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Design & Engineering Services

Hot Food Holding Cabinets Test for FWE

ET10SCE1310 Report

Prepared by:

Design & Engineering Services

Customer Service Business Unit

Southern California Edison

December 29, 2010

Hot Food Holding Cabinets Test for FWE ET10SCE1310

Southern California Edison Page ii Design & Engineering Services December 2010

Acknowledgements

Southern California Edison’s Design & Engineering Services (DES) group is responsible for

this project. It was developed as part of Southern California Edison’s Emerging Technology

program under internal project number ET10SCE1310. DES project manager Neha Arora

conducted this technology evaluation with overall guidance and management from Juan

Menendez and Paul Delaney. For more information on this project, contact

[email protected].

Disclaimer

This report was prepared by Southern California Edison (SCE) and funded by California

utility customers under the auspices of the California Public Utilities Commission.

Reproduction or distribution of the whole or any part of the contents of this document

without the express written permission of SCE is prohibited. This work was performed with

reasonable care and in accordance with professional standards. However, neither SCE nor

any entity performing the work pursuant to SCE’s authority make any warranty or

representation, expressed, or implied, with regard to this report, the merchantability or

fitness for a particular purpose of the results of the work, or any analyses, or conclusions

contained in this report. The results reflected in the work are generally representative of

operating conditions; however, the results in any other situation may vary depending upon

particular operating conditions.


Southern California Edison Page i Design & Engineering Services December 2010

ABBREVIATIONS AND ACRONYMS

ASTM American Society for Testing and Materials

BTU British Thermal Unit

CFM Cubic Feet Per Minute

CT Current Transducers

DAS Data Acquisition System

F Fahrenheit

ft Feet

FTC Foodservice Technology Center

in Inches

kW Kilowatt

kWh Kilowatt Hour

lb Pound

SCE Southern California Edison


Southern California Edison Page ii Design & Engineering Services December 2010

FIGURES

Figure 1. FWE HOT Food Holding Cabinet ........................................ 3

Figure 2. DAS Interface With National Instruments LabVIEW ............. 5

Figure 3. Cavity Thermocouple Installation ...................................... 7

Figure 4. Preheat Characteristics .................................................... 8

TABLES

Table 1. Summary of FWE TST-16-EPL Hot Food Holding Cabinets ...... 1

Table 2. Energy Input Rate ............................................................ 8

Table 3. Preheat and Idle Energy Rate ............................................ 9

EQUATIONS

EQUATION 1 ENERGY INPUT RATE .......................................................... 6

Equation 2. Energy Consumption (Idle Energy Rate) ......................... 6


Southern California Edison Page iii Design & Engineering Services December 2010

CONTENTS

EXECUTIVE SUMMARY _______________________________________________ 1

INTRODUCTION ____________________________________________________ 2

Background ............................................................................ 2

Objective ............................................................................... 2

Appliance Evaluated ................................................................ 3

TEST METHODOLOGY _______________________________________________ 4

Laboratory and Instrumentation Description ............................... 4

Thermostat Calibration............................................................. 5

Energy Input Rate ................................................................... 6

Preheat and Idle Energy Rate ................................................... 6

RESULTS__________________________________________________________ 7

Thermostat Calibration............................................................. 7

Figure 3. Cavity Thermocouple Installation .................................... 7

Energy Input Rate ................................................................... 7

Preheat and Idle Energy Rate ................................................... 8

CONCLUSION ____________________________________________________ 10

APPENDIX A _____________________________________________________ 11

REFERENCES _____________________________________________________ 13


Southern California Edison Page 1 Design & Engineering Services December 2010

EXECUTIVE SUMMARY The hot food holding cabinet is widely used and is a versatile piece of equipment generally

used in commercial kitchens. These cabinets are mostly used to; keep food at a safe serving

temperature; keep serving plates warm, and to transport food for catering events. In

addition, these hot food holding cabinets are lightweight for easy moving, yet strong enough

for everyday use.

These cabinets can be plugged into any wall outlet and sit on large wheels for easy mobility.

The insulated cabinet utilizes magnetic door gaskets, auto door closers etc that provides

additional energy saving attributes to these cabinets.

