CASE STUDY Supermarket Store #05 – Vinita, Oklahoma

Summary of Supermarket Applications

The KE2 Evap for Rack Efficiency (KE2 Evap-RE) controller controls all of the components and functions for an evaporator on a refrigeration system. These controls have been used by a supermarket chain for the last four years, initially as a way to eliminate service calls for icing issues in walk-in’s and frozen evaporator coils.

Since the initial installations the temperature performance in the walk-in, reduced service calls, and reduction of defrost cycles resulted in additional application programs. An initial case study was conducted on Store #05, Vinita, OK, to illustrate the savings.

ICE CREAM FREEZER

Figure 1: DEFROST FREQUENCY

BAS (Building Automation System) vs. KE2 Evap for Rack Efficiency (KE2 Evap-RE)

This graph shows 31 days of history of the evaporator coil temperature (blue line), and room temperature (green line).

BAS (right side of graph): This is the oldest information. The BAS initiated 4 defrosts per day, or 28 defrosts per week, as it was programmed. This was for the entire period of time we collected data.

KE2 Evap-RE Controller (left side of graph): The KE2 Evap-RE controller took control of the circuit, strategically defrosting only when it was required, averaging just 9 defrosts per week.

The spikes in room temperature between the defrosts are indications of heavy loading periods, typically door openings, which you can see occur throughout the 31 days.

Figure 2: BEFORE - Walk-in Using BAS

Ice build-up, as a result of long periods of door openings, and defrost cycles not properly managed.

Figure 3: AVERAGE DEFROST TERMINATION TEMPERATURE

On this graph we have highlighted the coil temperature to show the average termination temperature of defrost.

Average coil temperature at defrost termination:

BAS (right side of graph): was reaching around 71°F.

KE2 Evap-RE Controller (left side of graph): was terminating with a cooler average, around 48°F.

What this reveals: The higher average temperature at defrost termination is a good indicator that the BAS runs the defrost heaters for longer periods of time, putting more heat into the freezer during each defrost. The hotter coils contribute to the fogging effect in freezers, which results in more “snow and icing” build up on fan guards, ceilings, product, and racking.

Figure 4: EFFECTS OF DEFROST ON ROOM TEMPERATURE

On this graph, it is difficult to see the room temperature (in green) at defrost termination. However, the .csv data pulled from the controller clearly shows the average room temperature at defrost termination. For the BAS the average was 26°F, and for the KE2 Evap-RE controller the average was 15°F.

BAS is about 26°F

KE2 Evap-RE Controller is about 15°oF

What this reveals: Again, this is an indicator of how much more load the BAS is placing in the room during defrost. This additional load, warm moist air, also contributes to the frosted product, shelving, ceilings and walls. Additionally, this ‘extra load’ effects the temperature and integrity of the product in the space. This ‘extra load’ causes longer pulldown time after defrost, and contributes to nuisance room temperature alarms. The most obvious side effect is that the additional load must be removed by the compressors on the rack, which can be avoided, and result in a significant amount of energy savings*.

*See energy saving calculations below.

Figure 5: WEEKLY PERFORMANCE WITH KE2 EVAP-RE

This graph is the last week of data with the KE2 Evap-RE controlling the circuit. There were 9 defrosts this week, and the time period between defrosts varies, depending on the amount of loading/door openings. The BAS would have been scheduled to initiate 28 defrosts in this amount of time.

Figure 6:

BEFORE - Walk-in Using BAS

Ice build-up, as a result of long periods of door openings, and defrost cycles not properly managed.

AFTER - Walk-in Using KE2 Evap-RE

Frost & ice reduced on the coil, product, ceiling, and shelving is an indicator of a properly controlled refrigeration system.

ROI Summary *

Energy savings from evaporator performance efficiency
- With the KE2 Evap-RE the evaporator operates with a minimum of 90% of its efficiency or capacity. Clearly the BAS which causes service calls for iced up coils, does not maintain this level of operating efficiency.
- The amount of kW-hrs saved by this benefit is difficult to calculate on a rack system, with all the other circuit variables that can affect a long term test.
Energy savings from reduction of defrosts ($831)
- In the Vinita, OK Store #05 case study the KE2 Evap-RE reduced the defrost from 28 per week to 9. The reduction of kW-hrs to energize the heaters on an annual bases is calculated as: 7331 kW-hrs, roughly $660 annually.
- The reduction of load on the rack from these extra defrost is calculated to be .877 Tons per day, 320 Tons per year. This is estimated to cause the rack to consume an additional 1908 kW-hr of electricity annually, which is roughly $171.
Energy saving from more efficient defrosts ($269)
- From the graphs in this study, you can clearly see that the KE2 Evap-RE controls the defrost process of the equipment more effectively. As a result, the rise in room temperature during defrost is 11ºF cooler, on average than with the BAS. The BAS's additional rise in room temperature causes the rack to see an additional 47 Tons of load annually. This results in an additional 286 KW-hrs of electricity consumed, costing roughly $26 yearly.
- In addition to reducing temperature gain during the defrost cycle, the KE2 Evap-RE is running the heater approximately 15 minutes less per defrost. This saves 2701 kW-hrs annually, roughly $243 yearly.
Reduction, and in most cases elimination, of service calls ($3,000)
- The largest segment of savings benefit of the KE2 Evap-RE is found in the elimination of service calls caused by iced up coils. According to the supermarket technician at this store, the KE2 Evap-RE is conservatively eliminating 6 service calls annually. With an estimated service call costing $500, this results in a $3000 savings per year, per walk-in.
- Store personnel have also noticed that the working conditions in these walk-ins have improved.
- Icing on the floors has been reduced or eliminated
- Frost and icing on product to be placed in display cases no longer has to be wiped off.
- Ice and frost on shelving has been eliminated, or reduced to the point that boxes and containers no longer stick, and are easier to unload and move.

