This time of the year we are often being asked to provide forensic investigations regarding the cause and origin of damages to HVAC system or individual component(s). This is Part II of the HVAC damage claims blog; it addresses the typical causes of damage associated with HVAC systems. Claims dealing with theft of the copper wiring of these units as well as excessive replacement costs are certainly on the rise.
There are a number of components in an HVAC system that can fail, including the compressor, the condenser fan, the air handler blower, the refrigerant copper piping, the air filter, the evaporator coils, and so on. When it comes to damages caused by an insured peril such as lightning, the most common damage we have seen is damage to the electronics and the air compressor.
Typical Problems
We often see problems associated with contamination of the refrigerant, especially the mixing of the R22 with the R410 refrigerants. Other problems include, but are not limited to, corroded or loose terminal connections, high refrigerant pressure, refrigerant leaks, failed electronic controls and sensors, worn out internal components of the compressor, bad electric and mechanical installation, failed fans, a short to ground in the fan motor or a short to ground in the fan motor wires that lead to the motor, and so on. Over time, low refrigerant levels can cause overheating and premature failure of the compressor, often requiring complete replacement of the compressor or the entire condensing unit. The electronic controls and sensor that cause the air conditioner, fan and condenser to kick off and on properly, are often the first components to go. Sometimes these sensors are merely knocked out of position causing the air conditioner to cycle constantly or behave erratically.
The Refrigerant Charge Problem Is Widespread
In a recent study, for Arizona Public Service, heat pump or air conditioner systems were tested for their refrigerant level. The study results are indicated in the graph below. Only eighteen (18%) percent of all the units were properly charged (green bar). Seventy-eight (78%) percent of the units were under charged (yellow-red bars). While four (4%) percent were over charged (red). These results are consistent with previous industry research, from new home construction studies in California, Long Island and elsewhere.
The heart of the HVAC unit is the compressor, which is cooled by the refrigerant. Over time, low refrigerant levels can cause overheating and premature failure of the compressor, often requiring complete replacement of the compressor or the entire condensing unit.
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Did you know that most air conditioning compressor failures are caused by loss of lubricant and/or refrigerant? Older systems, especially before 2006 were connected with mechanical flare fittings that can rattle loose due to vibration of the system with leaks resulting. Most new units are welded at their connection points, reducing the chance for leaks to occur.
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Misconceptions about Cause of Failure
During the first step of our investigation we interview the insured and any witnesses to the damage. Witnesses typically tell us that they heard a sound and that they saw sparks and smoke coming out of the equipment; at other times they state that the compressor worked just before the storm and then it stopped working. Even the HVAC repair technicians many times state that the oil was black or that the insulation was burned or the terminal was blown. They then assume that a lightning hit the unit without performing an investigation into the actual mode of failure.
An electric failure does not necessarily cause mechanical failure of the equipment. On the other hand, a mechanical failure (a broken valve, worn bearing, blocked coils, rusty terminals, etc.) may have been the cause of an electrical failure. Thus, if the motor windings are electrically sound, then the compressor was not damaged by a surge voltage or lightning stroke.
The often heard statement “the blackened acidic oil indicates the motor was damaged by a lightning stroke” is also false. The compressor oil will blacken and form an acid only when the oil is exposed to excessive heat for an extended period of time. Overheating of the motor-compressor unit is the most frequent symptom of system problems. The heating and charring of motor winding insulation causes a chemical breakdown that combines with the oil. This will then blacken the oil and form an acid. When a motor fails as a result of a surge voltage or lightning stroke, the oil is normally in a like-new condition. A surge voltage or lightning strike occurs in an extremely short period of time which does not allow enough time for the oil to blacken and turn acidic. Thus, if the refrigerant oil is burnt or acidic there is a good chance that the damage is not lightning/power surge related. It should also be noted that burnt or acidic refrigerant oil does not require the replacement of the entire system as is commonly stated.
