High Energy Bills? "Pressure Drop" Might Be Stealing Your Profits!

When purchasing filters for HVAC systems, procurement managers and engineers often focus on common parameters like efficiency, airflow, and air velocity. However, there is another crucial indicator—Pressure Drop. Our energy bills are closely tied to this parameter. Today, Amorair will take you deeper into understanding what "Pressure Drop" is from multiple dimensions and how managing it can lower our energy bills.

CONTENTS

- What is Pressure Drop?

- Why Does Pressure Drop Affect Energy Consumption?

- Factors Influencing Pressure Drop

- How to Manage Pressure Drop to Reduce Energy Consumption

- FAQs About Pressure Drop

What is Pressure Drop?

>>> Definition of Pressure Drop

Pressure Drop, also known as airflow resistance or differential pressure, refers to the difference in pressure between the air inlet side (upstream) and the air outlet side (downstream) as air flows through a filtration medium (such as a filter screen or bag).

Imagine breathing while wearing a mask: If the mask is thin (low pressure drop), your breathing will be smooth. If the mask is thick or clogged with dust (high pressure drop), you need to breathe deeply and forcefully to get enough air. In an HVAC system, the fan acts as that person "struggling to breathe."

>>> Units of Pressure Drop

Pressure drop is typically measured using the following units:

 - Pascal (Pa):  The SI unit, most commonly used internationally.

- Inches of Water Gauge (in. w.g.): The Imperial unit, commonly found in American.

>>> How is Pressure Drop Calculated?

While complex fluid dynamics formulas (like the Darcy-Weisbach equation) are used in laboratories, the calculation in practical applications is very simple:

∆P=PInlet -PLetout

That is: Pressure Drop = Static Pressure upstream of the filter minus Static Pressure downstream of the filter.

>>> The Difference Between Initial and Final Pressure Drop

For filters, pressure drop needs to be measured twice: once when the filter is brand new, and again after the filter has been in use for some time and has adsorbed a significant amount of air pollutants.

- Initial Pressure Drop (Resistance): The resistance value when a brand new, clean filter is installed. Generally, the initial pressure drop of high-efficiency filters is higher than that of low-efficiency filters.

-Final Pressure Drop (Resistance): The resistance limit at which the manufacturer recommends replacing the filter. Exceeding this value will result in severely insufficient airflow, or the filter may be broken.

Why Does Pressure Drop Affect Energy Consumption?

In the filtration industry, there is a direct linear or even exponential relationship between pressure drop and energy consumption.

In modern HVAC systems, to maintain constant airflow, fans are usually equipped with Variable Frequency Drives (VFD). As the filter's pressure drop gradually rises, the operating resistance increases. To maintain stable airflow, the VFD automatically increases the fan speed. This directly translates to an increase in motor power.

Industry research indicates that for every 100 Pa increase in filter pressure drop, fan energy consumption increases by approximately 10%–15%. This means that over long-term operation, selecting HVAC filters with low resistance can significantly reduce system operating costs. For a large factory operating 24/7, this could mean thousands of dollars in extra electricity costs annually.

Factors Influencing Pressure Drop

There are many factors influencing pressure drop, primarily the following four:

Filter Media

The fiber thickness and weaving structure of different materials determine the difficulty of airflow passage. Among common filter materials, the pressure drop of fiberglass media is generally higher than that of synthetic fiber media.

Filtration Area

Increasing the filtration area can reduce the "face velocity" on the media surface, thereby significantly lowering pressure drop. This is why we design bag filters, V-bank filters, and pleated filters.

Dust Load

During use, as dust continuously accumulates on the media surface, the breathable pores become smaller, and pressure drop naturally rises. This is an unavoidable physical process.

Air Velocity

The faster the air velocity passing through the filter, the greater the friction and turbulence generated, and consequently, the higher the pressure drop.

How to Manage Pressure Drop to Reduce Energy Consumption

Through the explanation above, we now understand the relationship between pressure drop and energy consumption. So, what actions should we take?

