Airtight Test, Evacuation, And Refrigerant Charging - Mitsubishi Electric Y Série Manuel D'installation

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10.3. Airtight test, evacuation, and refrigerant charging

1 Airtight test

Perform with the valve of the outdoor unit closed, and pressurize the connection piping and the indoor unit from the service port provided on the valve of the outdoor unit.

(Always pressurize from both the liquid pipe and the gas pipe service ports.)

[Fig. 10.3.1]

(1) After pressurizing to the design pressure (4.15 MPa [602 psi]) using nitrogen gas, allow it to

stand for about one day. If the pressure does not drop, airtightness is good.

However, if the pressure drops, since the leaking point is unknown, the following bubble test

may also be performed.

(2) After the pressurization described above, spray the flare connection parts, brazed parts, and

other parts that may leak with a bubbling agent (Gupoflex, etc.) and visually check for bubbles.

(3) After the airtight test, wipe off the bubbling agent.

Caution:

Only use refrigerant R410A.

- The use of other refrigerant such as R22 or R407C, which contains chlorine, will deteriorate the refrigerating machine oil or cause the compressor to malfunction.

2 Evacuation

Evacuate with the valve of the outdoor unit closed and evacuate both the connection piping and the indoor unit from the service port provided on the valve of the outdoor

unit using a vacuum pump. (Always evacuate from the service port of both liquid pipe and gas pipe.) After the vacuum reaches 650 Pa [abs] [0.0943 psi/5 Torr], continue

evacuation for at least one hour or more. Then, stop the vacuum pump and leave it for 1 hour. Ensure the degree of vacuum has not increased. (If the degree of vacuum

increase is larger than 130 Pa [0.01886 psi/1.0 Torr], water might have entered. Apply pressure to dry nitrogen gas up to 0.05 MPa [7.25 psi] and vacuum

again.) Finally, seal in with the liquid refrigerant through the liquid pipe, and adjust the gas piping to obtain an appropriate amount of the refrigerant during operation.

* Never perform air purging using refrigerant.

[Fig. 10.3.2]

Note:

•

Always add an appropriate amount of refrigerant. Also always charge the system with liquid refrigerant.

•

Use a gauge manifold, charging hose, and other parts for the refrigerant indicated on the unit.

•

Use a graviometer. (One that can measure down to 0.1 kg [3 oz].)

•

Use a vacuum pump with a reverse flow check valve.

(Recommended vacuum gauge: ROBINAIR 14830A Thermistor Vacuum Gauge)

Also use a vacuum gauge that reaches 65 Pa [abs] [0.00943 psi/0.5 Torr] or below after operating for five minutes.

3 Refrigerant Charging

Since the refrigerant used with the unit is nonazerotropic, it must be charged in the liquid state. Consequently, when charging the unit with refrigerant from a cylinder, if

the cylinder does not have a siphon pipe, charge the liquid refrigerant by turning the cylinder upside-down as shown in Fig.10.3.3. If the cylinder has a siphon pipe like that

shown on the right of Fig.10.3.3, the liquid refrigerant can be charged with the cylinder standing upright. Therefore, give careful attention to the cylinder specifications. If

the unit should be charged with gas refrigerant, replace all the refrigerant with new refrigerant. Do not use the refrigerant remaining in the cylinder.

[Fig. 10.3.3]

A Siphon pipe

Airtight test procedure

Nitrogen gas

To indoor unit

Lo knob

Hi knob

Liquid pipe

Gas pipe

Service port

Observe the following restrictions when conducting an air tightness test to prevent

negative effects on the refrigerating machine oil. Also, with nonazeotropic refriger-