Air Conditioner and Heat Pump Compressor Burn-out

There may come a day when your air conditioner or heat pump system fails to cool your home or business and you call an air conditioning and heating contractor to fix the problem. The air conditioning and heating HVAC technician arrives and starts the process of troubleshooting the system. About 30 minutes later the air conditioning and heating HVAC technician reports back to you that your compressor is burned-out and it either needs replacing or the HVAC system needs to be replaced. HVAC Compressor burn out is a serious and costly matter. Replacing the system requires a judgment call on your part based on the cost of the burned out HVAC compressor replacement (if the burned out HVAC compressor is still under warranty you may still have to pay for labor to replace the burned out HVAC compressor), the current age of the air conditioning and heating HVAC equipment, and whether you have the money in your budget to replace the HVAC system. Before any of that you'll want to know what happened to cause the HVAC compressor to burn out in the first place. There are many reasons why an air conditioning and heating HVAC compressor can burn up but the primary causes are neglect. Here is a list of possible reasons a HVAC compressor can burn out. Some of these reasons for HVAC compressor burn out are beyond your control but the things that are in your control need to be addressed on a regular schedule.

• Poor Maintenance to the HVAC system especially the air conditioning or heat pump condenser. HVAC Compressors don't get compressor burn out because of poor maintenace on the HVAC compressor. Many hermetic HVAC compressors are maintenace free so you need to look at the condenser instead of the HVAC compressor. Over a period of time the air conditioning and heat pump condenser coils can become clogged with dust, dirt, and debris. This restricts air flow through the coils and causes pressures and temperatures to rise inside the air conditioner or heat pump condenser including the air conditioner or heat pump HVAC compressor. Under extreme operating conditions the air conditioner or heat pump HVAC compressor has to work harder to compress and pump the refrigerant through the air conditioner or heat pump system. When the compressor works harder it pulls more amperage which causes it to run hotter than normal. If the air conditioner or heat pump HVAC compressor surprises its normal rated operating temperature things inside the compressor start to break down and eventually over time the air conditioner or heat pump HVAC compressor will fail and the result is HVAC compressor burn out. There are built in protections against compressor overheating but these protections are prone to failure under extreme conditions or may allow the compressor to run at just below the temperature protection level but over time the air conditioning or heat pump HVAC compressor this higher than normal temperature will cause compressor burn out.
• Restriction in the refrigerant lines can also cause a compressor to burn out. Compressor burn out can occur as a result of a malfunctioning or clogged metering device or damage to the refrigeration line set. The copper lines that run between the condenser and the evaporator coil can be damaged or crimped which will restrict the flow of refrigerant. This refrigerant flow restriction causes an imbalance in the pressures of the air conditioning or heat pump system which causes the air conditioner or heat pump compressor to work harder. This causes higher compressor operating temperatures and amp draws which leads to burn out especially under extreme operating conditions. A refrigerant line can become damaged when someone steps on or twists one of the copper lines running from the air conditioner or heat pump condenser to the evaporator coil which is usually located in the air handler. The damage may or may not affect the cooling capacity of the air conditioner or heat pump system but it needs to be corrected as soon as possible. There are instances when the installation crews inadvertently crimped the lines upon installation and the problem can remain hidden until the air conditioner or heat pump system has a compressor burn out. A good air conditioning or heat pump technician using thorough air conditioning and heating troubleshooting techniques can resolve the issue and prevent a compressor burn out before it happens.
• Restricted or malfunctioning metering device can also cause the air conditioning or heat pump compressor burn out. This can be a very difficult problem to diagnose even for experience technicians especially when the problem is intermittent. The most common metering devices are fixed orifice metering devices and thermostatic expansion device (TXV). Fixed orifice metering devices can become clogged with trash or even ice up if moisture is in the system and this can lead to compressor burn out. The same thing can happen with a TXV metering device however the TXV is more complex than the fixed orifice metering device but it too can malfunction and result in compressor burn out. The TXV has moving parts and these moving parts can stick causing the system to experience restrictions. Burned out compressors have been replaced before and two weeks later the technician is back looking at another burned out air conditioner or heat pump compressor because this problem was intermittent and not diagnosed when the new air conditioner or heat compressor was installed. Now everyone is scratching their heads, the air conditioning or heat pump technician looks bad, and the customer is perturbed. It happens and the best thing to do is find the intermittent metering device problem and replace the old burned out compressor.
• Moisture in the refrigeration system can also cause air conditioner or heat pump compressor burn out. Moisture in the refrigeration system will eventually cause compressor burn out and is usually a result of poor installation. The oil in the refrigeration system mixes with moisture and creates an acidic sludge that slowly eats away at the windings on the compressor motor. It is important that the installation create uses proper installation practices when installing a new air conditioner or heat pump system or that the air conditioner or heat pump technician service technician use the proper methods and procedures when opening the air conditioner or heat pump refrigeration system for any reason. A triple evacuation along with nitrogen purge in many cases will eliminate all moisture and non-condensable gases in the air conditioning or heat pump system. This along with using the proper filter driers will prevent compressor burn-up from moisture. The filter drier should be replaced any time the air conditioner or heat system is opened for any reason.
• Oil loss from refrigerant leaks can be another reason for air conditioner or heat compressor burn out. This is common as many people do not want to pay to find a refrigerant leak when the cost of filling the air conditioner or heat pump system up with refrigerant is cheaper. Whenever there is a refrigerant leak oil from the system also leaks out through the same hole where the refrigerant is escaping. The proper oil level is necessary for good lubrication and also cooling the compressor. While the air conditioner or heat pump compressor is cooled mainly by the return suction gas the oil still contributes to keeping the air conditioner or heat pump compressor cool by reducing friction in the air conditioner or heat pump compressor. The best advice High Performance HVAC Systems can offer is that you have the technician find and fix the leak. This will cost more than just filling the air conditioner or heat pump system with refrigerant but the long term alternative will cost more. This is especially true for the new R-410A refrigerant systems which operate at higher pressures than the older R-22 systems.
• Compressor short cycling can also cause air conditioner or heat pump compressor burn out. This occurs when the unit is turned on and off quickly without giving it proper time to recover, equalize, and cool down. An air conditioner or heat pump compressor pulls a high amp draw on start up which is technically called locked rotor amps. The compressor has to start from a full stop to full blast in less than a second. It also has to overcome the head pressure and if the unit just quit (within the last 3 minutes) the head pressure is still high and equalizing. Starting and stopping and the compressor continuously under these conditions will create a lot of heat and this increased heat level can cause compressor burn out. An air conditioner or heat pump unit with the proper controls that prevent short cycling will prevent compressor burn up under these circumstances. Many modern digital heating and cooling thermostats have built protection for short cycling. The heating and cooling thermostat has a built in delay which prevents the user from turning the air conditioner or heat on and off and on again too quickly.
• Defective compressor can also be the cause of an air conditioner or heat pump compressor burn out. This is not very common but it does occur. Hopefully if this happens to you the air conditioner or heat pump compressor is still under warranty. Either way, it is important for the air conditioning and heating technician to look at the other issues described here before determining that it was a defective compressor. Other issues to look at in the air conditioner or heat pump compressor system are the capacitor and the proper amount of voltage the compressor is getting. The capacitor and the voltage should fall into plus or minus 10 percent of the rating by the compressor manufacturer. Anything out of this range can cause problems which lead to compressor burn-up or burn-out.
• Lightening strikes can fry an air conditioner or heat pump compressor and other components in the air conditioner or heat pump system. In this case hopefully your insurance will cover the cost of replacing the air conditioner or heat pump. A large amount of voltage and current passing through an air conditioner compressor which is running can have devastating effects the may damage the system beyond repair.

