Measuring Air Handler Flow Accurately Paul Morin The Energy Conservatory © Copyright 2014 The Energy Conservatory Presentation Housekeeping • If you do not hear anything from your computer’s speaker system you will need to dial in and listen to the presentation over the phone • If you have a question for the presenter, please type it in the question box at the right of the screen • The webinar will be available on The Energy Conservatory website and our YouTube site within a week Agenda • Why measuring air handler flow is important • Advantages of using the TrueFlow® • TrueFlow system components • Gauge options • Basic TrueFlow test procedures • TrueFlow procedure with two returns • The Duct Blaster® Pressure matching method Why measuring air handler flow is important • Insufficient airflow is a common problem • Low airflow can lead to: • Decreased heating and cooling capacity • Increased energy usage • Comfort problems • Optimize the performance of heat pump and air conditioner Advantages of using the TrueFlow® • Widely used methods are problematic or time consuming • Simple and accurate method • Proven success over years of field testing • Can be used with any manometer with a resolution of 1 Pascal (0.005 inches H₂O) TrueFlow® Specs • Flow Accuracy: • +/- 7% when using gauge w/1% accuracy • +/- 9% when using a Magnehelic gauge • Flow Range: • #14 TrueFlow Plate 365 – 1565 CFM • #20 TrueFlow Plate 485 – 2100 CFM • System Weight: • 13 lbs. TrueFlow System Components • Carrying Case • Flow Conversion Tables • 10’ blue and 30’ clear tubing • Operations Manual 2 Calibrated TF Plates 8 spacers for sizing adjustments 1 static pressure probe Gauge options Gauge with a resolution of 1 Pa. (0.005 inches H₂O) • DG-700 or DG-500 • DG-2 or DG-3 • Other digital manometers • Magnehelic gauge (+/- 9%) Basic TrueFlow test procedures Choose a location closest to the airhandler Basic TrueFlow test procedures Basic Test Procedure • With AH on and filter in place, measure NSOP • Replace filter with TF • Measure TFSOP • Measure airflow • Calculate a Flow Resistance Correction factor • Use Correction factor to calculate adjusted flow Setup • Replace dirty filters • Open all registers • Open a window • Open AH zone / outside Setup • Insert static probe: • Point the probe into the airflow • Side of supply plenum • Dead end corner of supply plenum • Side of return plenum w/o trunk line, return register or return duct connected to it • 24” from TrueFlow plate • 24” from 90° corners • 24” from return trunk line connections • TrueFlow plate at remote filter grille? • Don’t put probe in return plenum Enter NSOP using DG-700 • The process is simplified • Instead of: • Recording NSOP • Recording TFSOP • Use a chart to determine Flow Resistance Correction factor • You can: • Enter the NSOP into the DG-700 • DG-700 will adjust the flow Enter NSOP using DG-700 • Connect tubing from probe to gauge • Turn on the air handler • Set DG-700 to PR / AH mode • NSOP will begin flashing With AH on and filter in place, measure NSOP • Press the START button • Press the ENTER button Install the TrueFlow Plate • Remove the existing filter • Choose appropriate TrueFlow Plate • Install spacers on top & side • Face the front into airflow Install the TrueFlow Plate • All of airflow must pass through the plates (not around) • Air must pass over all of the plate • Obstructions 6” upstream or 2” downstream affect accuracy • Can be installed inside the AH cabinet (taped in place) Measure the Adjusted Total Air Handler Flow • Connect 2 tubes from the TrueFlow Plate to Channel B • Change the Device to TF • Change CONFIG to match the Plate being used • Turn on the air handler • If numbers fluctuate, switch to LONG term averaging • Record the adjusted flow reading TrueFlow procedure using other gauges • Same as with DG-700 except: • You need to convert pressure at TrueFlow Plates to flow using a chart • You need to adjust flow based on pressure differences between NSOP and TFSOP using a chart TrueFlow with other gauges • You need to convert pressure at TrueFlow Plates to flow using a chart TrueFlow with other gauges • You need to adjust flow based on pressure differences between NSOP and TFSOP: • Record NSOP • Record TFSOP • Use chart to determine multiplier TrueFlow with other gauges TrueFlow with other gauges TrueFlow procedure with two returns • If returns share a trunk, measure at air handler cabinet (if possible) • If returns enter cabinet from different sides, use both Metering Plates: • If second return is smaller than 14x20, use a transition (example: 14x14 to 14x20 transition) • Long tube for Channel A • Measure flows separately and add together Air Density Correction Charts Volumetric Flow • Cooling Air Flow Requirements • 350 – 400 CFM per Ton Humid • 400 – 425 CFM per Ton Dry • 450 CFM per Ton @ 7000’ elevation Air Density Correction Charts Measuring Total System Air Flow (Pressure Matching Method) Measuring Total System Air Flow (Pressure Matching Method) • Measure the Normal System Operating Pressure (NSOP) • Connect the Duct Blaster® Fan to the Duct System • All return air must be flowing through the Duct Blaster fan • Match the Normal System Operating Pressure (NSOP) Measure the NSOP • Replace dirty filters • Open all registers • Open a window • Open AH zone / outside Setup • Insert static probe: • Point probe into the airflow • Side of supply plenum • Dead end corner of supply plenum • Side of return plenum w/o trunk line, return register or return duct connected to it • 24” from TrueFlow plate • 24” from 90° corners • 24” from return trunk line connections • TrueFlow plate at remote filter grille? • Don’t put probe in return plenum Measuring Total System Air Flow (Pressure Matching Method) • Measure the NSOP: • Turn on the airhandler • Turn on gauge and write down the NSOP Measuring Total System Air Flow (Pressure Matching Method) • Connect the Duct Blaster® Fan to the Duct System Measuring Total System Air Flow (Pressure Matching Method) • Match the Normal System Operating Pressure (NSOP): • Connect tubing from DB fan to the DG-700 • Set DG-700 to PR/ FL mode • Turn on the air handler • Turn up the Duct Blaster fan to match the NSOP • Record the Total System Air Flow Measuring Total System Air Flow (Pressure Matching Method) • Unable to match the NSOP? • Turn Duct Blaster fan all of the way up • Record the CFM flow from the DG-700 • Record the operating pressure you were able to achieve • Use the Flow Resistance Correction Factor from Appendix B of the True Flow manual Unable to match the NSOP? • Use the Flow Resistance Correction Factor from Appendix B of the True Flow manual Measuring Air Handler Flow Accurately Questions? Paul Morin The Energy Conservatory (612) 827-1117 phone (612) 254-2162 direct Email: [email protected] website: www.energyconservatory.com.