As a leader in our field here in Lake Norman, NC, Rotunda HVAC receives lots of questions from clients about furnaces and furnace maintenance. One of the most common questions we receive is, “why is my furnace blowing cold air?”
While there are a few reasons for your furnace to stop working properly, there is one common denominator that often resides at the core of the issue – a dirty filter.
Changing Your Furnace Filter
Furnace filters should be changed once every 3 months, more during the winter when your furnace is used the most.
As your furnace creates hot air and distributes it through your home ventilation system, the filter captures dust and debris before it enters your vents. This keeps allergens out of your home.
Changing a furnace filter is easy, simply follow these steps:
- Turn off your thermostat and switch off the furnace
- Examine your filter to see if it’s dirty
- Slide the dirty filter out of the furnace
- Slide in the new filter
- Turn on your furnace and thermostat
If your furnace won’t turn back on, check the pilot light, it could be out. This is generally only an issue for older furnaces.
When in doubt, or if you experience any trouble, call an expert. At Rotunda HVAC, we’re always happy to help clients any way we can.
Why Does a Dirty Filter Cause my Furnace to Stop Blowing Hot?
Believe it or not, your furnace filter can attract so much dirt that it gets blocked. The more dirt and debris it contains, the less air can flow freely through the filter. When air gets trapped inside your furnace, the furnace begins to overheat.
Every furnace is equipped with a high limit switch, this is crucial to ensure your furnace doesn’t cause a fire, or worse, explode. The high limit switch turns your burners off when the furnace begins to overheat. This also keeps your heat exchanger from cracking under pressure.
Other Reasons for Cold Air
While a dirty filter is a common issue, it’s not the only problem that could cause a furnace to blow cold, such as:
It could also be your condensate line. This is a line in your furnace which moves water away from the heat exchange as moisture builds. If the condensate line is clogged, your furnace can’t ignite. Your furnace will still blow air into your home, but the air won’t be warmed, meaning you get cold air coming in through your vents.
Another issue could be the gas supply. If your gas supply is impacted by a leak or other issue, your furnace isn’t getting the fuel it needs to light. Fortunately, as scary as this sounds, modern furnaces are designed to turn themselves off if fuel is an issue.
Faulty Pilot Light
In older furnaces, your pilot light helps control the ignition of your furnace. If the light goes out, so does your heat. Most pilot lights can be relit, but if your pilot light is old or damaged, it might need to be replaced. Don’t try to replace a pilot light on your own unless you’ve done so before. Call an expert to have the pilot light replaced and your furnace reignited.
It seems like a silly one, but from time to time your furnace might not work properly simply because you’ve got your thermostat setting set too low. Your thermostat sends directions to your furnace on how much heat to deliver based on the temperature you wish to achieve. If your thermostat is set too low, your furnace won’t pump the hot air you need to warm up into your home.
Your furnace isn’t the only thing warming your house. Your entire ventilation system needs to run smoothly to deliver heat to your home. If your vents are blocked, closed, or dirty, it could cause a problem. Similarly, if a vent has a crack or leak, the hot hair could be sucked out before reaching the rooms of your home.
When to Call a Professional
If at any point you feel your furnace problem may be more than a filter changing issue, or you begin to feel unsafe managing the furnace maintenance on your own – call an expert.
Furnace technicians are trained in heating and cooling installation, repair, and upkeep. They’re also trained in safety protocols to ensure your furnace and your home remain safe throughout the maintenance procedure.