Your furnace can, technically, run without a filter. However, we strongly recommend you don't run your furnace without a filter for any length of time. With air constantly moving through your furnace and your home, dust and debris can quickly build up, even in a matter of minutes.
Technically, you can temporarily run a furnace without a filter. However, it's important to emphasize the word “temporarily” here. Running a furnace without a filter overnight, for example, isn't likely to cause problems, but you should never allow this to turn into a long term solution.
You just recirculate the air without filtration. A day or two is no big deal, but if you were to leave it unfiltered for several months you could see debris build up on the cooling coil which would make the machine less efficient because dirt and dust do not transfer heat very well and there would be less air movement.
If something happens and you have to pull your filter out for the day or even a day or two, it's probably not going to cause major problems right away. However, it's never a good idea to leave the filter out of your furnace for any longer than that.
A clean furnace filter will prevent large-sized debris from entering your actual heating system. A filter will catch things like pet hair, lint, dirt, dander, and more. Without it, all of these particulates could find their way onto and even into your furnace's most sensitive interior components.
Unkempt air filters may negatively affect indoor air quality by spreading pet dander, dust, and other allergens throughout your home. This may lead to irritated eyes, nose, and potentially breathing problems.
The simple answer is: not for long. Ideally, your AC should never operate without a filter for more than 6-8 hours. Going beyond this can negatively affect both your system's health and your home's air quality.
Without an air filter in place, the engine may also be sucking dirt and debris in at the same time. This can cause damage to internal engine parts, such as valves, pistons and cylinder walls. The result is excessive oil consumption, poor engine performance, and eventually engine failure.
A dirty filter in your furnace will generally lead to the following consequences: The furnace can overheat and turn off as a failsafe. Your home won't achieve the warmth or comfort you want. You can severely damage your furnace's internal components.
Air Filters
Even though the furnace is not producing any heat while operating the a/c, it still delivers the cold air throughout your home with the same blower, and passing through the same air filter. This is why, regardless of the season, you should regularly change your air filters.
If you don't have a filter in your HVAC, you're going to have a bunch of particles in your home. This will not only mean that you'll have to vacuum a lot more frequently, but you may be sneezing and wheezing a lot as well. The same thing will happen if you have a super clogged up old filter.
With a furnace blowing cold air, the first question you should ask is if the furnace has been turned ON. Two thermostat issues that could cause your furnace to blow cold air include (1) your thermostat is still set to COOL, not HEAT and (2) your thermostat fan is set to ON, not AUTO.
Running your AC for any time without an air filter is not recommended due to the permanent damage it can cause to the HVAC system. Dirt and dust that is normally absorbed by the filter can make its way into the AC system and wreak havoc on the mechanical components, often leading to expensive repairs.
The standard recommendation is to change your furnace filter every 1-3 months, depending on the type of filter you have and the conditions within your home. For instance, if you have pets or if someone in your household has allergies, you may need to change the filter more frequently to ensure optimal air quality.
The danger of not changing the air filter in the house for a long time is that it will eventually lead to furnace damage. This means that the entire system will get destroyed by the excess heat. Replacing the entire system can cost you enormous amounts of money, and it's almost the same as buying a new HVAC unit.
At Quality Heating, Cooling & Plumbing, we often hear the question, “can you run a furnace without a filter?” While it is possible, it isn't the best idea. Without the filter, dust and dirt particles will accumulate in your air ducts, circulate in the air, and lead to a less efficient furnace.
Is my AC not working because of the filter? Potentially, yes. While there are a whole host of issues that could cause problems with your air conditioning system, a dirty air filter should be the first thing to check if your central air conditioning unit isn't working as properly as it should.
You can run the furnace without installing a filter, but only temporarily (such as overnight, awaiting a new filter). If you let it run very long without filtration, contaminants will build up.
A clogged air filter can cause more harm than good. During the day, your AC should cycle on and off, but a dirty air filter can make those cycles more frequent than they should be. Cycling is not only noisy, but it also wastes energy.
Your furnace can, technically, run without a filter. However, we strongly recommend you don't run your furnace without a filter for any length of time. With air constantly moving through your furnace and your home, dust and debris can quickly build up, even in a matter of minutes.
As the system is working harder to get around clogged air filters, it can cause the entire system to overwork and eventually break. If this happens, you'll need to replace the entire system, which can cost anywhere from $4,000 to $12,000.
It Traps Dust and Allergens
You can probably guess what happens if there is no filter in the furnace. The filter helps maintain healthy indoor air quality by trapping allergens so they don't keep circulating throughout your house and get you sick.
How Often Do I Need to Change Out My Air Filter? Generally, most air filter manufacturers and HVAC companies recommend changing your air filter every 90 days, or 3 months. That can change based on where your home is located (ex. dusty, dry climates), if you have any pets, and the age of your system and equipment.