What are 3 causes that may lead to liquid slugging a compressor with liquid refrigerant?

Slugging can result in broken valves, broken head gaskets, broken connecting rods, and other major compressor damage. Refrigerant-cooled semi-hermetic compressors will often draw liquid from the suction line through hot motor windings in the motor barrel, which will assist in vaporizing any liquid.

What causes slugging?

Slugging is a short-term return of a mass of liquid, consisting of refrigerant or oil, or as a mixture of both. The slug enters the cylinders of the compressor instead of super-heated vapor. Slugging almost always occurs on startup, but a very rapid change in system operating conditions can also cause slugging.

What causes some liquid refrigerant to return to a running compressor?

Most commonly this liquid is refrigerant that has not boiled off in the evaporator. If the liquid refrigerant entering into the evaporator is not allowed to absorb heat by way of the indoor evaporator coil, it will not receive a change of state to a gas, thus allowing it to return to the compressor as a liquid.

What are the reasons for liquid flooding in the compressors?

Flooded starts occur when two factors are present: 1) the compressor is off, and 2) liquid refrigerant in the system and the compressor oil are allowed to be in contact with each other.

What happens when liquid refrigerant enters compressor?

What happens if liquid refrigerant enters the Compressor. Compressors are meant to compress gasses as gas is a compressible fluid. On the contrary, liquids are incompressible. If an incompressible fluid enters the Compressor, it can potentially damage the Compressor internals.

Liquid Slugging- HVAC Tech Tips

What causes AC compressor slugging?

Slugging can result in broken valves, broken head gaskets, broken connecting rods, and other major compressor damage. Refrigerant-cooled semi-hermetic compressors will often draw liquid from the suction line through hot motor windings in the motor barrel, which will assist in vaporizing any liquid.

How does liquid refrigerant affect the compressor crankcase?

When the compressor does turn on, the sudden pressure drop on the crankcase containing liquid refrigerant and oil will cause the refrigerant in the oil to flash to a vapor. This causes violent foaming in the crankcase.

How do you prevent flooding and slugging?

How do you prevent flooding and slugging? Keep superheat at proper levels.

What will happen to the refrigerant liquid?

If liquid refrigerant has to rise from the condenser or receiver to an expansion valve at a higher level, there will be a loss of static head, and the refrigerant may reach its boiling point and start to flash off.

What causes refrigerant migration?

Refrigerant migration occurs as a result of a difference in vapor pressure between the oil in the crankcase of the compressor and the refrigerant vapor in another part of the system.

What prevents liquid refrigerant from entering compressor?

Suction line accumulators are designed to protect the compressor when refrigerant flooding and/or migration do occur. They should be installed between the evaporator and the compressor on the suction line, usually as close to the compressor as possible.

What causes high liquid pressure?

Overcharging of refrigerant,

liquid slugging of the compressor, oil contamination and other sources can damage compressor valves. Refrigerant overcharging will show up as high head pressure, normal suction line pressure, normal superheat, high sub-cooling.

What is the most common cause of compressor failure?

Overheating is a common cause of compressor failure, and there are many factors at play. If direct sunlight falls on your outdoor unit and there is inadequate ventilation around it, it makes your unit's compressor overheated. High voltages can also damage the motor causing the compressor to overheat.

What causes scroll compressor failure?

After floodback and slugging, Park said the major causes of compressor failure, in order of importance, include bad contactors, system leaks, dirty evaporators, dirty filters, dirty condensers, rapid loading/unloading, mis-wired/misadjusted controls, low superheat, and wrong oil for the system refrigerant.

What is the main reason behind subcooling of liquid refrigerant at the condenser outlet in vapour compression refrigeration system?

Subcooling is beneficial as it increases the refrigeration effect by reducing the throttling loss at no additional specific work input. Also, subcooling ensures that only liquid enters the throttling device leading to its efficient operation.

What is the condition of the refrigerant inside the liquid line?

When the refrigerant leaves the compressor, the refrigerant in the discharge line is all vapor. As the refrigerant moves through the condenser it begins to cool, and changes state. At this point the refrigerant is a mixture of liquid and vapor.

What effects does water have when introduced in a system with refrigerant?

Moisture refers to water in any form (solid, liquid or gas). When moisture is introduced in the system, it may combine with the system refrigerant to form an acidic solution which can erode internal compressor components.

How do you prevent liquid migration?

The only sure solution to avoiding migration is to get rid of all the refrigerant in the evaporator, suction line, and crankcase before the off cycle. This can be accomplished by an automatic pumpdown system. In such a system, a thermostat controlling box temperature is wired in series with a liquid line solenoid.

What is the difference between slugging and flooding?

What is the difference between flooding and slugging? Flooding is a little liquid refrigerant reaching the compressor; slugging is a lot of liquid refrigerant reaching the compressor all at once.

What is the most common problem that enters a refrigerant system?

While there are many different potential causes of compressor failure, high compressor discharge temperatures represent one of the most common problems when it comes to commercial refrigeration.

What is the biggest problem caused by moisture in the refrigeration system?

Moisture will cause acid to form in the system causing serious damage to the compressor and expansion valve parts. It also deteriorates the insulation of the motor windings in the compressor. In the more advanced stages, compressor motor burnout and repeated compressor motor burnout happens.

What causes a compressor to trip on high pressure?

High pressure occurs when the needle valve gets partially stuck open and goes directly into the compressor's crankcase. This causes both high low-side pressures and low high-side pressures. You should closely monitor whether or not the oil return line is above or below the ambient surrounding temperature.

What can cause a high discharge pressure in a refrigeration system quizlet?

What can cause a high discharge pressure in a refrigeration system? Low evaporator level. Too much cooling water to the condenser.