Mechanical Systems
Mechanical studies are necessary to determine the cause of failure in heating, ventilation, and air conditioning (HVAC) systems and appliances. Allegations of manufacturing defects or malfunction vary widely, and Donan Engineering has the knowledge and experience to thoroughly evaluate mechanical systems to determine the source of a component failure.
HVAC Equipment
HVAC systems are made up of three basic components: a compressor, an indoor coil, and an outdoor coil (Figure 1) and will contain other secondary components such as fans, controls, and thermal expansion devices. The primary function of an HVAC system is to condition the occupied space in commercial and residential buildings. This is accomplished by heating, cooling, and dehumidifying the processed air, circulating it throughout the building. The average life expectancy for heat pumps and furnaces is 15 to 20 years. Typical warranties cover parts and labor for 10 years for the major mechanical parts, such as the compressor and heat exchangers.
Typical HVAC System Failure
Failures related to HVAC systems can be attributed to a variety of sources such as mechanical wear and tear, controls, loss of refrigerant, and dirty air filters. Compressor failures will usually result in replacement of the entire outdoor coil due to the replacement cost of the compressor. Most other failures can be readily fixed and are less costly.
Donan Engineering is often asked to determine if HVAC failures are related to lightning strikes. Lightning causes losses in the U.S. of over $5 billion per year. About 30% of the power outages are caused by lightning (worth over $1billion). Roughly 5% of annual insurance claims (other than fires) are lightning-related, costing more than $1 billion. Donan’s forensic engineers are skilled at determining whether damage is a result of lightning or if the damage is from age-related wear and tear.
An inspection for lightning damage may consist of examining the wiring for evidence of charring (Photo 1) and checking the resistance across the compressor terminals to determine if the compressor windings have shorted (Photo 2).
Appliances
There are several major appliances found in most residential homes including refrigerators, washers, dryers, dishwashers, and water heaters. Their primary function is to provide convenience for a variety of common household chores and for food preparation and preservation. The average life expectancy for major appliances ranges from 10 to 15 years. Typical warranties cover parts and labor for only one year.
Appliance Examinations
An allegation of appliance failure requires a complete examination of the appliance to determine the source of failure. Due to the harsh environments that appliances are subjected to—heat, detergents, chemicals, and moisture—there are a variety of common failures. Control system problems are a typical source of failure. A common malfunction in washers is related to the water level control system. This can result in a continuous flow of water which overflows from the washer, damaging the surrounding areas (Photo 3).
Dryer fires are another common problem that Donan Engineering investigates (Photos 4 and 5). Clothes dryers can be found in 80% of homes (81.5 million) throughout the United States. The U.S. Consumer Product Safety Commission (CPSC) estimates that 15,500 fires associated with clothes dryers occur annually. These fires account for an average of 10 deaths and 310 injuries and more than $84.4 million in property damage.
Lack of maintenance is a contributing factor. Reduced airflow resulting from lint buildup in the screen or other areas around the dryer can cause the dryer to perform poorly, operate at elevated temperatures, or overheat. Problems can also occur if consumers place improper items in their dryers, such as foam-backed rugs or athletic shoes, or vent their appliances with plastic or vinyl exhaust materials.
Donan’s experienced engineers are trained in a variety of disciplines and are able to evaluate the source of failures in mechanical systems. Our rapid response provides our clients with answers to a variety of engineering problems.