What is high discharge temperature?
High discharge temperature is the result of temperatures in the compressor head and cylinders becoming so hot that the oil loses its ability to lubricate properly. This causes rings, pistons and cylinders to wear resulting in blow by, leaking valves, and metal debris in the oil.
What should compressor discharge temp be?
225°F.The compressor's discharge temperature should be measured about 1 to 2 inches away from the compressor on the discharge line. This discharge temperature should never exceed 225°F. Carbonization and oil breakdown can occur if compressor discharge temperatures exceed 225°.
Where is the discharge temperature located?
The compressor's discharge line temperature can be measured by placing an insulated thermistor on the discharge line about 3 inches from the compressor. This discharge line temperature is a measure of the superheated refrigerant's vapor temperature.
What does a discharge thermostat do?
The discharge thermostat is a temperature sensing safety device that turns power off when the compressor discharge temperature exceeds 240°F. It is a bi-metal clip-on type with manual reset. If the discharge thermostat activates and turns power off, it can be reset by depressing the red button as shown in Figure 1.
How can I lower my discharge temperature?
Discharge temperature is greatly affected by the compression ratio, the larger the compression ratio, the higher the discharge temperature. Reducing the compression ratio can significantly reduce the discharge temperature, including increasing the suction pressure and reducing the discharge pressure.
What causes low discharge temp?
Low discharge superheat usually the situation occurs because of overcharge of refrigerant or overcharge of oil. Both condition gives lower discharge temperature. Once the refrigerant is saturated with oil low discharge will continue to occur.
What is a discharge AC line?
DISCHARGE LINE - Line connecting compress outlet to the condenser inlet. DRIER - A device containing a desiccant placed in series, usually in the liquid line, to absorb and hold excess moisture. Usually called receiver-drier.
What is discharge line in HVAC?
• Discharge gas lines (often referred to as hot gas lines) allow refrigerant to flow from the discharge of the compressor to the inlet of the condenser. • Undersizing discharge lines will reduce compressor capacity and increase compressor work.
What can cause high discharge pressure?
One common cause of high discharge pressure is the cooling medium (air or water) flowing across the condenser: either there is not enough or the temperature of the cooling medium is too high. This is normally easy to identify with a simple visual inspection of the condenser.
Why is discharge superheat important?
The higher temperature can cause oil breakdown, formation of the acid and failure of rings. The compressor will be considered overheated above this temperature limit. The system will work efficiently by continuous monitoring the discharge temperature of the compressor.
How hot should heat pump be?
Check the discharge (vapor) line; it should be 100°- 110° over the outdoor ambient temperature. Suction line temp should be 5°-15° cooler than the outdoor temperature. The liquid line should be 3°-15° warmer than the indoor temperature.
What temperature should the liquid line be?
Also, note how much warmer the liquid line is than the outdoor temperature. It should be between 3°F and 20°F warmer than the outdoor temperature. If it is above or below that range, connect gauges.
What is discharge pressure of a compressor?
Discharge pressure (also called high side pressure or head pressure) is the pressure generated on the output side of a gas compressor in a refrigeration or air conditioning system.
What causes high compressor discharge pressure?
One common cause of high discharge pressure is the cooling medium (air or water) flowing across the condenser: either there is not enough or the temperature of the cooling medium is too high. This is normally easy to identify with a simple visual inspection of the condenser.
What is the normal temperature difference between the air entering and air leaving the evaporator in an air conditioning system?
So even though there's no single ideal temperature, you do want a 16°–22° F difference from the supply air and return air. Professionals call this temperature difference the evaporator Delta T.
What is discharge temperature?
The discharge temperature is a measure of the superheated refrigerant’s vapor temperature. Since the compressor’s discharge temperature is a superheated vapor temperature measurement, a pressure/temperature relationship does not exist, and a pressure gauge cannot be used for its measurement. Pressure gauges can only be used for a ...
Why is my compressor discharge temperature so high?
Some of the reasons for high compressor discharge temperatures are: High condensing pressures; Low suction pressures; High compression ratios; and. High compressor superheats. Causes for the above reasons will be explored below.
Why is my compressor superheating?
High compressor superheats can be caused from the evaporator being starved of refrigerant. This can happen with a restricted liquid line, undercharge, plugged filter-drier, kinked liquid line, or TXV or capillary tube underfeeding.
What causes high condensing pressure?
Causes for high condensing pressure include dirty condenser coils, burned-out condenser fans, broken fan belts, undersized condenser coils, overcharge of refrigerant, noncondensables in the system, high ambient temperature, and recirculated air over the condenser.
