Phoenix Convention Center • Phoenix, Arizona
Package DX Units: Performance Package DX Units: Performance Optimization Strategy and Field Optimization Strategy and Field TestsTests
Package DX Units: Performance Package DX Units: Performance Optimization Strategy and Field Optimization Strategy and Field TestsTests
Michael West, PhD, PEAdvantek Consulting Engineering, Inc.
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EXPERT POWERED :: CLIENT DRIVENEXPERT POWERED :: CLIENT DRIVENEXPERT POWERED :: CLIENT DRIVENEXPERT 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 buildings100,000 units at USPS facilities / 30,000 buildings500,000 units at 65,000 “big box” retail stores
2ROOFTOP PORTABLE PAD MOUNT
RTU – Rooftop packaged air-conditioner UnitDOE – U.S. Department of Energy
EIA – Energy Information AdministrationUSPS – United States Postal Service
Background
Energy Exchange: Federal Sustainability for the Next Decade
Background
Unitary Efficiency Standards 6 – 11 12 – 20 21 – 60
Tons Tons TonsSEER
All 13 11.2 11 9.9 9.6All 14 10.3 10
50% Savings Beyond
90.1
All 15 12.8 12.3 11.3 10.9
- 18 - - -DOE High Performance
RTU Challenge
ASHRAE Climate
Zone
ASHRAE Standard
11.5
11.4 11.2 10.4
11.2
Adv
ance
d En
ergy
Des
ign
Gui
des
30% Savings Beyond
90.1
1,213
3-5
> 60 Tons
IEER90.1
189.1 11.8
5 Tons <
ASHRAE Standard 90.1-2010 Energy Standard for Buildings Except Low-Rise Residential BuildingsASHRAE Standard 189.1.-2009 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.
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“ How much cooling you get for the electricity used”Btuh per Watt (MBH per kW)
EER – Energy Efficiency Ratio Full Load @95F Ambient
IEER – Integrated Energy Efficiency Ratio Weighted Full Load & Part Load @95, 81.5, 68, and 65F Ambient
SEER – Seasonal EER Part Load @82F Ambient x 0.875 (Cyclic Performance Load Factor)
IPLV – Integrated Part-load Value Legacy rating (no longer standard)
Performance Ratings
ANSI/AHRI Standard 340/360-2007
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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 90.1-2013,
Green Standard 189.1-2014, 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 62.1-2013 s.5.9 (< 65%rh)
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OverviewFacilities 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
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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
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Ambient Air
Evaporator Evaporator CoilCoil
Condenser Condenser CoilCoil
CompressorCompressor
TXVTXV
Basic DX Cycle
Supply Air
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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
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Modified DX Cycle
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Psychrometric Chart, 101.193 kPa
TechniSolve Software cc
Temperature, °F94929088868482807876747270686664626058565452504846444240383634
Hum
idity,
gr/
lb
130
128126124122
120118116114
112110108106
10410210098
96949290
88868482
80787674
72706866
64626058
56545250
48464442
40
Node2
Node1
Node3
Node7
Node8
Node9
MixBranch2
MixBranch1
Cooler2
Significance of DX ModificationReleases 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
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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 http://www.EERoptimizer.com/
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RTUControllerGUI
Any Web DeviceTablet, Smart Phone, Laptop
Cloud Servers
PHP
Web
Sock
et
Data ConnectivityData Connectivity
LAN
VPN
or c
omm
erci
al W
AN Monitor Only
Energy Exchange: Federal Sustainability for the Next Decade
Optimizing Control Package
Liquid-Suction Heat Exchanger
Accumulator Bypass Damper
VariableFrequencyBlowerDrive
AdjustableThermostaticExpansionValve
VFD Condenser Fan
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Modified Package Unit
