The short answer is – when you get signs that your home is too dry. However, it may also depend on the season, your health condition, and other factors.
Summers are typically humid. Thus, you should be able to run the dehumidifier round the clock as modern dehumidifiers go off automatically when the built-in humidistat senses overly dry conditions inside the house. Winters are drier, meaning you need humidification rather than dehumidification.
Unfortunately, though, sometimes the home can dry even during the summer, especially after running the dehumidifier for too long. In addition, due to health conditions, some people may also run the dehumidifier in winter, occasionally resulting in arid indoor air conditions.
You’re advised to switch off the dehumidifier whenever you detect overly dry conditions to avert possible health and other risks. Let’s find out more.
How Dehumidifiers Work
Dehumidifiers remove excess moisture from indoor air to improve indoor air quality. The appliances work by drawing stale, humid air into a condenser unit where cold refrigerant lines condense the moisture contained in the air.
The now-dry air is then pushed out of the dehumidifier through a separate return duct system. At the same time, the condensed water collects in a special drain tank inside the condenser awaiting disposal.
Inside the dehumidifier is a unique instrument known as a humidistat that regulates the function of the dehumidifier.
A standard humidistat features a sensing element comprising a flat plate fitted with two metal conductors. In addition, a relay mechanism that reads signals is attached to the sensing element. This relay system provides accurate humidity level readings inside your home and relays the information to the sensing element.
The humidity level readings strictly guide the dehumidifier’s operations. Whenever the dehumidifier is plugged on and in the ON position, it will run and idle based on information from the sensor. If the sensor indicates that the air inside the home is too moist, the humidistat will send a “start” request to kick the dehumidifier into action. The reverse happens when the relay indicates that the home is too dry. The humidistat will send a “stop” request, causing the dehumidifier to stop running.
Remember that this only happens when the dehumidifier is plugged on and switched ON. Humidistats are OFF for as long as the dehumidifier is off.
Most dehumidifiers arrive, complete with the humidistat built-in. This applies to both portable and whole-home dehumidifiers (which connect to the home’s ductwork). However, some don’t. So, it’s always important to check. If the humidistat is missing, purchase one separately.
When It Becomes Too Dry Inside
Unfortunately, you may sometimes experience overly dry conditions inside the house when the dehumidifier is running. This can happen for several reasons, including;
You don’t have a humidistat
If it’s a new humidifier you just bought recently, the arid conditions when the unit is running could be because it doesn’t have a humidistat. That’s because in a dehumidifier with an in-built humidistat, the unit should automatically regulate indoor humidity levels, as we’ve seen above.
However, in the absence of the humidistat, the dehumidifier may run continuously because there’s no sensor to tell it when to pause. This often means that you end up removing too much moisture from the house, leaving it dry.
The humidistat has malfunctioned.
If the dehumidifier was running effectively a few days ago, but now it seems faulty and causes overly dry indoor air conditions, the humidistat may have failed.
The humidistat can malfunction for many reasons. Perhaps the voltage is low, or it’s not set correctly. In whole-house dehumidifiers, a leak in the water lines can also cause the humidistat to malfunction. Finally, a compromised transformer can also cause humidistat failure.
You have a health issue.
If you have a health condition such as asthma, even a humidity level that isn’t too dry may worsen symptoms. The same applies to people with other respiratory symptoms. Such people need plenty of moisture in the air to breathe normally. The slightest sign of dry air, which health people may not even notice, can trigger symptoms in such patients.
The same applies to people with dry skin. If you have dry skin, you’ll need a much higher humidity level than healthy people.
It’s the cold season.
Another reason you might be experiencing arid conditions is because the season has changed, and your area has entered the cold period. Cold weather is drier because cold air has a low capacity to hold heat. The molecules can still hold moisture. But it is a meager volume of moisture compared to warm weather air.
The good news is that most people already know that winter is a time to humidify (add moisture) to the home rather than dehumidify (remove moisture from home).
When to Turn Off the Dehumidifier
The exact point you need to turn off the dehumidifier depends on the problems you’re experiencing.
When you notice signs of dry air
One of the best ideas is to turn off the dehumidifier as soon as you notice signs of dry air in your home. Common signs of dry air include;
- Static electricity
- Breathing trouble
- Dry skin and lips
- Warping wood
- Cracking paint
Since all the four issues above tend to worsen the longer you stay in dry conditions, it’s wise to turn off the dehumidifier and address the issue immediately.
If your health condition is worsening
If you have a common cold or respiratory issues, such as asthma or bronchitis, you don’t have to wait until you see warping wood and cracking paint to turn off your dehumidifier.
Conditions such as asthma are fatal if you’re not careful – and dry conditions can worsen the problem very fast. So, the moment you start feeling difficulty breathing, you’re allowed to turn off the dehumidifier to raise the moisture levels in the house.
The humidistat has failed/malfunctioned.
A malfunctioned humidistat can cause the dehumidifier to stop removing moisture or remove moisture at an accelerated and perhaps dangerous rate. This can quickly deplete moisture in your home, causing nosebleeds and worsening respiratory issues.
So, here too, you’re allowed to turn off the dehumidifier to address the problem. The only challenge is that diagnosing the humidistat may require a professional’s opinion.
It’s the cold season.
Unless you have a health complication that requires you to maintain extremely low humidity levels in the home (as directed by the doctor), the cold season is a time to keep the dehumidifier OFF and the humidifier ON.
The only other time you should run a dehumidifier in winter is in the basement when your basement is too humid. However, make sure to turn it off as soon as you achieve a relative humidity of 60% or lower.
What Else Do You Need to Know?
Overly dry indoor conditions aren’t just bad for you and your family’s health, it’s also dangerous for your household items and the home’s structural integrity. When the home is too dry, your plans and pets will feel the heat just as the people living on the property. The plants may even wither and die. Meanwhile, your pets will experience dry and chapped skin just like you.
As for the home’s structural integrity, dry conditions are commonly associated with dry rot that can impact various woods. However, arid conditions can also cause shrinkage and subsidence.
Therefore, when turning off the dehumidifier to improve humidity levels in the home, you’re not just doing it for yourself. You’re also saving your plants, pets, and the property itself.