Why Does the Bathroom Fan Keep Running?

The noise of a constantly running bathroom fan can affect our concentration, sleep, and even our mental health. The long-term energy usage is bad for the environment and can strain our budget. Continually exhausting conditioned air from the home makes our HVAC system work harder and/or less effectively.

There are actually a lot of reasons why bathroom fans keep running. Most of them are not problematic and the solutions are clear-cut even if the execution is not always simple.

You Have a Continuous Operation Exhaust Fan

If you have recently moved into a house or apartment and noticed that the fan seems always to be running, then one possible reason is that it is a continuous operation exhaust fan as opposed to an intermittent operation fan, which is what we are all more used to.

This type of fan is more common in apartment buildings with centralized bathroom fan ventilation than in residential houses, but some houses do have them.

Typically, continuous operation exhaust fans are used in houses or apartments with windowless bathrooms and few other sources of ventilation, and particularly in homes that are very well sealed with little to insignificant air leakage in or out.

Often, they are centralized systems, serving the whole house, not just the bathroom. So, one or more fans are continually running, exhausting air from “problem” areas like bathrooms and kitchens.

Living areas can also be included in the system if there is a particular need for it.

The idea behind these fans is to ensure proper exhaust ventilation by removing the human element.

Bathroom ventilation is important to stop mold from growing and spreading, and to protect the house structurally from the effects of excessive moisture. High humidity and condensing water can also compromise the electrical infrastructure of the house and render insulation inefficient.

We so often turn off our fan too soon because we don’t want to forget it running, or we are leaving the house straight after our shower. If the fan is connected to the light and there is a window providing natural light, then maybe we don’t use the fan at all during daylight hours.

Because it is so important to ventilate a bathroom and because there are so many ways that we can misuse the system, continuous operation exhaust fans are a good and reliable solution.

If your bathroom fan operates as an intermittent exhaust fan and all of a sudden starts to run constantly, there is something else going on, and you need to read further.

Can It Be Turned Off?

Before we get to the “can”, let’s look into the “should”.

Bathrooms are required by law to have ventilation.

If the only source of ventilation is the continuous operation exhaust fan, then turning it off means contravening building codes, like the International Residential Code (IRC), and the requirements of organizations like, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

However, doing so temporarily is not a problem and is certainly possible as certain maintenance, repair, and inspection work cannot be completed with the fan running.

So, HVAC contractors and electricians are required to install an override control—a master on/off switch—in the home where it can be easily accessed by the service provider and homeowner.

HVAC installers and electricians have three location options for installing that override switch:

1. On the wall near your home’s thermostat:
   • This is probably the most convenient location for new homeowners since it sets up a central location for the house’s heating, cooling, and ventilation systems.
   • It will most likely be a control panel for the entire HVAC system.
   • Consult the manual to find the setting for turning off the fan.

2. In the electrical panel:
   • The continuously running exhaust fan may have a dedicated circuit and breaker in the electrical panel that should be labeled so that the system can be controlled through that single switch.
   • This is a less convenient option than that in a central location near the thermostat, but has the advantage of meaning the system is less likely to be turned off by accident.

3. Internally:
   • Continuously running exhaust fans can have an internal override mechanism and timer functions that are controlled by a switch, usually located with your bathroom light switch.
   • It’ll look a lot like a light switch but it may be labeled differently and have additional controls.

What Does It Cost to Keep The Fan Running?

Continuously operation exhaust fans run on electricity, so there is a cost for sure.

However, assuming your builder or contractor used an ENERGY STAR certified exhaust fan, and depending on the electricity costs in your area, the monthly running cost is not going to be very high.

The bathroom fan is probably costing you less than $2 per month. When you weigh this against the benefits of the exhaust ventilation system, it’s a small price to pay.

Is It Safe?

There are plenty of fans and appliances you wouldn’t want to run non-stop because they were never designed to do so.

However, a properly certified, installed, and maintained continuous exhaust fan is designed to run non-stop. It has been tested for this very application and can be used safely and reliably.

ASHRAE has established standards for designing ventilation systems to ensure acceptable indoor air quality.

Regulations established by the United States Department of Energy stipulate the requirements for installing and controlling these devices in American homes, whether new construction or retrofits.

The Bathroom Fan Is a Dual Speed Exhaust Fan

Does your bathroom fan’s running noise get louder if you flip the light switch? Does it have a separate switch that also increases the noise?

If you answered yes, then you are most likely dealing with a dual speed exhaust fan.

These fans have to overlapping settings. One setting is to continuously run at a lower exhaust rate. The other setting, which is a higher exhaust rate, kicks in when you flip the fan or light switch and turns off when the switch is flipped again.

