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What It Takes to Get an Installed HVAC System to Operate at Rated Capacity

What It Takes to Get an Installed HVAC System to Operate at Rated Capacity

What it takes to get an installed HVAC system to operate at rated capacity

Tuesday January 15 1:00 to 2:30 Room B 312

Rob Falke National Comfort Institute Content and illustrations © NCI Inc. 2019 “But all my systems do operate at rated capacity!” Congratulations, you’re in the top 1% of designers and installing contractors. We would be thrilled to review your installed system documentation.

This illustration represents the typical installed HVAC system performance from data gathered around the USA Equipment and an installed system are two different manufactured products “The industry often refers to equipment as a system” Equipment is: . A manufactured and shipped product . Built in a factory . Rated for capacity and efficiency according to time proven industry standards. . Normally sold to the installing contractor Equipment and an installed system are two different manufactured products An HVAC system is a different manufactured product. A system is: . Built by a mechanical contractor . It consists of ducts, fittings, grilles venting, , is attached to the building and the equipment . Now, it can also be measured and scored. Many believe installed system SIZING performance is found through CHART design 6” - 100 CFM . Dad’s Duct Sizing Chart 7” - 150 CFM 8” - 220 CFM . Began to purchase instruments and 9” - 300 CFM 10” - 400 CFM to test installed system values 12” - 600 CFM 14” - 900 CFM . Learn our designs did not perform 16’ - 1300 CFM as we assumed they did. 18” - 1800 CFM 20” - 2500 CFM . Began to make changes in design, equipment and installation. “So, how do I know my installed systems are operating as they should?” The Western HVAC Performance Alliance defines an efficient HVAC system by the ratio of the installed system delivered Btu/hr and the equipment rated 100% Btu/hr. Example: or Installed System delivered Btu/hr 48,000 Equipment rated Btu/hr 100,000 48%? Or, expressed as a percent 48% 1a. Airflow Measure Diagnose Repair . Traverse airflow . Compare actual fan . Adjust fan speed near fan airflow to required . Reduce restrictions . Plot fan airflow airflow in system . If actual is more or components or in less than 10% of air distribution design, make repairs system and adjustments 1b. Supply Register and Return Grille Airflow

Measure Diagnose Repair . . Air balance hood . Add together grille Adjust balancing or register airflows dampers . Traverse in duct or and compare total to . Repair or replace at grille with fan or required correction factors damaged or system airflows undersized ducting . Compare required . Replace register or room and zone diffuser airflows to actual airflows 1c. Static Pressure Profiles .50” Fan Rated Pressure

Pressure Actual Budget Total Ext. .83” .50” Filter .24” .10” Coil .29” .20” Return .22” .10”

.22” .46” .37” .08” Supply .08” .10” 1d. Static pressure testing Measure Diagnose Repair . Total external static . Compare each . Increase duct pressure pressure system capacity . Filter pressure drop measurement to . Remove restrictive specification . Coil pressure drop filters and fittings . Compare each . Clean coils . Supply and return pressure drop to duct pressure drop appropriate static . Remove . Obstruction pressure budget obstructions in duct pressure drop and reconnect duct 1e. Airflow Measure Diagnose Repair . Measure . Compare actual . Adjust economizer economizer airflow economizer airflow and at minimum to design airflow controls to meet position design airflow. . Measure . Replace economizer economizer airflow components and at full open position controls or replace economizer 1f. Power Measurement Measure Diagnose Repair . Verify fam motor . Compare measured . Reduce wattage by watt draw for motor watt draw to bringing blower variable speed fans watts reported for motor into spec. . Measure system equipment rating May require system watt consumption . If system Btu renovation and delivered delivered/EER Watts . Pinpoint system system Btu to consumed, continue defects deteriorating calculate installed testing to discover performance and system EER cause of low make needed repairs performance. 2. Temperature Measurements Air temperatures a. Equipment and ambient air temperatures are of little b. Supply and return duct diagnostic worth temperatures unless airflow c. Room temperatures values are d. and combustion circuit measured and temperatures considered. 2a. Equipment and ambient air temperatures Measure Diagnose Repair . Measure dry bulb . Subtract to find . Adjust fan speed temperatures for equipment . Repair defective heating and wet temperature change. equipment parts or bulb temperatures . Considering components for cooling equipment airflow, . Adjust refrigerant . Temperatures and ambient or combustion entering and exiting temperature, circuit the equipment evaluate . Ambient outdoor air temperature change 2a. Equipment and ambient temperatures

Measure Diagnose Repair . Equipment entering . Calculate equipment . Adjust airflow temperature change . Equipment exiting . Test and adjust and duct losses . WB Cooling refrigerant circuit . Compare to required . Test and adjust . DB Heating temperature change combustion circuit . Ambient air temperature 70° 75° 55° 60°

What is the equipment Δt? ______20° What is the system Δt? ______10° What is the return duct Δt? ______5° What is the supply duct Δt? ______5° 2b. Supply and Return Duct Temperatures Measure Diagnose Repair . Measure dry bulb . Subtract to find duct . Decrease duct temperatures system temperature leakage entering and exiting loss or gains. . Install additional the supply and . Total supply and insulation return duct system return temperature . Move ducts into . Measure air changes exceeding conditioned space temperatures in 10% of equipment duct locations ∆t may require repair 2c. Room Temperatures Measure Diagnose Repair . Each rooms air . Compare room . Balance the HVAC temperature (inside temperature system. wall, chest high, differences to . Prescribe building away from evaluate repairs windows, supply temperature registers or heat balance. sources.) 2d. Refrigerant and combustion circuit temperatures Measure Diagnose Repair . Complete airflow, . Compare . Make required temperature, draft combustion Combustion 02 and CO measurements to adjustments measurements and combustion testing (Airflow, venting, . Complete airside standards CO and Combustion measurement . Diagnose airside repairs) before connecting measurements. If . Make required refrigerant gauges needed, connect airside and gauges to continue refrigerant repays diagnostics 3. Btu capacity and delivery

a. System Btu delivery

Sensible Btu = Airflow in cfm x temperature change x 1.08 Total Btu = Airflow in cfm x change x 4.5 3a. Installed System Btu delivery Measure Diagnose Repair . Supply register . Apply the system . Make needed airflow delivered Btu repairs as directed . Average Supply formula by diagnostics Register air . Compare delivered . Typical repairs temperature and Btu to rated Btu include system average return grill . Use additional test renovation, air temperatures data to diagnose balancing, defects adjustment and verification Conclusion – Improve HVAC system delivered capacity

To measure, diagnose and repair is the universal process to improve performance: . Used by surgeons and physicians, consultants, the automotive Industry, accounting firms, manufacturers, engineers and maintenance professionals . HVAC professionals follow this process daily for typical repairs . New technology and training now enables HVAC professionals to measure, diagnose, repair and improve the delivery of HVAC system efficiency. Thank You! From National Comfort Institute For additional information call: 800-633-7058 For the latest training schedule: NCILink.com/ClassSched

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