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APPENDIX 5B. ERA MODEL DESCRIPTION

5B.1 INTRODUCTION

The Energy-efficient Refrigerator Analysis Program (ERA), formerly called the EPA 

Refrigerator Analysis Program, serves as an important tool in the engineering analysis, described 

in Chapter 5 of the TSD. Since its use in the 2011 residential refrigeration rulemaking, the 

Windows-based ERA has undergone extensive analytical upgrades and now implements features 

that specifically facilitate cooled cabinet modeling. This appendix provides program operation 

guidance for the user. The program has its own internal help utility to provide additional 

assistance to the user beyond the information provided in this appendix. Further information on 

the historical development of ERA can be found in Appendix 5B of the 2011 residential 

refrigeration Final Rule. 

5B.2 WINDOWS VERSION OF ERA

User Interface 

ERA uses a highly-graphical interface, providing multiple options for selecting from the 

various cabinet and component choices. It is designed to guide the user carefully through the data 

input and editing process to ensure data consistency. Prior to an actual simulation of the 

refrigeration appliance performance, the user is presented a summary of the selected design 

variables.

Cabinet Mode 

ERA operates in one of four view modes: 1) cabinet design mode (shown in the image), 

2) cycle design mode, 3) simulation mode, and 4) reports mode. Each is characterized by its own 

sidebar, containing hotspots for selecting component or report options. The color of the sidebar 

provides an additional visual clue to highlight the particular mode that is current. 

To define a new analysis, the user may either begin with a default set of design 

parameters and proceed through the editing process, or may read in an existing data file to be 

used as-is or edited. 
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Each analysis must begin with a selection of the basic cabinet design parameters: cabinet 

category (shown on the desktop) and the overall dimensions of the unit. Once these basic choices 

have been made, the remaining categories of cabinet design data may be specified in any order. 

Data wizards, similar to those illustrated above for the stand-alone programs, guide the user at 

each stage. 

As each category of data is processed, a check mark is drawn on the sidebar to indicate the 

completeness of the editing progress. In some instances, special-function dialogs may be summoned 

to assist in the preparation of an input value. For example, the image to the right shows a dialog used 

to calculate the effective resistivity of a cabinet wall that contains a vacuum panel or some equivalent 

high thermal resistance element. 

Cycle Mode 

Once the basic cabinet type has been selected, the user may specify the cycle parameters. 

This would begin with a selection of the basic cycle type (single evaporator, dual loop, dual 

evaporator, or Lorenz cycle). Once this choice has been made, a simple schematic of the chosen 

cycle category is displayed on the desktop. The user may then continue to define the cycle 

parameters by clicking on the desktop to select the component of interest, or may use the sidebar 

or the drop-down menu to select the next component to be defined. The displayed desktop image 

and its associated hotspots depend on the specific cycle category selected.
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Simulation Mode 

Prior to simulation of the cabinet loads and cycle behavior, the user is presented with a 

summary of the defined input. A data item can be selected for further editing by double-clicking 

on the summary line displaying the item in the data review dialog. Once the data has been 

reviewed and accepted, the user selects the Continue button to start the simulation. 

Reports Mode 

At the completion of the simulation (which is instantaneous for the cabinet loads), the 

program automatically switches to reports mode and displays the results on the desktop. The 

example here shows the calculated cabinet loads. Results for the cycle analysis, overall 

performance parameters, or a more detailed summary, can be selected using the side-bar or the 

drop-down menu for reports.