Fan Static Pressure Calculator

6 and this will increase to the ‘cube’ of the change in flowrate So new KW = Old KW x (1. 3,4 DIGIT NO. 2) = pt2 - pt1 - (pt2 - ps2) = ps2 – pt1 (10. Fan laws •Used to calculate changes in flow rate, pressure and power due to a change in fan speed. Dayton®, Venco® HVAC - Your Ventilation Information Resource - Exclusively from Grainger. Pumps and fans are vital parts of the process onboard a vessel 4 1. By multiplying air velocity by the cross section area of a duct, you can determine the air volume flowing past a point in the duct per unit of time. of the motor is 8. 40 APackage Includes2x Series SP LED High Static Pressure FanMounting ScrewsWarranty leaflet. Notice that the 72-inch fan has the highest static efficiency which is the proper metric for nonducted applications. When installed, the fan will operate on the total pressure developed, and so, by definition, one fan velocity pressure will be available to deal with the losses at the fan connections. This calculator is provided as a broad based indication of the energy cost of running a filter based air purification, and an indicative cost of running a Sanuvox system as an alternative. Use a duct calculator or the chart provided below to fig- ure the static pressure of 100 feet of a given diameter of duct at a given CFM. In series operation, the fans are stacked one upon the other, resulting in an increase of static pressure (doubling at shut-off, but less elsewhere). Infant Growth Charts - Baby Percentiles Overtime Pay Rate Calculator Salary Hourly Pay Converter - Jobs Percent Off - Sale Discount Calculator Pay Raise Increase Calculator Linear Interpolation Calculator Dog Age Calculator Ideal Gas Law Calculator Rule of 72 Interest Calculator Pump Calculator - Water Hydraulics Fluid Mechanics Equations. Pressure Drops Across Fans - posted in Student: Hi I have a problem understanding the pressure drop across fans. fan pressure varies with the square of fan speed ratio: 3. Centrifugal blowers provide directional air flow by maximizing static pressure. Very low static pressure suggests a low fan speed or leakage in the duct system. 1 inWG = 25. static pressure wc fan weight shipping weight 0” 10” 15” 20” 25” 35” with cord hs2000 23004-1 3”in / 2”out 150-270 18 14 110 72 40 - - - 17 20 hs3000 23004-2 3”in / 2”out 105-195 27 21 40 33 29 24 18 - 18 21. 78 which = -1291Pa Original KW was 3. This is the useful work required from the fan. XY plots of Static Pressure and Static Temperature vs position. For example, let's say you increased fan airflow by 10 percent. Why Choose Pipe Flow Wizard for Fluid Flow & Pressure Drop Calculations. 5" for Wood Mag. Static Pressure is measured in inches of water gage (˝wg). It gives a wind velocity much higher than the fan can achieve The wind velocity (which is difficult to measure directly) can be calculated from static pressures with a simple manometer. The fan laws enable pressure and power adjustments with a change in density relative to temperature and altitude. Static pressure. For the B#1 impeller, a sudden pressure rise exists near the design condition. P sf = P t2 - P t1 - P v2. Short answer: Static Thrust: It's a pretty good to decent ball-park estimate for all props, and a really good estimator for some props. (fan static pressure = fan discharge pressure – fan inlet pressure + velocity pressure) Static pressure is measured by a Water Gauge (WG) and is an indication of the air flow resistance inside your fan. Estimated Fan Requirements: Show Table (to get desired airflow when bin is full) Bin capacity (bushels): 5,542: Total airflow (cfm): 5,542: Estimated static pressure (inches of water): 7. and display pressure to 1/100 of an inch. The first curve shows the relationship between the static pressure capabilities of the fan compared to the fan’s air volume flow rate. The Best PC Builds 2020: Desktop Rigs For Different Prices Ranges Putting together a gaming PC build can be an intimidating process, but it doesn't have to be so hard if you know what you're doing. This calculation formula for the required airflows (ventilation rate) can be translated into a graph as shown in Fig. 08(VP1 - VP2) A Converging Outlet Cone, as illustrated in Figure C, is used to connect a small duct to the outlet flange of the fan. Notice that the 72-inch fan has the highest static efficiency which is the proper metric for nonducted applications. This is seen as one moves to the right in the table. This is measured in inches of water gauge (iwg). 8 inches static pressure (1. High Static Pressure Leads to Problems It’s important to check your system for high static pressure and correct it because otherwise you can end up with some very serious problems. The centrifugal fan displaces a constant volume of air in a given system regardless of air density. If the fan is dumping into an open area then 0 is the value for that side. Is there any equation for pressure generated by a fan, specifically a centrifugal blower. For 140mm fans, there is no such distinction: Both the NF-A14 and the NF-P14 redux models are true all-rounders that provide outstanding levels of airflow and static pressure. When a centrifugal fan is specified for a given CFM and static pressure at conditions other than standard, an air density correction factor must be applied to select the proper size fan to meet the new condition. rate, fan lift discharge static pressure, fan tip diameter, fan tip speed, and air density, respectively. The formula below provide a rough guide for converting static pressure to peak specific fan power. Using two fans, each fan would be required to move 10,080 CFMs of air. XY plots of Static Pressure and Static Temperature vs position. Temperature should be shown in degrees Fahrenheit (F). In this example, the water in the pipe moving at 5 m/s will exert 12,500 Pascals or 1. Expansion fans are isentropic. The STAT-probe Static Pressure Probe consists of multiple Fechheimer static pressure sensing ports positioned along the length of the probe to traverse the duct cross-section, average the sensed static pressures in the internal manifold, and provide a measurement of static pressure accurate to within 2-3% of actual pressure. Through an expansion fan, the Mach number increases, the static pressure decreases and the total pressure remains constant. You can calculate airflow from the pressure drop, length, duct type (and compression for flex duct) using the AllDuct Calculator. The static pressure drop across standard commercial VAV boxes is always lower than the total pressure drop since the velocity at the box inlet is much higher than the outlet ve-locity, resulting in static pressure regain. Pt = Pe + Pd The unit of pressure used is mmH2O (mm of column of water) and it is equivalent to: 1mmH2O = 9. Power requirements of SA Fan : Let us assume Fan efficiency as 70% and Motor Efficiency as 90%. Pumps and fans are vital parts of the process onboard a vessel 4 1. Fan capacity, expressed in horsepower and is based on fan. Area of cross-section in meters squared 3. When measuring and interpreting static pressure verify fan speed and inspect the condition of the fan. That’s why HVAC professionals have charts and tools at their disposal to make the whole process go smoother. Airflow vs Static Pressure. This equation does not compensate for temperature, density or airflow charateristics of any particular fan or blower. External Static Pressure is the measurement of all the resistance in the duct system that the fan has to work against. Take care of the definitions, Fan