Non-Condensibles

Eric Mele and Joe Shearer join Bryan to discuss the challenging issue of diagnosing and rectifying non-condensibles in the circuit.

Non-condensibles are gases that don't condense, including nitrogen. These are NOT moisture or contaminants, and they can be tricky to diagnose; the pressure readings will likely be normal, but the charge will actually be quite low (around 60-75% of the usual charge). These gases also don't just enter the system suddenly in significant amounts; non-condensibles typically enter the system when lots of technicians work on it, or the gases have been there all along.

One of the most telling symptoms of non-condensibles in the system is elevated head pressure and subcooling WITH flashing. (You can usually hear the flashing at the metering device if you listen.) Otherwise, the symptoms often mimic those of a metering device restriction, which is a much more common issue. The only real way to tell if you have non-condensibles is to weigh out the charge; you may recover the charge or pump down the system.

When you come across a system with non-condensibles, the customer may merely notice decreased cooling performance for an extended period. However, when a system is allowed to run with non-condensibles for a long time, there will likely be some long-term effects on your system. For example, these gases can erode the needle on a TXV.

Eric, Joe, and Bryan also discuss:

• Common misdiagnoses
• Metering device restrictions
• How metering device type affects non-condensible symptoms
• Liquid seals
• Pinching off the discharge line
• Copper plating on compressors
• Pumping down scroll compressors (and general pump down)
• Training other technicians to diagnose non-condensibles
• Liquid line and filter drier restrictions
• Long line sets and accessories