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Southern Oregon State College Computing Sciences Building

POWER SAVE

P.O. Box 880, Cottage Grove, OR. 97424 1-541-942-5560, FAX 1-541-942-4682

Testing Of LPA Retrofit Technology
Southern Oregon State College
Computing Sciences Building
Ashland, Oregon

80 Ton Trane Chiller

Test Period: June 11-20, 1996
Report Date: August 7, 1996

Prepared by: Gene Madison M.E., Power Save

TABLE OF CONTENTS

OVERALL TEST RESULTS SUMMARY

The LPA Retrofit project and testing objectives to verify the conservative project forecast energy savings rate of 1.4%/F were met. The overall test results at the test average of 65.8F and over the range of 48F to 78F show an energy savings rate of 1.78% per degree F reduction in the saturated condensing temperature (SCT) of R-22. This compares very favorably (16% higher) with Trane's Performance data of 1.53% per degree F at the ambient test average of 65.6F. This increase is due in part to the increased condenser surface area available at the maximum compressor loading of 50% experienced during this test. Based on the building load being carried by No. 1 as the lead chiller, this projects to an annual forecast of 35.3% for an estimated savings of 116,500 kWh/yr. using Trane's median rate of 1.53%/F (see Appendix for spreadsheet calculation). This test clearly demonstrates the savings which are achievable with the LPA Retrofit Technology applied to the 80 Ton Trane chiller.

The test average kWh/hr savings with the LPA Retrofit were 31%; correcting for the average ambient of 65.8F normalized the savings to 26.3%. The liquid injection circuit reduced the hot gas temperature by 60F from 165F to 105F. As the condenser capacity is not limited at or below design conditions (85F-95F), no measured savings from liquid injection were expected nor measured within the test range of 50F to 75F.

TEST SYSTEM
The system tested was the Trane Air Cooled Chiller Unit No. 1 of 2, a nominal 80 Ton unit servicing the Computing Sciences Building. This is a Trane Model No. CGAC-C80 Chiller with two Trane Model No. C40R compressor circuits (both with unloaders). Each circuit was retrofit with a HY-SAVE LPA860IND Liquid Pressure Amplifier including the installation of liquid injection into the superheated hot gas line.

It was decided with SOSC management to modify both compressor circuits on a single chiller rather than the original plan of modifying the lead circuits on both 80 Ton chillers. This application change was necessitated when it was learned that the Trane controller could not be adjusted to control a constant lead compressor position.

The subcooler section of each of the Trane condensers was bypassed to reduce overall pressure drop and subsequently further lower SCT's with the LPA providing the necessary liquid pressure subcooling for the circuit. The Trane compressor performance data is included in the Appendix section of this report. Head pressures are maintained by controlling the air cooled condensing unit fans in the package unit.

THEORY OF LPA RETROFIT TECHNOLOGY
The controls of the OEM Trane chiller units are factory set to maintain a minimum head pressure of approximately 210-220 psig at design conditions in order to maintain the refrigerant in its pure liquid form at the expansion valve. This is accomplished by operating one condenser fan at all times and then operating the other fans as ambient temperatures increases. Reducing the head pressure to achieve energy savings without Liquid Pressure Amplification, would create flash gas, which would then reduce the cooling capacity of the system, defeating the attempt to save kWh. Applying the LPA Retrofit Technology by:

   1. Installing HY-SAVE liquid Pressure Amplifiers into the liquid line of each circuit.
   2. Injecting liquid refrigerant into the hot gas lines ahead of the condenser inlet.
   3. Modifying the fan controls on the air condensing unit.

We expect to see the following results:

   1. A reduction in head pressure coincident with a drop in ambient temperatures by maximizing the flow of ambient air across the condensing coil. This reduces the compression ratio and the necessary compressor work of the refrigeration cycle.
   2. Increased refrigeration efficiency with colder liquid refrigerant (density and enthalpy) at the TXV.
   3. Reduced kW/Ton (or increased EER) from 1 and 2 above.
   4. Increased condenser capacity at ambient temperatures over 85F.
   5. Reduced hot gas temperatures entering the condenser increasing condenser surface area and adding system capacity at high ambient temperatures.

If these results are achieved, we expect to see the following benefits over a longer period of time:

   1. Reduced annual energy consumption, kW/yr.
   2. Increased system capacity due to the increased enthalpy content of colder R-22.
   3. Increased system capacity at high ambient conditions with liquid injection.
   4. Increased compressor life due to lower head pressures.
   5. Decreased service problems due to lower system head pressures.

