Fluke 922 Fluke Low Pressure Differential Meters - HVAC Pressure Applications - Page 4

TSP and ESP: Total Static Pressure (TSP) and External Static Pressure (ESP) are used in conjunction with the manufacturer's blower performance tables to ensure that the blower performance is sufficient to overcome airside device pressure drops and the pressure drop associated with duct friction and fittings losses. Manufacturer's blower performance tables will specify whether the tables are based on TSP or ESP. Once installed, the TSP or ESP is measured to select the appropriate fan RPM that will deliver the desired cfm. It's important to remember that manufacturer's blower curves are developed by AMCA test procedures that do not exhibit any system effect. Due to equipment installation space and configuration limitations, blower performance is rarely the same as system performance ("as-built" rarely performs exactly "asdesigned"). Initial blower set up is by TSP or ESP. Duct traverses that measure actual airflow are required for final blower set up. TSP is normally provided for commercial and industrial unitary equipment. TSP includes internal and external dynamic pressure losses the equipment fan must overcome. A static pickup is used on the inlet side of the fan to measure static pressure and the connecting tube is connected to the "-" port on the Fluke 922. A static pickup is placed on the discharge side of the blower and the connecting tube is connected to the "+" port on the Fluke 922. The displayed pressure is the TSP. ESP is normally provided for residential unitary equipment. ESP is provided for equipment that does not have optional components that can be added within the cabinet or when drilling holes to take TSP may violate equipment agency certifications. The blower tables are based on dynamic pressure losses external to the equipment, measured at the return opening and at the supply opening of the unitary equipment. Check the blower table instructions to determine whether or not the filter should be in place when measuring ESP. Place a static pickup in the return duct at the equipment return opening. Connect this tube to the "-" port of the Fluke 922. Place a static pickup in the supply duct at the equipment discharge opening before any external devices such as an external evaporator, if so equipped. Connect this tube to the "+" port on the Fluke 922. The displayed reading will be the ESP. FSP (Psf) is Fan Static Pressure and is used to independently rate a fan's ability to overcome all system dynamic pressure losses. A Pitot tube is used on the inlet side of the fan to measure total pressure and the connecting tube is connected to the "-" port on the Fluke 922. A static pickup is placed on the discharge side of the blower and the connecting tube is connected to the "+" port on the Fluke 922. The displayed pressure is the FSP. Conclusion Pressure is an often-misunderstood aspect of HVAC diagnostics. Everyone has refrigerant pressure gauges, but to understand why "the pressures are wrong," you need to think about fluid flow and heat transfer too, instead of just adding gas to force the pressures up. And, while everyone probably has a pressure gauge, it's not always the right kind for accurately reading low pressure systems. Now, with electronic meters like the Fluke 922, you not only get an accurate read, you can check the actual pressure differential instead of replacing pressure differential switches by default. Using the Min/Max/Avg feature The MIN-MAX feature on the Fluke 922, in addition to capturing minimum and maximum readings, will record and average readings when a fluctuating pressure, velocity, or airflow is encountered. Once you've captured pressure, velocity, and/or airflow readings and stored them in memory, they can be recalled per selected mode for review and deleted individually, or as a group. Applications for Min/Max/Avg include checking: • static pressure variations as zone dampers open and close • CAVB bypass sizing and damper operation The average function is most useful when air turbulence causes minor fluctuations in readings. The average feature smoothes out the slight variations, making pressure evaluations more accurate.  Fluke Corporation HVAC pressure applications with the Fluke 922 Fluke. Keeping your world up and running.™ Fluke Corporation PO Box 9090, Everett, WA USA 98206 Fluke Europe B.V. PO Box 1186, 5602 BD Eindhoven, The Netherlands For more information call: In the U.S.A. (800) 443-5853 or Fax (425) 446-5116 In Europe/M-East/Africa +31 (0) 40 2675 200 or Fax +31 (0) 40 2675 222 In Canada (800)-36-FLUKE or Fax (905) 890-6866 From other countries +1 (425) 446-5500 or Fax +1 (425) 446-5116 Web access: http://www.fluke.com ©2006 Fluke Corporation. All rights reserved. Specifications subject to change without notice. Printed in U.S.A. 12/2006 2817879 A-EN-N Rev A