- #1

fourthindiana

- 162

- 25

- TL;DR Summary
- Normally when one adds refrigerant to an air-conditioner, the superheat goes down. A few days ago, I added refrigerant to an air-conditioner, and the superheat went up. Why did the superheat go up when I added refrigerant?

On Friday I worked on a straight air-conditioner (A/C) package unit on the roof of an industrial facility. The straight A/C uses R-22 refrigerant. The straight A/C has a fixed orifice metering device. The compressor of the straight A/C was cold and had condensation on it. The dataplate for the A/C says that the factory charge of refrigerant is 9.1 pounds. When I first checked the evaporator superheat on the A/C, the superheat was 14 degrees. I added a pound of refrigerant to the A/C, and the evaporator superheat increased from 14 degrees to 15 degrees. Then I added another pound of refrigerant to the unit, and the evaporator superheat increased from 15 degrees to 17 degrees.

Here are some statistics of the situation immediately before I added refrigerant to the A/C on Friday:

Suction Pressure: 52 psig

Head pressure: 257 psig

Evaporator Superheat: 14 degrees fahrenheit

Subcooling: Approximately 30 degrees fahrenheit

Outside ambient temperature: 88 degrees fahrenheit

Delta T between return and supply: 16 degrees fahrenheit

Compressor superheat: 17 degrees fahrenheit

Actual compressor amp draw: 10.2 amps

RLA of Compressor: 9.7 amps

After I added a pound of refrigerant, the head pressure increased to 270 psig. The suction pressure stayed at 52 psig. The compressor superheat dropped from 17 degrees to 16 degrees.

Why did the evaporator superheat increase both times that I added refrigerant to the air-conditioner?

Here are some statistics of the situation immediately before I added refrigerant to the A/C on Friday:

Suction Pressure: 52 psig

Head pressure: 257 psig

Evaporator Superheat: 14 degrees fahrenheit

Subcooling: Approximately 30 degrees fahrenheit

Outside ambient temperature: 88 degrees fahrenheit

Delta T between return and supply: 16 degrees fahrenheit

Compressor superheat: 17 degrees fahrenheit

Actual compressor amp draw: 10.2 amps

RLA of Compressor: 9.7 amps

After I added a pound of refrigerant, the head pressure increased to 270 psig. The suction pressure stayed at 52 psig. The compressor superheat dropped from 17 degrees to 16 degrees.

Why did the evaporator superheat increase both times that I added refrigerant to the air-conditioner?