static pressure not similar to static pressure rise in system If pressure losses for all elements have been calculated, the fan selection has to be for total pressure Clients are often asking for fan static pressure although they require fan total pressure, there's a large potential to reduce costs. The static pressure of duct system is essentially a back pressure the fan must. The other, and more common, is the volume of air the fan delivers per minute or per hour. A temperature rise is also noticed since compression is a heating process. Axial vs Centrifugal Fans. Real measurements should be made in order to check if the engine can rotate the given propeller at the given RPM, or the engine can produce the given output performance shown in the documentation by using the propeller you. In this example, the water in the pipe moving at 5 m/s will exert 12,500 Pascals or 1. Things that can cause resistance to airflow include ducts, turns in ducts, air filters and any other obstruction to the airflow itself. For instance, if your blower should be moving 1000cfm through the system, your installer would want to verify (by looking at the blower chart) that at the static pressure of 0. Oriental Motor's measuring equipment is connected to a computer, providing extremely precise measurements in a short period of time. The high pressure blades concentrate the airflow to the centre of the fan achieving a strong static pressure. Today, electronic manometers are widely available. Available in three separate mounting configurations, the S. Fan CFM Calculator This fan calculator is typically used to calculate the CFM or cubic feet per minute of air exchange that may be desired in a building. If the fan is moving air in the right direction that can't be true. The fan was set up to always be pulling the air though the pipe. The FC wheel produces little static pressure in the wheel and relies on the scroll of the fan housing to change velocity into static pressure. 45 mmH2O ± 10% Fan Noise Level 6-20 dBA (Max) Fan Rated Current 0. The accurate prediction of pressure losses across in-duct fittings is of significance in relation to the accurate sizing and good energy efficiency of air-delivery systems. Static Pressure (SP) 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. The other, and more common, is the volume of air the fan delivers per minute or per hour. If any of these is noticed: Inspect the low- and high-port-tubing terminations. The cfm of a single fan depends on the horsepower of the motor, rpm of the motor, shape of the blades, the design of the shroud around the blades, the static pressure the fan is working against. Air moves from areas of higher pressure to areas of lower pressure through any available openings. Building differential static pressure fluctuates widely and/or rapidly. Static Pressure. If you already have a ductwork system and want simply to replace an existing baghouse/fan combo, you still need to calculate the CFM and static resistance from the. Rooftop Package Units • Cooling capacities 1 ton = 12,000 btu/hour 1 ton = 400 CFM (+/- 20% flexibility) unit capacity = total capacity NOT sensible capacity. The calculation method of the central air conditioning static pressure box: 1, Height * depth = static pressure box cross-sectional area, static pressure box cross-sectional area *2. Velocity Pressure of # 2 Entering Branch (inches Water): Note: Sum of flows in branches # 1 and # 2 must equal Flow Rate in ACFM input above. The formula I have for figuring the temperature rise of a fan that is in the air stream is: Temperature rise = Static Pressure rise through the fan X 0. 5″ of water column”. Measure the air pressure. The input parameters for the design of radial tipped centrifugal fan for fume extraction from SDS-9 texturing machine are summarized below. Online calculator to quickly determine Pressure Loss through Piping for Water. These fans are actually measured by how effectively they can tackle resistances, with high static pressure fans being more suitable to thick radiators than low static pressure fans. The ideal power consumption for a fan (without losses) can be expressed as. The below calculation sheet is very simple and all engineers can make use of it in order to estimate / calculate the External static pressure (ESP) of any fan in any HVAC equipment. Fig 2 shows the pressures through a fan, each of which is described below:. Consideration should be taken for STATIC PRESSURE ( S. cfm x static pressure (in. Estimated Fan Requirements: Show Table (to get desired airflow when bin is full) Bin capacity (bushels): 5,542: Total airflow (cfm): 5,542: Estimated static pressure (inches of water): 7. For this you require a fan which has a static pressure of 10. This specification is provided by the manufacturer. ) Kitchen Hood Exhaust 0. Well, how do you know what fan speed to set the blower at? Whether it's a PSC, X-13, or an ECM motor you have fan speed options. Static Pressure. As a primary static. Includes 53 different calculations. If you already have a ductwork system and want simply to replace an existing baghouse/fan combo, you still need to calculate the CFM and static resistance from the. V 2 , calculated by multiplying the space by the new air change requirements. This pressure is also called as "Total Head". Use a duct calculator or the chart provided below to fig- ure the static pressure of 100 feet of a given diameter of duct at a given CFM. Using the duct calculator. this slight difference in static pressure, the following formula can be used. Axial Fans Sometimes referred to as propeller fans, these fans. With high-efficiency inlet designs, lubricated maintenance-free ball bearings, and vibration-free operation, HVAC axial fans operate in temperatures from -30° to +60°C with 40,000 hours of operation. 5 HP at the desired performance level, a 5-HP motor would be. In these systems, fan speed is typically controlled to maintain a constant static pressure under all. These fans are actually measured by how effectively they can tackle resistances, with high static pressure fans being more suitable to thick radiators than low static pressure fans. The calculator can not check the reliability of the entered data therefore all inputs have to meet life-like value ranges. Static Pressure •Static pressure is the resistance to airflow from objects in the air stream •Filters, coils, heat exchangers, registers, grills, balancing dampers and, of course, the duct itself, are just a few •After the resistance of these objects is subtracted, the balance is what is available for the duct system. Static pressure is a measurement of how hard a fan has to work to move airflow through a duct system. The ideal power consumption for a fan (without losses) can be expressed as. Two extensive Programs are included for Fan External Static Pressure Calculations - Supply Fan and Return/Exhaust Fan Calcs. Ductwork static pressure is figured as friction loss per 100 feet of duct at a certain CFM. Static pressure losses are caused by increases in velocity pressure as well as friction and dynamic losses. An example would be the pressure inside a balloon. The two most common technologies to measure velocity are capacitive based pressure sensors and hot-wire anemometers. MicroMetl offers a “Air Duct Calculator” (See Video – How To Use A Duct Calculator) which allows a quick and easy static pressure calculation to be performed with the use of just a few design variables. The required capacity of a leakage test meter should be examined in relation to the duct leakage classification chart. Maximum Air Volume Measurement: The nozzle is opened and the auxiliary blower is used to lower the pressure in chamber A to Ps = 0. Equivalent Duct Calculator (Round vs Rectangular) GRD Cross Reference Calculator. In these systems, fan speed is typically controlled to maintain a constant static pressure under all. CFM is the most commonly changed variable, the example below is based on a change in CFM and illustrates how the new factors can be figured, based on this change. 