How to connect a fan with a humidity sensor: subtleties of connection and installation + selection rules

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Tatyana Anisimova
Last update: December 2019

Condensation, high humidity, unpleasant odor and fungus on the walls are problems that arise when there is no ventilation in the bathroom and toilet. Agree that the blackened seams between the tiles will spoil the look of any room. Moreover, such a neighborhood is harmful to health. Therefore, many homeowners equip forced ventilation by mounting fans. The most functional models of which are equipped with various sensors and timers.

In this article, we will discuss precisely such devices - equipped with a hygrostat. We will analyze in detail why to install an exhaust device, what to look for when buying a duct fan. We will also tell you in detail how to connect a fan with a humidity sensor and share working schemes.

Why install a fan in the bathroom?

In apartment buildings there are ventilation shafts. They are designed to provide air exchange. As practice shows, such designs are rarely maintained. Therefore, the exhaust air from the room is poorly removed.

According to the regulations, the outflow of humid air from the room must be at least 25 m3/hour. Fresh air is supplied through forced ventilation or through valves that mount in the windows and the walls.

Microclimate violations in the room can lead not only to the appearance of a fungus, but also to spoil household appliances and furniture: the washing machine rusts, the surface of the cabinets made of chipboard is deformed, the metal parts of the plumbing deteriorate.

Mold in the bathroom
Poor fresh air leads to increased humidity in the room. Condensation settles on the ceiling and walls.Constant dampness provokes the development of mold and mustiness, tiles and wall coverings deteriorate

It is recommended to install an exhaust device even if there is a window in the room. Because it is not able to fully ensure the removal of excess moisture. After prolonged ventilation, only adjacent walls become dry, and condensation remains on the rest. And in the winter, keeping a window open for a long time will not work.

Functions of exhaust fans:

  • elimination of excess moisture;
  • improved air circulation;
  • removal of unpleasant odors;
  • temperature regulation.

Thanks to the working hood in the bathroom and toilet, there will always be clean and fresh air.

Features of exhaust fans

There are several modifications of exhaust fans. They are shoelace, with timers, motion sensors, mode switches, etc.

Hood with humidity sensor
The most popular exhaust fan options are equipped with built-in humidity sensors. They draw stuffy air out of the room, control the moisture level and consume a small amount of electricity

The most effective models are those with a humidity sensor - they are automatically activated when the humidity level in the room rises. Manufacturers of exhaust systems have released such “smart” fan variations to increase the comfort level of users - after all, after taking a shower, you can also forget to manually turn the fan on or off.

How does a fan with a humidity sensor work?

Now let's talk about how the humidity sensor installed in the exhaust fan works. The internal structure and the principle of operation of such devices practically does not differ from standard exhaust devices. When the engine turns on, the blades begin to spin. This sets the air in motion and draws it along with moisture drops into the exhaust shaft.

A hood with a sensor can be mounted on a ceiling or wall ventilation shaft. The body and parts of the product are made of waterproof materials. Electrical parts have high-quality insulation.

Check valve fan
The most expensive models of exhaust systems with a humidity sensor are additionally equipped with a backlight, as well as a special non-return valve that does not allow unpleasant odors and dust to enter the room from the duct

The humidity sensor in the fan can work both on a timer and automatically. In the second case, the exhaust system turns on when the humidity level in the room exceeds the norm.

Fan circuit
The scheme of the fan with a sensor that controls the humidity level. When the moisture level rises, the product turns on and works until the indicators return to normal. Shutdown by delay timer

In general, a humidity sensor or a hygrostat in a fan is a special element that allows you to measure the level of humidity in the air and start the exhaust device without human intervention. And all this is due to the high sensitivity of the sensor to condensate. It works on the principle of a thermostat, ventilation is turned on only with humidity above 40%.

Exhaust systems with built-in hygrostat are optimally suited for installation in the bathroom, rooms for drying clothes, as well as toilets. Can be used as basement ventilation in private homes.

Types of built-in humidity sensors

Moisture sensors are usually equipped with axial duct fans. A small board is mounted in the body of the product. There are two limits in a hygrostat: upper and lower.

Humidity Sensor Setting
For the fan to work for a long time and correctly, you need to configure it correctly. There is a regulator in the sensor structure, which is equipped with a humidity scale. The moisture level is set by turning the potentiometer.

Some variations are factory-set and cannot be adjusted. On the rest, the response range can be set independently.

Types of sensors:

  • Resistive - when the humidity level changes, the product changes resistance and starts the fan motor.
  • Dielectric - has a capacitor in the design. With increasing humidity between the plates of the product, the dielectric constant of the medium changes.
  • Thermistor - An improved analogue of the resistive sensor. It has high accuracy.
  • Optic - determines the concentration of humidity by air transparency.
  • Mechanical - when there is more moisture in the room, the length of the material from which the sensor is made changes.

When the humidity level reaches the programmed values ​​in the sensor, a relay is activated. It closes the engine circuit and the fan starts to spin.

Tips for Buying a Hygrostat Fan

A high-quality exhaust fan for the bathroom should be silent, have high performance,water protection and go to the interior of the room. Now available options with an interesting design, the original design of the front grilles and panels. Therefore, it is not so difficult to choose an exhaust device for any style of bathroom decoration.

Suitable for use in a bathroom or toilet. duct fans. They are installed in the duct. The blades of products are made of metal or durable plastic. The design is not afraid of moisture and corrosive chemicals.

