Phoenix Convention Center Phoenix, Arizona Package DX Units: Performance Optimization Strategy and Field Tests Michael West, PhD, PE Advantek Consulting Engineering, Inc. 1 EXPERT POWERED :: CLIENT DRIVEN

Energy Exchange : Federal Sustainability for the Next Decade Unitary equipment is ubiquitous.  60% of US commercial space is cooled with RTUs (DOE)  54% of commercial building cooling primary energy consumption (EIA)  Total annual installations over 300,000 units  Estimated 1.6 million legacy units operating at low efficiency levels 100,000 units at DoD facilities / 20,000 buildings 100,000 units at USPS facilities / 30,000 buildings 500,000 units at 65,000 “big box” retail stores 2 ROOFTOP PORTABLE PAD MOUNT RTU – Rooftop packaged air-conditioner Unit DOE – U.S. Department of Energy EIA – Energy Information Administration USPS – United States Postal Service Background

Energy Exchange : Federal Sustainability for the Next Decade Background Unitary Efficiency Standards ASHRAE Standard Energy Standard for Buildings Except Low-Rise Residential Buildings ASHRAE Standard Standard for the Design of High-Performance Green Buildings Energy efficiency of unitary systems is much less than that of central plants. Typical large RTU efficiency IEER 11 = 1.09 kW/Ton. New chiller plant efficiency 0.5 kW/ton = IEER 24 Central plants can be over twice as efficient as typical unitary equipment.

Energy Exchange : Federal Sustainability for the Next Decade “ How much cooling you get for the electricity used” Btuh per Watt (MBH per kW)  EER – Energy Efficiency Ratio  Full Ambient  IEER – Integrated Energy Efficiency Ratio  Weighted Full Load & Part 81.5, 68, and 65F Ambient  SEER – Seasonal EER  Part Ambient x (Cyclic Performance Load Factor)  IPLV – Integrated Part-load Value  Legacy rating (no longer standard) Performance Ratings ANSI/AHRI Standard 340/

Energy Exchange : Federal Sustainability for the Next Decade Efficiency and Dehumidification Energy saving goals continue to rise  IEER - Integrated Energy Efficiency Ratio 10.0 to 13.0  EER – Energy Efficiency Ratio 9.7 to 11.7  Single-zone VAV and DDC requirements of Energy Standard , Green Standard , and LEED Dehumidification needs are increasing  Reduced sensible loads means lower SHR -Lower lighting Watts / sqft -Higher insulation R-values -Heat reflective / low-e glass -often addressed with energy intensive reheat  Part-load requirements of IAQ Standard s.5.9 (< 65%rh) 5

Energy Exchange : Federal Sustainability for the Next Decade Overview Facilities struggle with RTU limitations. 1. Basic unitary equipment cannot optimally match varying conditions.  Occupant diversity  Changes in ambient conditions from morning, to afternoon, to evening  Variations in weather from day to day  Seasonal differences between early, mid, and late summer 2. Energy managers have no easy way to operate and monitor units for maximum energy efficiency. 3. HVAC technicians rely on indirect indicators of performance.  Visual coil inspections  Refrigerant pressures  Manufacture date on nameplate  Occupant complaints 6

Energy Exchange : Federal Sustainability for the Next Decade Package unit design is a compromise in energy efficiency and dehumidification.  Controls cannot adjust operation to match climate. Loads drastically differ in Florida, California, Arizona, Illinois, …  In many applications at part-load – latent capacity is inadequate. Expensive reheat or hot-gas bypass is used for dehumidification.  Current designs maximize efficiency at AHRI rating points only. Factory controls were augmented with optimizing technology, and rigorous field tests of energy efficiency and dehumidification performance were carried out.  Demonstrated advantages of optimizing RTU control technology.  Technology installed on three RTUs in diverse climates.  Intensive monitoring and performance analysis over two cooling seasons. Overview

Energy Exchange : Federal Sustainability for the Next Decade Ambient Air Evaporator Coil Condenser Coil Compressor TXV Basic DX Cycle Supply Air

Energy Exchange : Federal Sustainability for the Next Decade Revises the traditional refrigeration cycle at a fundamental level. Improvement of evaporator refrigerant / two-phase heat transfer. Increased suction density improves compressor volumetric efficiency. Variable sensible heat ratio optimizes airside performance. REFRIGERANT CIRCUIT COIL HEAT TRANSFER TXV – Thermostatic Expansion Valve 9 Modified DX Cycle

Energy Exchange : Federal Sustainability for the Next Decade Significance of DX Modification Releases constraints on operating parameters. 1. Airflows, temperatures, and refrigerant can be optimized 2. Variable-Volume Constant-Temperature (VVCT) 3. Increase latent capacity as needed 4. Variable SHR (VSHR) 5. Single-Zone VAV 10

Energy Exchange : Federal Sustainability for the Next Decade Optimizing Control Technology Controls all operating parameters Target is maximum EER while meeting sensible and latent loads Continuously adjusts:  Supply Blower Speed  Condenser Fan Speed  Refrigerant Charge  Supply Air Temperature  Coil Temperature  Economizer Damper Continuously reports:  EER, IEER, Tons Capacity  Faults  Diagnostics 