40 APackage Includes2x Series SP LED High Static Pressure FanMounting ScrewsWarranty leaflet. Home » Attic Vent Calculator For years we have been working with Architects and Specifiers to ensure affordable roof ventilation that upholds building code standards. Graphical reports of interest with fans are as follows: Contours or profiles of Static Pressure and Static Temperature. Hood Static Pressure Calculator : Plenum Type: Exhaust Supply : Plenum:. Pressure dependent control does not use a device to measure inlet pressure as a means to determine flow. Volume of air required (cfm) 2. • Fan static pressure, FSP, is the difference between the fan total pressure and fan velocity pressure, or FSP = FTP - FVP (10. File Size: 759 Kb 1. There is a short answer and a much longer answer, but calculating duct system pressure requirements is both fundamental to system design and, frankly, a lot of fun. Step 5 Divide your answer by the system airflow in cubic feet per minute. Figure 6 shows my ventilation systems flow rate for the static pressure that I am assuming. If you connect the Total Pressure Probe to the HIGH port on a differential pressure sensor and the Static Pressure Probe to the LOW port on. Is there any equation for pressure generated by a fan, specifically a centrifugal blower. Static Pressure is rated in inches water gauge (inWG) or the metric equivalent, millimeters water gauge (mmWG). My system is setup for 350 CFM per ton so it’s required running at right around 700 CFM which means on my system this filter is going to add 0. Fan engineers often assume these standard conditions/density when asked to size a fan for a given air volume and static pressure when a client does not specify the inlet air density or conditions affecting the density. Once the pressure is builtup in the room there is no flow into the room as the fan static equals the room pressure. How To Calculate Static Pressure Of Axial Fan Amazing Woodworking Projects (🔴 No CC Required) | How To Calculate Static Pressure Of Axial Fan Lifetime Monthly Plans!! How To Calculate Static Pressure Of Axial Fan Start To Build Your Own Furniture (🔴 Step-By-Step Ideas) | How To Calculate Static Pressure Of Axial Fan Complete Instructions. Static pressure produced by a fan causes air motion in the ventilation system with a certain resistance. The higher the ventilation resistance in the system, the less air flow of the fan is. Density at sea level at 59°F; 0. where: P = static pressure K = load factor r = Fluid Density Q = Flow. Chapter 3: Review of Basic Vacuum Calculations Before we go any further, some time should be spent on some of the vocabulary specific to vacuum technology. Step 1 – Select your desired CFM. Straight and Adjustable Dynamic Loss Coefficient Table. Notice that the 72-inch fan has the highest static efficiency which is the proper metric for nonducted applications. wg])/6,356. Fan exiting pressure +1. Equivalent Static Pressure Use of the fan laws can sometimes be simplified by using Equivalent Static Pressure - ESP - defined as the pressure that would be developed by a fan operating at standard air density instead of the actual air density. The larger blades move more air per unit of energy input. The following is a generic equation to determine the required horsepower to drive the fan or blower element. Factoring in Surrounding Elements for Inlet Air Density. water • Internal to fan – can’t change this & no good data Need to control these system. 10 or 1/8-inch (0. Ps = Pa - Po. This contributes to the high TE and FEG values, but since this is a non-ducted application, the velocity pressure is lost. 0 in of water fan static pressure. The new PressureMAX blade profile generates 20 percent more static pressure and is 5-7 percent more efficient than standard airfoil fans, saving horsepower and fuel. Space Pressurization: Concept and Practice ASHRAE Distinguished Lecture Series Jim Coogan Siemens Building Technologies YEA Conference - Specialty Environmental Design ASHRAE research relates pressure to clean room contamination: RP 1344 and RP 1399 Bio lab experiments: Bennet, Applied Biosafety, 2005. The average static pressure of the duct fan system is less than 2 inch SP. The first curve shows the relationship between the static pressure capabilities of the fan compared to the fan's air volume flow rate. Airflow (CFM) Thick (mm) Conversion table 1m3/min=35. The purpose of the NEBB Procedural Standards for Testing Adjusting and Balancing of Environmental Systems is to establish a uniform and systematic set of criteria for the performance of the testing, adjusting and balancing of environmental or Heating, Ventilating and Air-conditioning (HVAC) systems. Luckily, software designers and engineers usually do most of the math for us when working in a large commercial or industrial environment, but when thinking about a residential or small scale application, static pressure takes a back seat to CFM. pressure set point and two typical reset methods. The static pressure is expressed in inch of water column in the English units, a typical value would be 1", the SI unit for pressure is Pa(Pascal). Now, imagine there is rushing water in the pipe, the pressure put placed by the water pushing out against the present liquid, this is known as dynamic pressure. Pressure Dependent A VAV box control strategy where the amount of air delivered to the space is dependent upon the inlet duct static pressure, as well as control damper position. This resistance is known as static pressure. The use of a “systems approach” in the fan selection process. Pressure measurements are then taken at each location. Measure pressure drop from position 1 to position 2 and calculate flow rate and more with this easy to use flow calculator. (fan static pressure = fan discharge pressure – fan inlet pressure + velocity pressure) Static pressure is measured by a Water Gauge (WG) and is an indication of the air flow resistance inside your fan. Most manufacturers' performance charts are based on Fan Static Pressure. Static Pressure is rated in inches water gauge (inWG) or the metric equivalent, millimeters water gauge (mmWG). Graphical Plots. ” For turkey growers, this simply relates to the occurrence of a slight decrease in pressure within a turkey building relative to outside air pressure when one or more exhaust fans are turned on. Authority Recommendations (Static Pressure Control) 1. This would equal an approximate static pressure increase of 21 percent. 78 which = -1291Pa Original KW was 3. There existed a sudden pressure drop in all three fans at the point the fans went into stall conditions. The below calculation sheet is very simple and all engineers can make use of it in order to estimate / calculate the External static pressure (ESP) of any fan in any HVAC equipment. The design keeps changing and you need to redesign the routings again and again. The 922 velocity and air flow calculations are based on. This test may sound good on the surface, but the result will be an inaccurate filter pressure drop. Static pressure fan total pressure decreases fanvelocity pressure. Dougherty, P. Therefore. static pressure Operating static pressure. Say Reynolds number as 4500. 