What is an Exv?

What is an Exv?

The EXV is a control valve driven by a geared motor for use in A/C systems for the chemical refrigerants R134a and R1234yf. It is increasingly used in electric vehicles equipped with heat pumps. In addition to serving as an expansion valve, it can also be used as a shut-off valve.

What is the function of thermostatic expansion valve?

A thermostatic expansion valve (TXV) (see Figure 1) is a refrigeration and air conditioning throttling device that controls the amount of refrigerant liquid injected into a system’s evaporator—based on the evaporator outlet temperature and pressure—called the superheat.

How do you diagnose a bad Txv valve?

Check the evaporator coil and remove the TXV’s sensing bulb from the suction line. Check the subcooling, superheat and pressures again. If there’s no change, that’s a further indication of a TXV problem. Another test is to put the sensing bulb in ice water and checking the pressures superheat, and subcooling again.

How do you fix a stuck Txv valve?

Opening of the valve should be relatively quick. Even holding he bulb in your hand should provide enough heat to open the valve. Next, place the TXV bulb into cold water. This should cause the expansion valve to close reducing the amount of refrigerant to pass thought the TXV into the coil.

How do you test an AC expansion valve?

How to Test an AC Expansion Valve

1. Make sure the AC unit is plugged in or, if it is in an automobile, turn the vehicle on.
2. Use the manual to locate the thermostatic expansion valve.
3. Lift the sensing bulb from the suction bulb well.
4. Hold the sensing bulb in your hands for two minutes or place it in warm water.

Can you clean an expansion valve?

It is very difficult to determine if a Thermostat Expansion Valve is clean. The only way to be sure the valve is clean is to put it back into operation and run a system performance test. If there is any malfunction, the unit must be disassembled again to change the valve.

How do I adjust my AC expansion valve?

Locate the adjustment needle on the thermostatic expansion valve. Turn the adjustment needle one quarter turn counterclockwise to decrease the temperature. Each quarter turn is equal to one degree. Turn the adjustment needle a quarter turn clockwise for each degree needed, to increase the temperature.

What happens if expansion valve is stuck open?

If the expansion valve is stuck open or clogged, the AC system won’t cool properly. A clogged valve leads to insufficient refrigerant, increasing the pressure in the system and causing the AC compressor to overheat.

What temp should my suction line be?

The suction temperature should be above 35°F and below 65°F entering the compressor and the discharge line temperature should be below 220°F and above 150°F (typically) on a properly functioning package unit.

What is the difference between suction line and discharge line?

The suction line connects the evaporator to the compressor, the discharge line connects the compressor to the condenser, and the liquid line connects the condenser to the expansion device. The expansion device is typically located at the end of the liquid line, at the inlet to the evaporator.

Why isnt my suction line sweating?

This can be caused by low air flow (dirty filter, slipping belt, undersized or restricted ductwork, dust and dirt buildup on blower wheel) or a dirty or plugged evaporator coil. Checking superheat will indicate if the low suction is caused by insufficient heat getting to the evaporator.

What causes the suction line to get hot?

The large suction line can be colder or warmer depending on the amount of refrigerant and the temp in the house. As refrigerant pressure begins to drop, the system doesn’t have enough capacity to handle the heat in the house. This will cause the line to be warmish…

Why is the liquid line smaller than the suction line?

or why the discharge line is smaller than the suction line?? If your talking about the discharge line off the compressor, it is smaller because the refrigerant vapor that goes through it is compressed, so the same quantity of refrigerant can move through a smaller line.

Why suction pipe is bigger than discharge?

The suction pipe of a centrifugal pump is not necessarily a larger bore (diameter) than the discharge pipe. They can be the same size. This is in order to ensure sufficient available Net Positive Suction Head (NPSHa) to meet the NPSH required (NPSHr) by the pump.