How To Check Superheat 410a. This helps avoid introducing air into the system. Once we establish that the valve is being fed with a full line of liquid at the appropriate pressure we check the superheat at the outlet of the evaporator to ensure that the valve itself is functioning properly and /or adjusted properly.
Negative superheat goes by another name subcooling and the only way a substance can be in the subcooled range is if it is 100% liquid and has given off additional heat below the saturated (mixed) state. Since suction line lengths can vary, so too can the superheat measured at the condensing unit. I recommend using an insulated cup!
Make sure airflow is right, charge fixed orifice by superheat, txv by subcooling.
With short line lengths (less than 30 ft.), the superheat should be between 10f and 15f. Vent hoses and manifold before installing gauges. Detach your txv's sensing bulb and submerse completely into crushed ice. Measure the actual temperature at the bulb location and compare the two.