Dual speed exhaust fans are not that common. For most houses, one or the other is sufficient.

The idea behind the dual action is to provide a base level of ventilation that keeps air circulating in the bathroom (and house—remember, continuous operation systems often serve the whole house/apartment).

Then, when you go to take a shower, the exhaust rate in the bathroom increases as it now has a harder job that requires greater and faster removal of air.

Continuous Operation/Dual Speed Fan Needs a Service

The ASHRAE standards mentioned earlier, include things like the amount of sound that a continuous use exhaust fan can emit to satisfy the requirements for an ENERGY STAR certified home.

While the fans are not required to be silent, they do need to be quiet, so if you can clearly and consciously hear your fan operating, then it might be in need of a service.

Fans can start making excess noise for a number of reasons including loose screws, dirt buildup, and age.

Give the fan a bit of a tidy, vacuuming away the dirt and tightening any loose screws. If this makes a difference, then great! If it doesn’t, you can consider calling in an HVAC specialist to have a look.

Humidity Sensing Function Is Broken or Set Wrong

Some bathroom fans have a humidity sensing function. This feature allows the fan to turn on and off in response to humidity levels rising above and dropping below a preset level.

The bathroom fan can run continuously when there is something wrong with this feature that results in it always registering a humidity above the preset level.

So, what could go wrong?

Lowered Humidity Preset Level

The humidity preset level could have been lowered. This could mean that the normal environmental humidity levels are triggering the bathroom fan sensor and the fan is running continuously.

Depending on how it is controlled (in the fan unit, on a wall-panel, or with a remote), children can sometimes alter the setting without realising.

The level may be accidentally adjusted during maintenance or cleaning.

The level may also reset after a power outage.

The solution is to simply reset the humidity level at which you want the fan to come on.

Weather Changes

The weather has sudden become more humid. With global warming, etc., sudden or unusual changes in weather are not as uncommon as they once were.

Humidity sensors are set based on normal humidity levels. If these suddenly change, the weather can be triggering your fan.

To stop the fan from functioning continuously in this situation, you will just have to adjust the settings.

Broken Humidity Sensor

The humidity sensor can be broken as a result of factory defect, wear and tear, physical damage, electrical damage, or low-quality materials.

Most often, broken humidity sensors do not work in a way that means the fan never turns on.

Sometimes, the opposite can happen and the humidity sensor receives a false signal instead of no signal at all.

I actually went through two cheap fans before I bought a quality model. Both of the cheap ones lasted just shy of 2 years.

I thought about replacing the sensor only, but after opening up the fan, I decided that the entire unit is of such low quality that I would rather buy a new one. I recommend you to do the same in such cases.

Broan-Nutone is famous for its reliable bathroom fans, I recommend getting something from their product range. Especially something with the new Sensaire technology.

How to Turn Off Malfunctioning Bathroom Fan?

While you wait for the new bathroom fan, it would be nice to turn the old one off to get some peace and avoid the problems that come with running an intermittent operation fan too long.

If your fan is not hardwired into the electrical system, then you can simply unplug it wherever it is plugged in (either the wall or in the ceiling behind the fan).

Hardwired bathroom fans will have to be turned off at the breaker box. If it is not clearly labeled, you may need to turn the breakers off one at a time until you find the one controlling the fan.

Fans With Timer Switch Are Broken or Set Wrong

Some fans come with timers. When you turn the fan on, a timer is activated and the fan will run for this amount of time and then turn off automatically.

If the preset time is accidentally set for a long period, the fan can seem to run continuously. It should stop after the preset time, but if it is long enough, you may have switched the fan on again, reseting the timer.

Alternatively, the timer can break and no signal is sent to turn it off.

There should be a way to turn the fan off before the timer is up or to override the timer if it is broken. You can check the instruction manual for the fan for this.

Faulty Wall Switches

Bathroom fan wall switches can fail as a result of manufacturing defects, physical damage, or simply wear and tear.

With certain failures, you can turn the fan on because the switch mechanism works to create the electrical contact that allows electricity to enter the fan’s motor. However, when you flip the switch off, the contact remains.

This means that the fan is off according to the position of the wall switch but it is still running.

To remedy this, you will probably need to replace the wall switch.

To check it, you can turn off the breaker to the fan circuit, remove the outer casing of the switch, take out the mechanism and see if pressing the switch on and off makes any difference to the contact point.

Sources

https://basc.pnnl.gov/resource-guides/continuously-operating-ventilation-and-exhaust-fans#quicktabs-guides=1