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Site 1: Retail StoreBeaufort, South Carolina2627 cooling degree-daysClimate zone 3A Warm-Humid
Sou
th C
arol
ina
Field Tests
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20-ton dual-circuitR-22 package DX unit Gas HeatManufactured 2/2003Found in “poor” condition
Fresh air intakeGas heating section
Compressors
Sou
th C
arol
ina
Field Tests
Energy Exchange: Federal Sustainability for the Next Decade17
Interior is typical of a large retail storeInterior is typical of a large retail storeSetpoint 74F day, 80F nightSetpoint 74F day, 80F night
Sou
th C
arol
ina
Field Tests
Energy Exchange: Federal Sustainability for the Next Decade
Ca
lifo
rnia
Site 2: Classroom BuildingMojave, CaliforniaElevation 2500 feet
Climate zone 3B Hot-Dry 3225 cooling degree-days2597 heating degree-days
Field Tests
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12½-ton dual-circuitR410a package DX unitHeat PumpInstalled 2010
Ca
lifo
rnia
Field Tests
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Site 3: Electronics Development LaboratoryCape Canaveral, Florida3633 cooling degree-days, Climate zone 2A Hot-Humid
Flo
rida
Field Tests
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8½-ton dual-circuitR410a package DX unit9 kW-heat Installed 1/2012
Flo
rida
Field Tests
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Interior zone is a precisely controlledInterior zone is a precisely controlledelectronics development laboratoryelectronics development laboratorytemperature 74F temperature 74F 1 degree-F, 45% humidity 1 degree-F, 45% humidity 5%rh5%rh
Flo
rida
Field Tests
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45 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 Humiditycoil entering, unit discharge, at
thermostat, outdoor• Space and Ambient CO2 level• Control point status
Performance Measurement Data available live via web linkhttp://www.tinyurl.com/CCAFS-EDL
Performance Analysis
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Four operating conditions satisfy the IEER rating criteria set forth in ANSI/AHRI Standard 340/360-2007 A, B, C, and D rating conditions 95F, 81.5F, 68F, and 65F ambient Linear interpolation between field-measured data points by section 6.2.2
“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 6.2.2IEER = (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)
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Performance Analysis
Energy Exchange: Federal Sustainability for the Next Decade
35
40
45
50
55
60
65
70
75
80
66 68 70 72 74 76 78 80
Dry Bulb Temperature F
Rela
tive H
um
idit
y %
rh
35
40
45
50
55
60
65
70
75
80
66 68 70 72 74 76 78 80
Dry Bulb Temperature F
Rela
tive H
um
idit
y %
rh MCASB System SHR vs Space RH
y = 9E-05x2 - 0.0224x + 1.6039
R2 = 0.2827
0.40
0.50
0.60
0.70
0.80
0.90
1.00
30
35
40
45
50
55
60
65
70
75
80
SPACE %RH
CA
LC
ULA
TE
D S
HR
MCASB System SHR vs Space RH
y = 9E-05x2 - 0.0224x + 1.6039
R2 = 0.2827
0.40
0.50
0.60
0.70
0.80
0.90
1.00
30
35
40
45
50
55
60
65
70
75
80
SPACE %RH
CA
LC
ULA
TE
D S
HR
Field Test Results
Energy Exchange: Federal Sustainability for the Next Decade
Damper Position Control Signal vs RHTest Site: Beaufort, SC
0
20
40
60
80
100
40 45 50 55 60 65 70
Space Relative Humidity [%rh]
% D
am
pe
r O
pe
n
OpeningClosing
Condenser Fan Speed Signal vs OATTest Site: Beaufort, SC
0
20
40
60
80
100
50 60 70 80 90 100
Outside Air Temperature [F]
% S
pe
ed
Stage 2
Stage 1
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
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Economic Analysis
Technology cost basis: $4,500Discount rate: 3.0%
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Economics
IEER Cost $ / Ton
Flagship Model * 18.5 25,666 2,053
Midline Model 11.4 11,857 949
Modified Base Model 13.7 14,166 1,133
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