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Understanding 3 Types Of Furnace Airflow Problems

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Furnaces can't operate without air, but more than one airflow problem can affect their operation. These issues can arise for various reasons, from your home decorating ideas to mechanical issues with your furnace unit. Unfortunately, airflow issues are more than just minor annoyances. These problems can cause damage to expensive furnace components or even result in unsafe heating.  

The best way to avoid these problems is to understand the three general categories of furnace airflow issues, what symptoms you're likely to experience, and what you can do to resolve them.

1. Ductwork Airflow

The air that flows through your home's vents is not the same air that your furnace uses for combustion. In fact, it's important for efficiency and safety purposes to keep this air separate. Instead, the air in your home travels over the heat exchanger in your furnace. The heat exchanger transfers heat energy from the hot exhaust gases without allowing these toxic fumes to enter your home.

Two things are likely to occur if too little air passes over your heat exchanger:

  • Your home will take longer to heat
  • The heat exchanger will become too hot

While the former is frustrating, the latter can quickly become expensive. An overheating heat exchanger usually triggers a safety shutoff, but this condition can eventually damage this essential component. A clogged air filter is the most common cause of air restrictions, but furniture or other obstructions in front of a return vent can also be a culprit.

2. Intake Airflow

Since your furnace doesn't use the air in your ductwork for combustion, it must instead rely on separate intake air. This air comes from the area around your furnace or a dedicated air intake pipe. An intake air blockage or restriction will prevent the furnace from achieving its ideal air-to-fuel combustion ratio, resulting in inefficient operation and increased carbon monoxide risks.

Intake blockages can occur for numerous reasons, although a clogged air intake pipe is one of the most common causes. Potential symptoms usually include increased energy bills, short cycling due to the furnace tripping a safety switch, or loud bangs due to delayed ignition. Any of these symptoms warrant further investigation by a trained HVAC technician.

3. Exhaust Airflow

The intake and exhaust systems on your furnace form a single stream that carries combustion air to the burners and harmful combustion gases away from your home. All modern furnaces include a draft inducer that helps to pull clean air into the furnace while also pulling exhaust through the exhaust piping. If there's insufficient pressure, your furnace will usually trip a safety switch and shut down.

As with an intake air blockage, an exhaust air blockage can create dangerous operating conditions. Exhaust airflow problems usually result from clogged exhaust flues or failed draft inducer motors, although "false positives" are also possible due to faulty pressure switches. A professional should always repair this problem to find the underlying cause and ensure your furnace operates safely.  

Contact furnace repair services to learn more.