This project assesses the energy efficiency level of the FWE model number TST-16-EPL hot

food holding cabinet to determine an appliance baseline and a minimum energy efficiency

level in order to qualify for the food service qualifying product list. This project also assesses

the energy input rate, amount of energy consumed during holding cabinet preheating and

idle energy rate. This test method was based on the reapproved version of ASTM F2140-01

(revised July 23, 2010) “Standard Test Method for Performance of Hot Food Holding

Cabinets”.

Testing was performed at the Southern California Edison (SCE) Foodservice Technology

Center (FTC) in Irwindale, CA. The test data provides key information to help determine the

operation costs and the percentage of total kitchen productivity a single appliance can

deliver.

Testing for the idle energy rate or energy consumption began after preheating the cabinet

and stabilized at 150° Fahrenheit (F) for two hours after inserting sheet pans at a

predetermined position in the cabinet. The preheat test is the measure of energy consumed

by the equipment in order to reach a temperature of 150°F, from a room temperature of 75

± 2.5°F. The idle energy test reports the energy required to maintain a 150°F setpoint for a

period of three hours or ten thermal cycles (whichever is longer). Idle energy consumption

can be used to calculate real-world energy usage of the equipment.

Table 1 presents a summary of the test results.

TABLE 1. SUMMARY OF FWE TST-16-EPL HOT FOOD HOLDING CABINETS

HOLDING CABINET

RESULTS

Nameplate Power (kW) 3.2 kW

Measured Power (kW) 3.1 kW

Percent Difference (%) 4.62%

Preheat Time (min.) 6.85 min

Preheat Energy (kW) 0.35 kW

Preheat Rate (°F/min) 16.53 °F/min

Idle Energy Rate (kW) 0.68 kW

Idle Duty Cycle (%) 21.9%



INTRODUCTION The hot food holding cabinet is widely used and is a versatile piece of equipment generally

used in commercial kitchens. These cabinets are mostly used to; keep food at a safe serving

temperature; keep serving plates warm, and to transport food for catering events. In

addition, these hot food-holding cabinets are lightweight for easy mobility, yet strong

enough for everyday use.

These cabinets can be plugged into any wall outlet and use large wheels for easy mobility.

The insulated cabinet uses magnetic door gaskets, and auto door closers that provide

additional energy saving attributes.

This project assesses the energy input rate, amount of energy consumed during hot food

holding cabinet preheating and idle energy rate. These parameters provide real world

performance, providing end users with valuable information for purchasing and operating

the hot food holding cabinets.

BACKGROUND Southern California Edison (SCE) is committed to the advancement of the food

service industry and is part of a statewide team offering a food service qualifying

product list. The qualifying product list identifies the most efficient commercial

kitchen appliances within a specific appliance category. The qualifying appliances are

eligible to receive incentives for their use. Currently, hot food holding cabinets are

not listed in any of the appliance categories on the food service qualifying list.

OBJECTIVE This project examines the operation and performance of the FWE hot food holding

cabinets. The operation and performance of the holding cabinet is evaluated using

the American Society for Testing and Materials (ASTM) standard test methods. The

intent of this project is to accurately record and represent the energy consumption of

these cabinets for long and short-term thermal cycles. The testing examines the:

Energy Input Rate: The peak rate at which a hot food holding cabinet

consumes energy, kilowatt (kW).

Preheat Energy: The amount of energy consumed, kilowatt hours (kWh), by

the hot food holding cabinets while preheating its cavity from the ambient

temperature to the specified thermostat setpoint, with the controls calibrated

to the setpoint.

Preheat Rate: The average rate at which the holding cabinet’s cavity is

heated from the room temperature to the predefined setpoint.

Preheat Time: Time required by the cabinet to preheat from the room

temperature to the predefined setpoint.

Idle Energy Rate: The rate of energy consumed (kW) by the cabinets when

empty that is required to maintain its cavity temperature at a specified

thermostat setpoint.