8,9 DIGIT NO. In other words, it's the maximum CFM without any imposed resistance to the flow. It may or may not. Sound Calculator – Calculates sound power, sound pressure and Noise Criteria from input of octave band sound data. Fan Selection: Ideal selection at right side of maximum static pressure. fan duct diameter watts max. Static Pressure. Static Pressure (in w. Program runs in 32-bit and 64-bit Windows systems. 33 Required extractor fan size in M 3 /H= (Volume of active growing space (m) x 60) x 1. The centrifugal fan displaces a constant volume of air in a given system regardless of air density. Corsair, for example, sells “Quiet Edition” high-static pressure fans. 7 x 1 inch Fan MTTF 490,000 Hours Fan L-10 Life 70,000 Hours Rated Voltage 12 VDC Fan Power Connector 4-Pin (PWM. Then in the second phase you calculate the static pressure (SP) of your system to determine the size of your baghouse (how many filters and what size) and power of your system fan. (length of ductwork, number of elbows etc. It is used to determine a fans power by showing how much it would increase the static pressure if a fan was blowing into a sealed system. 78 or –725 x 1. air flow, manufacturers are painstaking in their calculation of the amount required to meet specified performance, and in the application of a fan/motor combination which will move that quantity of air against the static pressure encountered within the tower. This is the useful work required from the fan. Ideally, VAV dampers should run in the 50% to 75% range (when the. 0 in of water fan static pressure. Likewise the converse is true, the smaller the pressure difference, the slower the air will enter the house. Measure the pressure difference between chamber A and chamber B (Pd). The image file shows the Online Help Basic Fan information explaining how the pressure drop and flow rate is determine depending which option was. A major factor regarding the performance of the air handling system is the static pressure that will exist between the negative side of the system (the return) and the positive side of the system (the supply). 1 inches of water column (i. Air Flow Measurement; Static Pressure measure Ment; Power Measurement; Fan Selection guide. HVAC axial fans efficiently move large quantities of air in high static pressure situations. 2 Static back pressure measurement To determine the static back pressure of the fan a manometer needs to be used. From what I understand is you would want fans with higher static pressure for your heatsink fan(s) and higher cfm for your intake/exhaust. 25 inches of H 2 O. For the B#1 impeller, a sudden pressure rise exists near the design condition. 5m/s= fan coil air volume, as for how to match the height and depth, according to the requirements of their configuration; 2. A single intake fan with no exhaust fan is positive pressure. 8 inches static pressure (1. In more words - no pressure drop, or 0 static pressure. static pressure Operating static pressure. The low-side should be near 30 PSI at 90 degrees Fahrenheit or less. Axial fans are predominantly suitable for high airflow in systems with low static pressure, while centrifugal fans offer lower airflow, but can deliver it against higher static pressure. Dedicated VFD for each fan and motor combination. Print usage (How To Calculate Static Pressure For Exhaust Fans Start To Build Your Own Furniture 18 Jun 2020 (☑ Watch Anywwere) | How To Calculate Static Pressure For Exhaust Fans Step-By-Step Blueprints!!how to How To Calculate Static Pressure For Exhaust Fans for for 1 last update 2020/06/18 P-ELP-EL). Sixteen desktop calculators, fourteen calculators as the web application, three calculators for Android smartphones are available at the moment. Values for density and dynamic viscosity are specified in the Mechanical Settings dialog. Computer Fan Sounds Like It's Hitting Something Lithium Grease Computer Fan Computer Cooling Fan Price In Bd Cpu Fan Speed Control Software Download Computer Fan On But No Display Fan Art Computer. Vaneaxials are typically the most energy-efficient fans available and should be used whenever possible. Flow Discharge Q = 0. 45 mmH2O ± 10% Fan Noise Level 6-20 dBA (Max) Fan Rated Current 0. 8,9 DIGIT NO. And combining that with your hardware fans etc etc, since the delayed arrival of my new case i wanted to share here before finishing my article. 26″wc of extra static to the return side of the blower. Since the velocity at the stagnation point is zero, The stagnation or total pressure, p_0, is the pressure measured at the point where the fluid comes to rest. water if no cooling coil) • Cooling Coils -0. These examples show the most common type of static pressure taps, however there are many different static pressure tap options. The PB110 is specified to move 110 CFM of air with a static pressure of 0. Fans and blowers provide air for ventilation and industrial process requirements. Fan Static Pressure. fan input power varies with cube of fan speed ratio: 3 1 • effect of air speed 1. Room dimensions are of no. Based upon the curves in figure 2, CUI Devices' CFM-6025V-131-167 dc axial fan has been selected for the project. fan air flow rate varies directly with fan speed ratio: n 2. In most cases, the fan or blower manufacturer will specify how much power (in horsepower) is required to turn the blower at the proper speed to produce the required air flow at the desired minimum static pressure. This calculation formula for the required airflows (ventilation rate) can be translated into a graph as shown in Fig. if a standard PSC, multiple-speed motor is employed by the air handling system. Consequently, oversized fans not only cost more to purchase and to operate, they create avoidable system performance problems. Likewise the converse is true, the smaller the pressure difference, the slower the air will enter the house. A sound source produces sound power and this generates a sound pressure fluctuation in the air. The Spruce Dryer Boost Kit P/N 28131 (SDB110P) operates the fan with a pressure switch that activates the fan when the appliance is turned on. 8 cubic ft (14. Computer Fan Sounds Like It's Hitting Something Lithium Grease Computer Fan Computer Cooling Fan Price In Bd Cpu Fan Speed Control Software Download Computer Fan On But No Display Fan Art Computer. A small crack or hole can admit significant amounts of air, if the pressure differentials are high enough (which may be very difficult to assess). A single intake fan with no exhaust fan is positive pressure. Duct Size Calculator Ductulator is an engineering tool to calculate air duct dimensions based on given inputs including air-flow, duct material roughness and either air pressure static loss (friction method) or air velocity (velocity method). of static pressure. Static Pressure (SP) 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. Fan operating pressure 2. 0 63 14 10 45 51 018702-30 $72. 50 efficiency Large fan 0. 78 which = -1291Pa Original KW was 3. At the inlet to the duct, the static pressure produces an area of low pressure. 