When measuring static pressure, the unit of measurement used is
inches of water column
, which is often shown as an abbreviation such as “in. wc,” “in. wg” or “in. H2O.” One key to interpreting and diagnosing static pressure is to first understand how pressures change throughout an HVAC system.
How is static air pressure measured?
Static pressure is measured using
a manometer with pressure probes
. Early manometers used a column of water to reflect system pressure. The air pressure physically elevated the water in a measured in inches, which is why static pressure is expressed today in inches.
What is the unit of static pressure?
Static pressure is the amount of air pressure that can be produced by the fan in an enclosure. In this case, the static pressure is measured in
Pascals (Pa)
, or inches of water (inH
2
O). The pascal (Pa) is the SI derived unit of pressure used to quantify internal pressure, stress…etc.
What can be used to measure static pressure?
Manometers or pressure gauges
have been used to measure air pressures for more than 200 years. The fathers of our industry used these gauges to learn about the mysteries of fans and duct systems. Manometers or pressure gauges have been used to measure air pressures for more than 200 years.
What is static pressure in air flow?
Static Pressure is
the resistance to airflow (friction)
caused by the air moving through a pipe, duct, hose, filter, hood slots, air control dampers or louvers. Static Pressure is rated in inches water gauge (inWG) or the metric equivalent, millimeters water gauge (mmWG).
What is maximum static pressure?
Static Pressure: This is
the maximum pressure produced by a fan when this is maximum resistance and no air flow
, such as in a sealed box. Generally, for a wide open application, airflow is more important.
How do you read static pressure?
To determine operating total external static pressure. Measure pressures where air enters and leaves packaged equipment.
Add the two readings together
to find total external static pressure. You can still measure the pressure drop of the coil and filter to check for blockage.
How do you calculate CFM from static pressure?
- (cfm
2
÷ cfm
1
)
2
x SP
1
= SP
2
… - (cfm
2
÷ cfm
1
)
2
x SP
1
= SP
2
… - (1,200 ÷ 1,040)
2
x .08 = SP
2
… - 1.152 x .08 = SP
2
… - 1.32 x .08 = SP
2
… - .11 in.
What causes high static pressure?
There are a number of things that can cause static pressure to become high. It could be
faulty installation of your ductwork or a problem with its design
. When there are numerous turns, dips, or bends in the ductwork it can impede good airflow. Ideally, the solution would be to replace the existing ductwork.
How do I reduce static pressure?
Dirty or high-MERV filter: Having a dirty air filter or one with too high of a MERV rating can also cause high static pressure at the return air intake. We recommend using
cheap, low-MERV filters
and changing them monthly to prevent this problem.
Can static pressure too low?
Low static pressure can also mean
trouble
. Low pressure may indicate leaking ductwork or plenums, missing filters, low fan speed, or separated ductwork. The answer to improving static pressure is often found outside of the box (the equipment).
Is higher or lower static pressure better?
yes higher is better
, High static pressure fans are best of heatsinks and radiators. High airflow fans are best for open spaces. Keep in mind that those fans are quite loud, and you are trading performance for low noise.
What does CFM vs static pressure mean?
water static pressure and deliver a
given airflow rate in cubic feet per minute
(cfm) at a particular static pressure. … The performance of a fan is defined as the amount of airflow in cfm at a given static pressure.
What is normal static pressure?
An instrument called a “manometer” is used to measure pressure and ideally the static pressure should be
. 82”
. When your system static pressure is proper all is good, but when it’s high is when the problems start to happen.
What is a good static pressure rating?
The pressure in return and supply ducts should
not exceed 20 percent of the fan’s rated capacity
. This is the same value used in gauging the pressure drop of an air filter. On a fan rated at 0.5 inch of wc, you wouldn’t want to see any more pressure than 0.1 inch of wc in your supply and return duct pressure reading.