While compressor burn out is quite common for compressor failures another common problem is compressor lock up. An air conditioner or heat pump compressor is a mechanical and electrical device. It has mechanical parts which are driven by an electric motor. If the mechanical parts lock up or seize up and the electric motor in the compressor does not have the horsepower to overcome the lock up or seizing of the mechanical parts then the compressor is mechanically locked up. There are techniques a good air conditioning and heat pump technician can use to unlock the compressor but approximately 25 percent of compressor lock ups cannot be unlocked. It becomes necessary to replace the air conditioner or heat pump compressor or the whole condenser. The important thing is that you have a regular maintenance schedule for the air conditioner or heat pump system to prevent most problems that can cause compressor burn out, burn up, or mechanical lock up.

Here is a video of a man explaining preventive maintenance on condenser coils. Dirty condenser coils contribute greatly to burned-out compressors.

Comments (2)

Professional Mechanical Engineer
written by Richard P. Grelle P.E., August 16, 2008

This is a very poor article, and misleading to may technicians that may devote the time invested in reading it!

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written by WEBMASTER, August 16, 2008

It is easy to wave a magical wand and say something is bad. This is technical information and so when someone is critical of it then they must have hard evidence or scientific fact to back up the reason why they were critical if the article. Please educate us as to why you say what you said Mr Grelle P.E. We are anxiously awaiting your scientific facts about the reason this is a bad article for technicians.

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