Measurement & Verification Report for Alltemp Refrigerant: Preliminary Results Macy s Department Store Manhattan Beach, CA

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1 Measurement & Verification Report for Alltemp Refrigerant: Preliminary Results Macy s Department Store Manhattan Beach, CA Mark Stetz, P.E. CMVP CRM BEAP Stetz Consulting LLC Durango, CO / mark@stetzconsulting.com 15 January 2016

2 1 Executive Summary To demonstrate the efficacy of Alltemp refrigerant in typical applications, Sky Green converted an existing rooftop unit at Macy s in Manhattan Beach, CA. Macy s is a retail department store that is open seven days a week. Two Carrier 50-EK series rooftop units were monitored for several weeks. RTU-5 was monitored for two weeks in October / November 2015, converted to Alltemp-m, and monitored until 4 January During the monitoring period, there were several problems with the data loggers and the unit was undercharged by 25% with Alltemp for the first half of the monitoring period. Also, cooler temperatures in late November and December reduced the amount of mechanical cooling needed and limited the overlap of ambient temperatures. Despite the data collection limitations, Alltemp showed a reduction of compressor power of ~25% over all temperature ranges observed. Preliminary Results of Alltemp-m at Macy s, Manhattan Beach, CA Page 2

3 2 Data Collection Methods The Macy s department store in Manhattan Beach is open seven days a week. Eight Carrier 50-EK series rooftop units provide heating & cooling. Each unit has two reciprocating compressors using 25 lbs of R-22 for each circuit. Air-cooled condensers with have two fans; the head pressure controller disables one fan when ambient temperatures are below 55 F. Two mechanical thermostatic expansion valves are designed to maintain 10 F to 13 F superheat when using R-22. The EK models are variable airflow with variable speed drives designed to maintain a constant duct static pressure setpoint. An economizer with a powered exhaust fan provides cooling in mild conditions. RTU-5 was designated as the unit to be converted to Alltemp refrigerant. The unit was monitored for baseline performance for two weeks from 23 October 2015 through 6 November Outdoor daytime temperatures ranged from 67 F to 97 F. Alltemp-m replaced the R-22 on both circuits and the unit was monitored for 9 weeks until 5 January Circuit #1 was undercharged, so on 12/18/15 seven lbs of Alltemp-m was added to bring the charge to the correct level. Ambient daytime temperatures from 11/6/15 to 12/18/15 ranged between 61 F and 91 F; from 12/18/15 to 1/5/16 between 52 F and 72 F. Onset UX data loggers were used to record temperature and relative humidity observations in 15-minute intervals. Outdoor air was measured near the condenser air intake; the mixed air inside the filter bank, and the supply air at the evaporator fan inlet. Return air conditions were not measured. Each compressor was measured with a Wattnode three-phase true-power transducer coupled to an Onset UX pulse data logger set to record in 15-minute intervals. To capture actual compressor runtimes, an additional current transducer was installed on a single phase to record compressor current in 1-minute intervals. Evaporator fan power was not measured, so there is no data to evaluate whether airflow remained constant or varied with cooling conditions. This is a known weakness of this analysis. A hardware problem prevented communication between the Wattnode transducer and the data logger on compressor #1, so no true power data is available until the communications link was fixed on 12/18/15. Between 12/18/15 and 1/5/16, both the Wattnode transducer and the current transducer operated correctly. The two recording devices were compared and the Wattnode data was used to calibrate the single-phase current measurement results within 2% so that reliable power readings could be obtained for the entire monitoring period. For reasons not yet understood, the relative humidity sensors on both the outdoor air and mixed air data loggers failed on 12/10/15. The temperature function appeared unaffected; the supply air data logger appears to be functioning normally. The loss of relative humidity measurements prevents calculating the enthalpy change across the cooling coil after 12/10/15. Preliminary Results of Alltemp-m at Macy s, Manhattan Beach, CA Page 3

4 3 Preliminary Findings Macy s department store is located in Manhattan Beach, CA, a temperate, coastal climate zone (4A) located southwest of downtown Los Angeles. One Carrier RTU was converted to Alltemp-m on 6 November No other changes were made to the system. Designation Serves York Model Cooling Capacity RTU-5 Retail space Compressors Electric Heating Capacity 50-EK-034--C6--QD 30 tons 2, reciprocating 35 kw / 120 kbtuh Figure 1 shows the compressor power during the monitoring period. Compressor 1 provides the first stage of mechanical cooling; compressor 2 operated only occasionally. The economizer provided cooling when the outdoor air conditions were sufficient to meet the cooling load, so there are several multi-day periods of no compressor operation. Figure 1: Compressor Power Macy's RTU Comp 1 kw Comp 2 kw OSAT Compressor kw OSAT, F 5 R-22 Alltemp-m /23/15 10/30/15 11/6/15 11/13/15 11/20/15 11/27/15 12/4/15 12/11/15 12/18/15 12/25/15 1/1/16 0 Measured current was converted to power (kw) assuming 460 V and then calibrated to match the Wattnode results. Compressor current was measured in 1-minute intervals while the Wattnode is configured to measure in 15-minute intervals. This makes the current measurement a better indicator of compressor runtime as it can show the on-off transitions more accurately. Power for periods when only compressor #1 was operating for at least 13 of 15 minutes (steadystate) was compared to outside temperature. Compressor power decreased 20% - 25% over all temperature ranges when operating with Alltemp. There did not appear to be any observable change in compressor power after circuit #1 was topped off on 12/18/15. The very low Preliminary Results of Alltemp-m at Macy s, Manhattan Beach, CA Page 4