APPLIANCE EVALUATED Figure 1 shows the FWE TST-16-EPL hot food holding cabinet. It is comprised of a

bottom refractory brick deck and stainless steel walls. The holding cabinet has a top-

mounted forced air blower system. The holding cabinet has a maximum holding

temperature of 225° Fahrenheit (F). The chamber has a nominal depth of 34.5”

(inches) and a nominal width of 24.5”. The chamber doors are flush mounted,

stainless steel, insulated, and gasketless. The temperature controls are electronic

with highly accurate intuitive thermostat, heat cycle indicator light, and a master

ON/OF switch with a master indicator light. The holding cabinet contains fan-cooled

blower motors to distribute heat evenly. The FWE holding cabinet has a rated

electrical input rate of 3.2 kW. Appliance specifications and the manufacturer's

literature are included in Appendix A.

FIGURE 1. FWE HOT FOOD HOLDING CABINET



TEST METHODOLOGY Laboratory testing of the FWE hot food holding cabinet was performed according to the

ASTM F2140-01(Reapproved 2007)- Revised July 23, 2010 test method for hot food holding

cabinets.1 The test data provides key information to determine:

Energy input rate

Preheat energy

Preheat rate and time

Idle energy rate

LABORATORY AND INSTRUMENTATION DESCRIPTION Testing was performed at the SCE Foodservice Technology Center (FTC). The FTC is

a 2,000 square-foot demonstration and equipment test center. The center is a part

of the Customer Technology Application Center, located in Irwindale, CA. It is a

certified ASTM and ENERGY STAR® test lab. The FTC is equipped with regulated

voltages of 120, 208, and 240. These outlets have amperages that range from 20 to

100 amps and have a wide variety of plug configurations that can accommodate

multiple appliance tests. The FTC is also equipped with a Data Acquisition System

(DAS). The DAS interface is a National Instruments LabVIEW-based piece of software

pictured in Figure 2. The DAS interface can monitor power, amperage, voltage,

power factor, frequency, and VAR from all outlets and display results in a real-time

graph during testing. The electrical use is logged in intervals of 1 second. In addition,

the DAS system can log and display data from 36 thermocouples and 8 resistant

temperature detection sensors. The interface allows the user to configure the

monitoring parameters and select the specific monitoring hardware.



FIGURE 2. DAS INTERFACE WITH NATIONAL INSTRUMENTS LABVIEW

The DAS system is equipped with multi-functional digital transducers, integrated

serial current transducers (CTs) and voltage leads. The multi-functional digital

transducers create power readings from CT and voltage inputs and have an accuracy

of ± 0.5% over the full-scale readings. The CTs used in this project are Data Stream

RS485 and have an accuracy of ± 0.5% over the full-scale readings. The DAS

system uses Omega K type2 thermocouples and connectors. The K type

thermocouples can read a temperature range of -328 to 2,282°F. To determine the

cavity temperature, a fiberglass insulated 24-guage thermocouple was used. For the

probes, a micro needle product probe with a response time from ambient to 200°F of

less than 20 seconds was used. The margin of error for the micro needle

thermocouples is the greater of 2.2°F or 0.75% above 32°F or 2.0% below 32°F. The

DAS system was calibrated in November 2009.

THERMOSTAT CALIBRATION Thermostat calibration is verified by installing a thermocouple in the geometric

center of the cavity. Calibration is necessary since the placement of holding cabinet

cavity temperature sensors can differ greatly between varying models and

manufacturers. When performing a thermostat calibration, the holding cabinet

stabilizes for one hour before taking readings of the cavity thermocouple. After the

one-hour idle period, cavity temperatures are recorded at 30-second intervals for a

minimum of 60 minutes. If the thermocouple reads an average temperature of 150 ±

5°F for a 60-minute period, then the thermostat is considered calibrated.



ENERGY INPUT RATE The energy input rate is used to confirm proper operation of the hot food holding

cabinets and to ensure that all test results are determined at the same temperature.

The energy input rate is the peak energy consumption of the cabinet while

preheating the cabinet cavity from ambient temperature to a setpoint of 150°F. The

peak energy consumption must be operating within 5% of the nameplate energy input rate. Energy input rate is calculated using EQUATION 1.

EQUATION 1 ENERGY INPUT RATE

60Model E35input

Eq

t

Where:

qinput = measured peak energy input rate, (kW)

E = energy consumed during period of peak energy input, (kWh)

t = period of peak energy input, (min.)

