Did I understand correctly that static pressure is directly related to CFM? Can I compare it with °C and Kelvin? As one increases, the other also increases. but the values start at a different point and the distances between the values are different? :)
An increase in static pressure in an HVAC system typically results in a decrease in total CFM (cubic feet per minute) of airflow. This occurs because the fan or blower in the system must work harder to overcome the higher resistance caused by the increased static pressure.
Here is a great source to explain how to calculate stairwell pressurization and a lot more. www.cedengineering.com/userfiles/Stairwell%20Pressurization%20Systems.pdf Hope this helps.
i have yet to figure out a formula to determine a static pressure for an exhaust system that is not yet in existence. i need to know how to determine what it will be prior to aire flow being possible. can you help with a formula to determine exhaust static pressure for kitchen hood.?
You need to determine the total static pressure (TSP), which is the sum of the static pressure losses across each component, such as the exhaust hood, ductwork, filters, dampers, and any other devices in the airflow path. The first step is to determine the airflow requirement for the kitchen exhaust system, which is typically given in cubic feet per minute (CFM). The required CFM depends on the kitchen equipment, cooking type, and hood size. The exhaust hood manufacturer usually provides guidelines for calculating the required CFM. Let’s say the components have the following pressure drops: Exhaust Hood: 0.4 in. w.g. Ductwork (based on length, diameter, velocity): 0.6 in. w.g. Elbows and Transitions: 0.2 in. w.g. Grease Filters: 0.5 in. w.g. Dampers: 0.1 in. w.g. The Total Static Pressure (TSP) = 0.4 + 0.6 + 0.2 + 0.5 + 0.1 = 1.8 in. w.g. Once you have the total static pressure, select an exhaust fan that is rated to deliver the required CFM at that static pressure. Most fan manufacturers provide performance curves that show the fan’s airflow at different static pressures. It's best to hire a professional mechanical engineer to ensure that the design meets all applicable codes and standards, as the system will need to be submitted to the local code authorities for approval and a permit.
A 20% Increase in CFM doesn't correlate to a 20% increase in Static Pressure. Using the Fan Law Formula the math looks like this. SP2 = SP1 x (CFM2 / CFM1)2. Now with the given values SP2 = 2 x (12,000/10,000)2, further reduced to SP2 = 2 x (1.2)2, then we get SP2 = 2 x (1.2 x 1.2), SP2= 2 x 1.44 = 2.88. I hope that helps.
You have to look at the particular fans Flow Chart, as each fan performs at different efficiencies on a curve. At low or high Flows the efficiency can drop off from the system curves best point of operation. Google " Centrifugal Fan Charts" and look at one to see how they effect efficiency.
Sir, basically the calculation method used in this video is done by applying a fan law in which we gotta need the same situation for the size of duct area, right ?. but I'm a bit confused suppose if I wanna start to design a fan from zero. the main parameters for this are the air flow, static pressure (pressure rise), and the fan speed (rpm). How to determine the static pressure ? can we put it as much as we want or is there any basic calculation to wisely select the proper SP for the design parameters ?. pls help me.
If you are starting from the beginning and designing a ductwork system with a fan attached, you would calculate how much CFM is passing through a duct or fitting at a particular size. You would add up all the losses (Static Pressure Losses) from the friction of the air passing through each duct section or fitting, including any dampers or other items.. You want to size the fan with the correct static pressure from your calculations, you never want to oversize a fan as its just a waste of money and energy. The Fan Law is useful if you're trying to determine a new outcome from changing any of the existing factors. The Fan Laws are not needed when sizing a new system from the beginning. hope that helps.
Did I understand correctly that static pressure is directly related to CFM? Can I compare it with °C and Kelvin? As one increases, the other also increases. but the values start at a different point and the distances between the values are different? :)
An increase in static pressure in an HVAC system typically results in a decrease in total CFM (cubic feet per minute) of airflow. This occurs because the fan or blower in the system must work harder to overcome the higher resistance caused by the increased static pressure.
How to calculate esp of fans that is indicated at equipment schedule of the plans for lift and staircase pressurization?