TESTING OBJECTIVES
The primary objective of this test was to verify the rate of energy savings assumption of 1.4% per degree F reduction in condensing temperatures used in the initial project savings forecast as well as the 1.53%/F based on Trane Performance Data.

The secondary objectives of the test were to compare the operating parameters and efficiencies of this retrofit Trane unit with and without the HY-SAVE LPA Liquid Pressure Amplifier operational with both compressors retrofit.

TESTING EQUIPMENT
The test equipment used was the DATREX Multi-Channel Data logger. Because of the duration of the test, the data was logged every 10 seconds and averaged every 5 minutes. The following parameters were monitored:
   Suction Pressure
   Head pressure
   True kW for Compressor
   Suction Temperature
   Liquid Line Temperature
   Hot Gas Bypass Temperature
   Liquid Injection Temperature
   Chilled Water In/Out Temperatures
   Ambient Temperature

TESTING PERIOD
To assure that all savings were due to the application of the LPA Technology retrofit, all routine maintenance procedures and adjustments were performed by SOSC's service contractor before the testing was started. The data logging was initiated on May 30, 1996. The initial reslults were lost due to internal battery problem with the Datrex. The test comparison data was logged from June 11-June 20, 1996.

OVERALL TEST RESULTS

General Background of Test
The ambient temperature ranged from the high 40's to the high 70's and the maximum load on either compressor was 50%. This provided a relatively wide range with adequate load and sufficiently low ambient to demonstrate the LPA technology. The average temperatures for both phases of the test for all minutes logged was 65.8F for the w/o LPA test and 62.5F for the LPA test. The savings calculations were normalized to the w/o LPA test average.

It is important to note that the data logging equipment does not start and stop when the compressors turn on; it averages data for each five minute period even though the compressors may be off or are running from 0 to 100% of the time. Therefore, the only

Accurate method of comparison to calculate the savings is to use the averages of all of the data for each phase of the test, not the individual data points, or temperature cell

Averages. This approach takes into account not only the savings with lower head pressures but improvements in efficiency and subsequently lower run times.

For system comparison while compressors were running, the data was averaged into 5 Degree F cells (avg. 65F = 62.5 to 67.5). Averages of these temperature cells with all zero run times removed were the graphed to show the relationship of system operating parameters with ambient temperatures when the compressors are running.

Overall Savings and Savings Factor
As can be seen from the "Averaged Test Results With LPA Retrofit Technology" table, with the LPA operational, the average head pressure (including zero run times) dropped from 172 psig (w/o LPA) to 137 psig with a corresponding reduction in kWh consumption of 31% at the average temperatures of 62.5F and 65.7F respectively. Correcting for the differences in ambient reduces this to 26.3%. This corresponds with an average reduction of the R22 condensing temperature from 91.4 to 76.7F, or 14.7F.

The calculated savings factor is the = 26.3%/14.7F = 1.78%/F and is +16% greater than the 1.53%/F projected from the Trane Performance Data.

When applied to the annual bin hour distribution, the more conservative Trane data of 1.53/F factor yields an annualized savings of 116,500 KWH or 35.3%.

PROCESS TEST RESULTS BY TEMPERATURE CELL

Operating Parameters
For system comparison while compressors were running, the data was averaged into 5 Degree F cells (avg. 65F = 62.5 to 67.5). Averages of these temperature cells with all data less than 50% load removed were then compiled to show the relationship of system operating parameters with ambient temperatures when the compressors are running at 50% load. The data between cells was smoothed using the incremental sum averaging technique.

The table titled "Averaged Test Results With LPA Retrofit Technology" summarizes these test results at the average temperature cells. Graphs also follow for the following characteristics:
   Figure 1. Percentage Savings with Ambient Temperature
   Figure 2. Head Pressure with Ambient Temperature
   Figure 3. Compression Ratio with Ambient Temperature
   Figure 4. Liquid Injection Temperature with Ambient Temperature
   Figure 5. Liquid Line Temperature with Ambient Temperature
   Figure 6. Compressor kW with Ambient Temperature
   Figure 7. Compressor Capacity with Ambient Temperature
   Figure 8. Compressor kW/Ton with Ambient Temperature

NATIONAL ENVIRONMENTAL IMPACT
In addition to the substantial energy and cost savings, there is a major national environmental impact from this project in terms of the annual reduced consumption of hydrocarbons and subsequent emissions approximated as follows:    1. Reduction in pounds of CO2 = 179,400
   2. Reduction in pounds of coal = 123,400 or
    Reduction in pounds of gas/oil = 90,000

These numbers are based on national averages compiled by the Rocky Mountain Institute, 1990.