Mitsubishi Electric CITY MULTI PUHY-P-YKB-A1 Manuel D'installation page 31

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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.

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.

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.

・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

Service port

Three-way joint

Valve (vacuum pump)

Valve (for charging refrigerant)

Refrigerant tank

To indoor unit

Outdoor unit