Whole House Fan Wiring Instructions: DIY Step-by-Step Guide

You bought a whole house fan to save money and cool your home. Now you need to wire it safely without starting a fire or tripping breakers every time you flip the switch. The instructions that came in the box probably show a basic diagram but skip the details that matter when you cut into drywall and start connecting live wires.

This guide walks you through the entire wiring process from planning your circuit to making your final connection. You will learn how to size the right wire, choose between switches and timers, run cable through your ceiling, and connect everything according to electrical code. No guesswork.

We cover four main steps. First you will learn what to check before you touch a wire. Then you will plan your circuit and pick the right controls. Next comes running cable and making safe connections at the fan. Finally you will wire your controls and test everything before you button it up. Each step includes clear instructions so you can wire your whole house fan correctly the first time.

What to know before you touch a wire

You need to understand local electrical codes and permit requirements before you wire your whole house fan. Most jurisdictions require a permit for new electrical circuits, and an inspector will check your work to verify it meets the National Electrical Code (NEC). Call your local building department to confirm what paperwork you need and whether you can legally do the work yourself. Some areas only allow licensed electricians to install new circuits.

Check your electrical panel capacity

Your main electrical panel must have available amperage and an open breaker slot to handle the new circuit. Most whole house fans pull between 5 and 15 amps depending on motor size. Add up all the existing circuit loads on your panel and compare that total to your service capacity (typically 100, 150, or 200 amps for residential homes). If you are already close to capacity, adding a fan circuit could overload your system and require a panel upgrade.

Gather the right wire and tools

You will need 14/2 or 12/2 NM cable (Romex) depending on your fan's amperage draw. Use 14-gauge wire for fans that draw up to 15 amps on a 15-amp circuit, or 12-gauge wire for 20-amp circuits. Gather wire strippers, a voltage tester, wire nuts, electrical tape, a drill with a spade bit, and cable staples before you start.

Always verify power is off with a non-contact voltage tester before touching any wires.

Step 1. Plan the circuit and choose controls

You need to match your circuit size to your fan's power requirements and pick controls that fit how you will use the system. Check your fan's installation manual or the motor nameplate to find the amperage draw. Most whole house fans require a dedicated 15-amp or 20-amp circuit, and you cannot share this circuit with other devices or outlets.

Calculate your fan's electrical load

Your whole house fan wiring instructions will specify the exact amperage, but most residential fans fall into predictable ranges. Single-speed fans typically draw 6 to 10 amps, while variable-speed models can pull 12 to 15 amps at maximum setting. Multiply the amperage by 1.25 to determine your minimum circuit capacity (NEC requires circuits to handle 125% of continuous loads).

Never undersize your circuit breaker or wire gauge, or you risk nuisance tripping and potential fire hazards.

Pick between switches and timers

Standard single-pole switches work fine for manual on/off control and cost under $5. Multi-speed switches let you adjust fan velocity and typically run $15 to $30. Digital timers automate operation based on temperature or schedule, costing $40 to $100, and some integrate with smart home systems. Choose based on whether you want simple control or automated operation that runs the fan during cool evening hours without you remembering to flip a switch.

Step 2. Shut down power and run cable

You must kill power at the main breaker before you touch any wiring. Flip the main disconnect to the off position, then use a non-contact voltage tester to verify that no electricity flows through the panel. Test multiple circuits to confirm the tester works properly. Tape a written warning note on the panel door so nobody flips the breaker back on while you work.

Turn off power at the breaker

Locate the circuit breaker or open slot where you will install the new breaker for your fan circuit. Double-check that power is dead by touching your voltage tester to the bus bars inside the panel. You should see zero voltage before you proceed. Remove the knockout plate from the panel where your new cable will enter, then install a cable clamp to secure the wire and meet code requirements.

Never assume power is off based on a breaker position alone, always verify with a tester.

Route cable from panel to fan location

Drill a three-quarter-inch hole through the top plate of the wall cavity directly above your electrical panel, then feed your NM cable up into the attic space. Run the cable along the attic joists toward the fan location, securing it with cable staples every four feet and within 12 inches of any bend. Keep the cable at least six inches away from heat sources like recessed lights or chimneys. Leave 18 inches of extra cable at both the panel and fan ends to make connections easier.

Step 3. Make safe connections at the fan

You are now ready to connect your fan to the circuit you just ran. Open the junction box on your whole house fan housing and locate the wire leads inside. Most fans include three wires: black (hot), white (neutral), and green or bare copper (ground). Strip half an inch of insulation from the ends of your circuit cable using wire strippers, being careful not to nick the copper conductor underneath.

Strip and connect the wires

Match wire colors to make your connections: black circuit wire to black fan lead, white to white, and ground to ground. Twist the bare copper ends together clockwise using lineman's pliers, then screw on a wire nut that matches your wire gauge (yellow nuts for 14-gauge, red for 12-gauge). Tug each connection gently to verify it holds firm.

Never rely on tape alone to secure wire connections, always use properly sized wire nuts that meet UL standards.

Wrap electrical tape around the base of each wire nut where it meets the wires to provide extra protection against moisture and vibration. Push all connected wires carefully back into the junction box, making sure no bare copper shows outside the wire nuts.

Secure the ground connection

Your fan housing must connect to the equipment grounding conductor to prevent electrical shock if a fault occurs. Attach the bare copper or green ground wire from your circuit to the green grounding screw inside the junction box using a screwdriver. Some whole house fan wiring instructions require bonding the metal housing to the ground wire with a separate pigtail, so check your manual for specific requirements before you close the box.

Step 4. Wire controls, then test and label

You finish the installation by wiring your switch or timer at the wall location and verifying everything works safely. Your whole house fan wiring instructions should specify which wires from the fan connect to your control device, but the standard approach uses the black hot wire switched through your control and the white neutral connected directly through to complete the circuit.

Wire your switch or timer

Run your circuit cable to the wall box location where you want to mount your control, leaving 8 inches of wire extending from the box. Strip the cable sheath back one inch and connect wires according to your control type. For a basic switch, connect the black circuit wire to one brass terminal and a short black pigtail from the other terminal to your fan. Connect all white neutral wires together with a wire nut. Attach the ground wire to the green grounding screw on the switch body.

Always connect ground wires first so the safety path exists before you complete hot connections.

Restore power and test operation

Return to your electrical panel and install the new breaker, connecting the black wire to the breaker terminal and white wire to the neutral bus bar. Flip the main breaker back on, then test your fan at each speed setting. Listen for unusual noises and verify smooth operation.

Label everything clearly

Write the circuit number and "Whole House Fan" on the breaker with permanent marker. Place a label inside the junction box at the fan showing the circuit number and installation date.

Flip the switch with confidence

You completed your whole house fan wiring according to proper electrical code and safety standards. Your new ventilation system will deliver years of reliable, cost-effective cooling while cutting your energy bills significantly. The connections you made following these whole house fan wiring instructions meet NEC requirements and keep your home safe from electrical hazards and fire risks.

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