What Is Subcooling

The most basic meaning of subcooling is any temperatures below the saturation temperature. Generally, the lowest temperature a condenser can achieve, the better. In other words, the colder the refrigerant is as it flows into the evaporator coil, the more heat it will be able to absorb.

What does subcooling measure?

The lowering in temperature of the liquid refrigerant in the condenser coil is called the Subcooling. That is really what we are measuring! If we know the temperature of the saturated refrigerant in the condenser, then we know the starting temperature of the liquid before it starts to lower in temperature.

What is subcooling on AC?

Subcooling is the condition where the liquid refrigerant is colder than the minimum temperature (saturation temperature) required to keep it from boiling and, hence, change from the liquid to a gas phase.

Where can I find subcooling?

To measure liquid subcooling:
Attach your gauge manifold to the liquid line service port. If you use a quick-connect fitting on the end of your hose, make sure it’s a low-loss fitting. Take a pressure reading. Next, attach an accurate digital thermometer to the liquid line.

Why is subcooling needed?

Subcooling is normally used so that when the refrigerant reaches the thermostatic expansion valve, all of it is in its liquid form, thus allowing the valve to work properly. If gas reaches the expansion valve a series of unwanted phenomena may occur.

How is subcooling done?

Subcooling occurs when you cool a vapor below the temperature at which it turns into a liquid. Let’s use the same refrigerant with a high pressure boiling point of 120 degrees for the following example: The refrigerant is a 140 degree vapor heading into the condenser.

What is high subcooling?

High Subcooling is an indication that more than the designed amount of refrigerant is “backing up” or “packed” into the condenser. This can be caused by overcharge, restriction (such as a contaminated line drier or kinked liquid line), or an undersized or failing closed metering device.

How do you Subcool and superheat?

Subtract the Liquid line Temperature from the Liquid Saturation Temperature and you get a Subcooling of 15. “Typically” on TXV systems the Superheat will range between 8 to 28 degrees with a target of about 10 to 15 degrees. The Subcool range on TXV systems will range from about 8 to 20.

How do you read a Subcool?

To check subcooling, attach a thermometer to the liquid line near the condenser. Take the head pressure and convert it to temperature on a temperature/pressure chart. Subtract the two numbers to get the subcooling.

What happens if subcooling is too low?

A reminder why subcooling is important: Among other things, if the subcooling is too low, the condenser will “run out of” refrigerant prematurely at higher load conditions, overheating the compressor and reducing performance and efficiency.

What should Subcool be 410a?

Most heating and cooling systems should operate at a superheat of 10F at the evaporator and between 20F to 25F at the compressor. if your HVAC system has a thermostatic expansion valve (TXV), the subcooling should be between 10F and 18F.