Here is a great source to explain how to calculate stairwell pressurization and a lot more. www.cedengineering.com/userfiles/Stairwell%20Pressurization%20Systems.pdf
Hope this helps.
@@MEPAcademy Thank you!
i have yet to figure out a formula to determine a static pressure for an exhaust system that is not yet in existence. i need to know how to determine what it will be prior to aire flow being possible. can you help with a formula to determine exhaust static pressure for kitchen hood.?
You need to determine the total static pressure (TSP), which is the sum of the static pressure losses across each component, such as the exhaust hood, ductwork, filters, dampers, and any other devices in the airflow path. The first step is to determine the airflow requirement for the kitchen exhaust system, which is typically given in cubic feet per minute (CFM). The required CFM depends on the kitchen equipment, cooking type, and hood size. The exhaust hood manufacturer usually provides guidelines for calculating the required CFM. Let’s say the components have the following pressure drops:
Exhaust Hood: 0.4 in. w.g.
Ductwork (based on length, diameter, velocity): 0.6 in. w.g.
Elbows and Transitions: 0.2 in. w.g.
Grease Filters: 0.5 in. w.g.
Dampers: 0.1 in. w.g.
The Total Static Pressure (TSP) = 0.4 + 0.6 + 0.2 + 0.5 + 0.1 = 1.8 in. w.g.
Once you have the total static pressure, select an exhaust fan that is rated to deliver the required CFM at that static pressure. Most fan manufacturers provide performance curves that show the fan’s airflow at different static pressures. It's best to hire a professional mechanical engineer to ensure that the design meets all applicable codes and standards, as the system will need to be submitted to the local code authorities for approval and a permit.
How does this math work?
Since the CFM increased by 20% would your SP also not increase the same? 2.4"
Please explain if I'm wrong. Thanks
A 20% Increase in CFM doesn't correlate to a 20% increase in Static Pressure. Using the Fan Law Formula the math looks like this. SP2 = SP1 x (CFM2 / CFM1)2. Now with the given values SP2 = 2 x (12,000/10,000)2, further reduced to SP2 = 2 x (1.2)2, then we get SP2 = 2 x (1.2 x 1.2), SP2= 2 x 1.44 = 2.88. I hope that helps.
@@MEPAcademy Good stuff
How lower /Heigher SP effect to fan efficiency? Plz explain
You have to look at the particular fans Flow Chart, as each fan performs at different efficiencies on a curve. At low or high Flows the efficiency can drop off from the system curves best point of operation. Google " Centrifugal Fan Charts" and look at one to see how they effect efficiency.
Sir, basically the calculation method used in this video is done by applying a fan law in which we gotta need the same situation for the size of duct area, right ?. but I'm a bit confused suppose if I wanna start to design a fan from zero. the main parameters for this are the air flow, static pressure (pressure rise), and the fan speed (rpm). How to determine the static pressure ? can we put it as much as we want or is there any basic calculation to wisely select the proper SP for the design parameters ?. pls help me.
If you are starting from the beginning and designing a ductwork system with a fan attached, you would calculate how much CFM is passing through a duct or fitting at a particular size. You would add up all the losses (Static Pressure Losses) from the friction of the air passing through each duct section or fitting, including any dampers or other items.. You want to size the fan with the correct static pressure from your calculations, you never want to oversize a fan as its just a waste of money and energy. The Fan Law is useful if you're trying to determine a new outcome from changing any of the existing factors. The Fan Laws are not needed when sizing a new system from the beginning. hope that helps.
@@MEPAcademy Thanks
Dear Sir . I need technic for measurement static pressure of kitchen make up and exhaust fan .if you have any recommend please share for me
Here is the NEBB book that has everything you'll need for the proper method of measuring static pressure. www.nebb.org/assets/1/7/PST_TAB_2005.pdf
@@MEPAcademy Thanks a lot
@@MEPAcademy please upload this document on G-drive and then share the link as this link is showing error
@@MEPAcademy It says page not found
ohh chaman teacher what is the heading and what are you teaching
This channel is for the Mechanical Trades, HVAC, Electrical and Plumbing.