scope:

FOREWORD

The first edition of Standard 90.4 was published in July 2016. Accordingly, the Electrical Loss Component (ELC) data were based on the performance of electrical distribution equipment on the market and deployed in the industry at that time. In the years following the initial publication of Standard 90.4, the market has witnessed material improvements in the efficiency of core electrical distribution equipment, particularly in the performance of the UPS module. This has been borne out via two distinct developments:

a. UPS modules have become incrementally more efficient.

b. The UPS module efficiency curve has flattened such that the modules maintain the higher efficiency levels along a greater extent of the curve, including at the lower end of the x-axis (Load %), where previously the efficiency would exhibit a sharp drop-off. This is the case both for the movement by manufacturers of bringing transformerless solutions to market (as illustrated by the example in the displayed graph) and for general improvements in efficiency across the board for various UPS module technologies.

Further, this development is consistent across the offerings of the major UPS vendors and independent of operating mode (e.g., economy mode, among others.)

Note: In this addendum, changes to the current standard are indicated in the text by underlining (for additions) and (for deletions) unless the instructions specifically mention some other means of indicating the changes.