3 to 2 times the required air volume. Since the velocity at the stagnation point is zero, The stagnation or total pressure, p_0, is the pressure measured at the point where the fluid comes to rest. Select a fan Select a fan with a maximum air flow of 1. Return or relief fans operate near 100-percent speed most of the time. Various types of HVAC equipment establish an airflow through ducts, and two common examples are air-handling units (AHU) and packaged rooftop units (RTU). Fresh air supply fans also known as make up air fans can be used when exhaust fans are present and fresh air is needed to equalize the pressure in the room. txt) or read online for free. It may or may not. 78 or -725 x 1. Building differential static pressure fluctuates widely and/or rapidly. of static pressure. A typical, 2-core radiator will create about 0. Values for density and dynamic viscosity are specified in the Mechanical Settings dialog. At least one window should be open before the fan is operated. Friction losses for air in air ducts as well as resistance of the networking equipment (a filter, silencer, heater, valves and dampers, etc. Where does the unplanned exfiltration go? The air relieves within the stud space and out the top. Fan exiting pressure +1. 78 New Static Pressure = original Static Pressure x 1. Add total elbow equivalents to the length of straight duct to arrive at the total system duct length. Chapter 3: Review of Basic Vacuum Calculations Before we go any further, some time should be spent on some of the vocabulary specific to vacuum technology. Fan Types – Why Choose a Backward Curved Centrifugal fan? Backward Curved Motorised Impeller. It can be used as liquid, gas or air flow meter and the results can be checked against the textbook formula to gain confidence in using this easy to use orifice plate. Calculate the flow rate (Q). At first glance, Fan Law 2 looks. 33)3 New KW. Fan static pressure is the resistance pressure the fan has to blow against to move air in the desired direction. The pressure loss is a function of the velocity through that section and the roughness of the wall. The calculation works by keeping the static pressure in the ductwork constant throughout the system. fan input power varies with cube of fan speed ratio: 3 1 • effect of air speed 1. where, L is length and subscriptst stands for static and f for friction. So, in any case, it is not difficult to maintain necessary pressure differences between the corridor and the vestibule, and between the corridor and the elevator shaft. Air velocity (distance traveled per unit of time) is usually expressed in Linear Feet per Minute (LFM). Contrary to what we might imagine, air is really heavy. of the motor is 8. A cone-shaped exhaust stack that recaptures static pressure from velocity pressure. The fan static pressure (FSP) component of the rating is determined from the flow requirements. Being able to measure and calculate static pressure is a basic, yet important, skill for any HVAC professional. Expansion fans are isentropic. The maximum allowable filter velocity is 300 feet per minute (fpm) on disposable filters. Vacuum: from a practical sense, vacuum may be defined as the condition of a gas under less than atmospheric pressure. Notice that the 72-inch fan has the highest static efficiency which is the proper metric for nonducted applications. 3 If efficacy is not listed, it can be calculated from published watts and specified airflow (cfm) as is shown in. Lower static pressure mean smaller fans, smaller ductwork, less noise and of course less cost to operate. Available in three separate mounting configurations, the S. 5 cm of water at a volume flow rate of 0. The two most common methods are the Darcy-Weisbach equation and the Hazen-Williams equation. Since the exhaust outlet is reduced to focus air to a specified direction, these blowers are used for spot cooling. Hello, no need to calculate the static pressure in these cases, just install the fan and connect its exhaust with the same size flexible exhaust duct and you will fall within its rated static pressure capability. The static pressure drop across standard commercial VAV boxes is always lower than the total pressure drop since the velocity at the box inlet is much higher than the outlet ve-locity, resulting in static pressure regain. It is a measure of the total mechanical energy added to the air by the fan. If the inlet pressure correction had been used up front, then the system line and the fan curve would cross at 5800 cfm at -14 inches SP but with a 1937 fan. Figure 2: System requirements, airflow versus static pressure. air flow rate remains the same with a change in air density. In most cases, the fan or blower manufacturer will specify how much power (in horsepower) is required to turn the blower at the proper speed to produce the required air flow at the desired minimum static pressure. Therefore, the flow rate as well as the pressure will be low compared to design. 1 inH 2 O with no airflow, and also provides the graph in figure 3. The typical manufacturer's fan-rated total external static pressure is 0. The total air moving capacity of the tunnel fans is then divided by the cross-sectional area of the house to obtain an average tunnel air velocity. Wg 1 Pa (Pascal) = 1 N/m2 FAN TESTING Fan testing aims to determine the airflow and pressure they provide, as well as all their electrical data and sound levels,. At the inlet to the duct, the static pressure produces an area of low pressure. CFM vs BHP Curves. 1 inH 2 O with no airflow, and also provides the graph in figure 3. Fan Selection: Ideal selection at right side of maximum static pressure. Set on low, these fans runs at 1,450 RPM and push 37. Static Pressure based on 100′ of Pipe; Elbow to Straight Pipe Conversion; Figure System Resistance (SP) The total static pressure is several factors added together. CFM is the most commonly changed variable, the example below is based on a change in CFM and illustrates how the new factors can be figured, based on this change. How will a change in grain depth affect the air delivery of my existing fan?. Static pressure fans are designed to pull or push air with extra force, which is ideal for areas with more restricted airflow—like a water cooling radiator or a large CPU cooler with lots of fins. For this application, the value of ∆pt to be used in Equation 1 would be equal to the design static pressure generated by the fan. We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. In part 1 of this video, the basics of static pressure are demonstrated and explained how they affect grain drying. 2) = pt2 - pt1 - (pt2 - ps2) = ps2 - pt1 (10. 0: For variable volume fan systems, this spreadsheet tool calculates energy savings from one or a combination of the following measures: Reducing VAV box minimum flow setpoint; Reducing duct static pressure setpoint ; Resetting duct static pressure setpoint. Where does the unplanned exfiltration go? The air relieves within the stud space and out the top. The fan power is lower under partial load conditions. Question asked by Park Sang-Hyun on Jan 10, 2017 Latest reply on Jan 15, 2017 by Dave Bond. 11 DIGIT NO. The static pressure of duct system is essentially a back pressure the fan must. Upvote (2) Views (16884) Followers (7). The same is true of a static pressure reading. To move air, the fan must overcome two resistances, which are measured as pressure drops across the fan. This spreadsheet allows the user to determine the amount of leakage area a poultry house has by conducting a static pressure test. The static pressure drop across standard commercial VAV boxes is always lower than the total pressure drop since the velocity at the box inlet is much higher than the outlet ve-locity, resulting in static pressure regain. Like • Show 0 Likes 0; Comment • 5 I would like to calculate the static pressure inside the Chamber, except for the part of the fan. CALCULATION OF FURNACE BLOWER FAN ENERGY CONSUMPTION 7-C. It is what we normally call just Pressure. ) Density of air 6356 x Efficiency Density of standard air Small fans 0. Duct Entrance Losses from Plenum Fan Cabinet To achieve the air velocity in the discharge duct and overcome the loss associated with the air entering the ductwork, additional resistance must be added to the external static pressure (ESP) requirements of the fan. For 140mm fans, there is no such distinction: Both the NF-A14 and the NF-P14 redux models are true all-rounders that provide outstanding levels of airflow and static pressure. As airflow varies inversely with static pressure, manufacturers typically present the information using graphs. 