Reach-in Freezer Energy Test
Performed for BPA, PECI, & PSE by Emerson DSN
Energy Usage of a Reach-in Freezer
With Various Gasket Conditions
Design Services Network
August 21, 2008
(Updated September 19, 2008)
Test Performed by:
Max Gingrich
Design Services Network
Report Prepared by:
Steve Pfister, PE & Georgi Kazachki, PhD
Design Services Network
1351 North Vandemark Road
Sidney, Ohio 45365
(937) 493-2747
Prepared for:
Bonneville Power Administration (BPA) and
Portland Energy Conservation Inc. (PECI) and
Puget Sound Energy (PSE)
Table of Contents
1.0 Overview 3
2.0 Test Setup & Procedure 3
2.1 Equipment Tested (Reach-In Freezer with Defrost Heater) 3
2.2 Test Simulators 3
2.3 Instrumentation 3
2.4 Test Conditions 4
2.5 Test Procedure 4
3.0 Gasket Conditions 5
3.1 Full Gasket Condition 5
3.2 Damaged Gasket Condition 6
3.3 No Gasket Condition 6
4.0 Summary of Test Results 7
5.0 Observations and Recommendations 8
Appendix A – Reach-in Freezer 9
Appendix B – Condensate Measurement 11
Appendix C – Test Simulator Placement 12
Appendix D – Thermocouple Wire Placement 14
Appendix E – Environmental Room Setting – Psychrometric Chart 15
Appendix F – Full Gasket Performance 16
Appendix G – Damaged Gasket Performance 18
Appendix H – No Gasket Performance 20
List of Figures
Figure 1 - Full Gasket 5
Figure 2 - Average Simulator Temperature - Full Gasket 5
Figure 3 - Simulated Damaged Gasket 6
Figure 4 - No Gasket 6
Figure 5 – Control Sensor in Evaporator 8
Figure 6 – 3 Glass Door Freezer 9
Figure 7 – Freezer Specification 10
Figure 8 – Condensate Collection Pan & Scale 11
Figure 9 – Simulator Map - Front 12
Figure 10 – Simulator Map - Rear 13
Figure 11 – Freezer Setup in Environmental Room 13
Figure 12 – Thermocouple Wire Placement 14
Figure 13 – Psychrometric Chart 15
Figure 14 - Full Gasket Ambient Conditions 16
Figure 15 - Full Gasket Average Simulator Temperature 16
Figure 16 - Full Gasket Simulator Temperatures 17
Figure 17 - Full Gasket Power Measurement 17
Figure 18 - Damaged Gasket Ambient Conditions 18
Figure 19 - Damaged Gasket Average Simulator Temperature 18
Figure 20 - Damaged Gasket Simulator Temperatures 19
Figure 21 - Damaged Gasket Power Measurement 19
Figure 22 - No Gasket Ambient Conditions 20
Figure 23 - No Gasket Average Simulator Temperature 20
Figure 24 - No Gasket Simulator Temperatures 21
Figure 25 - No Gasket Power Measurement 21
1.0 Overview
This report shows the difference in energy consumption due to gasket conditions on a Reach-in Freezer. A number of utility incentive programs include measures to replace damaged or missing gaskets installed on walk-in box or reach-in case doors. Bonneville Power Authority (BPA) and Portland Energy Conservation Inc. (PECI) have commissioned Emerson DSN to perform controlled and monitored tests of refrigeration system energy use differences based on gaskets in good condition as well as various stages of disrepair.
2.0 Test Setup & Procedure
2.1 Equipment Tested (Reach-In Freezer with Defrost Heater)
The equipment used for the test is a 3 glass door freezer with interior fluorescent lighting. The Model Number is ULG80BCP-5 (SN 0623705) supplied by National Refrigeration. See Appendix A for specifications. The condensate drain tube is relocated from the condensate heater to collection pan where it is measured (weight scale) during the defrost cycle. See Appendix B for the condensate drain setup.
Defrost is time initiated, temperature terminated. The initial test setting is to cycle the defrost 24 hours. An additional heater is located outside the cabinet in the condensate drain pan to evaporate the drain water.
2.2 Test Simulators
Test Simulators are prepared using 1 US liquid pint plastic containers filled with a solution of 50% ± 2% propylene glycol and 50% ± 2% distilled water, with a lid. The containers are 4” ± 3/8” wide, 4” ± 3/8” long, and 2 3/4” ± 3/8” tall including the lid. The bottom surface is free of protrusions. The wall thickness is approximately 1/32”. A sponge material is cut to fit inside the container. A thermocouple is placed inside the simulator, centered in all dimensions.
