The Impact of Delivered Efficiency on Overall HVAC System Performance
Poor installation and inconsistent maintenance can destroy a system’s efficiency
HVAC systems typically consume the highest percentage of a building’s energy cost. That said, how efficiently do you think the average package unit or split system operate at? If two identical units in the same building are consuming twice as much power and delivering only 50 percent of rated capacity, how apt would you be to address the poor performer?
We’ve found many systems are delivering only 50 percent of their rated capacity into the indoor conditioned space. Combine poor installation and service-related issues with inconsistent maintenance practices or, even worse, a run-to-fail scenario, and we find that many systems operate far below the manufacturer’s Air-Conditioning, Heating, and Refrigeration Institute (AHRI) laboratory rated efficiency.
For decades, the ability to proclaim a package unit and split system’s efficiency has been the right of our federal government through the U.S. Department of Energy (DOE) and the manufacturer’s AHRI laboratory standards. The yellow sticker on the equipment declared that contractors and customers understood what the operating efficiency would be. Guess what — it’s not even close to the actual installed system’s performance.
Contractors’ proposals may highlight the equipment’s laboratory-rated efficiency, but this is not the efficiency of the entire system. Package units may have a rating of 10.1 or 11.2 EER, but that is just a laboratory rating, not how they will perform connected to old and undersized ductwork.
The EER ratings on individual pieces of equipment do not consider the overall quality of installation. The most critical and often ignored portion of the system is its air-distribution system. ACCA-ANSI Standard 5 provides detailed guidelines on what a quality installation looks like. A standard-/code-based installation of equipment provides a solid foundation from which to benchmark the overall performance.
For far too long, the impact of the overall system performance and energy efficiency performed by professional contractors who employ trained installers and technicians have been greatly minimized by government regulators, manufacturers, and the marketplace. It’s time for everyone to recognize the added value a professional contractor provides with a holistic-system approach to delivered efficiency. The temptation of a lower-first-cost option versus the long-term life cycle value is always there for consumers as are the contrasts between “Pete in a Pickup” and a quality, licensed craftsman.
Today, that paradigm is starting to change. Now, the authority to document the delivered efficiency of a system has moved into the hands of field technicians. This is done as a technician measures the actual efficiency of an installed system. Understanding the impact of restrictive static pressure alone dramatically decimates a system’s yellow sticker rating. These field measurements are far more critical and important than the yellow sticker we all referred to in the past.
WHAT IS DELIVERED EFFICIENCY?
HVAC efficiency has been redefined. In the past, it was the efficiency and capacity that a box (or piece of equipment) was documented to deliver under a set of standard (and somewhat unrealistic) conditions in a laboratory. Once again, these ratings are still valid and essential. However, of far more interest to customers is a rating or score representing the actual heating and cooling (delivered efficiency) they receive from a system once it is installed.
This change in how efficiency is determined is the most significant change influencing the HVAC industry in decades. This change places the power to proclaim installed efficiency back where it belongs — in the hands of the contractors and technicians who actually build, service, and maintain every HVAC system.
To ensure installed efficiency, there are five points that need to be employed for every quality installation, replacement, and renovation: deploy protocols that measure delivered efficiency, verify the design with field measurement of the installed system, balance and commission each system, test before replacing equipment (test in), and verify the installation (test out).
The current standards that support the yellow sticker are completely valid and needed. But, in my opinion, laboratory equipment efficiency ratings only serve as a holdover from the last century. Rating overall system efficiency will become a more pertinent and accurate representation of what our customers deserve — a complete, system-quantified, delivered efficiency rating.
We all have a new opportunity to ensure delivered efficiency. I eagerly anticipate continuing to share these principles with you and invite your ideas, suggestions, and comments as we work to move the HVACR industry forward.