Heating and Air Conditioning: Testing and Inspection

Fig. 3 Manifold Gauge Set Connections:

1. Connect manifold gauge set to high and low sides of system at compressor service valves, Fig. 3.
2. Start engine and allow to run at approximately 2000 RPM, then activate air conditioner.
3. Set blower switch to HI position and temperature lever to COOL position.
. Open all windows and doors, then position dry bulb thermometer in cool air outlet and psychrometer (combination dry/wet bulb thermometer) near to evaporator inlet.
5. Check that high pressure gauge reading is between 200-220 psi. If high pressure gauge reading is above specified range, pour water on condenser until specified range is reached. If gauge reading is below specified range, cover condenser front surface area.
6. Ensure dry bulb portion of psychrometer is 77-95°F, then operate system until all gauges and thermometers have stabilized.

Fig. 4 Relative Humidity Graph:

7. Compare temperatures of dry and wet bulb portions of psychrometer, then determine relative humidity using graph, Fig. 4. Record reading.
8. Measure the difference in dry bulb temperatures at cool air outlet and evaporator inlet. Record reading.

Fig. 5 Temperature Humidity Chart:

9. Using information gathered in steps 8 and 9, determine if system is operating properly by using graph, Fig. 5. Intersection of the two points should be within the diagonal lines as shown.