1: Vacuum ranges Vacuum Description Range Low vacuum 25 to 760 Torr. 375 CFM 98 94 93 84 52 Static pressure is a measure of the resistance of air move-ment through a duct system. Pipe Elevation Changes and Effect on Pressure Loss As fluid flows through a piping system, where pipes rise and fall, changing elevation, the pressure at a particular point in a pipe is also affected by the changes in elevation of the fluid that have occured. This calculation formula for the required airflows (ventilation rate) can be translated into a graph as shown in Fig. And Pa is the absolute pressure, both can be measured using an instrument e. Figure 6 shows my ventilation systems flow rate for the static pressure that I am assuming. By definition, fan static pressure is the total pressure at the fan outlet minus the total. : = Air Capacity in M /Hr x Total Pressure In mm SWG x 0. For rigid pipes, the celerity of the pressure wave or wave speed, c, is found by: c = √ E B /ρ. Fan static pressure Calculation. Calculate the amount of heat produced internally from the device, s input/output and efficiency etc. Static Pressure and Duct Run: A ventilating fan must overcome resistance when pushing air from the inlet, through the duct, to the outside of the building. • Total pressure loss=static pressure loss. 1 inH 2 O with no airflow, and also provides the graph in figure 3. For initial estimates, evaluate a fan's performance based on its air flow capacity at 0. Static pressure produced by a fan causes air motion in the ventilation system with a certain resistance. Duct Entrance Losses from Plenum Fan Cabinet To achieve the air velocity in the discharge duct and overcome the loss associated with the air entering the ductwork, additional resistance must be added to the external static pressure (ESP) requirements of the fan. The rated capacity calculation is useful in determining the total water supply at a given point in the hydrant or water main. •Because the static pressure is below atmospheric at a fan inlet, air will flow from the higher atmospheric pressure through an intake and any connecting ductwork until it reaches the area of lowest static pressure at the fan inlet. ) Radio/DVD/CD. Density at sea level at 59°F; 0. V = 4005 x(√ΔP) in ft/min. 2) = pt2 - pt1 - (pt2 - ps2) = ps2 – pt1 (10. This is because removing the filter decreases total external static pressure (TESP), so the match to find the filter pressure drop doesn’t calculate. If a fan's performance is specified in terms of Ps, the fan designer can simply use a large diffuser at the outlet of the fan to bump up the static pressure. AND PRESSURE LOSS USING EQUAL FRICTION. This would equal an approximate static pressure increase of 21 percent. Staircase pressurization fan , what is the equation to calculate the air flow and static pressure for fan ? HVAC Air Conditioning. It will give the HVAC technician an idea of our system’s general health. The combined total pressure across both fans will be the sum of the individual total pressure of each fan. The two most common technologies to measure velocity are capacitive based pressure sensors and hot-wire anemometers. requires circuit co-efficient of friction column compressor cooling cubic foot density is 075 determined dry air dry bulb temperature. As always feedback or pointing out errors is welcome, the file is view only simply download it to use it. How much of an impact depends on how a fan is selected, installed, and operated. These assume motor efficiency of 0. Different types of duct entrances and locations will require varying correction. It may or may not. You can then calculate the pressure rise through the fan. txt) or read online for free. For example a carbon filter or a heating coil, or between the inside of the system and outside atmosphere. Fan A mechanical device that moves air and creates static pressure. 6% (ASHRAE 1993, Chapter 32, Table 7). Static Pressure is measured in inches of water gage (˝wg). ure N db K T C RH MC 1 ( ) Henderson EMC: ln(1 ). P = K r Q n. The fan impeller is fabricated from 30 thin sheet metal vanes, the ratio of the passage width to. Fluid Dynamic Viscosity - u = 0. Hence, this peak total efficiency is used to determine the FEG value. When sizing the fan a few things have to be taken into consideration. It is most often used in the high pressure ductwork between the main AHU and the VAV boxes. This is the useful work required from the fan. Flexible Multiple external static pressures designed based on the unit’s cooling capacity, meeting the air supply. This graph gives pressure drop based on specific gravity of water 1. Static pressure is a term used in fluid dynamics to define the amount of pressure exerted by a fluid that is not moving. A single intake fan with no exhaust fan is positive pressure. This equation does not compensate for temperature, density or airflow charateristics of any particular fan or blower. xls - Free download as Excel Spreadsheet (. Pressure Drop • Any method above initially • Determine the index run • Resize to ensure pressure loss similar to index • Better pressure balanced system • Small duct sizes Reduced capital and spatial costs • Tedious Calculations • Higher velocities at take offs may be noisy • Dampering of Larger ducts may be as or more noisy. Air volume, pressure drop and noise requirements should be specified first and in preference to fan speed. To complete the measurement of static pressure, you will need to have static pressure tips and tubing for making connections to the manometer. A cheap radial-vaned centrifugal fan is required to provide a supply of pressurised air to a furnace. What has to be appreciated is that where irregular flow conditions are present, there will be a component of velocity pressure present and may be recorded as well as the static pressure and this will lead to erroneous readings. In case of fire in a high rise building, a Stair Pressurization Fan (SPF) uses clean outside air to pressurize the air in stairwells. L for Duct Parts 3. The cfm of a single fan depends on the horsepower of the motor, rpm of the motor, shape of the blades, the design of the shroud around the blades, the static pressure the fan is working against. The easiest way to set the blower speed is to measure TESP (total external static pressure), cross reference the TESP to the manufacturers blower chart in the installation manual, and adjust the blower speed. Revit computes pressure losses in piping based on the geometry and roughness of piping, fluid density, and fluid dynamic viscosity. static pressure, it act equally in all directions. FAN PERFORMANCE:. Cooling Tower Fan Selection; Heat Exchanger or ACC Fan Selection. ρᵢ {use '+' if the direction of. CFM = air flow. Computation of Natural Gas Flow Rate using a Spreadsheet Ayoade KUYE and Uzoma EZUMA f tf 460 T 520 F + = (5) h P b F 1 w f r = + (6) where SG is the specific gravity; Tf is the flowing temperature, OF; and b is a constant that is dependent on the pipe diameter, viscosity, density and velocity of gas. These pressures are the Impact pressure and the Static pressure (see photo below). This fan can move 200 cfm of air at a static pressure of 1" and is capable of moving 50 cfm at greater than 2" of static pressure. For pressure drop estimation graphs are referred. These pressures are the Impact pressure and the Static pressure (see photo below). Dayton®, Venco® HVAC - Your Ventilation Information Resource - Exclusively from Grainger. If a fan's performance is specified in terms of Ps, the fan designer can simply use a large diffuser at the outlet of the fan to bump up the static pressure. (static pressure plus velocity pressure) at the fan outlet minus the total pressure at the fan inlet. 