Midea MV8M-120WV2RN1 Engineering Data page 80

V8 Mini R410A VRF 50Hz
4.8.2 Procedure
Notes for installers
Warning
Only use nitrogen for flushing. Using carbon dioxide risks leaving condensation in the piping. Oxygen, air, refrigerant,
flammable gases and toxic gases must not be used for flushing. Use of such gases may result in fire or explosion.
Procedure
The liquid and gas sides can be flushed simultaneously; alternatively, one side can be flushed first and then Steps 1 to
8 repeated, for the other side. The flushing procedure is as follows:
1. Cover the inlets and outlets of the indoor units to prevent dirt getting blown in during pipe flushing. (Pipe flushing
should be carried out before connecting the indoor units to the piping system.)
2. Attach a pressure reducing valve to a nitrogen cylinder.
3. Connect the pressure reducing valve outlet to the inlet on the liquid (or gas) side of the outdoor unit.
4. Use blind plugs to block all liquid (gas) side openings, except for the opening at the indoor unit which is furthest
from the outdoor units ("Indoor unit A" in Figure 3-4.14).
5. Start to open the nitrogen cylinder valve and gradually increase the pressure to 0.5MPa.
6. Allow time for nitrogen to flow as far as the opening at indoor unit A.
7. Flush the first opening:
a) Using suitable material, such as a bag or cloth, press firmly against the opening at indoor unit A.
b) When the pressure becomes too high to block with your hand, suddenly remove your hand allowing gas to
rush out.
c) Repeatedly flush in this manner until no further dirt or moisture is emitted from the piping. Use a clean cloth
to check for dirt or moisture being emitted. Seal the opening once it has been flushed.
8. Flush the other openings in the same manner, working in sequence from indoor unit A towards the outdoor units.
Refer to Figure 3-4.15.
9. Once flushing is complete, seal all openings to prevent dust and moisture from entering.
Figure 3-4.15: Pipe flushing sequence
Notes:
1. 1-2-3-4-5-6 working towards the outdoor units.
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Figure 3-4.14: Pipe flushing using nitrogen
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