Humidistat: What It Is and Why You Need One

Presidential Heating & Air Conditioning

Gaithersburg HVAC Contractors


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What is a Humidistat and What Does it Do?

a picture of a thermostat that also doubles as a humidistat showing a really high percentage of humidity in the air which affects the indoor air quality of the homeA humidistat is a device that measures the amount of moisture in the air. The device itself consists of a sensing element that is composed of a flat plate fitted with alternate metal conductors. Attached the sensing element is a relay amplifier, which reads signals sent by the sensing elements to give accurate humidity levels.

It works by causing an electrical resistance between the conductors mounted on the sensing element based on the amount of humidity in the air. The relay amplifier measures the resistance. Based on that measurement, the humidistat turns the humidifier on if the electrical resistance shows the air is too dry or turns off the humidifier once the ideal humidity level is achieved.

When you purchase a portable humidifier or a dehumidifier, it frequently comes with a humidistat. The attached humidistat will ensure that you do not over-humidify or -dehumidify the room. It will effectively monitor and control the humidity in the air near the machine, but it will not measure the humidity in other parts of the home. For that, a hygrometer is useful, though a hygrometer will not control the humidity level like a humidistat does. You can use the hygrometer readings to adjust the moisture in the room and achieve an optimal humidity level.

In a whole-house system, a humidifier/dehumidifier is connected with your central HVAC system. In such cases, the humidistat will also adjust the valves, dampers or other switches of the HVAC system to regulate airflow and control the humidity throughout your home.

You can also wire a humidistat into your thermostat. It will run your air conditioner to control the humidity level inside the house independently of temperature. The humidistat will not let the air conditioner turn on if the temperature is high but the humidity level is low. When the indoor humidity level gets into an unacceptable range, the humidistat can run the air conditioner until the humidity level is reduced. Using a humidistat this way lets you maintain the desired levels of humidity in your home while you are away without having to run the HVAC system more than is needed.

Why You Should Have a Humidistat

a home that has central air which can automatically filter out the humidity in the house if the humidistat reads more than 58 percentA humidistat keeps the humidity at optimal levels automatically. Controlling the amount of humidity in your home is important for several reasons. One reason is economical. Keeping the humidity at an optimal level will allow you to run your HVAC less. Another is comfort. The right humidity level is a key factor in making your home comfortable. Another important reason to have a humidistat is that an optimum humidity level is important to your health.

Inside your home, an ideal setting on your humidistat is no higher than 58%. This accommodates the readings on the humidistat being off by as much as 10%.

What Can Go Wrong When Indoor Humidity Is Too High

When you allow the humidity level in your home to exceed 50%, the air becomes muggy and uncomfortable, and it may feel hot and clammy. You will crank up your AC, when in fact the relief you need is less humidity.

Moreover, high humidity creates the perfect environment for the growth of bacteria, viruses, fungi, mold, and mildew. It also invites dust mite infestations. These microorganisms can trigger the onset of allergies and create real health issues for anyone with severe allergies or asthma.

High indoor humidity levels can also create other problems in your home. It causes condensation to form on your windows, which can pool and rot your window trim. High humidity can cause your paint and wallpaper to peel, your wood floors to cup and buckle, and your furniture to become mildewed.

With a humidistat and a dehumidifier, the indoor humidity would remain at or near optimal level. Before the humidity ever reaches such an undesirable level, your humidistat would signal your dehumidifier to turn on. Once the desired humidity level is reached, the humidistat will turn off the dehumidifier.

Problems When Indoor Humidity Is Too Low

woman reading her book next to the fireplace with hot chocolate in the winter time due to very low humidity in the air as well as relatively cold temperaturesToo little humidity is equally destructive. When the humidity is too low, the indoor air becomes uncomfortably dry. This is more common in the wintertime when the outside air is drier than in summer.

In the winter, you run your furnace to keep your home comfortably warm. Heating the indoors makes the already dry wintertime air even drier. When the indoor air is too dry, you will often experience static electricity and dry skin. You can also have frequent bleeding in your air passages, chapped lips, sinus infections, and sore throats.

Extreme dryness can wreak havoc in other ways, too. Inadequate moisture in the air can cause damage to everything made of wood. For example, your wood floors, door and window frames, and your furniture can become so dry they will splinter and crack. The overly dry air can aggravate asthma and allergies. You may feel cold because the dry air is robbing moisture from your skin, causing you to turn the heat up and make the air even drier.

In such a case, a humidistat will cause your humidifier to turn on. Even in humid regions of the country, a humidifier in the winter months makes the indoor air more comfortable. You will feel warmer without having to keep turning up the heat. When the air has achieved the right humidity level, the humidistat will signal the humidifier to turn off the vapor.

Consult a Professional HVAC Technician for More Information

The climate conditions where you live will dictate the amount of humidity in your home. Regardless of where you live, a humidistat will help you keep the humidity at healthy levels. You can install a humidistat yourself, following the manufacturer’s instructions, or you can have one installed. The professional HVAC technicians at Presidential Heating & Air can advise you on the benefits of air quality control appliances such as a humidifier and a dehumidifier and provide you a free quote for a humidistat installation.

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