5 regression coefficients (r 2 ) indicate that both refrigerants show only a slight sensitivity to ambient temperature. Figure 2 shows these results. Alltemp data was segregated into the periods before and after 12/18/15. The only apparent difference is that ambient temperatures were lower in December-January than in October-December. Figure 2: Compressor Power as a Function of Outdoor Temperature Compressor kw R-22 Macy's Manhattan Beach RTU-5 Compressor 1 Alltemp 12/18/15 Alltemp > 12/18/15 Linear (R-22) Linear (Alltemp 12/18/15) Linear (Alltemp > 12/18/15) y = x R² = y = x R² = y = x R² = OSAT, F Table 1 shows the comparison of compressor #1 power (kw) as a function of outdoor temperature at different temperature bins during single-compressor steady-state operation. Power reduction is 24% - 27% over the temperature range observed. All observations are statistically significant. Table 1: Compressor #1 Power as a Function of Outdoor Temperature R-22 Alltemp Comparison OSAT Bin Avg kw Std Dev n Avg kw Std Dev n kw kw % t Significant % TRUE % TRUE % TRUE % TRUE % TRUE % TRUE Preliminary Results of Alltemp-m at Macy s, Manhattan Beach, CA Page 5

6 To assess whether Alltemp achieved a reduction in total energy use, Figure 3 shows the total daily energy use (kwh) of both compressors compared to the average daily temperature (ADT). RTU operation appeared to occur only between 8:00 AM and 10:00 PM (or less) seven days per week, so the period from 10:00 PM to 8:00 AM was excluded from analysis 1. Figure 3: Total Daily Energy Use as a Function of Average Daily Temperature 800 Macy's Manhattan Beach RTU-5 Compressors 1 & 2 Daily kwh R-22 Alltemp Alltemp ADT > 64 Linear (R-22) Linear (Alltemp ADT > 64) y = x R² = y = x R² = ADT, F The trend lines were added to show the strong relationships between daily energy use and average daily temperature. The Alltemp data shows that cooler temperatures in December & January resulted in a number of days where the economizer could handle some or all of the load, which resulted in a significant number of days where energy use was zero. Table 2 shows the daily energy use (kwh) for both compressors over the range of temperatures observed. Due to the limited number of observations, comparisons using 5 F bins could not be used, so 10 F bins were used. The 70 F bin covers 65 F 75 F, so economizer operation is effectively excluded. Daily energy use decreases between 24% and 41% for the two bins when operating with Alltemp. Although the decrease in 70 F bin is not statistically significant, it is close. The large standard deviation and small sample size (n=8) with R-22 drives the significance down. 1 This does not affect the calculation of energy use but it does affect the calculation of average daily temperature. Preliminary Results of Alltemp-m at Macy s, Manhattan Beach, CA Page 6

7 OSAT Bin Table 2: Comparison of Daily Energy Use as a Function of Outdoor Temperature Avg kwh R-22 Alltemp Difference Std Avg Std Dev n kwh Dev n kwh kwh % t Significant % -1.7 FALSE % -2.2 TRUE In addition to energy use, system performance and characteristics between refrigerants was evaluated. Figure 4 shows the supply air temperature as a function of outdoor temperature. R-22 operation showed typical supply temperatures between 57 F and 63 F, increasing slightly with increasing outdoor temperatures. Supply air temperatures with Alltemp were not easily characterized. For the period 10/23/15-12/18/15 there were two operating regimes. One regime was characterized with low supply air temperatures (54 F - 62 F) and having a high sensitivity to outdoor temperature, the other with higher supply air temperatures (62 F - 67 F) and a lower sensitivity to outdoor temperature. No apparent relationships between these two SAT regimes and time of day, date 2, mixed air temperature, status of compressor #2, or ambient humidity level were found. The cause of the two temperature regimes continues to be investigated. After the refrigerant charge was topped off on 12/18/15, typical supply air temperatures ranged between 56 F and 63 F and appeared to be a continuation of the High SAT regime showing similar outdoor temperature sensitivity. 2 If circuit #1 had a leak that resulted in a loss of charge, the low SAT regime would be expected to occur near one end of the monitoring period or the other. This was not the case. Preliminary Results of Alltemp-m at Macy s, Manhattan Beach, CA Page 7

8 Figure 4: Supply Air Temperature as a Function of Ambient Temperature. 70 Macy's Manhattan Beach RTU-5 Compressor 1 65 Supply Air Temperature, F OSAT, F Alltemp <12/18/15 Alltemp > 12/18/ A better indicator of delivered cooling is the enthalpy change across the evaporator coil, where enthalpy represents the total energy of the air including moisture content. Unfortunately, the mixed-air relative humidity sensor failed on 12/10/15 (before circuit #1 was topped off), making humidity and enthalpy measurements impossible after that date. Preliminary Results of Alltemp-m at Macy s, Manhattan Beach, CA Page 8