Arkansas HVACR NewsMagazine November 2018

S tate, National, Chapter News Tech News

login. For those sites requiring an account, obtaining an account can be as simple as registering, no credentials required, while others may require permission from a local distributor, or they may require the applicant to have an EPA number or contractor license number.

Balancing Load and Equipment Capacity

Taken from an article by Bill Smith President, Elite Software

The latest residential code (IRC) requires that a designer calculate the correct heat load of the building and compare that calculated load against the actual net capacity of the equipment being installed. One of the greatest difficulties in doing this is finding expanded ratings data and software that helps you determine the actual net capacity of a unit for the given operating conditions. Expanded ratings data for HVAC equipment are data that show how the capacity and efficiency of the equipment vary under different operating conditions. The capacity of a unit varies primarily from changes in the outdoor dry bulb temperature, but also from changes in air flow and the entering dry and wet bulb temperature of the indoor air entering the cooling coil. Given that there are four parameters that affect the cooling performance of a unit, there are many variations in the way that manufacturers show these data sets in table form. Some HVAC manufacturers make their expanded ratings data open and available to the public, while others have special web sites that require an account in order to

Capacity vs Load

Note that for many manufacturers there are multiple sites containing product data. Sometimes a manufacturer will offer both a public and private login site for these data sets. Typically, the data will be provided as a pdf, with nominal capacity data listed up front, and the expanded ratings data shown at the very end of the document. Continued next page Comprehensive performance data is required for the equipment selection process. This data should document the sensible and latent capacity of the equipment for a wide range of operating conditions.

ACCA ,Manual S, Section 3