Photograph of a
commercial air conditioning compressor charging gauge set (C) Air Conditioner / Heat Pump Refrigerant Pressure Too Low - Undercharged
Effects of a low charge, under-charged refrigerant pressures and leaks: not enough refrigerant

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Low refrigerant or refrigerant undercharge effects on air conditioners & heat pumps or other HVACR equipmet: this article explains the symptoms of and problems caused by not enough refrigerant in cooling equpment.

Refrigerant charge quantity for air conditioners & heat pumps: This air conditioning repair article series discusses the the diagnosis and correction of abnormal air conditioner refrigerant line pressures as a means for evaluating the condition of the air conditioner compressor motor, which in turn, is a step in how we evaluate and correct lost or reduced air conditioner cooling capacity. We explain how overcharging or undercharging of refrigerant in an air conditioner or heat pump is detected and we list the effects of overcharged or undercharged refrigerant. We also explain the various causes of liquid slugging a compressor motor.

Green links show where you are. © Copyright 2015, All Rights Reserved.

Effects of Undercharging the Refrigerant Level in an Air Conditioner, Heat Pump, or other refrigeration equipment

Photograph of a
commercial air conditioning compressor charging chartEffect of too little refrigerant in the system

When we undercharge an air conditioner, heat pump, or other refrigeration equipment

  • Improper operating refrigerant pressures, too low: surprisingly to the novice, too little refrigerant in the system can actually drop the temperature in the cooling coil below its normal operating range; that's why we mention at FROST BUILD-UP on AIR CONDITIONER COILS that a cause of coil frosting in the air handler might be an early sign of a refrigerant leak.

    Loss of cooling capability: eventually when enough refrigerant leaks out of the system temperatures rise again because we no longer have any heat exchange between the condenser coil and the outdoor air nor between the then empty cooling coil and the indoor air.
  • More expensive operation: There is not enough refrigerant in the system, for example to properly fill the cooling coil - then we remove less heat (per unit of time operation of the equipment) so we are decreasing the operating efficiency of the system.
  • Cooling Coil Frosting: Too-low refrigerant levels in some systems also can cause frosting and freezing at the cooling coil.
  • Compressor motor damage: Too little refrigerant in an air conditioner, heat pump, refrigerator, or even a dehumidifier is likely to cause overheating of the compressor motor. That is because in a properly-charged refrigeration system, the refrigerant is cooling the electric motor that is sealed inside the compressor unit. An overheated A/C motor may trip a circuit breaker, may have trouble starting, and eventually will fail to run at all.

    Watch out: when an air conditioner or heat pump motor "burns out" the result is a costly contamination of the entire refrigeration system as burned lubricants and even shellac or coatings on motor windings will have been circulated through the refrigerant piping system.

    That's why an experienced HVAC repair person will insist on cleaing the entire system and installing one or more "burnout" refrigerant filter/driers (REFRIGERANT DRIERS & FILTERS) on the refrigerant lines when the compressor is replaced.

Bottom line about undercharging refrigerants: For residential equipment such as air conditioners, heat pumps, refrigerators, freezers, to work properly you must have exactly the correct charge in the system.

At FROST BUILD-UP on AIR CONDITIONER COILS we also explain that in a properly tuned and adjusted refrigeration system there will be liquid refrigerant found all the way to just at the end of the evaporator coil - this gives us maximum cooling efficiency of the equipment.

Effects of Overcharging the Refrigerant Level in an Air Conditioner, Heat Pump, or other refrigeration equipment

The effect of too much refrigerant in the system - overcharging, over-metering, or other high refrigerant pressure situations are detailed at EFFECTS of OVER CHARGING of REFRIGERANT

If your air conditioning or heat pump system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS.

See How to determine the cooling capacity of air conditioning equipment if the system seems to be working but is inadequate to cool your building. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Continue reading at TEV INSTALL & REPAIR

or see LOST COOLING CAPACITY or select a topic from the More Reading links shown below.

More Reading

Green link shows where you are in this article series.


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Publisher's Google+ Page by Daniel Friedman

Click to Show or Hide Citations & References