DIY Guide:
Adding a Humidistat to Your Existing Humidifier

Maintaining the optimal humidity level in your home is crucial for comfort, health, and preserving your furnishings. Too little humidity can cause dry skin, irritated sinuses, and static electricity, while too much can promote mold growth and dust mites. Many humidifiers come with built-in humidistats, but if your existing unit doesn’t have one, adding an external humidistat is a smart and cost-effective upgrade.

In this comprehensive DIY guide, we’ll walk you through the process of adding a humidistat to your current humidifier. This modification will allow you to automatically control the humidity levels in your home, ensuring your space stays comfortable and healthy year-round.

What Is a Humidistat and Why Add One?

A humidistat is a device that measures the relative humidity (RH) in the air. It functions similarly to how a thermostat measures temperature. When the humidity level falls below or rises above a set threshold, the humidistat triggers the humidifier or dehumidifier to turn on or off accordingly.

Benefits of Adding a Humidistat

• Energy Efficiency: Prevents overuse of your humidifier, saving electricity.
• Consistent Humidity Levels: Maintains an ideal humidity range (usually 30-50%) automatically.
• Extended Equipment Life: Reduces wear and tear by preventing constant running.
• Improved Comfort and Health: Avoids issues caused by both low and high humidity.

What You’ll Need Before You Start

Here’s a list of materials and tools required for adding a humidistat:

Materials

• External plug-in humidistat (available online or at hardware stores)
• Extension cord (if needed)
• Electrical tape
• Zip ties (optional)

Tools

• Screwdriver (if opening your humidifier)
• Wire strippers/cutters (only if hardwiring is involved)
• Voltage tester (for safety)

Important Notes

• Most external humidistats are designed as plug-in devices, meaning you plug them into an outlet, then plug your humidifier into the humidistat.
• If you prefer a more integrated approach with your device’s internal wiring, it may require more advanced electrical work and knowledge.
• Always prioritize safety: unplug devices before working on them and use appropriate protective gear.

Step 1: Choose the Right Humidistat for Your Needs

There are two primary types of humidistats suitable for DIY addition:

1. Plug-In Humidistats

These are simple devices that are plugged into an electrical outlet; your humidifier plugs into them. The device monitors room humidity using an internal sensor and switches power on or off based on preset levels.

Pros:

• Easy installation
• No wiring required
• Portable between rooms or devices

Cons:

• May be bulky depending on outlet size
• Sensor location is fixed near the device; may need extension cords for ideal placement

2. Inline/Electromechanical Humidistats

These units require wiring into your humidifier’s power supply line, controlling operation by breaking or completing the electrical circuit based on humidity levels.

Pros:

• Seamless integration
• Less visible hardware

Cons:

• Requires electrical knowledge
• Riskier if not installed correctly

For most homeowners, a plug-in humidistat offers the best balance between ease-of-use and functionality.

Step 2: Selecting an Ideal Location for Your Humidistat Sensor

Where you place your humidistat sensor affects its accuracy:

Tips for Optimal Placement:

• Avoid placing near doors or windows where outdoor air may skew readings.
• Keep away from direct airflow from heating/cooling vents.
• Position at breathing height in commonly used rooms.
• Ensure it’s not blocked by furniture or curtains.

If using a plug-in model with a built-in sensor, simply install it in a frequently used room near where you want accurate humidity control.

If the model has an external probe sensor with wires, route it carefully to an optimal spot while keeping wiring tidy.

Step 3: Testing Your Existing Humidifier

Before connecting any additional device:

1. Test your humidifier’s functionality. Make sure it powers on/off correctly when plugged in.
2. Inspect the power cord and plug for damage.
3. Confirm wattage specifications on the humidistat packaging match or exceed your humidifier’s requirements to prevent overload.

Step 4: Installing a Plug-In Humidistat

This is the simplest method for most users:

Installation Steps:

1. Plug the humidistat into an available wall outlet.
2. Plug your humidifier into the output socket of the humidistat device.
3. Set your desired humidity level using the dial or digital controls on the humidistat.
4. Place the sensor at an appropriate location as discussed earlier.
5. Turn on your humidifier — now controlled by the humidistat!

Once powered, the humidistat reads room humidity and will only activate your humidifier when RH falls below the set point.

Step 5: Wiring an Inline Humidistat (Advanced Users)

Note: This step involves working with mains voltage electricity — proceed only if experienced and comfortable with electrical wiring.

Tools & Safety Gear Needed:

• Insulated screwdriver
• Wire strippers
• Multimeter/voltage tester
• Electrical tape or wire nuts
• Safety glasses & gloves

Procedure Overview:

1. Unplug your humidifier.
2. Open its power input section to access wiring terminals.
3. Identify live wire in power cord (usually black or brown).
4. Cut live wire lead and strip insulation about ½ inch at both ends.
5. Connect both cut ends to corresponding terminals on inline humidistat according to manufacturer instructions—this usually means connecting one side of the power line to one terminal and feeding the other terminal back to complete circuit.
6. Secure connections with wire nuts or screws, then insulate with electrical tape.
7. Close housing securely.
8. Mount or place sensor probe per instructions.
9. Plug in unit, set desired RH level on humidistat, test operation carefully.

If unsure at any point, consult an electrician — improper wiring can cause fire hazards or damage equipment.

Step 6: Calibrating Your Humidistat for Best Results

After installation:

1. Use a separate hygrometer to verify room RH accuracy.
2. Adjust device settings until desired comfort range (typically between 40% – 50%) is maintained consistently.
3. Monitor over several days; fine-tune if necessary.
4. Avoid setting RH too high above 50% to prevent condensation issues.

Step 7: Maintenance Tips for Your Enhanced System

To keep things running smoothly:

• Regularly clean both your humidifier and sensor areas to avoid dust build-up affecting readings.
• Change water in your humidifier daily to prevent bacteria growth.
• Replace filters/wicks as recommended by manufacturer.
• Periodically check connections if using wired setup.

Troubleshooting Common Issues

| Problem | Possible Cause | Solution |
|——————————–|————————————————-|—————————————————-|
| Humidifier runs constantly | Humidistat sensor malfunction or incorrectly set| Check sensor placement; recalibrate settings |
| Device never turns on | Wiring error (inline) or faulty plug-in unit | Verify wiring; test with another device |
| Erratic humidity readings | Sensor exposed to drafts or enclosed spaces | Reposition sensor away from vents/windows |
| Plug-in unit doesn’t fit outlet | Bulky design blocking adjacent sockets | Use power strip with spaced outlets |

Final Thoughts

Adding a humidistat to your existing humidifier is an excellent way to upgrade home comfort without investing in new appliances. Whether choosing a simple plug-in model or taking on an inline installation challenge, controlling indoor humidity levels accurately brings many benefits—from improved health to energy savings.

With some basic tools, careful planning, and attention to safety precautions, you can accomplish this project yourself — transforming your home environment one step at a time!

Remember: If at any point you feel unsure about handling electrical components, don’t hesitate to seek professional help for installation.

Happy DIY-ing!