Energy Auditing Techniques for
Small Commercial Facilities
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9/20 9/22 9/24 9/26 9/28 9/30 10/2 10/4
Sean Harleman, kW Engineering
HVAC Systems
Learning Objectives
•
•
•
•
•
Recognize common system types and controls
Understand economizers and outside air
Gather useful nameplate data
Provide recommendations for replacements
Do some simple energy savings calculations
Energy Auditing Techniques
Energy Auditor Role and Activities
Basic
• Inspect HVAC equipment
• Record nameplate information
• Review equipment operating schedules and controls
• Develop a list of energy efficiency measures (EEMs)
• Present EEMs, savings, incentives, and costs to the client
Advanced
• Above items plus:
• Log existing power use (status, amps, or kW)
• Log economizer operation (OAT, MAT, etc.)
Energy Auditing Techniques
HVAC Fundamentals
• Heating
– Offset heat that is lost to the environment
– Temper ventilation air
• Ventilating
– Provide fresh air to building occupants
• Air Conditioning (or Cooling)
–
–
–
–
Offset heat that gained from the environment
Offset heat generated internally
Control interior moisture (Relative Humidity)
Temper ventilation air
Energy Auditing Techniques
Why is HVAC Important?
CA Commercial Sector Electricity Use
California Commercial End Use Survey, Itron, CEC-400-2006-005.
Energy Auditing Techniques
Primary Purposes of HVAC
1. Comfort for occupants (ASHRAE 55)
– Temperature
– Humidity
– Air movement
2. Fresh air (ASHRAE 62.1 & T24)
– We need about 15 cfm per person (occupancy)
– Remove dust, pollutants, contaminants
& “bio-effluents”
Energy Auditing Techniques
Heat Sources, Sinks & Paths
• Envelope
– Solar
– Conduction
• Ventilation Air
– Required for IAQ
• Internal Loads
–
–
–
–
Lighting
Computers
Equipment
People
Energy Auditing Techniques
What is a HVAC Zone?
• A discreet physical area
that is conditioned by an
HVAC system
• Heat enters/leaves a zone
through Conduction,
Convection and Radiation
• Borders on zones are not
always clear, obvious, or
tangible
• Distinct zones in HVAC
system marked by
separate thermostats
Return
Air
Exhaust
Air
Outside
Air
Energy Auditing Techniques
COLD
HOT
Single Zone HVAC System
Return
Air
Exhaust
Air
Outside
Air
COLD
HOT
T
Energy Auditing Techniques
Primary Cooling Technologies
• Mechanical Cooling
– Unitary equipment uses a direct expansion (DX)
cooling coil
• accounts for ≈ 67% of all commercial and ≈ 90% of all
small commercial
• this will be our focus today
– Chilled water systems used in large buildings
en.wikipedia.org
Energy Auditing Techniques
Unitary HVAC Equipment
• Unitary refers to equipment where components are
matched and rated together. These components include
a compressor, condenser, evaporator and fan.
