Pressure in HVAC Systems

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Pressure in HVAC Systems

While addressing COVID-19 health issues and getting back to normal, one of the major concerns, especially for education, is acceptable ventilation.

Unfortunately, due to COVID-19, one of the leading conferences in this area, the Michigan Industrial Ventilation Conference, will not be held this year. In its place, a series of webinars facilitated by conference instructors will cover the fundamentals of industrial ventilation.

As noted in the seminar description for the first of the these webinars that will start March 3, pressure, as  well as temperature, elevation, and moisture content impacts an airstream’s density and density factor.

Another webinar will specifically address difficult testing situations and detail selection methods for providing the most accurate representation of pressure and airflow possible. Yet another will cover techniques and equipment for monitoring industrial ventilation systems to ensure that the system operates properly.

Those interested in more information on alternatives being offered to the 2021 conference should click here.

All Sensors Corporation MAMP Series P1NS Package

Those who are interested in accurate pressure sensors in the low-pressure range to detect clogged filters and airflow in HVAC systems should consider All Sensors MAMP Series of calibrated amplified output that can address 5 to 120 cmH2O measurements.

Do you have a pressure sensing question? Let us know and we’ll address it in an upcoming blog.
Email us at [email protected]

Fan Static Pressure

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Fan Static Pressure

Fan static pressure is one of the two parameters that define the performance of a fan. The other, and more common, is the volume of air the fan delivers per minute or per hour. Fan static pressure is the resistance pressure the fan has to blow against to move air in the desired direction.

For PC gamers, high airflow and high-pressure static fans are two distinct classifications. High-pressure static fans are used on radiators, central processing unit (CPU) and graphic processing unit GPU coolers, in front of hard drives, and other places where airflow might otherwise be blocked by an object. Because of their high-pressure capability, they can overcome the restrictions caused by the blockage.

Cooler Master Masterfan Pro 120 Air Pressure Fan

The Masterfan Pro 120 Air Pressure Fan is ideal for funneling concentrated air short distances at hot components or through tight spaces.  Image courtesy of Cooler Master.

In wood drying operations, kiln static pressure is not a constant and depends upon the performance of the fan chosen. For example, replacing a small fan generating 45,000 cubic feet per minute (cfm) at an estimated pressure of 0.5 inches H2O in a kiln with a larger fan rated at 60,000 cfm at 0.5 inches of H2O will not achieve 60,000 cfm. The actual air flow will be less than 60,000 cfm due to the rise in the static pressure – a situation that can cause complications in the end application.

In heating, ventilating and air conditioning (HVAC) systems, static pressure measures the effectiveness of the fan to the ducts in a particular installation.  If the static pressure is too high, the HVAC unit will have to work harder to push the air through the duct work.

In all of these low-pressure situations, an accurate microelectromechanical systems (MEMS) pressure sensor with a digital output, such as All Sensors DLLR Series, can address the manufacturing, installation verification or ongoing operation measurements.

Comments/Questions?
Do you have a pressure sensing question? Let us know and we’ll address it in an upcoming blog.
Email us at [email protected]

Controlling Building Pressure

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll discuss proper indoor versus outdoor pressure in commercial buildings.

Controlling Building Pressure

Proper indoor versus outdoor pressure is important in commercial buildings. When indoor pressure is less than the outside pressure, outdoor air leaks, or infiltrates into the building. In addition to impacting heating, ventilation and air conditioning (HVAC) effectiveness, excessive infiltration can also cause uncomfortable drafts, especially in stairways, as well possible odor migrations and even encourage microbial growth depending on the outside weather conditions.

The opposite pressure condition, exfiltration, occurs when indoor pressure is greater than the outside pressure, indoor air leaks out of, or exfiltrates from the building. Excessive exfiltration negatively impacts temperature control by reducing supply airflow into occupied spaces, makes opening and closing doors difficult and creates noisy high-velocity airflow around doors and windows.

In addition to the operation of its mechanical ventilation system, a building’s pressure can be positive or negative due to the impact of wind and weather. Using either a return fan or a relief fan, for direct control of building pressure, manages the combined effects of weather, wind, and mechanical ventilation. This control requires pressure sensors mounted inside and outside of the building to determine the actual pressure difference. Depending on the desired exfiltration and infiltration goals, the pressure difference is typically less than 0.1-inch water gauge (wg) and can be either positive or negative.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation ([email protected])

Pressure Sensing and Improved HVAC Efficiency

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll look at pressure sensing and how it improves HVAC efficiency.

Pressure Sensing and Improved HVAC Efficiency

Clean air in heating, ventilating and air conditioning (HVAC) systems requires filtering to eliminate dust, pollen and other airborne contaminants in residential, commercial and industrial buildings for the health of occupants and equipment. Some locations such as clean rooms in semiconductor and other manufacturing operations as well as hospital operating rooms and research laboratories have very special requirements. Clean air depends on the filter’s initial efficiency and the pressure drop across it, which increases with usage. The pressure drop is also called the air filter resistance.

The National Air Filtration Association (NAFA) says, “Most large HVAC commercial grade systems are designed to handle pressure drops of one inch, possibly more, for the air filter resistance. Matching filter initial, final and average resistance to the system is critical for proper air filtration and air exchange rates. Also, providing pressure drop reading devices such as manometers or electronic pressure sensors is an absolute requirement.”

According to the Lawrence Berkeley National Laboratory (Berkeley Lab or LBL) Design Guide for Energy-Efficient Research Laboratories – Version 4.0, for HEPA filters, the “pressure drops can be as low as 0.1 inches water gage (w.g.) (24.9 Pa) and as high as 1.0 inches w.g. (249 Pa), with significant energy use impacts resulting from the nonlinear power use requirements of higher pressure drop filters.”

Filters are rated in static pressure at a specified cubic feet per minute (CFM) air flow. In 103 – Filtration Fundamentals, one company states that most heating /cooling systems in the residential and light commercial markets are designed to move 900 CFM to 2000 CFM at a total system static pressure of approximately 0.5″ to 0.7″ total pressure drop including the resistance through the ductwork and the filter.

With usage, the total pressure drop increases causing the filter to draw more power and increase the stress on the air handling equipment. The point where the pressure drop increases the electrical power consumption and overtakes the initial cost of the filter indicating that a filter change is required is called the optimal change-out point and is shown in Figure 1.

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Figure 1. The optimum final pressure drop across an air filter.

The equation used to determine the energy cost based on the final pressure drop is:

Energy Consumption (in kWh)= Q ∆P t / η 1000

Where:

Q = airflow (m3/sec)

ΔP = avg. pressure loss (Pa)

t = time in operation (hours)

η = fan efficiency

In the summary for pressure drop considerations for air filters, NAFA concludes, “Pressure drop reading devices are essential to determine optimum performance results and filter change-out frequency.”

Achieving the optimum performance leads to efficient filter operation and safe, clean air.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation ([email protected])