ARLINGTON, Va. - The Air Conditioning Contractors of America (ACCA) has announced its opposition to a proposed ANSI standard on commercial load calculation offered by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).

On May 6, ASHRAE released for a 45-day public review period its proposed ANSI Standard 183P, "Procedures for Performing Peak Heating and Cooling Calculations in Buildings Except Low-Rise Residential Buildings." The scope of the procedure is aimed at all commercial buildings.

ACCA says it has reviewed the proposed standard and determined that there are significant flaws in its application to small commercial buildings.

According to ACCA, procedures and approaches that may be acceptable for large buildings are not fully appropriate or practical for small buildings. The mechanical equipment, practitioner expertise, application economics, customer expectations, and construction turnaround times are all different for light commercial buildings as opposed to larger commercial buildings.

"Rather than satisfying a real industry need, the proposed standard significantly increases liability exposure of HVAC contractors, engineers, and other professionals who undertake small building load calculations," stated Greg Leisgang, chairman of the ACCA board of directors. "Additionally, ASHRAE's proposal effectively precludes the use of many of today's load calculation procedures that are widely accepted and practiced by design professionals working in the light commercial sector."

Leisgang continued, "Adoption of this proposal as a standard by the American National Standards Institute would place contractors, engineers, and other design professionals in real jeopardy as the procedure is simply not realistic for light commercial applications. A separate standard is required to address the unique needs of light commercial applications from those of large commercial, industrial, and institutional applications."

For the bulk of small buildings in the United States (such as churches, retail stores, garages, etc.), architects and professional engineers are generally not involved in HVAC equipment sizing, equipment selection, or equipment location, says ACCA. For these, especially during simple change-outs and upgrades, many design professionals utilize "manual" procedures to calculate equipment loads. The proposed ASHRAE standard, as written, requires numerous re-calculations ("at least one day per month" ... "all appropriate hours of the day") that essentially negate the possibility of doing load determinations by hand.

"While the ASHRAE procedure may make sense for large commercial applications, which by necessity involve the use of professional engineers who make up ASHRAE's membership, it makes absolutely no sense for the small applications that make up a large number of installations in the U.S.," Leisgang said. "When it comes to small buildings, the proposal will hurt contractors, increase liability, drastically raise construction costs, and provide no benefit in terms of either occupant comfort or environmental impact."

ACCA recently invited interested persons to join a team developing load calculation standards for light commercial buildings. The purpose of the industry team is to create a standard for calculating heat loss/gain in commercial structures using equipment nominally sized at 25 tons (300,000 Btuh) and less.

ACCA is encouraging contractors to review ASHRAE's proposed standard and provide comments during the 45-day public review period. A link to the proposal, along with an outline of ACCA's concerns and instructions on submitting comments, can be found at

Publication date: 05/23/2005