• Unitary equipment has two main classes: Packaged and
Split-System
– Packaged equipment houses all components in the same
enclosure
– Split-Systems have the compressor & condenser in one
enclosure and the evaporator and fan in another, connected by
refrigeration tubing
• Units can be cooling only or cooling with heating
• All units circulate air, most provide ventilation
Energy Auditing Techniques
Unitary Equipment Identification
• Packaged Unit
– All components contained in one location
– Ventilation is introduced through the unit
– Heating is supplied by a gas furnace, heat pump,
electric resistance or a hot water coil
http://www.carrier.com
Energy Auditing Techniques
Packaged Unit Components
Economizer
EA
OA
Cooling
Coils
SA
Filter
Condenser
Fan and
Coils
Heating
Supply Fan Coils
RA
Controls
T
Thermostat
Compressor
Packaged Unit
Energy Auditing Techniques
Building
Packaged With Horizontal Discharge
http://www.carrier.com
Energy Auditing Techniques
Packaged With Vertical Discharge
http://www.carrier.com
http://www.carrier.com
Energy Auditing Techniques
Unitary Equipment Identification
• Split-System
– Compressor Component Only
– No Ventilation provided by unit
– Only heating is heat pump
http://air-condition-units.com
Energy Auditing Techniques
Split-System
www.carrier.com
Energy Auditing Techniques
Split-System Examples
www.geo4va.vt.edu/A3/A3.htm
Energy Auditing Techniques
Split-System Examples
www.amvair.com/typesofac.html
www.letricharddoit.com/products.htm
Energy Auditing Techniques
Unclear on the concept
Energy Auditing Techniques
Primary Cooling Technologies
• Mechanical cooling (e.g. DX) energy use can be
reduced through the use of economizers and
evaporative cooling
• HVAC equipment is sized for design day loads,
but operates the majority of the time under part
load (~30-50% average is typical)
Energy Auditing Techniques
Economizers
• The economizer cycle refers to using controls and
dampers to make use of outside air for “free” cooling
when it makes sense
• Controls used to bring in outside air instead of return
air
• An “economizer” is generally not a single piece of
equipment, although people may refer to it as such
Return
Air
Exhaust
Air
Outside
Air
Energy Auditing Techniques
COLD
HOT
Economizer Offsetting All Cooling
Return Air
10,000 CFM, 75 deg F
Exhaust Air
8,000 CFM
2,000 CFM
Cooling Heating
Coil
Coil
Outside Air
8,000 CFM,
50 deg F
Discharge Air
10,000 CFM,
55 deg F
Mixed Air
10,000 CFM,
55 deg F
Energy Auditing Techniques
Reduced Mechanical Cooling
Return Air
10,000 CFM, 75 deg F
Exhaust Air
10,000 CFM
0 CFM
Cooling Heating
Coil
Coil
Outside Air
10,000 CFM,
60 deg F
Discharge Air
10,000 CFM,
55 deg F
Mixed Air
10,000 CFM,
60 deg F
Energy Auditing Techniques
Air Side Economizer
• Easy to show it’s not working, harder to show that it is
working
• Spot checks not conclusive; must trend data over time
– Is the economizer bringing in 100% outside air when
appropriate?
– Is the system always providing minimum ventilation air?
Energy Auditing Techniques
Economizer Expected Performance
Expected Economizer Operation
80
Minimum outside air
75
Outside Air Temperature
65
Return Air Temperature
60
55
Mixed Air Temperature
Supply Air Temperature
100% Outside air
50
45
40
Mixed return and outside air
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Temperature
70
Noon
Midnight
Time
Energy Auditing Techniques
Economizer Expected Performance
• Data taken from a
study in Southern
California
Average Compressor Loading
100%
90%
80%
Desert
• Building type is
Small Office
• Percent Loaded is
calculated as
Compressor Run
Hours / by Total
Cooling Hours
Percent Loaded
70%
60%
Inland Valley
50%
40%
Inland
30%
Coastal
20%
10%
0%
Energy Auditing Techniques
Climate
Economizer
No Economizer
Economizers: Implementation
• Assess economizer operation by observing damper
positions for various ambient conditions
• Use temperature data loggers to better estimate
economizer performance
• Consider add-on economizer kits for existing units
with failed economizers
• Check for adequate relief for outside air
Energy Auditing Techniques
Evaporative Cooling
• Cools air via evaporation of
water
• Direct evaporative coolers draw
air through evaporative media
lowering the temperature and
increasing humidity
• Indirect evaporative coolers use
a heat exchanger to reduce the
air temperature without
increasing humidity; less
effective
Energy Auditing Techniques
www.muntersamerica.com/
Direct Evaporative Cooling
www.wikipedia.com
This image has been (or is hereby) released into the public domain by its creator, Buster2058. This applies worldwide.
