Airtight Test, Evacuation, And Refrigerant Charging - Mitsubishi Electric City Multi PUHY-P72TKMU-A Installation Manual

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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]

Airtight test procedure

(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 (Kyuboﬂex, 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. Repeat the evacuation process three or more times until the vacuum pressure is lost by 130 Pa or below.) 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:

- For evacuation, the following procedures can be referred.

•

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 or Micron Gauge)

Do not use a manifold gauge to measure vacuum pressure.

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

•

Evacuate the system to 4,000 microns from both service valves. System manifold gauges must not be used to measure vacuum. A micron gauge must be

used at all times.

- Break the vacuum with Nitrogen (N2) into the discharge service valve to 0 PSIG.

•

Evacuate the system to 1,500 microns from the suction service valve.

- Break the vacuum with Nitrogen (N2) into the discharge service valve to 0 PSIG.

•

Evacuate the system to 500 microns. System must hold the vacuum at 500 microns for a minimum of 1 hour.

•

Conduct a rise test for a minimum of 30 minutes.

3 Refrigerant Charging

Do not use refrigerant other than the type indicated in the manuals provided with the unit and on the nameplate.

- Doing so may cause the unit or pipes to burst, or result in explosion or ﬁre during use, during repair, or at the time of disposal of the unit.

- It may also be in violation of applicable laws.

- MITSUBISHI ELECTRIC CORPORATION cannot be held responsible for malfunctions or accidents resulting from the use of the wrong type of refrigerant.

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.