Whole-House Fan: Wiring Requirements
Wiring a whole-house fan correctly means running 14 AWG copper on a 15-amp circuit. This guide covers the complete wiring requirements per NEC 2023, including wire gauge, breaker size, cable type, and installation specifics for your HVAC system. Whether you are hiring an electrician or planning the circuit yourself, the specifications below ensure your installation meets code.
What usually triggers this search
You want to cut AC costs by pulling cool evening air through the house. The fan mounts in the attic and you need a dedicated switch and circuit run up through the ceiling.
What goes wrong
Whole-house fans draw modest power but the installation creates a unique hazard: cutting a large hole in the ceiling between living space and attic. The electrical failure isn't usually the circuit itself but the switch location. The fan must have a switch that's accessible and clearly labeled, and many installations put the switch in the attic where nobody can reach it in an emergency. Timer switches are the standard now. A QuietCool or AirScape unit typically draws 3-5 amps at 120V, so a 15A circuit on 14 AWG is adequate. But if the fan shares a circuit with attic lights or receptacles, the breaker trips when someone plugs in a work light while the fan is running. A dedicated circuit avoids this.
What the inspector checks
- Switch accessible from living space (not in the attic)
- Circuit rating matches fan motor nameplate
- No exposed Romex across the attic where it contacts insulation improperly
- Fan mount is structural and doesn't rely on ceiling drywall alone
- Timer or speed control switch matches manufacturer specifications
Should you hire an electrician?
The electrical portion of a whole-house fan is straightforward: a switch and a 15-20A circuit to the attic. The harder part is cutting the ceiling opening and ensuring proper structural support. If you're comfortable running Romex through an attic and wiring a switch, this is a reasonable DIY electrical project. Budget $150-300 for an electrician to do just the wiring.
Whole-House Fan electrical specifications
| Minimum wire gauge | 14 AWG copper |
| Breaker size | 15A single-pole |
| Voltage | 120V (120V single-phase) |
| Typical draw | 120-600W (1-5A) |
| Dedicated circuit | Can share with other outlets on the same circuit |
| Cable type | 14/2 NM-B (Romex) or 14 AWG THHN in conduit |
| GFCI required | Depends on location |
Circuit requirements for whole-house fan
Wire sizing: The minimum wire for a 15A circuit is 14 AWG copper. Use 14/2 NM-B cable (hot, neutral, ground) for standard residential runs in walls and attics. For wire runs over 50 feet, check voltage drop - you may need to upsize to 12 AWG to keep voltage drop under 3%.
Breaker sizing: A 15A breaker (single-pole, 120V) protects this circuit. The breaker must match or exceed the appliance nameplate rating but never exceed the wire capacity. 14 AWG copper is rated for well above 15A, providing adequate safety margin.
Installation notes
HVAC wiring notes: Air conditioning and heat pump circuits are sized from the unit nameplate - look for the MCA (minimum circuit ampacity) and MOCP (maximum overcurrent protection) values. The wire must handle the MCA, and the breaker must not exceed the MOCP. A disconnect switch within sight of the outdoor unit is required per NEC 440.14.
Receptacle type: Use standard NEMA 5-20R (T-slot) receptacles on 20A circuits, or NEMA 5-15R on 15A circuits. All receptacles must be tamper-resistant (TR) in new construction per NEC 406.12.
Safety and code requirements
GFCI: GFCI protection depends on the installation location. Kitchen, bathroom, garage, outdoor, basement, and laundry locations all require GFCI. See our GFCI guide by room to check whether your specific location requires it.
Ground wire: The equipment grounding conductor (green or bare wire) must be continuous from the panel to the appliance. For a 15A circuit, the minimum ground wire is 14 AWG copper per NEC Table 250.122. NM-B cable includes the correct ground wire size automatically.
Permits: Most jurisdictions require an electrical permit for adding a new circuit. The inspector will verify wire size, breaker rating, grounding, and GFCI protection. Check your state’s NEC adoption and call your local building department before starting work.
Typical installation
HVAC equipment wiring connects from a dedicated breaker in the main panel to a disconnect switch mounted within sight of the outdoor unit, then from the disconnect to the unit. The disconnect is typically a non-fused pull-out type mounted on the wall near the condenser. Use THHN wire in conduit for the outdoor portion. The indoor air handler connects via a separate low-voltage thermostat wire (typically 18/5 or 18/8).
Estimated materials cost
For a typical 50-75 foot run, expect to spend approximately $20-$56 on materials:
| 14/2 NM-B cable (50-75 ft) | $12-$41 |
| 15A breaker | $8-$15 |
| Estimated materials total | $20-$56 |
Material costs are approximate based on retail pricing as of Feb 2026. Actual costs depend on cable length, local pricing, and copper market conditions. Does not include labor, permits, or inspection fees.
Frequently asked questions
What size wire do I need for a whole-house fan?
14 AWG copper on a 15A breaker at 120V. This is the minimum per NEC Table 310.16. For runs over 50 feet, check voltage drop and consider upsizing to 12 AWG.
Does a whole-house fan need a dedicated circuit?
Not necessarily. A whole-house fan can typically share a general-purpose circuit with other outlets, as long as the total load does not exceed the breaker rating.
Does a whole-house fan need GFCI protection?
It depends on the location. If installed in a kitchen, bathroom, garage, outdoor area, basement, or laundry room, GFCI is required. Otherwise, GFCI is not specifically required but is always recommended near water.
Can I wire a whole-house fan myself?
In most states, homeowners can do their own electrical work on their primary residence with a permit and inspection. However, this is not a DIY task if you are unfamiliar with electrical work - improper wiring can cause fires or electrocution. Check your state licensing requirements and always get a permit.
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NEC 2023 references verified April 2026