Filler packages are the same dimension as the Test Simulators, and are filled with the same solution. The sponge is not required in filler packages, nor is the thermocouple.
Test simulator and filler package placement is shown in Appendix C – Test Simulator Placement. The packages fill approximately 80% of the freezer volume.
2.3 Instrumentation
Temperatures inside the freezer cabinet are measured using thermocouples. The wires are prepared with the cabinet to minimize air leaking past the door gasket. See Appendix D – Thermocouple Wire Placement.
Condensate water drainage is weighed periodically during defrost cycles. The total water weight drained during the defrost cycle is reported.
The simulator temperatures in addition to the data shown are measured and recorded at 60 second intervals.
Measurement / Description / Units1 / Pressure / Compressor Suction / psig
2 / Pressure / Compressor Discharge / psig
3 / Electrical / Freezer Current / Amps
4 / Electrical / Freezer Voltage / Volts
5 / Electrical / Freezer Power / Watts
6 / Temperature / Ambient dry bulb temperature (RTD) / °F
7 / Temperature / Ambient wet bulb temperature (RTD) / °F
8 / Temperature / Evaporator coil inlet – First return “U” bend / °F
9 / Temperature / Evaporator coil outlet / °F
10 / Temperature / Condenser coil inlet / °F
11 / Temperature / Condenser coil middle – Middle “U” bend / °F
12 / Temperature / Condenser coil outlet / °F
13 / Temperature / Evaporator air inlet / °F
14 / Temperature / Evaporator air outlet / °F
15 / Temperature / Control bulb or sensor / °F
16 / Temperature / Suction line temperature / °F
17 / Temperature / Condenser air inlet / °F
18 / Temperature / Condenser air outlet / °F
19 / Temperature / Compressor suction / °F
20 / Temperature / Compressor discharge / °F
2.4 Test Conditions
The Freezer is tested inside an environmental room with controlled temperature and humidity. The room is controlled as follows:
Condition / ValueDry Bulb Temperature / 75°F ± 2°F
Humidity / 55% RH ± 2% (64ºF Wet Bulb)
Air Flow around freezer / Less than 50 fpm
2.5 Test Procedure
The freezer temperature is adjusted such that the average product simulator temperature is 0.0± 2.0°F in steady state condition with the full gasket. Steady state condition is achieved when the average temperature is stable (returns to the same temperature, +/-1.0°F after subsequent defrost cycles), and the condensate drain water is stable (measured to be less than 10% on subsequent defrost cycles). The temperature setting is not adjusted during subsequent tests for various conditions.
Defrost is initially set to 1 defrost per day. If the evaporator freezes completely as manifested by rising simulator temperatures, another defrost is added. The freezer performance and power consumption is recorded during the test.
The procedure is repeated for the various gasket conditions.
3.0 Gasket Conditions
3.1 Full Gasket Condition
A flexible magnetic gasket is contacting the cabinet around 100% of the perimeter of the door. Some weather stripping is added above the top edge of the door to further reduce any incidental air leak near the thermocouple wires. Clamps are placed on the top edge of each door to compress the gasket tightly on the thermocouple wires to create a similar seal to normal operating conditions.
Figure 1 - Full Gasket
A single defrost cycle is sufficient to maintain the average simulator temperature at 0.0 +/-2°F.
Figure 2 - Average Simulator Temperature - Full Gasket
3.2 Damaged Gasket Condition
The damaged gasket is simulated by placing a ¼ inch spacer under the gasket on the bottom corner below the handle. The resulting air gap is approximately ¼” wide and 6 inches long on both the bottom and side edges of each door. Approximately 7% of the original gasket length of 172 inches (per door) has an air gap. The damaged gasket is intended to simulate typical damage that occurs due to incidental contact with the gasket during normal consumer use and maintenance.
Figure 3 - Simulated Damaged Gasket
The simulated damaged gasket condition required 2 defrost cycles per day to prevent evaporator freezing. Performance details are shown in Appendix G.
3.3 No Gasket Condition
The entire magnetic gasket is removed from each door. The top of the doors have a small piece of tape to prevent the door from opening. To prevent the average simulator temperature from rising above 40°F, additional tape is placed over the gap along the hinge edge of each door. The doors have sizeable leakage along the top and bottom edges. The handle edge is making contact with the cabinet, but does not form a seal without a gasket.