Energy Exchange : Federal Sustainability for the Next Decade RTU Controller GUI Any Web Device Tablet, Smart Phone, Laptop Cloud Servers PHP WebSocket Data Connectivity LAN VPN or commercial WAN Monitor Only

Energy Exchange : Federal Sustainability for the Next Decade Optimizing Control Package Liquid-Suction Heat Exchanger Accumulator Bypass Damper Variable Frequency Blower Drive Adjustable Thermostatic Expansion Valve VFD Condenser Fan 13 Modified Package Unit

Energy Exchange : Federal Sustainability for the Next Decade Modified Package Unit

Energy Exchange : Federal Sustainability for the Next Decade 15 Site 1: Retail Store Beaufort, South Carolina 2627 cooling degree-days Climate zone 3A Warm-Humid South Carolina Field Tests

Energy Exchange : Federal Sustainability for the Next Decade ton dual-circuit R-22 package DX unit Gas Heat Manufactured 2/2003 Found in “poor” condition Fresh air intake Gas heating section Compressors South Carolina Field Tests

Energy Exchange : Federal Sustainability for the Next Decade 17 Interior is typical of a large retail store Setpoint 74F day, 80F night South Carolina Field Tests

Energy Exchange : Federal Sustainability for the Next Decade California Site 2: Classroom Building Mojave, California Elevation 2500 feet Climate zone 3B Hot-Dry 3225 cooling degree-days 2597 heating degree-days Field Tests

Energy Exchange : Federal Sustainability for the Next Decade 12½-ton dual-circuit R410a package DX unit Heat Pump Installed 2010 California Field Tests

Energy Exchange : Federal Sustainability for the Next Decade 20 Site 3: Electronics Development Laboratory Cape Canaveral, Florida 3633 cooling degree-days, Climate zone 2A Hot-Humid Florida Field Tests

Energy Exchange : Federal Sustainability for the Next Decade 21 8½-ton dual-circuit R410a package DX unit 9 kW-heat Installed 1/2012 Florida Field Tests

Energy Exchange : Federal Sustainability for the Next Decade 22 Interior zone is a precisely controlled electronics development laboratory temperature 74F  1 degree-F, 45% humidity  5%rh Florida Field Tests

Energy Exchange : Federal Sustainability for the Next Decade Sensors on each RTU Compressor Amps (2) Fan and Blower Amps Total Unit Power Refrigerant Pressures (4) Refrigerant Temperatures (12) Refrigerant Flows (2) Air Temperatures at thermostat, return, outdoor, coil, entering & leaving coil, unit discharge Air Humidity coil entering, unit discharge, at thermostat, outdoor Space and Ambient CO 2 level Control point status Performance Measurement Data available live via web link Performance Analysis

Energy Exchange : Federal Sustainability for the Next Decade 24 Analysis

Energy Exchange : Federal Sustainability for the Next Decade Four operating conditions satisfy the IEER rating criteria set forth in ANSI/AHRI Standard 340/  A, B, C, and D rating conditions 95F, 81.5F, 68F, and 65F ambient  Linear interpolation between field-measured data points by section  “EER is determined by plotting the tested EER vs. the percent load and using straight line segments to connect the actual performance points.” Operational IEER calculated with respect to section IEER = (0.020 A) + (0.617 B) + (0.238 C) + (0.125 D) where A, B, C, and D are the interpolated / field-measured EERs (Btuh per Watt) Accuracy  Field-estimated IEER is ±4.7% or ±0.6 Btuh/Watt via sensitivity / propagation of error uncertainty analysis  All comparisons performed with data from same sensors installed in same positions, therefore uncertainty in the baseline field-estimated IEER equally applies to the modified unit’s field-estimated IEER (high or low) 25 Performance Analysis

Energy Exchange : Federal Sustainability for the Next Decade Field Test Results

Energy Exchange : Federal Sustainability for the Next Decade Field Test Results

Energy Exchange : Federal Sustainability for the Next Decade 28 Field Test Results

Energy Exchange : Federal Sustainability for the Next Decade 29 Field Test Results

Energy Exchange : Federal Sustainability for the Next Decade 30 Field Test Results

Energy Exchange : Federal Sustainability for the Next Decade Results Summary Efficiency increase ranged from 15% to 37% Operational IEER raised by 1.9 to 2.9 points Comparable improvement in EER vs IEER CA unit showed most improvement

Energy Exchange : Federal Sustainability for the Next Decade Economic Analysis Technology cost basis: $4,500 Discount rate: 3.0%

Energy Exchange : Federal Sustainability for the Next Decade Economics IEERCost$ / Ton Flagship Model * ,6662,053 Midline Model11.411, Modified Base Model13.714,1661,133 Cost comparison of three 12½-ton package units. * Flagship model with variable speed inverter scroll compressors, plenum airfoil fans, electronic expansion valves, proprietary digital controls

Energy Exchange : Federal Sustainability for the Next Decade Conclusion 34 Optimizing RTU Control Technology