PREHEAT AND IDLE ENERGY RATE The preheat test records the required amount of time and energy needed to raise the

holding cabinet cavity temperature from ambient to a safe serving temperature. In

this test, the holding cabinet was considered to at a safe serving temperature when

the cavity reached 150°F. Once the cavity reached its setpoint of 150°F, it stabilizes

for a period of two hours. After stabilization, the idle energy rate was taken by

monitoring the consumption of the holding cabinet for a 3-hour period or ten thermal

cycles (whichever is longer). The idle energy rate is the holding cabinets required

rate of energy consumption (kW), when empty, needed to maintain its cavity

temperature at a specified thermostat setpoint. The formula in Equation 2 calculates

the idle energy rate.

Equation 2. Energy Consumption (Idle Energy Rate)

60idle

Eq

t

Where:

qidle = energy consumption (idle energy rate), (kW)

E = energy consumed during the test period, (kWh)

t = test period (min.)



RESULTS

THERMOSTAT CALIBRATION The thermostat calibration reading was verified by installing a thermocouple in the geometric center of the cavity, as shown in Figure 3. While performing thermostat

calibration, the holding cabinet was allowed to stabilize for 60 minutes before a one-

hour average reading of the cavity thermocouple was taken. Data was recorded for

one-hour, sampled every 30 seconds, and the resultant average temperature was

155°F. Because this result is within 5°F of 150°F, the cabinet’s thermostat was

deemed properly calibrated.

Figure 3. Cavity Thermocouple Installation

ENERGY INPUT RATE The input rates were always checked to be within ± 5% of the manufacturers

specifications before any tests were taken on any given day. Table 2 lists the results

of the input rate, taken on each of the individual test days, and are calculated using EQUATION 1.



Table 2. Energy Input Rate

Holding Cabinet

Results

Nameplate kW 3.2 kW

Measured kW 3.1 kW

Percent Difference (%) 4.6%

PREHEAT AND IDLE ENERGY RATE The holding cabinet was preheated from room temperature at the thermostat

calibration temperature of 150°F. The cavity reached 150°F after 6.85 minutes while

the cabinet consumed 0.35 kWh. The holding cabinet’s preheat curve is shown in

Figure 4. The preheat curve shows that the heating elements never turned off or

cycled while heating to the cavity setpoint.

Figure 4. Preheat Characteristics

The holding cabinet was stabilized for two hours following the preheat test and then

the energy demand was monitored for a three-hour period. The idle energy rate was

Preheat Curve

70

80

90

100

110

120

130

140

150

0 1 2 3 4 5 6

Time (min)

Te

mp

era

ture

(°F

)



0.68 kW. The duty cycle, or percentage of the holding cabinet’s actual energy

consumption rate compared to the 3.1 kW measured energy input rate was 21.9%

during idle conditions. Results of the preheat and idle tests are calculated using EQUATION 1 and are listed in Table 3.

Table 3. Preheat and Idle Energy Rate

Holding Cabinet

Results

Preheat Time (min) 6.85 min.

Preheat Energy (kWh) 0.35 kWh

Preheat Rate (°F /min) 16.53 °F /min

Idle Energy Rate (kW) 0.68 kW

Idle Duty Cycle (%) 21.9%



CONCLUSION The following parameters of the FWE TST-16-EPL holding cabinet were determined during

testing:

Energy Input Rate: The maximum energy input rate recorded during the test was

3.1 kW.

Preheat Energy Rate: The holding cabinet took 6.85 minutes to reach the

temperature of 150°F, yielding a preheat energy rate of 16.53°F/min.

Idle Energy Rate: The idle energy rate, the amount of energy required to maintain

a 150°F setpoint, was recorded as 0.68kW.

Hot Food Holding Cabinets Test for FWE ET 10.31


APPENDIX A



REFERENCES

1 American Society for Testing and Materials, 2005. Standard Test Method for performance of Hot Food Holding Cabinets. ASTM Designation F2140-01 (reapproved 2007)-Revised July 23, 2010. In Annual Book of ASTM Standards, West Conshohocken, PA

2 http://www.omega.com/temperature/z/pdf/z204-206.pdf

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