Energy Auditing Techniques
Evaporative Cooling: Implementation
• Best when high percentage of outside
air is required
• Supply air temperature limited by
ambient conditions
• Direct evaporative cooling is best
suited for areas where high humidity
won’t cause problems
• Indirect evaporative cooling can be
used when humidity needs to be
controlled or mechanical cooling will
also be used
Direct Evaporative Cooler
www.muntersamerica.com/
Energy Auditing Techniques
Primary Heating Technologies
• Gas Furnaces are the most common source for heat in small
commercial applications
– Range of efficiencies available
– Forced & Induced draft
• Electric Heat Pumps provide both heating and cooling
– Air source
– Water Source
– Ground Coupled
highperformancehvac.com
• Electric Resistance Heat Strips can be convenient if natural gas is
limited or combustion exhaust is an issue, but Heat pumps are
more energy efficient
• Hot water or Steam coils can also be used, but are generally found
in larger systems or systems with many zones
Energy Auditing Techniques
Air Source Heat Pump
Utilizes same vapor compression refrigeration cycle, only
now the condenser can be used to add heat to the space
Energy Auditing Techniques
Air Source Heat Pump
oee.nrcan.gc.ca/publications/infosource/pub/h.
..
Energy Auditing Techniques
Air Source Heat Pump
oee.nrcan.gc.ca/publications/infosource/pub/h.
..
Energy Auditing Techniques
Air Source Heat Pump
• Use air as heat sink
• Therefore:
Efficiency depends on air temperatures (minimum outside
operating temperature is ~ 17 °F)
• Typically smaller systems / single zone
• Best applicability: mild climates
• SEERs range from 8 to 16
• Title 20 Sets minimum
standards by size
• Also:
www.fmcs.coop/.../electrical_heat/air_source.htm
– Water Source
– Ground Coupled
Energy Auditing Techniques
Field Identification of HVAC Zones
• Ask facility staff/engineer
• Review as-built mechanical
drawings
• Inventory the number of
thermostats and HVAC units
• Observe placement of units to
thermostats
• Last resort: go after hours and
observe response to changed
setpoints
Energy Auditing Techniques
Unitary HVAC Nameplate
•
•
•
•
Brand/Model #
Age
Voltage/Amperage/kW
Other information:
–
–
–
–
–
–
Rated efficiency
Heating/cooling capacity
Air flow rate
Liquid flow rate
Pressure rise
Refrigerant
Energy Auditing Techniques
It’s not always easy to get the size
Energy Auditing Techniques
It’s not always easy to get the size
Energy Auditing Techniques
Reinforcement Activity
• HVAC system exercise…
Energy Auditing Techniques
Energy Efficiency Opportunities
• Retrofits
– High Efficiency Units
– Evaporative Cooling
• Controls
– Scheduling / reduce operating
hours
– Programmable thermostats
– Economizer operation
– Demand control ventilation
• Operations
– Reduce cooling loads
– Keep units maintained
Energy Auditing Techniques
www.carrier.com
High Efficiency Replacements
• Package unit replacement isn’t generally cost
effective on energy savings alone
• So where are the opportunities?
– Older units
– Early retirement
– New additions
• How do we promote it?
– Comfort
– Reliability
– Reduced O&M Costs
www.trane.com
Energy Auditing Techniques
What to specify: Unitary AC and HP
• For larger units, use
Consortium for Energy
Efficiency (CEE) guidelines
(www.cee1.org)
• Specify Tier 1 or 2
Efficiency level
www.trane.com
Energy Auditing Techniques
What to specify: Unitary AC
© 2009 Consortium for Energy Efficiency, Inc. All rights reserved. www.cee1.org
Energy Auditing Techniques
What to specify: Heat pumps
© 2009 Consortium for Energy Efficiency, Inc. All rights reserved. www.cee1.org
Energy Auditing Techniques
Unitary HVAC: Calculations
• Average Demand
– kW = (Cooling CapacitykBtu/h) / (SEER)
• Annual Energy Use
– kWh/yr = (kW) * (hours per year)
Energy Auditing Techniques
Evaporative Pre-cooling
• Lower head
pressure by precooling condenser
air by direct
evaporation
• New units use
microprocessor
controls to minimize
excess water
• Water off for
outside air temps
less than 70°F
• Evaporative pre-cooling is
available as add-on kit to fit
many unitary systems
Energy Auditing Techniques
Evaporative Pre-cooler Details
Energy Auditing Techniques
Evaporative Pre-cooler Details
Energy Auditing Techniques
Evaporative Pre-Cooling
Dining Unit 1 Evaporative Condenser Performance
85
Temperature exiting media (F)
80
75
70
65
60
55
55
60
65
70
75
80
Temperature entering media (F)
Energy Auditing Techniques
85
90
95
100
Evaporative Pre-cooler
Energy Auditing Techniques
Control Measures
• On/off
• Setbacks
• Demand Control Ventilation
Energy Auditing Techniques
The Opportunity: Controls
General Concepts
• Controls are generally the most cost
effective of EEMs
• Whatever doesn’t have controls
probably needs it
• Controls reduce opportunity for
human “enhancements”
• Limit hours of operation
• Use to maximize system
efficiencies
Energy Auditing Techniques
Scheduling
• Mechanical Time Clocks
http://www.moonlightinglls.com/
Energy Auditing Techniques
Commissioning is key
Even with simple equipment
Energy Auditing Techniques
Setbacks and Programmable Thermostats
• Install Programmable
Thermostats on all units
• Scroll through settings
during audit
www.white-rodgers.com
Energy Auditing Techniques
Where there’s a will…
Energy Auditing Techniques
Setback Thermostats / Scheduling
• Pitfalls
– Need to be set correctly, not in “hold”
mode
– Persistence: document with a system
manual how things are intended to work
• Savings
– Range widely depending on occupancy
and use. Typical is 5% to 50%.
