Arkansas HVACR NewsMagazine September 2019

S tate, National, Chapter News Tech News

blower etc. • Metering device allowing too much refrigerant flow – piston too large, TXV failing open, piston seating improperly

copper • Dirty Condenser Coil on New High- Efficiency Condensers ( Increased Condensing Temp Can Actually Result in Higher Subcooling ) • Having an H.R.U. in the discharge line ( old school I know ) • Internal evaporator restriction High Evaporator Air Temperature Split • Low air flow – dirty filter, dirty evaporator, kinked return, return too small, not enough supply ducts, blower wheel dirty, blower not running correct speed, insulation pulling up against the blower etc. • Abnormally low humidity (WB Temp) • Blower not running the correct speed or running backward Low Evaporator Air Temperature Split • Undercharge • Severe Overcharge with fixed orifice metering device – because saturation temperature is increased with overcharge • Metering device not functioning properly – restricting too much flow or allowing too much flow • Too much airflow through the evaporator – blower not running correct speed

• Low return air temperature • Abnormally low humidity • Internal evaporator restriction

• Very Poor Compression (Compressor, reversing Valve Issues) but will also be combined with VERY HIGH suction

High Superheat • Low on charge

• Metering device restricting flow / underfeeding / overmetering – piston too small, piston or TXV restricted, TXV failing closed • High return air temperature • Liquid line restriction – clogged filter/drier, clogged screen, kinked copper

Low Subcooling • Low on charge

• Metering device allowing too much refrigerant flow – piston too large, TXV failing open, piston seating improperly • Compressor not pumping properly – leaking suction valve, leaking discharge valve, bad or broken crank

• Reversing valve bypassing • Discharge Line Restriction • Compressor not pumping

High Subcooling • Overcharge

• Heat strips running with air • Abnormally high humidity • Liquid line restriction

• Metering device restricting too much flow – piston too small, piston or TXV restricted, TXV failing closed • Liquid line restriction – clogged filter/drier, clogged screen, kinked

• Compressor not pumping properly – bad suction valve, bad discharge valve, bad or broken crank