Total Estimated Savings from reduction of energy, $1100, and service, $3000, results in a $4100 in annual savings per walk-in.
All of these figures were generated from current large and mid-size supermarket applications.
* Energy savings calculated based on utility rate of $0.09/kW-hr

Recent Data

Recently, more support data was collected from 16 walk-in freezers in 5 stores; Arnold, MO #4151, Broomfield, CO #1435, Maplewood, MO #0515, Moore, OK #772, and St. Louis, MO #1322

The following is a summary of the calculations and data collected from these five supermarkets. The data collected is for the last 30 days of operation (mid-March to mid-April 2018). Note that the St. Louis, MO area stores experienced heavy periods of rain in these data sets. Here is a brief explanation of the calculations:

Annual Heater Savings:

Base line power use = watts of the heater power (measured)*scheduled heater runtime.
- Schedule heater runtime with the current BAS is 4 times per day for 45 mins. The BAS is set to terminate at a room temperature of 55°F or 45 min, whichever occurs first. However, none of the historic data we have collected has indicated that the BAS ever achieves a room temperature of 55°F in less than 45 min. Therefore we have determined that the heaters run 4 times per day for 45 min when using the BAS.
KE2 Therm usage = watts of the heater power (measured)*data logged heater run time
- KE2 Therm system typically runs the heaters less during defrost and initiates fewer defrosts per week. The demand defrost algorithm only initiates defrost when needed.
Annual heater savings is the difference in the KW-hrs used between these two control schemes multiplied by $0.09, an estimated average power cost.

Annual Cooling Savings:

Any extra defrost heater runtime results in more heat being dumped into the freezer which must be removed by the refrigeration system. Annual Cooling Savings is a calculation estimating how much energy is used by the rack to remove this extra heat.
- With the recorded room air temperature after a defrost, run by a standard BAS, the BTU’s required to lower the room temperature back to the room set point can be calculated. These BTU’s are multiplied by the difference in number of defrost cycles required by the BAS vs. the KE2 Evap-RE controls. Example: If the BAS defrosts 28 times per week, and the KE2 Evap-RE system only required 12 defrost cycles, we saved the cooling load required to recover from 16 fewer defrost cycles. (The room air temperature after defrost for a BAS was captured on two supermarket systems in the past and averaged for these systems since no BAS system runtime was captured on these sites for this exercise. The actual room sizes and number of defrosts for each individual walk-in were used in the calculation of savings.)
- The estimated power usage of the rack for this calculation was found by using a standard ‘off the shelf’ condensing unit and evaporator. We used the catalogue cooling capacity and power consumption of this ‘generic unit’ and calculated the runtime to remove the BTU’s from the extra heater runtime (calculated above). With that unit runtime we can calculated the power needed to run that ‘generic unit.’ (We believe this is an extremely conservative approach. This method assumes that the unit is running at peak efficiency without startup time to get to conditions and meets catalogue published capacity.)
- Since the KE2 Evap-RE does not run the heaters as long during a defrost cycle, the room temperature does not rise as much as when the BAS runs the heaters for 45 mins. So, for each defrost, the rack has an additional BTU load needed to remove the added room temperature rise of the BAS, compared to the KE2 Evap-RE system. We calculated the difference in required BTU’s to pull down the room from these different temperatures, as described above. The power usage to remove this difference in BTU’s is added to the Annual Cooling Savings.

The Average Annual Energy savings per walk-in is estimated to be $693.36, assuming a nationwide average of $0.09/KW-hr.

These energy savings only account for defrost heater runtime and pulldown after a defrost. KE2 Therm’s rack efficiency algorithms monitor evaporator performance and initiate a defrost cycle on demand once the buildup of frost on the coil has degraded efficiency by 10%. This reduces compressor HP/run time required to overcome the loss of heat transfer caused by too much frost build up during a normal refrigeration cycle between conventional scheduled defrost schemes.

This reduction in HP/compressor run time is not captured in this data. It is difficult to capture this on rack systems that are also controlling other cases. However, when these controls are applied to racks or RCU’s that are only controlling one walk-in the total operating energy savings shows this performance gain.

