The wax constant temperature component is known to everyone and is an indispensable throttling mechanism for HVAC systems. In the troubleshooting of expansion valves, there is a point that is often overlooked, that is, the location of the wax thermostatic element.
Expansion valve and wax thermostatic element position
1. The expansion valve must be installed in the liquid pipeline located before the evaporator;
2. The wax constant temperature element should be fixed on the suction line as close to the evaporator as possible.
If there is an external pressure equilibrium, the balancing tube must be connected to the suction line immediately after the wax thermostatic element is released.
The wax thermostatic element is in the trachea position
The wax thermostatic element is best installed on the horizontal suction tube, and the orientation should be the corresponding position between 12 and 4 o'clock of the clock.
The position depends on the outside diameter of the tubing.
Since the oil located at the bottom of the line can generate false signals, the wax thermostatic element can never be located at the bottom of the suction tube.
For specific locations, you can refer to the following two points:
1. When the diameter of the horizontal return pipe is less than 7/8" (22mm)
The wax thermostatic element should be installed at the upper end of the return tube, that is, the "12 o'clock to 2 o'clock position" of the suction tube. The purpose of this is that the temperature sensed by the wax thermostatic element is gaseous and is not affected by liquid substances.
2. When the diameter of the horizontal return pipe is greater than 7/8"
The wax thermostatic element is installed below the axis of the return line, that is, at the "3-4 o'clock" position of the suction tube.
Because installing the wax thermostatic element in the upper part of the suction pipe will reduce the sensitivity of the reaction, it may make the evaporator have too much refrigerant; Installing the wax thermostatic element at the bottom of the suction tube will cause a disturbance in the liquid supply, because there is always a small amount of liquid refrigerant flowing to the location where the wax thermostatic element is installed, and this flow is not continuous (one moment and one moment none) resulting in a rapid change in the temperature of the wax thermostatic element.
Wax thermostatic elements need to be insulated
We all know that after the wax constant temperature element of the expansion valve is fixed, it is necessary to insulate the wax constant temperature element;
The temperature felt by the wax thermostatic element must be the temperature of the HVAC system, if not insulated, the wax thermostatic element is easy to feel the external temperature, which will lead to inaccurate adjustment of the expansion valve opening.
The wax thermostatic element must be able to sense the temperature of the superheated intake vapor and must therefore not be located in a place with external heat/cold interference.
If the wax thermostatic element is exposed to a hot gas stream, it is recommended to insulate the wax thermostatic element.
The general expansion valve wax thermostatic element belt can safely and reliably install the wax thermostatic element on the pipeline to ensure that the wax thermostatic element can have the best thermal contact with the suction pipe. However, the expansion valve generally does not have thermal insulation materials when leaving the factory, so when installing wax constant temperature components on site, you must remember to do a good job of insulation.
Precautions for the position of wax thermostatic elements
The wax thermostatic element cannot be installed behind the heat exchanger, because at this position it will send an incorrect signal to the expansion valve.
2. The wax constant temperature element must not be installed close to the mass component, because this will also cause an incorrect signal to be sent to the expansion valve.
3. The wax constant temperature element must be installed to the horizontal part of the suction line immediately after passing through the evaporator. The wax thermostatic element must not be installed on the collection tube or rising pipe behind the reservoir.
4. The wax constant temperature element of the expansion valve must always be installed before any hydraulic lock (U-shaped oil return bend);