86 cfm x 6786 bu. Revit computes pressure losses in piping based on the geometry and roughness of piping, fluid density, and fluid dynamic viscosity. 5 cm of water at a volume flow rate of 0. To find the size of fan needed, multiply the cubic feet x the # of air exchanges (15) then divide by 60 (minutes in an hour). Fan static pressure is measured in inches of water gauge. It is a measure of the total mechanical energy added to the air by the fan. Equation: P = (Q x p)/(229 x ) or. Take the static pressure measurements on both the Return and Supply Plenums of the furnace (with filter (s) in place. The 922 velocity and air flow calculations are based on. Is it right that the pressure drop across the FD fan is the sum of pressure drops across the preheater, burner. 20 m or 5-8” static pressure ranges. It is the sum of the suction pressure (negative) and discharge pressure (positive) created by the equipment blower. Sound level SPL conversion sound pressure level SPL to dB intensity unit calculate calculating calculation Conversion of sound pressure to sound intensity sound units pressure intensity dB air sound units level ratio decibel Pa kPa acoustic energy power convert decibels to pascals audio engineering sound pressure is the effect - Eberhard Sengpiel sengpielaudio. where the point e is far upstream and point 0 is at the stagnation point. , as listed for a 12-foot depth in Table 4). The static pressure is exerted equally in all dvelocity irections and the. The amount of static pressure depends on the duct length, type of duct, elbows and the roof jack or wall cap. Therefore, head loss will always act to reduce the pressure head, or static pressure, of the fluid. For example, suppose fan #4 from Table 7 (see the fan performance data section above) is drying 10 tons of hay and the static pressure reading in the attached duct is 1 inch of water. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan. Due to our precision balancing, KEHO fans last many years longer. air density. So if you put the Flow versus Back Pressure lines for both designs on the same graph, they cross. P = K r Q n. This measurement takes into account the speed of the wind that the fan produces and also the size of the fan's blades. Static pressure fans are a better option when pushing air through objects like a CPU heat sink, a water-cooling radiator or other obstructions. Includes 53 different calculations. From the manufacturer’s data sheet we know that to deliver this performance, the RPM (U 1 ) of the fan is 865u/min. On the other hand, static pressure is total pressure minus velocity pressure. Plot fan airlow on the equipment manufacturers fan tables. For example, A 30' x 96' greenhouse would be 20,160 CFMs. HVAC axial fans efficiently move large quantities of air in high static pressure situations. We began as a fan company in 1947. How To Properly Select a Fan or Blower Explanation or in metric equivalent, it is rated in Pascal's (Pa). The easiest way to set the blower speed is to measure TESP (total external static pressure), cross reference the TESP to the manufacturers blower chart in the installation manual, and adjust the blower speed. Air Performance Testing; Sound Testing; AMCA 260; Vibration Testing; Seismic Testing; Bump Testing; Operational Modal Testing; Jet Fan Thrust Testing; Overspeed Testing. And we have included a calculator search facility, that can be accessed from every page by clicking on the 'magnifying glass' logo at the top-left of every page, or from the page-footer. The across-the-cone change in velocity pressure is added to the fan’s static pressure. For example a carbon filter or a heating coil, or between the inside of the system and outside atmosphere. Revit uses the Darcy-Weisbach equation to compute pressure drop on pipe segments. & similar, 3. Therefore, head loss will always act to reduce the pressure head, or static pressure, of the fluid. Pressure Dependent A VAV box control strategy where the amount of air delivered to the space is dependent upon the inlet duct static pressure, as well as control damper position. Total efficiency can be used to calculate another important variable, a fan's static efficiency, which is defined as the ratio of fan static pressure (FSP) to fan total pressure (FTP), multiplied by the fan total efficiency. xls), PDF File (. Either of them works excellent both for case cooling and for use on radiators and heatsinks. To give us an idea, the static pressure that the atmosphere exerts upon us due to its weight is equal to approximately 407 inches of water. Calculate the required air flow Calculate the volume of air required for a set temperature. Cellulose pads can be used with airflows of up to 230 CFM per square foot of pad. A Static Pressure Probe aligned at a right angle to the airflow senses only the static pressure. (Velocity pressure excluded). The centrifugal fan displaces a constant volume of air in a given system regardless of air density. Accurate RPM is easily obtained and a good quality tach will measure it real close. Pressure (p v) + duct static pressure (p s) = duct total pressure (p t), where the term ‘duct static pressure’ will be taken to mean ‘duct static pressure relative to the surrounding air’. A typical, 2-core radiator will create about 0. One way of viewing this is that the impact pressure is converted to static pressure; thus, a static pressure rise is seen as air flows through a divergent duct and is compressed. 78 which = -1291Pa Original KW was 3. BASIC FAN LAWS Existing Flowrate (CFM): Existing Static Pressure (in. The ideal power consumption for a fan (without losses) can be expressed as. The fan impeller is fabricated from 30 thin sheet metal vanes, the ratio of the passage width to. The pressure in car tires can be in the range of 180 to 250 kPa. Static pressure in a house using inlets is basically an indirect measure of inlet air speed. In this step, you calculate the Static Pressure (SP) or the resistance of your system that your dust collection unit must overcome. Fan Laws Relationships that describe theoretical, mutual performance changes in pressure, flow rate, rpm of the fan, horsepower, density of air, fan size, and sound power. Where does the unplanned exfiltration go? The air relieves within the stud space and out the top. requires circuit co-efficient of friction column compressor cooling cubic foot density is 075 determined dry air dry bulb temperature. How to Calculate Static Pressure - calculate the pressure loss in the duct, using your preferred method. To measure the pressure drop over a return air ilter grille, use only one hose, pierce the ilter, the pressure drop over