KE2 Evap-RE controller also avoids service calls due to frozen evaporators. If two service calls are avoided per year we estimate an annual savings of $1,000.00.

With the exception of the Broomfield, CO store (we do not know the service history of this store), the KE2 Evap-RE is avoiding many more than 2 service calls annually per walk-in based on the store's service history.

Total estimated average savings for these five sites, per walk-in, is $1,693.36 per year.

Climate Considerations

We believe that these sites; Broomfield, CO, Moore, OK, and St. Louis, MO area represent a good nominal weather condition for the country. As you move to drier climates the controls will save more in reduction of defrosts and cooling savings. As you move to higher humidity climates you will see more savings in reduced service calls and refrigeration efficiency with cleaner, ice free, coils.

Regardless of where the controls are applied, they will adapt and optimize the operation of the equipment for that environment. If the door is open a lot, or a little, the KE2 Evap-RE maximizes the efficiency of the refrigeration system. The ‘standard’ BAS is not designed to adjust to these variables in operating conditions. It will defrost the same number of times, for the same length of time, at the same time every day, regardless of conditions. If the door is never opened, if the walk-in is in Phoenix or New Orleans, regardless if it is winter, spring, summer, or fall, the BAS does not adapt to maximize the performance of the equipment.

Arnold, MO Store #4151

Circuit	Annual Heater Savings	Annual Cooling Savings	Annual Energy Savings	Estimated Service Cost Savings	Total Annual Savings
A4	$732.88	$368.65	$1,101.53	$1,000.00	$2.,101.53
A9	$248.65	$219.66	$468.31	$1,000.00	$1,468.31
B1	$227.68	$27.82	$255.50	$1,000.00	$1,255.50
B7	$637.94	$142.59	$780.53	$1,000.00	$1,780.53

Broomfield, CO Store 1435

Circuit	Annual Heater Savings	Annual Cooling Savings	Annual Energy Savings	Estimated Service Cost Savings	Total Annual Savings
B3	$241.88	$79.42	$321.30	$1,000.00	$1,321.30
B8	$475.77	$171.92	$647.69	$1,000.00	$1,647.69
B9	$717.23	$436.87	$1,154.10	$1,000.00	$2,154.10
A2	$265.80	$562.07	$827.87	$1,000.00	$1,827.87

Maplewood, MO Store 0515

Circuit	Annual Heater Savings	Annual Cooling Savings	Annual Energy Savings	Estimated Service Cost Savings	Total Annual Savings
A1	$554.13	$249.78	$803.91	$1,000.00	$1,803.91
A2	$545.34	$249.77	$795.11	$1,000.00	$1,795.11

Moore, OK Store 772

Circuit	Annual Heater Savings	Annual Cooling Savings	Annual Energy Savings	Estimated Service Cost Savings	Total Annual Savings
LTA1	$659.96	$522.73	$1,182.69	$1,000.00	$2,182.69
LTB1	$197.84	$43.62	$241.46	$1,000.00	$1,241.46
LTB2	$368.98	$156.74	$525.72	$1,000.00	$1,525.72
LTB3	$227.06	$72.30	$299.36	$1,000.00	$1,299.36

St. Louis (Telegraph) Store #3122

Circuit	Annual Heater Savings	Annual Cooling Savings	Annual Energy Savings	Estimated Service Cost Savings	Total Annual Savings
*A8	$84.05	$28.21	$112.26	$1,000.00	$1,112.26
B9	$615.83	$379.56	$995.39	$1,000.00	$1,995.39

*A8 Data from the controller on this circuit indicates that there is an issue that started 20-25 days ago. With some evaluation and troubleshooting it should be able to perform much better. We did not include this circuit due to system issues. Details seen in the graph below.

31 Day Performance Graph from the St. Louis (Telegraph) Store 3122 Circuit B9

31 Day Performance Graph from the Broomfield, CO Store 1435 Circuit B3

31 Day Performance Graph from the Broomfield, CO Store 1435 Circuit B8

31 Day Performance Graph from the Broomfield, CO Store 1435 Circuit B9

Additional Benefits

From our experience on many applications, the graphing and diagnostic capabilities of the KE2 Therm controllers will also help technicians identify systems that are not operating efficiently, before they become a problem. Periodic checkups on walk-ins during regular store visits will quickly identify potential issues with the data and graphs available. (Example; door opening issues, drain pan / line issues, product stacking issues, set point adjustments, defrost heater function) The graph below is an example of how an issue can be identified.

31 Day Performance Graph from the St. Louis (Telegraph) Store 3122 Circuit A8

Additional Benefits

31 Day Performance Graph from the St. Louis (Telegraph) Store 3122 Circuit A8

Summary

The KE2 Evap-RE controller provides many benefits over a ‘standard’ BAS. Ease of troubleshooting system issues, maintaining a tighter room temperature, product temperature stability, and reducing service costs are some of those benefits. With the data collected for this project the estimated average savings are:

Average Savings Per Walk-in