Midea MDFA-76CRN2, Manual

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MCAC-UTSM-12
79
After the pipes between the indoor unit and the outdoor unit are connected, replenish compressed nitrogen to
perform airtight test.
NOTE:
1. The airtight test is performed by using the compressed nitrogen [2.94MPa (30kg/cm
2
G)].
2. Tighten the spool of the gas valve and liquid valve before compressing the nitrogen.
3. Compress the nitrogen at the air vent of the gas valve.
4. The gas valve and liquid valve are closed in the process of compressing the nitrogen.
5. Do not use oxygen, flammable gas or toxic gas in the airtight test.
3.7 Vacuumize
Use a vacuum pump to make a vacuum. Do not use refrigerant gas to expel air.
When making the vacuum, start from the air side.
3.8 Open All Valves
3.9 Additional Charge of Refrigerant
According to the diameter and length of the connective liquid side pipe of the outdoor unit and indoor unit,
calculate the refrigerant replenishment quantity. The refrigerant for replenishment is R407C
.
Table 2:
Diameter of liquid line Quantity of refrigerant replenished for 1m pipe length
Φ
12.7 0.115kg
Φ
16
0.190kg
3.10 Remove Trash and Moist in the Pipe

Trash and foreign matters may come into the pipe in the process of installing the refrigerant pipe. Be sure to
blow them off with nitrogen before connecting the pipe to the outdoor units.

Use high-pressure nitrogen to clean the pipelines. Do not use the refrigerant of the outdoor unit for cleaning.
3.11 Refrigerant Leak Precautions
This air conditioner uses refrigerant R407C. The R407C is safe refrigerant which is harmless and
non-flammable. The room for placing the air conditioner should have a proper space. Even if refrigerant
leakage occurs, the density threshold will not be crossed. Additional measures may also be taken.
1) Density threshold: Density of the Freon gas that does not harm the human body. Density threshold of
R407C: 0.3 [kg/m3]

Calculate the total quantity of refrigerant to be replenished (A [kg]). Total refrigerant quantity for 10HP =
refrigerant replenishment quantity upon shipment (11[kg]) + additional refrigerant replenishment
corresponding to the pipe length

Calculate out the indoor volume (B [m3]) (according to the minimum volume)

Calculate out the refrigerant density:
2) Measures against crossing of the refrigerant density threshold

In order to keep the refrigerant density below the threshold value, please install a mechanic ventilation
device. (Perform ventilation often)

In case frequent ventilation is impossible, please install the leakage detection alarm device linked with the
mechanical ventilation device.
3.6 Airtight Test