GAP ON TOP
GAP ON BOTTOM
Figure 4 - No Gasket
4.0 Summary of Test Results
The measured energy includes all energy used by the freezer including compressor, condenser fan, defrost heater, lighting, and controls.
The following table summarizes the measurements taken during the tests. The test indicates that approximately 0.6 kW-hrs additional energy per day is used due to gasket damage and that approximately 3.1 kW-hrs additional energy per day is used due to missing gaskets on reach-in freezer doors.
Parameter / Full Gasket / Damaged Gasket / No GasketNumber of Defrost cycles per day / 1 / 2 / 4
Average Ambient Dry Bulb Temperature (°F) / +75.1 / +74.5 / +74.6
Average Ambient Wet Bulb Temperature (°F) / +63.8 / +64.5 / +63.1
Average Condenser Air Intake Temperature (°F) / +74.8 / +72.5 / +73.5
Average Simulator Temperature (°F) / 0.0 / -0.5 / +29.6
Minimum Simulator Temperature (°F) / -12.0 / -13.1 / +15.0
Maximum Simulator Temperature (°F) / +15.0 / +15.0 / +47.2
Condensate Drainage per Defrost (oz) / 6.8 / 19.5 / 83
Condensate Drainage per Day (oz) / 6.8 / 39.0 / 332
(1)Duty Cycle (%) / (1)70.8% / (1)75.1% / (1)94.3%
Average Power (Watts) / 2190.2 / 2260.3 / 2578.8
24 Hour Energy (kW-hrs) / 52.6 / 54.3 / (2)61.9
Energy Increase per Day (kW-hrs) / Baseline / +1.68 / (2)+9.33
% energy increase / Baseline / 3.2% / (2)17.7%
(1) Duty Cycle calculated during periods when defrost heater is off, including period during defrost recovery.
(2) 17.7% energy increase plus elevated temperatures indicate that additional energy would be needed to maintain freezing temperatures.
The results are based on a 3-door freezer with approximately 172 inches of gasket on each original door. Doors were not opened during any of the test periods. Therefore the results provide an indication of additional heat load due to gasket damage during periods when doors are closed. The results do not provide any insight to energy used during door openings. A presentation of the test results is shown below on a “per door” basis.
Parameter / Full Gasket / Damaged Gasket / No GasketEnergy per day per door (kW-hrs) / 17.5 / 18.1 / 20.6
Energy increase per day per door (kW-hrs) / Baseline / +0.56 / +3.11(2)
The reach-in freezer is able to maintain safe product temperatures with minor gasket damage, although there is occasional condensation on the glass door. Significant gasket damage prevents the freezer from maintaining the product temperature below freezing. This creates conditions for unsafe food storage.
Observations and Recommendations
It is common for reach-in freezers to locate the control sensor in the evaporator. This causes the freezer to cycle more frequently. It has the benefit to help the freezer operate more consistently in varying conditions, but the additional cycles result in higher energy consumption. A preferred position of the control sensor could result in a more efficient freezer. Additional review of control sensors in the reach-in freezer industry might show where best practices could be more standard.
Figure 5 – Control Sensor in Evaporator
For the example during normal operation, if the control sensor was located closer to the return air before entering the evaporator, the cycle frequency would be less. The overall efficiency would increase by reducing the loss due to compressor cycling. This would have a result of higher temperature gradient in the cabinet. Lower temperature gradients are desired and can be achieved with balanced air flow throughout the cabinet. For another example with a damaged gasket, and placing the control sensor closer to the return air – the duty cycle would increase closer to 100% if the product temperatures are not cold enough. A hypothetical test result …
Full Gasket / Damaged / No GasketDuty Cycle (%) / 70.8% / 75.1% / 99%
Average Product Temperature (°F) / 0.0 / 0.0 / 20
24 Hour Energy (kW-hrs) / 51.1 / 52.8 / 63.4
% energy increase / baseline / 3.1% / 24.2%
After making efficiency improvements to a design, the additional heat load due to damaged gaskets has a greater impact to energy use. The same test performed in this study resulting in 3% energy increase will have a much higher percentage increase to a more efficient freezer. As energy initiatives drive up the efficiency of the commercial equipment, the gasket condition will become more critical to energy savings. Further analysis, including a review of the cabinet insulation, will help understand the gasket benefits as insulation and refrigeration technology improve. A hypothetical test result with improved insulation and/or more efficient fans ….