house exhaust fan, central exhaust fan, ceiling exhaust fan.
What the Whole-House Fan symbol means
The Whole-House Fan symbol identifies a high-volume ceiling fan that creates a negative pressure in the living space, pulling warm air up through a ceiling grille into the attic and simultaneously drawing cooler outdoor air through open windows throughout the house. In a wiring diagram the symbol marks the circuit termination point at the fan location and shows the Hot and Neutral power connections required by the branch circuit.
Because whole-house fans are high-current appliances (often requiring a dedicated 15 A or 20 A, 120 V branch circuit, or a 240 V circuit for large units), the symbol alerts the electrician to install adequate wiring and a properly sized circuit breaker. Many units also require a two-speed switch, timer, or occupancy-sensor controller shown elsewhere on the same diagram.
How to identify the Whole-House Fan symbol
The symbol is drawn as a standard fan circle glyph—a circular outline with fan blade lines radiating from the centre—but is differentiated by its location label (attic floor or ceiling) and by the 'WH FAN' or 'WHOLE HOUSE FAN' annotation. The Hot terminal exits from the top and the Neutral terminal from the bottom of the symbol, representing the two conductors of the dedicated branch circuit.
Function in a circuit
A whole-house fan draws ambient outdoor air into the living space when outdoor temperatures are cooler than indoor temperatures—typically in the evening and night hours—providing evaporative cooling, odour removal, and ventilation. The large-diameter fan (typically 24–48 inches) moves 2,000–6,000 CFM at relatively low static pressure, requiring attic vents sized at 1 square foot of net free area per 750 CFM of fan capacity to prevent pressure build-up. The fan replaces air-conditioner runtime during mild weather, reducing cooling energy consumption by 50–90% on suitable days.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617 does not define a specific symbol for a whole-house fan; large ventilation fans are represented by the general fan/motor symbol per IEC 60617-06 (rotating machines) with a capacity and location annotation. |
|---|---|
| ANSI/IEEE 315 | ANSI/ASHRAE Standard 62.2 governs residential mechanical ventilation requirements; NEC Article 210.23 and 422 cover appliance branch circuits. In electrical drawings, the whole-house fan is shown as a generic fan symbol (circle with blades) per NFPA 70 / NEC conventions, annotated with CFM rating and circuit details. |
| Key difference | IEC and ANSI/NEC both use a circular fan symbol; IEC 60617-06 uses a circle with a stylised blade cross, while NEC/ANSI residential drawings use a circle with radiating blade lines. The functional meaning is identical; CFM rating and circuit specification are always noted separately. |
Terminals / pins
| Pin | Name |
|---|---|
| hot | Hot |
| neutral | Neutral |
Typical values
Typical airflow: 2,000–6,000 CFM; motor power: 250 W–1,500 W; voltage: 120 V (small/medium units) or 240 V (large units); circuit size: 15–30 A dedicated branch circuit; noise level: 1.5–5 sones at high speed; required attic ventilation: 1 sq ft net free area per 750 CFM.
Where the Whole-House Fan symbol is used
- Residential attic-floor installations providing whole-house ventilation cooling in mild climate zones
- Ranch and single-storey homes where ceiling-mounted exhaust is practical from bedrooms and hallways
- Two-storey homes with central hallway ceiling installation to exhaust the entire floor plan
- Energy-efficient home designs supplementing or replacing air-conditioning during spring and autumn
- Garage ventilation systems using a downrated whole-house fan unit to remove vehicle exhaust fumes
Example
In a residential electrical plan for a 2,000 sq ft single-storey home, the whole-house fan symbol appears in the central hallway ceiling, connected by a 12 AWG, 20 A, 120 V dedicated branch circuit routed from the main panel; a two-speed timer switch symbol appears on the adjacent hallway wall, and a note specifies 8 square feet of net free attic ventilation area required.
Key facts
- The Whole-House Fan symbol has two terminals: Hot and Neutral, representing the two conductors of the dedicated 120 V or 240 V branch circuit.
- Whole-house fans typically require a dedicated 15 A or 20 A branch circuit per NEC Article 422 for appliances exceeding 50% of the circuit ampere rating.
- Required attic ventilation area is calculated at 1 square foot of net free area per 750 CFM of fan capacity to prevent attic pressure build-up that reduces fan efficiency.
- Whole-house fans must not be operated when outdoor air contains smoke, high humidity, or when windows are closed—operating without open windows can back-draft combustion appliances.
- Two-speed or variable-speed motors are common; low speed provides quieter operation for sleeping hours while high speed delivers maximum ventilation.
- Insulated automatic shutters or dampers are installed on the ceiling grille to prevent conditioned air loss when the fan is off during heating season.
- A whole-house fan can cool a home using 90% less energy than central air conditioning on nights when outdoor temperature falls below indoor temperature.
Frequently asked questions
What does the whole-house fan symbol mean in a wiring diagram?
The whole-house fan symbol represents a large ceiling-mounted exhaust fan that ventilates an entire home by pulling air through windows and exhausting it to the attic. In a wiring diagram it marks the fan location and the dedicated branch-circuit connections required for the motor.
What electrical circuit does a whole-house fan require?
Most whole-house fans require a dedicated 15 A or 20 A, 120 V branch circuit. Large units rated above 1,200 W may need a 240 V circuit. The circuit must be dedicated to the fan (no other loads) per NEC Article 422 for appliances drawing more than 50% of circuit capacity on a continuous basis.
What is the CFM rating of a typical whole-house fan?
Typical whole-house fans are rated 2,000–6,000 CFM. A commonly used sizing rule is 1–1.5 CFM per square foot of conditioned floor area; a 2,000 sq ft home typically requires a 2,000–3,000 CFM fan for effective ventilation.
What is the IEC vs ANSI symbol difference for a whole-house fan?
Both IEC and ANSI/NEC drawings use a circular fan symbol with radiating blades; IEC 60617-06 specifies a stylised cross-blade in a circle for rotating ventilation equipment, while North American electrical plans use a simpler blade-line circle. Both are annotated with capacity and circuit information rather than conveying these details through the glyph alone.
How much attic ventilation does a whole-house fan require?
A minimum of 1 square foot of net free attic ventilation area per 750 CFM of fan capacity is required. A 3,000 CFM fan therefore needs at least 4 square feet of net free attic vent area (gable vents, ridge vents, or soffit vents combined) to prevent excessive attic pressure that reduces airflow.
Can a whole-house fan be used with central air conditioning?
Yes, but not simultaneously. Central air conditioning must be turned off when the whole-house fan operates, because running both systems simultaneously wastes energy and may cause the AC compressor to work against the fan's airflow. A whole-house fan is used instead of AC on cooler evenings and nights.
What switch is used to control a whole-house fan in a wiring diagram?
Whole-house fans are typically controlled by a two-speed wall switch, a timer switch (commonly 1–8 hours), or a programmable thermostat/timer. Some modern units include a wireless remote or smart-home controller. The control switch symbol appears separately from the fan symbol on the wiring diagram.
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