Refrigerant Charging

Superheat and subcooling methods, weigh-in, fixed-orifice vs. TXV charging, overcharge/undercharge symptoms and charging in cold weather.

5 guides

• Charging a Fixed-Orifice (Piston) System by Superheat
  Step-by-step method for charging a fixed-orifice (piston) system to a target superheat using indoor wet-bulb and outdoor dry-bulb, including why the target moves with conditions.
• Charging a TXV System by Subcooling
  How to charge a TXV (or TEV/EEV) system to the manufacturer's subcooling target, why subcooling is the right lever on a TXV system, and the conditions that must be right before you trust the number.
• Charging in Cold Weather (Low Ambient)
  Why superheat and subcooling charging get unreliable in cold weather, what your real options are (weigh-in, manufacturer low-ambient procedures, charging in heat on a heat pump), and the gotchas of low outdoor temps.
• Overcharge vs Undercharge — Reading the Symptoms
  A side-by-side of how overcharge and undercharge show up on the gauges and in superheat/subcooling, so you can tell them apart fast and not just add refrigerant by reflex.
• Weigh-In Charging and Adjusting for Line-Set Length
  How to charge a system by weight using the factory charge plus a line-set length adjustment, why weigh-in is the most accurate method on a new or evacuated system, and how to do it cleanly.

← All HVAC topics