– Demand savings are minimal
• Non-Energy Benefits
– Reduced wear on equipment
Energy Auditing Techniques
www.white-rodgers.com
Web-enabled Thermostats
• Web-based now
available
• About $170 to $300
each
• Include ability to
monitor remotely
www.proliphixstore.com
Energy Auditing Techniques
For Classroom Control
• Occupancy-based HVAC
controls e.g. Bard CS2000
Energy Monitor
• “Learns” occupancy patterns
• No programming required
• Can control lighting too
• Outside air off when unoccupied
www.proliphixstore.com
www.doersales.com
Energy Auditing Techniques
Demand Control Ventilation (DCV)
• Primary purpose of HVAC is to provide
adequate ventilation
• Basic method has been to provide
sufficient ventilation for design
conditions at all times
• DCV provides sufficient ventilation
based on actual occupancy, rather than
worst case
• Requires continuous monitoring of CO2
as proxy for occupancy
Energy Auditing Techniques
DCV: CO2 and Ventilation Rates
Energy Auditing Techniques
DCV: Implementation
• All major controls companies support
• Best practice is to measure outside air and indoor air CO2
concentrations
• If only indoor concentrations monitored, typical outside CO2
concentration is 400 ppm
• Controls typically set to introduce OA when indoor concentration
is about 500 ppm higher than outside (T-24 requires 600 or better)
• DCV should be overridden when system in economizer mode
• Commission to ensure ventilation rates are not compromised
• Select equipment that automates building purge for overnight
buildup of contaminants
Return
Air
Exhaust
Air
Outside
Air
Energy Auditing Techniques
COLD
HOT
Load Shifting for Small Commercial
• “Ice Bear” makes ice at
night for use the next day
• Thermal Energy Storage
• Capacity = 5 tons
• Storage = 30 tonhrs
• Primary savings are in
cost of energy due to load
shifting
• Peak kW cost savings
• May have small energy
savings too, depending…
Energy Auditing Techniques
www.ice-energy.com
Ice Bear Installations
www.ice-energy.com
Energy Auditing Techniques
Ice Bear Performance
www.ice-energy.com
Energy Auditing Techniques
Operations and Maintenance
•
•
•
•
Commissioning: check set points, schedules and resets
Check for controls overrides (e.g. bypassed time-clocks)
Filter changes for IAQ
Check fixed damper and minimum damper positions
• Adjust/tighten/replace belts
• Lubricate rotary equipment
Energy Auditing Techniques
Operations and Maintenance (cont.)
