Refrigerant Gauges6-Clues That Your Non-TXV System Is Low On Refrigerant Charge

When it comes to properly diagnosing a refrigeration circuit, there are six core measurements that must be performed:

  1. Suction pressure & saturated temperature, commonly referred to as the "lo-side"
  2. Liquid pressure & saturated temperature, commonly referred to as the "hi-side"
  3. Superheat at the condensing unit
  4. Subcooling at the condensing unit
  5. Delta-T across the indoor evaporator coil, return air DB minus supply air DB
  6. Compressor "C" amps

Analyzing these six pieces of data will lead you to the correct diagnosis when your Non-TXV system (cap-tube, piston, etc) is running short on refrigerant charge.

Suction Pressure: It will be LOW, because there is not enough refrigerant in circulation to build to acceptable levels.

Liquid Pressure: It will be LOW, because there is not enough refrigerant in circulation to build to acceptable levels.

Superheat: It will be HIGH, because the refrigerant shortage means lower liquid pressure to force as much saturated refrigerant through the metering device to enter the evaporator coil, and what is metered is being boiled-off more quickly than desired in the first sections of the coil, so that as additional btu's continue being absorbed by the remaining sections of coil they are excessively "superheating" the refrigerant vapor above the normal acceptable range.

Subcooling: It will be LOW, because the lack of an adequate amount of refrigerant in circulation means lower liquid pressures, which results is less liquid "back-up" from the metering device backwards to the condenser coil where the subcooling actually takes place.

Delta-T: It will be LOW, because the bulk of cooling capacity comes from the latent heat exchange inside the evaporator coil, by boiling off saturated refrigerant through most of the coil, not just the first sections, with superheat occuring just in the last sections. Low charge means that there is less latent vaporization of the refrigerant (most of the cooling capacity) and more sensible superheating of the refrigerant (less of the cooling capacity). Losing the bulk of capacity, means the evaporator cannot absorb as much heat, therefore the temperature drop will be lower than desired.

Compressor Amps: It will be LOW, because inadequate refrigerant means lower system pressures, both hi & lo-side, due to less pounds of refrigerant in circulation. Less refrigerant being "pumped" or circulated by the compressor means less work. Lower pressures and less work translate into lower amperage. 

Pay attention to these 6-Clues and you'll be able to correctly diagnose any refrigeration circuit.

 


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