Evacuation Of The System - Mitsubishi Electric CITY MULTI PUHY-HP-TNU-A Série Manuel D'installation

9-8. Evacuation of the system

Do not purge the air using refrigerant. Use a vacuum pump to evacuate the system.
- Residual gas in the refrigerant lines will cause bursting of the pipes or an explosion.
Use a vacuum pump with a check valve.
- If the vacuum pump oil flows back into the refrigerant lines, the refrigerant oil may deteriorate
and the compressor may malfunction.
<Evacuation procedures>
① Evacuate the system from both service ports, using a vacuum pump with the service valves closed.
② After the vacuum reaches 650 Pa, continue evacuation for at least one hour.
③ Stop the vacuum pump and leave it for an hour.
④ Verify that the vacuum has not increased by more than 130 Pa.
⑤ If the vacuum has increased by more than 130 Pa, water infiltration is suspected. Pressurize the system with dry
nitrogen gas up to 0.05 MPa. Repeat ① though ⑤ until the vacuum is increased by 130 Pa or below. If the
results persist, then perform the "Triple Evacuation" below.
<Triple Evacuation>
① Evacuate the system to 533 Pa from both service ports, using a vacuum pump.
② Pressurize the system with dry nitrogen gas up to 0 Pa from the discharge service port.
③ Evacuate the system to 200 Pa from the suction service port, using a vacuum pump.
④ Pressurize the system with dry nitrogen gas up to 0 Pa from the discharge service port.
⑤ Evacuate the system from both service ports, using a vacuum pump.
⑥ After the vacuum reaches 66.7 Pa, stop the vacuum pump and leave it for an hour. A vacuum of 66.7 Pa must
be maintained for at least one hour.
⑦ Verify that the vacuum has not increased for at least 30 minutes.
Ⓝ
Ⓝ
Ⓐ
HI
LO
Ⓑ Ⓒ
・Use a scale that can measure down to 0.1 kg (0.1 oz).
・Recommended vacuum gauge: ROBINAIR 14830A Thermistor Vacuum Gauge or Micron Gauge
・Do not use a gauge manifold to measure the vacuum pressure.
・Use a vacuum pump capable of attaining a vacuum of 65 Pa (abs) within five minutes of operation.
Ⓓ
Ⓔ
Ⓕ
Ⓞ
Ⓖ
Ⓘ
Ⓗ
Ⓚ
Ⓙ
Ⓛ
Ⓐ Gauge manifold
Ⓑ
Low pressure knob
Ⓒ High pressure knob
Ⓓ
Service valve
Ⓔ Liquid piping
Ⓕ
Gas piping
Ⓖ Service port
Ⓗ Three-way joint
Ⓘ
Valve (vacuum pump)
Ⓙ Valve (for charging refrigerant)
Ⓜ Ⓚ
Refrigerant tank
Ⓛ Scale
Ⓜ
Vacuum pump
Ⓝ To indoor unit
Ⓞ
Outdoor unit