•
•
•
•
•
Clean condenser coils
Clean evaporator coils
Insulate suction lines
Check refrigerant charge
Check thermostat/sensor
calibration
• Insulate/seal ductwork
Energy Auditing Techniques
O&M horrors from HVACfun.com
Energy Auditing Techniques
www.energy.ca.gov/pier
PIER Buildings Program Design Guide: Big Savings on Small HVAC Systems
Small HVAC: Frequent Issues
Energy Auditing Techniques
Reinforcement Activity
• HVAC calculation system exercise…
Energy Auditing Techniques
Key Points to Remember
• Economizers fail frequently and make a big difference in
CA climates
• HVAC units are sized for design-day conditions, but
typically operate at 40-50% load
• Calculating unitary HVAC annual energy use:
Energy (kWh/yr ) = [Capacity (kBtu/h) *hours (hr)] / SEER
• Evaporative pre-cooling can yield big savings in dry
climates
• Record the entire model number from HVAC units
• DCV provides savings for building with variable
occupancies
Energy Auditing Techniques
References and Resources
• PG&E http://www.pge.com/mybusiness/
• Database for Energy Efficiency Resources
http://www.deeresources.com
• CEC Guide to Preparing Feasibility Studies for Energy Efficiency
Projects www.energy.ca.gov/efficiency
• Consortium for Energy Efficiency(guidelines for specifying EERs
& rough costs/savings) www.cee1.org
• Energy Design Resources www.energydesignresources.com
• Washington State University (calculators & other resources)
www.energyexperts.org
Energy Auditing Techniques
Course Tracker
Please take a moment to fill out your
Course Tracker excel sheet.
Energy Auditing Techniques
What is that?
1. Split - condenser
2. Packaged unit
3. Exhaust fan
4. Split - evaporator
A.
C.
Exhaust fan
Split - evaporator
B.
Packaged Unit
D.
Split - condenser
Energy Auditing Techniques
Model number: DPS-007-AHCY3
1. Cooling capacity: 7.5 tons
3. Line voltage: 230
2. EER: High? Need more info 4. Heating type: None
Energy Auditing Techniques
Appendix
Energy Auditing Techniques
VFD’s for Fans
• Many systems use variable flow
air distribution
• Fan power laws dictate that
power is roughly proportional to
the flow rate cubed
• VFD quality/reliability have
improved greatly over time
• VFD costs have dropped
significantly with wider adoption
• Now required by code for many
applications in new construction
Energy Auditing Techniques
www.abb.com
Why Fans with VFD’s Save Energy
VFD
100%
Power
80%
60%
40%
20%
0%
0%
20%
40%
60%
80%
100%
Flow
This relationships between fan energy and fan flow are taken from the California Energy Commission Guide to
Preparing Feasibility Studies and the 1998 Nonresidential ACM Approval Manual. Note that a typical system curve,
DOE2 default, is assumed and these relationships are not applicable to all systems.
Energy Auditing Techniques
A Note on IPLV
• IPLV is being replaced by IEER
– Integrated Energy Efficiency Ratio (IEER)
– IEER Used for unitary equipment ≥ 65 kBtu/h
– AHRI is dropping use of IPLV because it did not
accurately represent efficiencies for units with multistage compressors
– AHRI Standard 340/360 2007 defines IEER as "a
single number figure of merit expressing cooling partload EER…”
– Incorporated by addendum into ASHRAE 90.1 2007
– Not yet adopted by CEE, but soon
Energy Auditing Techniques
A Note on IPLV
• Source: http://www.cee1.org/com/hecac/Prog_Guidance_IEER.pdf
Energy Auditing Techniques
DCV Savings
www.energy.ca.gov/pier
