Troubleshooting an Air Condition System

Troubleshooting your AC system usually concerns airflow, mechanical and refrigerant problems, either one of the issues mentioned above or a combination of one or more. In this article, we will take a closer look at some of the most common air conditioning problems, according to air conditioning experts. It will cover AC issues like inefficient compressors, air temperature problems as well as issues in the refrigeration system.

Condensers and Air Temperature

Air temperature entering the condenser at very low pressure can cause problems with the condenser because of excessive transfer of heat between cold ambient air and the refrigerant in the unit’s condenser coil. Low head pressure can lower refrigerant flow rates through the metering device. 

It has a capacity rating that is dependent on the difference in air across them. The lower air pressure difference is less airflow through the device. It reduces the refrigerant flow rate and can cause a problem in the evaporator. 

In turn, it can cause low suction pressure and high super-heat. But the issues in the system, as well as its inefficiencies, can be offset by increasing the sub-cooling of the lower ambient temperature that enters the condenser coil. 

The drop in the system capacity can decrease the unit’s heat removal capabilities if the unit is not designed for it. If the air conditioner is not adequately developed, the liquid will start to go back to the condenser and can cause an increase in condenser liquid sub-cooling. 

Not only that, if it has less refrigerant circulating, it means the compressor will have less work, so the compressor’s ampere draw will be lowered. If your AC system is designed for a low condenser air temperature, the head pressure can be set up to float or it can be changed when the ambient temperature is also changing. It will give a lower pressure with increased efficiency. 

An adequately matched TXV or thermostatic expansion valve to handle the lowered pressure drop across the unit’s orifice can be incorporated into its design to keep the refrigerant flow rate acceptable. Thermostatic expansion valves with balanced-port designs are usually used in these types of scenarios.

To find out more about TXV, check out https://www.brighthubengineering.com/hvac/59422-working-of-the-thermostatic-expansion-valve/ for more information.

Common symptoms of a unit with low condenser entering temperature include:

  • Lower suction pressure
  • Lower head or condensing pressure
  • Higher super-heat
  • Lower ampere draws

High condenser sub-cooling

TXV system will maintain the evaporator super-heat, even if the it drops across all the valves. It might be out of the unit’s control range at higher ambient temperatures. The condenser sub-cooling can be normal, but the flow rate through the capillary metering device will depend on how much pressure difference all over the metering device. 

Higher head pressure can increase the flow rate using the metering device. It pushes the sub-cooled liquid at the bottom of the condenser using the metering device at a much faster rate. Because of this phenomenon, the condenser sub-cooling will decrease, the same with the evaporator super-heat, since the flooded unit evaporator coil will have a flash gas in its entrance.

Inefficient compressors

Because the compressor is responsible for circulating the refrigerant all over the AC system, an inefficient compressor can lower the heat transfer capabilities of the air conditioning unit. In cases of reciprocating compressors, worn piston rings, as well as leaky valves, are considered as the most common problems that can lead your compressors to be inefficient. 

One symptom of an inefficient compressor is a high suction pressure with low head discharge. If your compressor is inefficient, evaporators can’t handle high heat loads because of decreased refrigerant flow rates, as well as the conditioned space temperature starting to rise. 

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The rise in return temperature will make the evaporator overload with heat. It can cause a high suction pressure, as well as higher-than-average super-heats. A blown piston ring and leaks in the reed valve can also create a high suction pressure from the re-circulation of the refrigerant. 

It can also cause a low flow rate in the coolant. The condenser will see a decrease in heat load to reject the lower mass flow rate of refrigerant that is flowing through it. It can cause lower condensing pressure and temperature. 

The ampere draw of the compressor will minimize from less work because of the expansion with the low flow rate of the refrigerant from recirculated ones. Condenser sub-cooling should be a bit low from reduced heat loads on the air conditioning condenser.

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