AR No. # - Refrigeration Suction Pressure
Recommendation template version 2013a
Recommendation
Adjust refrigeration suction pressure set points from 24.0 psig (10.2°F) to 34.0 psig (20.5°F). This will increase
system efficiency, decreasing compressor energy consumption by 20%.
Annual Savings Summary
Source
Electrical Consumption
Electrical Demand
Total
Quantity
251,010
344
856.7
Units
Cost Savings
kWh (site)
kW Months / yr
MMBtu
$12,550
$1,719
$14,270
Implementation Cost Summary
Description
Implementation Cost
Cost
Payback
$0
0.0
Facility Background
The facility currently uses (insert compressor information here). During the site assessment, facility personnel
explained (compressor operating conditions). (Talk about current set points). Motor information was collected
for each system and is summarized in the following Motor Analysis Tool page.
Technology Background
Refrigerant evaporation temperature is directly related to compressor suction pressure. Compressors require less
power and energy to operate if the pressure differential between suction and discharge pressure (lift) is reduced.
Raising suction pressure increases refrigeration efficiency by decreasing this lift and the compression ratio
(discharge pressure divided by suction pressure). Typically, 2% to 3% of refrigeration compressor energy can be
saved for each degree Fahrenheit increase in suction temperature and associated suction pressure.
Proposal
Change the suction pressure setpoints on the refrigeration system's controllers. Completing this procedure can be
done in regular working hours by maintenance personnel so that there are no implementation costs. These
actions will decrease the compression ratio, reducing associated annual energy consumption by 251,010 kWh,
resulting in an annual cost savings of $14,270.
Notes
Put any additional notes or references at the end. Things like alternative proposals, considerations, and potentials
problems or side-effects should all be noted.
AR No. # - Refrigeration Suction Pressure
Recommendationand
template
version 2013a
Put any additional notes or references at the end. Things like alternative proposals, considerations,
potentials
problems or side-effects should all be noted.
Based on
Unmodified Template
Data Collection
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Author
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Orange Team Review
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AR No. # - Analysis
Recommendation template version 2013a
Data Collected
Equations
Refrigeration System Data
Analysis Equations
Refrigerant Type
Cooled Medium Target Temperature
Ammonia
(TT)
35.0 °F
(pC)
24.0 psig
10.2 °F
24.8 °F
Eq. 1) Temperature Differential (ΔT(C,P))
TT  T( C , P )
Current Conditions
Current Suction Pressure Set Point
Current Suction Temperature Set Point
Current Temperature Differential
Eq. 2) Suction Temperature Increase (ΔT)
(TC)
(ΔTC)
(N. 2)
ES  ICE
Eq. 4) Demand Cost Savings (CSD)
(pP)
(TP)
(ΔTP)
34.0 psig
20.5 °F
14.5 °F
DS  ICD
(N. 1)
(N. 2)
Eq. 5) Cost Savings (CS)
CSE  CSD
(Eq. 1)
Incremental Cost Data
Incremental Electricity Cost
Incremental Demand Cost
Eq. 3) Energy Cost Savings (CSE)
(Eq. 1)
Proposed Conditions
Proposed Suction Pressure
Proposed Suction Temperature
Proposed Temperature Differential
TP  TC
(N. 1)
Table Equations
(ICE)
(ICD)
$0.05000 /kWh
$5.00 /kW·mo.
(Rf. 1)
Eq. 6) Current Demand (DC)
PC  tM
(Rf. 1)
Eq. 7) Current Energy (EC)
PC  t H
Compressor Analysis
Savings
Savings Factor
Suction Temperature Increase
Eq. 8) Demand Savings (DS)
(F%S)
2.0% /°F
(N. 3)
(ΔT)
10.2 °F
(Eq. 2)
EC  T  F% S
Energy Savings
Current Energy
Energy Savings
Energy Cost Savings
(EC)
(ES)
(CSE)
1,226,400 kWh/yr.
251,010 kWh/yr.
$12,550 /yr.
(Rf. 2)
(Rf. 2)
References
(Eq. 3)
Rf. 1) Incremental energy costs developed in
the Utility Analysis of the Site Data section.
(Rf. 2)
Rf. 2) Demand and energy values developed
in the Compressor Summary Table on the
following page.
Demand Savings
Current Demand
Demand Savings
Demand Cost Savings
(DC)
(DS)
(CSD)
1,680.0 kW·mo.
343.8 kW·mo.
$1,719 /yr.
(Rf. 2)
(Eq. 4)
Economic Results
Cost Savings
Implementation Cost
Payback
DC  T  F% S
Eq. 9) Energy Savings (ES)
(CS)
(CI)
(tPB)
$14,270 /yr.
$0
0.0 yrs.
(Eq. 5)
(Rf. 3)
Notes
N. 1) Data collected on-site during the assessment. See analyst site report for details.
N. 2) Saturated refrigerant temperature at corresponding pressure.
N. 3) An industry accepted value to determine compressor energy. (2% of compressor
energy saved for each degree Fahrenheit that suction temperature increases).
Rf. 3) Adjusting suction pressure can be
done in regular working hours by
maintenance personnel so there are no
implementation costs
AR No. # - Analysis
Recommendation template version 2013a
Compressor Summary
Description
Rated
Power
Operation Operation
Months
Hours
Input
Power
Current
Demand
Current
Energy
Demand
Savings
Energy
Savings
(WR) (N. 1)
(tH) (N. 1)
(tM) (N. 1)
(PC) (N. 4)
(DC) (Eq. 6)
(EC) (Eq. 7)
(DS) (Eq. 8)
(ES) (Eq. 9)
(hp)
(hrs./yr.)
(mo./yr.)
(kW)
(kW·mo.)
(kWh)
(kW·mo.)
(kWh/yr.)
Compressor No. 1
Compressor No. 2
100
100
8,760
8,760
Totals
200
12
12
70.0
70.0
140.0
840.0
840.0
1,680.0
Notes
N. 4) Motor power obtained from the Motor Analysis Tool (MAT) on the previous pages.
613,200
613,200
1,226,400
171.9
171.9
343.8
125,505
125,505
251,010