PIER Buildings Program Design Guide: Commercial Buildings Breathe Right with Demand-Controlled Ventilation
Energy Auditing Techniques
DCV Savings
Case studies
show real
energy savings
with payback
periods of 2
years or less
www.energy.ca.gov/pier
PIER Buildings Program Design Guide: Commercial Buildings Breathe Right with Demand-Controlled Ventilation
Energy Auditing Techniques
Water-source Heat Pumps
•
•
•
•
•
•
•
•
•
AKA “California Heat Pump” system
Uses water loop as heat sink
Requires supplemental heat rejection/supply
Cooling mode: rejects heat water loop
Heating mode: absorbs heat from water loop
Efficiency depends water loop temperatures
Typically mid-sized commercial systems / multiple zone
Best applicability: mild climates
Title 20 Sets minimum
standards by size
McQuay Water Source Heat Pump Design Manual, C:330-1
Energy Auditing Techniques
McQuay Water Source Heat Pump Design Manual, C:330-1
Water-source Heat Pump Configuration
Energy Auditing Techniques
Equipment Efficiencies
• Efficiency: Ratios developed to represent equipment
ability to transfer or generate heat relative to the input
energy required by that equipment
• COP - Coefficient of Performance (unit less)
What you get divided by what you pay for (in same units)
• EER - Energy Efficiency Ratio (BTU/Watt-hrs)
Fully loaded unit output / electrical input
• SEER - Seasonal Energy Efficiency Ratio (BTU/Watt-hrs)
Average output over a range of conditions / Electrical
input
• IPLV - Integrated Part Load Value (units vary)
Weighted average at four part load conditions
• HSPF - Heating Seasonal Performance Factor
(BTU/Watt-hrs) Similar to SEER (same units) but for Heat
Pump heating
• AFUE - Annual Fuel Utilization Efficiency (%)
Efficiency of gas furnaces and small boilers measured as
the useful energy output divided by the input
Energy Auditing Techniques
Equipment Efficiencies
Equipment Type
Single Point Efficiency
Multi-Point or
"Seasonal" Efficiency
Chiller
Packaged AC
Furnace
Boiler
Heat Pump
kW/Ton
COP / EER
Thermal Efficiency
Combustion Efficiency
COP / EER
IPLV
SEER / IPLV
AFUE
AFUE (<300kBTUh)
HSPF
Energy Auditing Techniques
Units
• Energy
– Btu = Raises the temperature of 1 pound of
water 1 degree Fahrenheit under standard
conditions
– Watt-Hour = 3.413 Btu
– kilowatt-hr = 1000 Watt-hours = 1 kWh
– 100,000 Btu = 100 kBTU = 1 therm
• Rates (units of energy per time)
– Watt = 3.413 Btu/h (Btu’s per hour)
– kilowatt = 1000 Watts = 1 kW
Energy Auditing Techniques
Handy Equations
• Motor Draw
– kWh = (hp)(0.746 kW/hp)(%Loaded)(hours)/Efficiency
– kWh = (FLA)(Volts)(PF)(%Loaded)(hours)(Phase^½)
• Conduction
– Btu/h = (U-Value)(Area in sq ft)(Toutside-Tinside)
– Surface heat gain/loss due to Convection & Radiation
• Ventilation / Infiltration
– Btu/h = (1.085)(CFM)(Toutside-Tinside)
• Radiation
– Btu/h = Assess qualitatively
Energy Auditing Techniques
More Handy Equations
• Efficiency Conversions
– kW/ton = 12 / EER
– COP = EER / 3.412
– COP = 3.516 / (kW/ton)
• Heat Transfer in Water
– Capacity (kBTUh) = GPM * ΔT / 2
• Power from hp
– Power (kW) = 0.746 * Power (hp)
• Pump power
–
–
–
–
Water Power (hp) = (ft of head) * (GPM) / 3960
Pump Power = Water Power / [Pump eff * Motor eff]
Fan power
Fan Power (hp) = (cfm)*(SP) / [6354*ήfan* ήmotor]
Energy Auditing Techniques
Estimating Savings – Billing Data
• Estimate amount of bill dedicated to air
conditioning
• Estimate the average efficiency of the existing
equipment - SEER
