Hvac basics: expand the correct way of adjusting the pneumatic valve

（ ） Before adjust thermal expansion pneumatic valve, must confirm air conditioning refrigeration exception is caused by thermal expansion pneumatic valve deviating from the optimal working point, rather than because of less freon, dry filter clogging, filter, blower, belt and so on caused by other reasons. At the same time, it is necessary to ensure the correctness of the thermal packet sampling signal, temperature sensing installation position must be correct, absolutely not installed in the pipeline directly, in case of the pipe at the bottom of the product oil influence factors such as the correct thermal heat pack.
( ） Thermal expansion pneumatic valve adjustment matters needing attention when the thermal expansion of the pneumatic valve work, must be conducted under the normal operation of the refrigeration equipment. Because the evaporator surface can't place the thermometer, can use the compressor suction pressure as the saturation pressure inside the evaporator, look-up table to get approximate evaporation temperature. With a thermometer to measure the temperature of the muffler, and evaporation temperature contrast to check degree of superheat. Adjustment, if feel too hot too small, can put the adjusting screw clockwise rotation ( That increase the spring force, reducing thermal expansion pneumatic valve opening) And reduce traffic. Conversely, if feel too hot too large, the feed flow is insufficient, can put the adjusting screw in the opposite direction ( Counterclockwise) Turning, make traffic increases. Due to the fact that the thermal expansion work pneumatic valve thermal system there exists a certain thermal inertia, the formation of signal transmission lag, run stable rear can be adjusted to the next. Must be careful so that the whole adjustment process, adjustment screw rotation of lap time shoulds not be too much too fast.
( ） Thermal expansion pneumatic valve adjustment of specific steps:
) Downtime. Will the digital thermometer probe is inserted into the evaporator back to port ( The corresponding thermal package location) The thermal insulation layer. The pressure gauge connected to the compressor low pressure pneumatic valve tee.
) Boot, let the compressor running more than minutes, enter a state of stable operation, pressure indicator, and temperature display is made to reach a stable value.
) Read digital thermometer temperature T and pressure gauges measured the pressure of the temperature T, degree of superheat of T - the difference between the two readings T。