What is the temperature of a compressor?
The limit to any compressor discharge temperature is 225 degrees F. If the discharge temperature gets higher than 225 degrees , the system may start to fail from worn rings, acid formations, and oil breakdown. Remember, if the discharge temperature is 225 degrees, the actual discharge valve will be about 75 degrees hotter.
What is the hottest part of a compressor?
The back of the compressor’s discharge valve is actually the hottest part of the system, but it is impossible for a service technician to measure. The next closest place, however, is the discharge line of the compressor. The limit to any compressor discharge temperature is 225 degrees F.
What temperature does oil vaporize?
This will bring the actual compressor’s discharge valve to 300 degrees. It is a known fact that most oil may start to break down and vaporize at 350 degrees. If this occurs, serious overheating problems will happen.
What is the discharge line temperature?
This discharge line temperature is a measure of the superheated refrigerant’s vapor temperature. Remember, superheated refrigerant refers to a refrigerant vapor that is at a higher temperature than its saturation temperature for a certain pressure. The certain pressure would be the condensing pressure for the high side of the system in this case.
What does the discharge temperature of a compressor tell you?
The compressor’s discharge temperature can tell the service technician what is going on inside a refrigeration or air conditioning system. The compressor’s discharge temperature is a reflection of the hottest part of a refrigeration system, and there are limits as to how hot a discharge temperature should be. READ MORE ABOUT.
What causes high condensing pressure?
Causes for high-condensing pressures can include: Recirculated air over the condenser. A high condensing temperature causes a high condensing pressure. In this case, the compressor must work harder — thus, generate more heat of compression — in compressing the suction pressure to the higher condensing pressures.
How to measure compressor discharge temperature?
The compressor’s discharge line temperature can be measured by placing an insulated thermistor on the discharge line about 3 inches from the compressor. This discharge line temperature is a measure of the superheated refrigerant’s vapor temperature. Remember, superheated refrigerant refers to a refrigerant vapor that is at a higher temperature ...
Why is the compressor discharge temperature higher?
This happens because more heat of compression will be generated when compressing the gases through a greater pressure range. Causes for high compressor superheats can include the evaporator being starved of refrigerant.
What happens if a compressor is overheating?
If the compressor’s discharge line temperature gets higher than 225°F, the system may start to fail from worn rings, acid formations, and oil breakdown. Remember, if the discharge temperature is 225°F, the actual discharge valve temperature will be about 75°F hotter, which will bring the actual compressor’s discharge valve to 300°F. It is a known fact that most oil may start to break down and vaporize at 350°F. If this occurs, serious overheating problems will happen. Since compressor overheating problems are today’s most serious compressor field problems, service technicians must always monitor compressor discharge temperatures and keep them under 225°F.
What is superheated refrigerant?
Remember, superheated refrigerant refers to a refrigerant vapor that is at a higher temperature than its saturation temperature for a certain pressure. The certain pressure would be the condensing pressure for the high side of the system in this case.
Why is the discharge temperature important?
However, it is very important because it 's an indication of the amount of heat absorbed in the evaporator and suction line, and any heat of compression generated by the compression process.
What temperature should a compressor discharge be?
This discharge temperature should never exceed 225°F. Carbonization and oil breakdown can occur if compressor discharge temperatures exceed 225°. The three causes for high discharge temperatures are: ...
What causes a compressor to discharge at high pressure?
Low evaporator pressures also may cause a high compressor discharge temperature. When evaporator pressures are low, the compressor must compress refrigerant from this lower evaporator pressure to the condensing temperature. This added work of compression would make the heat of compression higher. Thus, the compressor's discharge temperature will be higher.
What happens when the condensing temperature is high?
When the condensing temperature is high, the compressor must compress the refrigerant from the low-side (evaporating) pressure to an elevated high-side (condensing) pressure. This added work done by the compressor would raise the heat of compression. Thus, the compressor's discharge temperature will be higher.
What causes a frosted evaporator coil?
Frosted evaporator coil from a bad defrost heater or other defrost component malfunction.
How far away should the discharge temperature be from the compressor?
The compressor's discharge temperature should be measured about 1 to 2 inches away from the compressor on the discharge line.
Why is there a pressure-temperature relationship with the condensing temperature?
There is a pressure-temperature relationship with the condensing temperature because of the phase change. A gauge reading on the high side of the system is all that is needed to find the condensing temperature. Convert this pressure to a temperature using a pressure-temperature chart. This is the condensing temperature.