• Select new efficiency based on available
equipment
• Estimate savings as:
 SEERExist 
NewBill  OldBill 

 SEERproposed 
SEERExist 


or Savings  OldBill 1 
 SEERproposed 
Energy Auditing Techniques
Estimating Savings
• Simplified Full
Load Hour
Calculation
• Bin Simulation
• SPC Software
– PGE.COM/SPC
– Order CD
Single Zone Simulation (Constant Volume)
Supply Air
Flow rate
(CFM)
Fan kW
3
Supply Air
Average
Space
Temp (F)
Avg RAT
(F)
72
Bin Midpoint
10.00
OSA LO (F)
0
107.5
102.5
97.5
92.5
87.5
82.5
77.5
72.5
67.5
62.5
57.5
52.5
47.5
42.5
37.5
32.5
27.5
22.5
4
10
38
74
114
163
219
263
318
436
558
483
330
226
105
38
8
1
TOTAL
3,388
450
Balance
Temp (F)
60
Hours/yr
COOLING
HEATING
VENTILATION
3,000
74
EER
Cooling
Minimum Minimum
OSA
OSA
% OSA
15%
Minimum
Supply Air
Flow
100%
N
32
Efficiency
Heating
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
15%
79
78
78
77
76
75
75
74
73
72
72
71
70
69
69
68
67
66
3,846 kWh
366 Therms
10,163 kWh
Energy Auditing Techniques
55
Design Htg Design Clg Temp
Temp (F)
(F)
Econ
MAT (F)
Design SAT
SAT (F)
55
55
57
59
61
63
65
67
69
71
73
75
77
79
81
83
85
87
80%
Heating
(kBtu/yr)
102
OSA LO (F)
120
Cooling
(kBtu/yr)
0
0
0
0
0
0
0
0
0
0
1,807
6,264
7,478
7,310
4,082
1,836
469
49
278
759
2,576
4,338
5,546
6,353
7,093
5,976
4,125
1,412
0
0
0
0
0
0
0
0
29,295
38,456
Est Min
SAT (F)
55
Estimated
Max Zone
Load
100%
Example Calculation: The Problem
•
•
•
•
•
Existing 5 ton air conditioner is on 24/7
Site is Sunnyvale, CA
EER is 10.0
Furnace is 80% efficient
Office environment with fan in “on” position
(i.e. not “auto”)
• Propose to schedule M-F, 7 AM to 6 PM
Energy Auditing Techniques
Here’s the nameplate
Energy Auditing Techniques
Example Calculation: Scheduling RTUs
•
•
Energy Savings from scheduling RTUs off
consist primarily of two parts:
1. Reduced fan energy savings
2. Reduced ventilation loads
No simple way to take credit for transient effects
Energy Auditing Techniques
Example Calculation: Part 1 Fan Savings
• Fan draw:
– 208V * (1 phase)^½ * 5.7A * (0.9 PF) = 1.07 kW
• Hours reduced:
– Was 24*365 = 8760 hrs/yr
– Now 11 hrs per day * 365 days * 5/7 ≈ 2868 hrs/yr
– Savings: 5892 hrs/yr
• Savings = 1.07 kW * 5892 hrs = 6304 kWh
• Assuming $0.15/kWh → $945.60
Energy Auditing Techniques
Example Calc: Part 2 Ventilation Savings
• Use Sunnyvale bin weather data
• Ventilation load
Btu/h = (1.085)(CFM)(Toutside-Tinside)
• If positive, then cooling load
• If negative, then heating load
• Multiply by hours in bin
• Divide by equipment efficiency
Energy Auditing Techniques
Example bin method calc:
Calculating decrease in ventilation loads
Min OA
Outside
Air Temp
97
92
87
82
77
72
67
62
57
52
47
42
37
32
27
Total
5 tons
400 cfm/ton
2,000 cfm
15%
hrs
1
6
18
75
172
278
437
671
1,076
1,229
976
562
262
116
13
5,892
Room T
72
72
72
72
72
72
72
72
72
72
72
72
72
72
72
Ventilation Ventilation Ventilation Ventilation
Cooling
Cooling
Heating
Heating
Load
Load
Load
Load
(kBtu/h)
(kBtu)
(kBtu/h)
(kBtu)
8.0
7.0
5.0
3.0
2.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
8
42
90
225
344
0
0
0
0
0
0
0
0
0
0
709
0.0
0.0
0.0
0.0
0.0
0.0
2.0
3.0
5.0
7.0
8.0
10.0
11.0
13.0
15.0
0
0
0
0
0
0
874
2,013
5,380
8,603
7,808
5,620
2,882
1,508
195
34,883
Energy Auditing Techniques
Cooling
EER
$
$
709
10.0
71
0.15
10.64
kBtu
kBtu/kW
kWh
/kWh
Heating
Efficiency
34,883
80%
43,604
436
$
1.00
$
436
kBtu
kBtu
therms
/therm
Savings Summary
Energy Auditing Techniques