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Cause of High Discharge Temperatures

HVAC unit

Perhaps the single most important component inside of your air conditioning system is the compressor. The compressor circulates refrigerant throughout the system, and it consists of a motor used to increase the pressure of the refrigerant flowing back to the outdoor condenser unit from the evaporator coil located inside your home.

In the process of raising the refrigerant's pressure, the compressor also increases its temperature. While a natural part of the process, this temperature increase can also lead to serious problems if the refrigerant becomes overheated.

HVAC technicians gain valuable insight into the health of an air conditioner by measuring the discharge temperature of a compressor. Discharge temperatures in excess of 275 degree Fahrenheit will wreak havoc on your system. Fortunately, once a technician has identified an excessive discharge problem, they can move on to nailing down the specific cause.

This article will increase your awareness of air conditioner mechanics by discussing one of the most common causes of high discharge temperatures: an elevated condensing temperature.

Condensing Temperature

In order for refrigerant to effectively absorb heat inside of the evaporator coil, its temperature must first be reduced, while still maintaining high pressure. The condenser carries out this important task.

The condenser includes a copper tube embedded inside of thin aluminum fins, which help to disperse the heat of the refrigerant. A fan circulates outdoor air across the fins. The refrigerant entering the condenser has a temperature much higher than that of the outdoor air, and this difference allows the heat exchange to occur with relative efficiency.

Once the refrigerant's temperature has dropped to a certain point, it changes back into a liquid. The temperature at which this occurs goes by the name of the condensing temperature. Contrary to popular belief, condensing temperatures do not always remain constant. Instead, the condensing temperature changes in relation to the condensing pressure.

As the condensing pressure rises, the compressor has to work extra hard to bring the refrigerant to the necessary temperature. As a result, the discharge temperature may reach dangerous levels. Unless a technician addresses the underlying problem, the issue may only grow worse.

Causes of High Condensing Temperature

Now that you understand the link between condensing temperature and discharge temperature, you are probably curious about the things that can lead to excessive condensing temperature. A wide variety of issues may be at play. Most of these issues have to do with things that reduce the efficiency of the condenser's heat transfer.

A dirty condenser coil represents one of the most common causes of high condensing temperatures because a dirty coil makes it harder to get rid of the refrigerant's heat. In order to overcome this added difficulty, the refrigerant must be more pressurized. And, as discussed above, higher pressures always come with higher temperatures - for both the refrigerant and the compressor.

High condensing temperatures may also be the result of inefficient air movement. Debris, shrubs, or other vegetation may have blocked airflow into the condensing unit. Alternately, the condenser fan may have burned out. This fan ensures consistent cooling by pulling air into - and then out of - the condensing unit.

Condensing temperatures also change in relation to the outdoor air temperature. As ambient temperatures grow higher, the temperature difference between the refrigerant and the outdoor air shrinks. At a certain point, the system has to compensate by increasing the refrigerant's pressure.  

Regular maintenance ensures that all parts of your air conditioning system continue operating within acceptable limits. This prevents potentially catastrophic problems like high discharge temperatures. For more information on keeping your air conditioner running strong, please contact the pros at Action Plumbing & Heating Maintenance.