Round duct fan
There are several variations in the design of duct fans in shape. They are round, square and rectangular. A model is selected for the shape of the exhaust shaft in the room

The duct fan should be selected taking into account the parameters of the room and the diameter of the duct. To select the productivity of the product, first determine the volume of the room: for this, the width, length, and also the height of the room are multiplied among themselves. The resulting value is multiplied by the standard rate of air exchange.

The parameter of the normative rate of air exchange for the shower and the bathroom is 7-9. If several people use the room, the maximum value should be taken. Example: room volume 22.5 m3 * 9 (air exchange rate) = 202.5 m3. In this case, you should buy a duct fan with a capacity of over 202.5 m3.

Channel systems also differ in other parameters: electric motor power, noise level, blade rotation speed, etc. Available in different colors, as well as types of decorative grilles.

For installation in the bathroom, fans with a non-return valve are quite popular. We recommend that you familiarize yourself with top ten offers on the market.

Mounting a fan with a humidity sensor

An exhaust system with a humidity sensor is mounted similarly to a simple fan. Only the device connection diagram can differ. Be sure to look at the fan installation instructions. Usually, manufacturers give the correct connection diagram in the passport.

Install the exhaust product with a disconnected mains voltage. Before installation, it is necessary to prepare the exhaust shaft and check it for patency and the presence of blockages.

Stage # 1 - Natural Ventilation Check

Before connecting the exhaust system, the ventilation shaft must be cleaned of debris, dust and remove cobwebs. Next, check the duct with a burning match, a lighter or a sheet of paper.

Ventilation draft check
To check for air flow, an open flame is brought to the ventilation hole. If the flame deviates towards the duct, then there is a draft
Checking Traction Using a Sheet
You can check natural ventilation without special devices. To do this, a sheet of paper is applied to the exhaust hole (stuffing box) and released. If the sheet does not fall, then with a stream of air everything is fine

With a weak air flow or its absence, you need to find a blockage and clean the exhaust system. If it is not possible to detect a blockage on your own, you can contact the special services, they clean mine.

Before installing the fan, you need to make sure that fresh air enters the bathroom or toilet. He can get into the room through windows or cracks under the doors. If the room is completely tight (dull windows, there is no gap between the door leaf), special grilles must be installed in the door.

Step # 2 - Choosing a Fan Connection Diagram

To connect a fan in the bathroom or toilet, several connection schemes can be used. They differ among themselves by the option of supplying power to the exhaust device.

It is better to lay the wiring under the hood during the repair in order to hide it in the wall. If this is not possible, you can mask the cable using a decorative box or special overlays.

The exhaust system is connected to the mains using a separate switch, to the light switch or through a sensor.

Connection diagram of a fan through a light bulb
Connection diagram of a fan through a light bulb. The device is connected in parallel with the lighting. When the light turns on, the channel fan starts to work. When the light is off, the product does not work
Exhaust device connection diagram
Connection diagram for exhaust fan with separate switch. In this option, you need to independently turn on and off the exhaust device

For exhaust devices with a hygrostat, such connection methods are not suitable.

There is a special circuit for turning on a channel fan by a humidity sensor.

Connection diagram for fan with sensor
Connection scheme through automation. It is suitable for fans that are equipped with a humidity sensor, as well as for devices that operate on a timer

It is not difficult to connect a fan with a sensor or timer if you read the instructions and do everything according to the scheme. To the 220 V network, the product is connected through the terminal box located under the fan cover.

Connecting wires to the terminals:

  • LT - a cable with a phase coming from an external switch;
  • N - zero;
  • L - wire with phase.

Connect the product through three wires - all terminals are signed. The exhaust system can be tied to a light bulb. The fan will start to work when voltage is applied to the terminal marked LT (light on). Deactivation is performed 2-30 minutes after the lamp is turned off.

A fan with a humidity sensor can turn on automatically when the humidity in the room exceeds the set level on the hygrometer. When moisture becomes less, the product will work for some more time according to the delay timer and turn itself off.

Stage # 3 - installing a fan in the duct

Before mounting the fan into the shaft, make sure that all wires are connected. Remove the decorative grille from the duct. You can connect the device to the mains through the terminal box.

Mounting the fan in the duct
Each wire has its own color coding: the phase can be red, white or black, and zero can be blue

The exhaust device is fixed by means of self-tapping screws. First, holes for dowels are drilled in the wall. Then they install a fan and tighten the screws. In rooms with ceramic wall tiles, it’s difficult to make holes accurately. Therefore, the fastening of the ventilation system is carried out using building sealant.

Step # 4 - Verify Fan Operation

After installing the fan with a hygrostat, you need to check how it works. To do this, close the door in the bathroom and turn on the hot shower for a while.

From the hot water in the room, steam forms and becomes damp. In such conditions (60-90% humidity), the fan will automatically start. Next, you need to wait for the ventilation system to draw moist air into the shaft. If the device is correctly connected, the device will turn off when the moisture level reaches the lower limit set on the hygrometer.

Conclusions and useful video on the topic

Visual instruction for installing a duct exhaust fan is shown in the video below:

Old exhaust systems that have not seen repair and maintenance for years are not able to provide a normal microclimate in the bathroom. Homeowners are forced to mount forced ventilation. The best option for apartments and private houses is to install a duct fan.

Especially popular are models with a built-in humidity sensor. They work for a long time and turn on automatically when the humidity level in the room “rolls over”. Using the connection schemes of such devices discussed above and the features of their installation, you can install an exhaust fan yourself.

Using a fan with a humidity sensor? Share your experience with other visitors to our site, tell us about the significant disadvantages of the device found during operation, participate in discussions - the comment form is located below.

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Visitors Comments
  1. Alexander

    What normative act regulates the installation of forced ventilation in the bathroom, where the fungus forms?