the ilter and grille will be displayed on the monometer. xls), PDF File (. For more explanation, see the discussion about “Adjusting Design Airflow” (page 7) in. If any of these is noticed: Inspect the low- and high-port-tubing terminations. Peak Specific Fan Power (W/l/s) = Static Pressure (Pa) / 501 IP Peak Specific Fan Power (W/cfm) = Static Pressure (In H2O) * 4. K-factor editor for local pressure loss The program includes 2 procedures placed on customized command bar use to know the value of the coefficient K. 28 m or 10-11” or greater, and work best in the 0. ” For turkey growers, this simply relates to the occurrence of a slight decrease in pressure within a turkey building relative to outside air pressure when one or more exhaust fans are turned on. Pump head calculation uses Bernoullis Principle, which states that the total energy at a given point in a fluid depends upon the energy of movement of the fluid, plus energy from static pressure in the fluid, plus energy from the height of the fluid relative to a specific data. All you need to know is the fluid’s speed and height at those two points. Technicians typically measure static pressure in inches of water gauge. Static pressure is typically measured using a force divided by an area, or measured in length units when using a pressure head. Static Pressure • The resistance to flow (energy added by the fan) measured in Inches of Water Gauge (in wg) Fan selection is typically based upon a CFM and Static Pressure (i. When the alarm becomes active the unit stops all operation and locks out. Very low static pressure suggests a low fan speed or leakage in the duct system. Elbows (choose up to three different elbow types):. 5" for Wood Mag. Johnson Controls YORK® YDFC fan coil units are ceiling mounted, high air flow, high static pressure air conditioning terminals. ), the blower can. It is the sum of the suction pressure (negative) and discharge pressure (positive) created by the equipment blower. Since the exhaust outlet is reduced to focus air to a specified direction, these blowers are used for spot cooling. • Total External Static = 0. These fans are actually measured by how effectively they can tackle resistances, with high static pressure fans being more suitable to thick radiators than low static pressure fans. Roughness is specified in the type properties for pipe/pipe fitting component families. Two air movers in parallel will produce double the free flow of one, while air movers in series increase the shut off pressure to twice that of a single device. Mechanical Horsepower (MHP):Mechanical horsepower is the measure of the power produced by the fan, a function of the air flow rate measured in cubic feet per minute (CFM) and the total static pressure (TSP) measured in “in. More than just fan selection software, Element is a comprehensive tool to design an air moving solution for your application. The fan power is lower under partial load conditions. The static pressure curve shows the relationship between the static pressure capabilities of the fan compared to the fan's air volume flow rate at a given fan speed. how to calculate static pressure for exhaust fanshow to how to calculate static pressure for exhaust fans for Building your have syndicate tabularise is a rewarding If you have some basic woodworking skills you hindquarters homemade pool table plans ramp up type A quality hardwood This website contains I get together to the APA leagues. The following is a generic equation to determine the required horsepower to drive the fan or blower element. pdf), Text File (. The fan exhaust was discharged. This function is derived from conservation of mass, momentum, and energy for very small (differential. My air system will have somewhat more static pressure, so the air flow will be slightly lower. When a centrifugal fan is specified for a given CFM and static pressure at conditions other than standard, an air density correction factor must be applied to select the proper size fan to meet the new condition. They are usually selected for free delivery of air into the zone or with minimal ductwork having a static resistance of less than 0. What has to be appreciated is that where irregular flow conditions are present, there will be a component of velocity pressure present and may be recorded as well as the static pressure and this will lead to erroneous readings. where, L is length and subscriptst stands for static and f for friction. fan pressure varies with the square of fan speed ratio: 3. The SPRDs automatically respond to the air pressure in duct as the various zone dampers open and close. xls), PDF File (. When a flow turns around a smooth and circular corner, these waves can be extended backwards to meet at a point. Across a shock wave, the Mach number decreases, the static pressure increases, and there is a loss of total pressure because the process is irreversible. Hi Don, I’d tend to agree with your installer, as long as the “right” amount of air is moving through the system at that pressure. Likewise the converse is true, the smaller the pressure difference, the slower the air will enter the house. 58iwc external static pressure (ESP), see #20 below. The typical manufacturer's fan-rated total external static pressure is 0. The formula I have for figuring the temperature rise of a fan that is in the air stream is: Temperature rise = Static Pressure rise through the fan X 0. The Future As a result of Keith Dixon-Roche's discoveries in physics , we at last have a wonderful opportunity to actually improve life on our planet; for. The static pressure measurement is a vital fact for the selection process. 0 inches water adiabatic compression air flowing air horsepower air passes air-vapour mixture Airway Area approximately Atkinson's formula average barometric pressure c. A major factor regarding the performance of the air handling system is the static pressure that will exist between the negative side of the system (the return) and the positive side of the system (the supply). Of course you also need to re-size the required static for your selected fans at the same time. 25 cfm per square foot of floor space) and measuring the resultant level of static pressure. And combining that with your hardware fans etc etc, since the delayed arrival of my new case i wanted to share here before finishing my article. The radial fan is rated at 2000 ft 3 /min and 5. How to Calculate CFM for Bathroom Fan. The component details within AHU are listed in Table 1. 0079], which is not the. Suitable for low pressure applications like domestic furnace, medium size air conditioning units up to 25 tons. A fan curve simulating multiple, identical fans in parallel may be constructed by scaling the fan curve air flow axis data in direct proportion to the number of fans. To one of your other questions, if the fan is rated at 500 CFM without giving a static pressure, I think you would have to assume that it's for the free-running condition. Equivalent Static Pressure Use of the fan laws can sometimes be simplified by using Equivalent Static Pressure - ESP - defined as the pressure that would be developed by a fan operating at standard air density instead of the actual air density. water) plotted vs. The STAT-probe Static Pressure Probe consists of multiple Fechheimer static pressure sensing ports positioned along the length of the probe to traverse the duct cross-section, average the sensed static pressures in the internal manifold, and provide a measurement of static pressure accurate to within 2-3% of actual pressure.