Wiring Combo Humidity Sensor & Fan Control with Light Switch

Electrical Technology

How to Wire a Combination Humidity Sensor and Fan Controller with Light Switch

Table of Contents

Combo Humidity Sensor & Fan Control with Light Switch

A humidity sensor and fan control with light switch is a combination single-pole device designed to automatically control a ventilation fan and a light fixture to reduce excess humidity in areas such as bathrooms, basements, laundry rooms, and spas.

This combination humidity-sensing fan control automatically detects elevated moisture levels in the air and activates the ventilation or exhaust fan to reduce condensation. By removing excess humidity, it helps prevent mold and mildew growth while reducing energy consumption through automatic fan operation. In other words, the fan runs only when needed.

The device uses a microprocessor combined with advanced digital sensing technology to continuously monitor and regulate humidity levels in areas of the home that are prone to condensation and mold.

The combination switch can be easily wired and installed in new construction or as a replacement for an existing single-pole switch. Depending on the model, it can be installed with or without a neutral conductor. The switch is compatible with incandescent, LED, CFL, ELV, and MLV lighting loads.

These devices help improve indoor air quality and support compliance with building codes and standards such as the 2019 and 2022 CALGreen Standards (Part II), ASHRAE Standard 62.2, and California Title 24 (Part 6).

Rating & Features

Name: Combination Humidity Sensor and Fan Control with Light Switch – Decora DHD05
Poles: Single-Pole
Voltage: 120V 1-Phase AC Supply – 60 Hz
Fan Load: ¼ Motor Fan, 300W LED/CFL, 600W Incandescent/Halogen or 400VA (ELV/MLV)
Light Load: 150W LED/CFL, 250W Incandescent/Halogen or 200VA (ELV) / 250VA (MLV). 2A resistive load
Time Delay: 10, 20, 30, and 45 Mins.
Wire Size: #14 – #12AWG Copper
Neutral Wire: Preferred, but not needed
Termination: Wired Leads

Wiring a Combination Humidity Sensor and Fan Control with Light Switch

In this wiring tutorial, we will show how to install a combination humidity sensor and fan controller with a single-pole light switch. Once installed, the controller can be configured for automatic ventilation and air-circulation modes, allowing continuous operation with selectable hourly preset time-out settings.

The following wiring diagram illustrates a combination humidity sensor, fan control, and light switch (DHD05) used to control a ceiling, exhaust, or ventilation fan, along with either a built-in light fixture or a separate lighting point. The humidity sensor switch is supplied through a 15A, 120V circuit breaker connected to a 120/240V panelboard.

Before installing a new switch or replacing an existing single-pole switch, make sure the power is completely disconnected at the circuit breaker or fuse.

As shown in the wiring diagram, the combo humidity sensor with 5 built-in wires is connected to the branch-circuit conductors as follows:

The hot (black) wire from the circuit breaker is connected to the LINE terminal.
The neutral (white) wire from the panel is connected to the N (Neutral) terminal of the switch and then continued to the load.
The equipment grounding conductor (bare copper or green wire) from the panel is connected to the G (Ground) terminal.
The light is connected to the LIGHT LOAD terminal through the switch’s built-in red wire.
The fan is connected to the FAN LOAD terminal through the switch’s built-in blue wire.

This switch requires a neutral wire connection for proper operation. If there is no neutral wire in the box, just connect the ground (Equipment Ground Conductor “EGC”) to the neutral terminal (white wire). If neutral present, remove the green sleeve from the white wire and connect it to the branch-circuit neutral conductor.

Since the DHD05 humidity sensor switch controls both the fan and the light, both the red and blue wires are used. If only the fan is to be controlled, cap the red wire with a wire connector (wire nut) and leave it safely inside the electrical box as an unused conductor. Alternatively, you may install other humidity sensor models without a built-in light switch, such as the DHS05 or IPHS5.

If the fan and light are on the same line (hot), there is no need to connect the red wire to the light. In this case, the fan switch will control both the fan and the light.

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Good to Know:

The humidity sensor should be installed in a location where it can easily detect steam within the bathroom.
Do not install the sensor directly above a heater or near air drafts, ventilation openings, doors, or windows.
It is not recommended to use this device to control a fan/light combination unit when the light is the only source of illumination in the room.
In enclosed or confined spaces, the humidity sensor and fan controller may not operate effectively unless a properly sized ventilation or exhaust fan is installed.

Testing & Setting

Restore power to the switch and wait 20 seconds for the sensor to properly power up. During this time, the green light on the switch will blink every 5 seconds.

Press both buttons to test the load (fan and light). If everything is working as planned, install the wall plate to mount the in-wall switch.

The device can be set up for 10, 20, 30, or 45 minutes. By default, it is configured for 20 minutes, with Auto-ON high sensitivity and a humidistat set at 50% Relative Humidity (RH), while the bath fan operates in Auto ON/OFF mode.

For programming the setting type and operating mode (such as Test Mode, Bath/Fan Mode, Air Cycle Mode, or Humidity Stat Mode), refer to the step-by-step user manual and follow the instructions provided.

Despite the automatic operation, the exhaust fan can be activated manually by pressing the fan icon on the face of the switch.

Instructions & Precautions.

Always disconnect the power supply by switching OFF the circuit breaker at the main service panel before performing any electrical work.
Do not use aluminum wires with this device. Only use copper or copper-clade conductors.
Do not install the switch directly above a heat source or in locations where hot or cold air drafts can blow directly onto the sensor. Because the motion sensor is sensitive to temperature changes, such conditions may result in false triggering or reduced detection performance.
Humidity sensor based devices are intended for indoor use only.
If you are unsure about any part of the installation, consult a licensed electrician and ensure compliance with applicable local electrical codes.

Disclaimer:

The author will not be liable for any losses, injuries, or damages from the display or use of this information or if you try any circuit in wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous. If you are unsure, contact a licensed electrician to do it according to the local area codes.