In our previous article we discussed the problems associated with not fitting a compressor overload this time we are looking at what can happen when engineers fail to replace the compressor electrics after a compressor failure. It is customary to fit a contactor, with an overload protector, into the electrical control circuit of the compressor, [...]
Read the Beginners HVAC Tech’s Guide for Understanding Superheat by ACHR News. Superheat is oftentimes the most confusing measurement taken in the field. TRICKY CALCULATION: Superheat is actually the difference between two measurements. And the term “heat” causes confusion, since the value can be negative. Much like subcooling, understanding and calculating superheat can be somewhat [...]
Checking refrigeration, air conditioning and heating systems for leaks is a complex challenge. For example, even the wrong choice of leak test method, such as the water bath method, can cause the tester to overlook leaks because he has not considered the deformability and volume change of the test piece. Inficon has compiled a top 10 checklist of [...]
One of the most common and simplest of causes of compressors failure is due to the plant electrics not having a compressor overload fitted. When large Semi-Hermetic or Hermetic Compressors are fitted to systems where the compressor contactor has no overload fitted, the compressor is left wide open to liquid washout, Valve breakages or even [...]
Lack of lubrication can be categorised under two main headings. They are: Lack of lubrication Lack of oil Lack of lubrication: Lack of lubrication is where the oil either cannot lubricate the bearings due to the oil being degraded, or when the lubricant cannot reach the bearings due to blockages or loss of oil. Oil [...]
Compressors naturally run warm due to the heat from the Motor, from friction and from the Compression cycle. Providing the compressor runs within its design limits then it will give long and reliable service. When the compressor is run outside of its design limits or some other external situation exists that creates this problem then [...]
Liquid Slugging is where extreme cases of Flooded Start or Liquid Flood Back occur. When large quantities of liquid refrigerant enter the compressor and then mix with the lubricating oil in the compressors sump. The resulting liquid/oil mixing and diluting, then creates major amounts of liquid and oil droplets in a frothy foam mixture. [...]
Flooded starts are probably the major cause of compressor failures. Flooded starts occur when liquid refrigerant has migrated from the system and condensed into the compressor oil. Migration can occur in all systems up to a point, due to the vapour pressure of the refrigerant being greater than the vapour pressure of the oil. It [...]
Refrigerant flood back occurs during the running cycle of the machine. This is where large volumes of liquid refrigerant are returned to the running compressor down through the Suction pipe work, in an uncontrolled manner. Depending on the degree of liquid returning to the compressor, determines as to what damage will occur. This can often [...]
We will post a few blog posts from Danfoss learning on why compressors fail to assist Technicians and Refrigeration Engineers in understanding the causes of compressor failures, their diagnosis, rectification and prevention. There are 5 main reasons for compressor failure: Refrigerant Flood Back Flooded Starts Liquid Slugging Overheating Lack of Lubrication The first 5 blog posts will [...]