Focus on LCC (Life Cycle Cost)

When buying filters, do not just look at the price. Cheap filters usually have low Dust Holding Capacity and their resistance rises quickly. Purchasing premium filters with low initial resistance and high dust holding capacity, although slightly higher in unit price, will save enough on electricity bills to cover the procurement costs.

Regular Monitoring

Install manometers (pressure gauges) to monitor data in real-time, rather than replacing filters based on guesswork.

Timely Replacement

Although manufacturers provide a recommended final resistance, do not wait until the absolute limit to replace. Usually, replacing the filter when it reaches about 80% of the final pressure drop is often the optimal balance point for the energy efficiency ratio (electricity cost vs. procurement cost).

Multi-stage Filtration System

 Adding a layer of low-resistance pre-filter before the high-efficiency filter can protect the expensive main filter at the rear and delay the increase in pressure drop.

FAQs About Pressure Drop

1.Does the pressure drop of an air filter change?

Yes. It is a dynamic process. As the filter captures more and more particulate matter, the air passages narrow, and the pressure drop will gradually rise over time until it reaches the load limit.

2. What is Static Pressure?

Static Pressure refers to the pressure exerted by air on the duct walls or filter surface (excluding the kinetic energy generated by air movement). In HVAC, we need sufficient static pressure to overcome the resistance of filters, coils, and ducts to deliver air into the room.

3. What are the signs of excessive Static Pressure?

- Reduced Airflow: Weak airflow at the vents.

- Uneven Heating/Cooling: Temperatures in certain areas of the room fail to reach the set point.

- Increased Noise: The fan spins at high speed to overcome resistance, generating noise.

- Abnormal Electricity Bills: Electricity costs are rising even without adding new equipment.

4. What is the relationship between Pressure Drop and Airflow?

The higher the pressure drop, the greater the restriction on airflow; the lower the pressure drop, the easier it is for air to pass through the filter. Assuming you try to force double the airflow through the same filter, the pressure drop will increase by more than double (theoretically close to quadruple). Therefore, selecting the correctly sized filter is crucial.

5. Does filter material affect Pressure Drop?

Yes. Even with the same efficiency rating, there are differences in resistance between different filter materials.

6. Does higher efficiency always mean higher Pressure Drop?

Traditionally, yes, but not necessarily anymore. In the past, increasing efficiency meant making the filter paper denser, leading to higher resistance. However, modern technology, through increasing the number of pleats (increasing surface area) or using electrostatic electret technology, can manufacture filters that are both high efficiency and low resistance.

7. How do I judge the Pressure Drop level?

The most accurate method is to check the Performance Curve provided by the filter manufacturer. This chart displays the specific resistance value of that filter model at different airflow rates.

8. How do I decide if a filter needs replacement based on Pressure Drop?

Every filter has a recommended "Final Resistance." For example, for a filter with an initial resistance of 100 Pa, the manufacturer might suggest replacing it at 200 Pa or 250 Pa. When your manometer reading approaches this value, it is time to replace it. (As mentioned earlier, replacing it at around 80% of the final pressure drop is often the optimal balance point for cost-efficiency.)

9. How do Amorair air filters help improve energy efficiency?

Amorair focuses on developing low-resistance filtration solutions. Our product designs aim to optimize airflow structure and use media with high dust holding capacity, ensuring that while meeting filtration efficiency standards, we maintain a lower average operating resistance compared to the industry standard. This means your fans can run more effortlessly, directly saving you money on monthly electricity expenses.

Pressure drop is not just a technical parameter; it is directly related to corporate operating costs. When procuring air filters, we need to consider multiple factors and balance energy consumption with efficiency according to the specific needs of the cleanroom. In this way, you not only obtain clean air but also see tangible returns in your monthly electricity bills. Welcome to contact the Amorair team; we provide free filter energy consumption assessment services for you.