Air Supply Leaks can reduce HVAC efficiency by over 40%

The energy penalty imposed on an HVAC system by a leaking return duct can reduce the efficiency of a system by as much as 40% during extreme weather conditions. What is staggering is that unless you measure to discover it, this defect is invisible to you and your customer.

In the Picture above, a Fluke TIR32, Thermal Infrared Camera is used to detect Air Supply side - air leaks in the positive pressure side of the HVAC. Because normal cool Air conditioned air will typically be 54F, to 58F, anything below that temperature, is an indication of excess Air Leakage. This air leakage was invisible, and remained undetected for over 10 years since the AC duct was installed.

This is just one of many Air leaks in the HVAC, that caused condensation to form and present as a possible roof leak - but it was in fact just condensation from the extremely cold air, impinging on surfaces and making them cold enough for Dew to form.

Many laymen - forget that Dew Point or Condensation Formation occurs when the surface of a substrate is below the Dew Point Temperature. The Dew Point Temperature is not the same as Relative Humidity, and should not be confused.

The (Dry) dew point temperature is the temperature at which condensation will form on ANY surface. The (Wet Bulb) Wet Dew point temperature is the temperature at which a surface will condense water - when it is already wet. This is because a surface that is already wet, will absorb more thermal energy through conduction, than a dry air surface. Dry Air is less conductive than Moist Air, or water on a surface.

Fortunately a New Study Quantifies Efficiency Losses Due to Improper HVAC Installation and this backs up what we see in the field - all the time.

The ACCA has announced the availability of a new report that the association says confirms that HVAC equipment requires a quality installation (QI) in order to perform at rated efficiency.

The research, undertaken by the U.S. Department of Commerce’s National Institute of Standards and Technology (NIST), found that substantial equipment efficiency is lost due to design and installation deficiencies. The NIST report presents faulty practices commonly performed by contractors and details the resultant additional energy consumption.

The recently-published report is the culmination of a three-year study that included the impact of building effects, equipment effects, and climate effects on HVAC equipment efficiency. The study found that installation faults significantly increase annual energy consumption.

Extensive laboratory testing and computer simulations indicated that the following installation faults have the most potential to significantly degrade equipment efficiency:

A. Air Supply and Return Duct leakage

B. Refrigerant Under/Over Charging

C. Low Indoor Air Flow

D. Oversized Equipment with Undersized Ductwork

E. Oil in Refrigerant

The report also shows that when two or more simultaneous faults occur, the efficiency degradations can be additive, compounding the increased energy consumption.

“This report quantifies what many industry experts already know — profound efficiency losses occur when HVAC equipment is not installed properly,” said Paul Stalknecht, ACCA president and CEO. “This report should help consumers understand why it is important to hire a contractor who follows the QI Standard. When consumers start asking for QI from every contractor, it will raise the performance bar in the industry, and result in significant energy savings while increasing occupant comfort.”

ACCA notes that the ANSI/ACCA 5 QI Standard, HVAC Quality Installation Specification, specifies what to measure, how to measure, and the measurement tolerances for unitary residential and commercial HVAC systems. This reduces faults associated with design, installation, and commissioning. Failure to meet the design and installation elements specified in the ACCA 5 QI Standard will impact equipment performance and undercut the deemed energy savings assumed by many energy efficiency programs.

A full copy of the NIST report, entitled “Sensitivity Analysis of Installation Faults on Heat Pump Performance,” can be downloaded at no charge at

www.acca.org/standards/quality/.