Another misconception about lightning is that it can damage a motor-compressor unit even if the equipment is turned off during a storm. If a surge voltage or lightning stroke has enough voltage to gap the open contacts on the main contactor, then there will be damage to various other components in the air-conditioner and possibly to the building’s entire electrical system. Therefore, the insulation melts and could possibly start a fire before the air-conditioner is damaged.
Dirty Condenser Coils or Fan will lead to Premature Failure
Air Conditioner or Heat Pump Condenser Coils, if are not cleaned regularly, can get plugged up by dust, dirt, pollen, grass, and other foreign debris. See Figure 1.
Figure 1. Dirty condenser coil that led to seizure of the fan and compressor. Power surge was not the cause of this loss. It was caused by lack of regular maintenance.
Sometimes these obstructions to the flow of air are not seen by just looking at the condenser; the interior of the condenser must be opened up and examined very carefully. Problems caused by this condition:
· Unit loses the ability to remove heat from the system.
· Results in higher pressures in the condenser which causes the compressor to pull higher amps.
· Higher amp draw means more stress on the motors, overheating of the motor, and potentially leading to premature failure.
· At other times we observe that the outdoor fan is not running; this could be caused by a damaged capacitor, bent fan blades of fan motor failure. Wear & tear is the most common reason for a failing exterior fan. Another common reason for failure is the accumulation of dirt and debris on the fan blades, and loose or corroded terminals and contactors, i.e., lack of regular maintenance.
· Lack of adequate air flow through the condenser causes the condenser fan motor to run hotter than normal and the compressor to run hotter because of the higher load conditions; all these lead to premature failure of these components. Most of the time, the HVAC tech will state that power surge caused the damage to the equipment.
Loose or Corroded Terminal Problems will also lead to Failure
Problems with loose or rusted terminal pins are also a common cause of AC compressor failure. See Figure 2. If the terminal pins are loose or “blown” on a compressor, then the compressor will need to be replaced. However, pin failure does not indicate damage by a surge voltage or lightning stroke. The most likely cause of a burned electrical terminal on a compressor is a loose electrical connection. This loose connection causes a buildup of heat and results in a burned terminal.
Rusty terminal connections also create the same low voltage condition as loose terminal pins. When a low voltage condition occurs, the motor will slowly fail. This low voltage condition also causes even higher heat to develop at the terminal pin connection causing even greater rust. This results in additional disintegration of the connection and causes low voltage to be supplied to the motor which eventually causes the motor to fail or the terminal pin(s) to become dislodged.
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Did you know that repeat compressor failures are usually due to system contamination (sludge or metallic particles from a previous compressor failure)?
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It is possible to have damaged pins due a lightning strike, but this is limited to situations where the lighting strike damage is severe. In these cases there is a lot of other evidence of a lightning strike. The condenser fan motor or other electrical components of the system will have been damaged. The wires are burnt and there is evidence of arc marks to the cabinet where the wires run close to the cabinet. There is also considerable damage to other motors and appliances as well as to the electric panel.
Figure 2. Burned compressor plug due to defective (loose) connection to the compressor. Initially the HVAC techs claimed that this was caused by power surge. However, there was no other evidence (storms, lightning, utility reports, etc.) to support that claim. A power surge big enough to do that damage to the compressor plug would have damaged the whole control section, capacitor, contactor and most of the wiring. No such evidence was observed during our investigation.
In case of any equipment or HVAC compressor-related problem, it is important to identify the root cause, without jumping to the conclusion that the equipment was damaged by lightning or power surge. If the compressor is replaced without attending to the root cause, the replaced compressor surely will also fail.
Metropolitan Engineering, Consulting & Forensics (MECF)
Providing Competent, Expert and Objective Investigative Engineering and Consulting Services
P.O. Box 520
Tenafly, NJ 07670-0520
Tel: (201)293-6064
E-mail: metroforensics@gmail.com
Web pages: https://sites.google.com/site/metropolitanenvironmental/
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