Static pressure is the resistance a cooling and heating unit faces when trying to push air throughout your house. It’s an important factor in evaluating the performance of your HVAC unit. However, it’s the root of many cooling and heating problems in residential properties with ductwork. In many cases, you can significantly improve your home’s comfort while lowering energy bills when you address HVAC static pressure. Therefore, checking this parameter regularly to understand the basics will help you spot problems with your home’s air conditioning more easily. Below is a detailed guide about HVAC static pressure and how it affects your home’s comfort and HVAC unit.

What Is HVAC Static Pressure?

Static pressure in HVAC units refers to the resistance to airflow within the air ducts. For your HVAC to function correctly, it needs to push air through the air ducts with greater intensity than the static pressure level within the pipes. If your system does not meet this condition, airflow will get affected.

Your cooling and heating system relies on ductwork to distribute conditioned air. Without a proper duct system, the HVAC unit cannot cool or heat your living space as it should. On the other hand, sufficient air ducts provide consistent and even temperatures in your house. The better the indoor air circulates, the more your HVAC system provides comfortable and clean air to every part of your home. The right amount of HVAC static pressure will also enable your air filter to do its job and work better. This way, you’ll have fewer germs, allergens, and dust particles in your indoor air.

How to Measure HVAC Static Pressure

Like your blood pressure, HVAC static pressure has an acceptable range and should not exceed certain values. Too low or too high static pressure indicates an issue with your cooling and heating unit. To read static pressure values in your ducts, your HVAC contractor will drill several test ports and then insert a manometer within the ductwork.

This device measures static pressure in inches per water column (in WC), which is related to PSI (pressure per square inch). An ideal system operates at 0.5 in WC. However, if your static pressure is below 0.9 in WC, you are still within the ideal range. The higher the value, the stronger your static pressure will be and the weaker the airflow.

Signs of HVAC Static Pressure Problems

Several signs indicate static pressure problems within your HVAC unit or ductwork. The following are the common indicators of static pressure problems in your home.

A Noisy HVAC Unit

If your HVAC produces loud mechanical noises when distributing conditioned air within your home, it might be a sign of high static pressure. Air moves through your unit’s return grille, vents, and ducts faster than normal. Due to the decreased airflow, the blower motor will have to work harder to push air through it, producing loud noises. You are hearing the unusual sounds because the blower motor is currently running at maximum speed.

Increasing Energy Bills

HVAC units with correct and balanced static pressure work efficiently to offer consistent indoor comfort. However, if your energy bills are increasing steadily, you need to call an HVAC technician to check your unit. That’s because it might be suffering from high levels of static pressure. If left unchecked and your system continues working too hard for long periods, high static pressure can cause HVAC breakdowns or premature failure.

Uneven Cooling and Heating

Uneven cooling and heating or cold and hot spots in your living space is a common indicator of high levels of static pressure in the HVAC system. It shows that some parts of your house are receiving too much cool or warm air while others are not getting enough of it. In many cases, uneven cooling and heating occur due to poor air circulation in some parts of your system.

Causes of Static Pressure Problems in Your Ductwork

During HVAC preventative maintenance, your technician will measure static pressure in two locations within your unit. By doing so, the professional can zero in on where the air resistance is occurring. The following are the common causes of static pressure problems in HVAC systems.

Undersized Air Returns

Generally, improperly designed or undersized ductwork increase static pressure. Undersized air intake returns can also cause static pressure problems. Air return ducts draw air from the rooms and send it back to your cooling and heating system. If you have undersized air returns, it will be harder for the HVAC system’s blower motor to pull air into the unit to keep circulating. This problem is more apparent after installing new HVAC equipment or repairing and sealing air ducts.

Undersized air returns can also cause air conditioner problems. Air conditioning involves circulating the refrigerant through your unit in a closed-loop, and a lack of enough return air will throw off the refrigerant loop. This problem can cause major issues with time, including expensive repairs and system breakdowns.

Dirty or Small Coil

Clogged ductwork creates airflow resistance, leading to elevated static pressure. Too much debris or dust inside your ducts can prevent balanced air movement. Small coils can also cause static pressure problems. Like the air return vents, if your coil isn’t big enough, it restricts airflow.

The coil is usually responsible for heat transfer. In the winter, the coil heats the air that later circulates throughout your home. During the summer months, the refrigerant liquid carrying heat from your living space evaporates before passing via the coil. The HVAC system’s coil transfers this heat so the refrigerant can change into liquid form and travel back via the unit to attract more heat. Therefore, when there’s an issue with the coil, there’ll be a problem with the entire unit.

The coil will create air resistance just like the filter but not enough to cause problems. However, if the system’s coil is dirty, that’s a different story altogether. Dust, debris, and other buildups on the coil can restrict airflow within the unit and ductwork.

Restrictive or Clogged Air Filters

The air filters act as screens, preventing pollutants like dust, dirt, and allergens from circulating through your air vents and ductworks. As air passes through the filter, it traps the particles and adds more resistance. Normally, that is not a problem. However, if you fail to replace your filters for several months, they’ll get clogged, causing more resistance. To prevent that from happening, invest in filters with a higher MERV rating and regularly change your unit’s filters.

Work With the HVAC Pros

Too low or too high static pressure in your HVAC system may seem like a complicated problem to solve, but it doesn’t have to be. You can talk to your HVAC technician about the main issues mentioned above during routine maintenance visits. The professional can take new static pressure readings and then compare them with previous ones to determine the performance of your unit.

If you are experiencing cooling or heating problems due to static pressure issues or any other factor, our HVAC experts are ready to help. At Level 9 Heating, Cooling, and Plumbing, our HVAC maintenance programs can help prevent your unit from experiencing breakdowns and ensure it runs efficiently during its service life.

We also offer air conditioning, air quality, heating, geothermal, and commercial HVAC services to the residents of Washington, MO, and its surroundings. Call us today if you notice problems with your home’s HVAC system or to schedule your service appointment.

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