Aircon's Condenser and Evaporator

Run the unit and check operating pressures. When the space has cooled down and is about 5 degrees above design temperature, look for the following pressures and temperatures.

• Suction pressure should be in the range of 35 to 40 degrees below return air.

• Discharge pressure should be in the range of 20 to 35 degrees above ambient air.
• Superheat should be 20 to 30 degrees at the compressor.
• Subcooling should be 10 to 15 degrees at the outlet of the receiver or condenser.
• Air temperature rise through the condenser should be 20 to 30 degrees.
• Air temperature drop through the evaporator should be 15 to 20 degrees. If all of your operating characteristics fall within these ranges, the unit is running well.

do these temperatures are in Celsius or Fahrenheit?

Good answer from Shogun7. If those conditions are met, then the system is performing well, and probably delivering rated capacity. However, if the system has mix-match components, then that is a different story. If the question is how to take a measurement, then remember that cooling capacity is a combination of both temperature change and moisture removal. To take a measurement: (A) measure duct airflow. You cannot do this with a single sensor, but there are several ways to either measure (Using an air hood) or calculate airflow. (B) Measure indoor air temperature drop (Using before and after temperature sensors. (C) Measure the amount of moisture removed (Weigh the condensate water). There are formulas for calculating the performance for (B) and (C) separately, and together. Frankly, accurate measurent of dehumidification makes accurate readings difficult.

Here is a quick and dirty method using imperial measurements: (a) Measure condenser air flow (In CFM), (b) measure condenser air Temperature Difference (In Fahrenheit), (c) Apply the values to this formula: BTUH = CFM x TD x 1.08. (d) this is the amount of heat rejected by the condenser, (e) Assume that the heat absorbed by the evaporator is 80% of the condenser heat. Good Luck.

what are the formulas used to calculate B and C?

what is the use of the factor "1.08'?

It is derived from: 1 btu/hr = 1 cu ft. /min x 60 min./hr x 0.0749 lbs/cu ft(70*F) x 0.24 btu/lb *F x 1 which becomes 1btu/hr = 1.08 x cfm x T1-T2 this is for air at 70 *F if air is 60* F then 1.08 becomes 1.1

what are the formulas used to calculate B and C?