Midea MAW User Manual page 9

How To Handle Equipment Containing Flammable Refrigerants (cont.)
11. Removal and evacuation.
When breaking into the refrigerant circuit to make repairs - or for any other purpose - conventional
procedures shall be used. However, for fl ammable refrigerants it is important that best practice be
followed, since fl ammability is a consideration. The following procedure shall be adhered to:
- Safely remove refrigerant following local and national regulations;
- Evacuate;
- Purge the circuit with inert gas (optional for A2L);
- Evacuate (optional for A2L);
- Continuously fl ush or purge with inert gas when using fl ame to open circuit; and
- Open the circuit.
The refrigerant charge must be recovered into appropriate recovery cylinders if venting is prohibited by
local and national codes. For appliances containing fl ammable refrigerants, the system should be purged
with non-fl ammable refrigerants that are oxygen-free. Under no circumstances should compressed air or
oxygen be used for purging refrigerant systems.
For appliances containing fl ammable refrigerants, purging must be conducted by initially breaking the
vacuum in the system with oxygen-free nitrogen. Nitrogen should be continuously added until the desired
working pressure is reached, then vented to the atmosphere. Subsequently, the system should be pulled
down to a vacuum (this step is optional for A2L refrigerants). This purging process should be repeated until
no refrigerant remains in the system (optional for A2L refrigerants). After the fi nal charge of oxygen-free
nitrogen is used, the system should be vented to atmospheric pressure to facilitate further work.
The outlet for the vacuum pump shall not be close to any potential ignition sources, and ventilation shall
be available.
The refrigerant charge shall be recovered into the correct recovery cylinders if venting is not allowed by
local and national codes. For appliances containing fl ammable refrigerants, the system shall be purged
with oxygen-free nitrogen to render the appliance safe for fl ammable refrigerants. This process might
need to be repeated several times. Compressed air or oxygen shall not be used for purging refrigerant
systems. For appliances containing fl ammable refrigerants, refrigerants purging shall be achieved by
breaking the vacuum in the system with oxygen-free nitrogen and continuing to fi ll until the working
pressure is achieved, then venting to atmosphere, and fi nally pulling down to a vacuum (optional for A2L).
This process shall be repeated until no refrigerant is within the system (optional for A2L). When the fi nal
oxygen-free nitrogen charge is used, the system shall be vented down to atmospheric pressure to enable
work to take place. Ensure that the outlet for the vacuum pump is not close to any potential ignition
sources and that ventilation is available.
12. Charging procedures.
In addition to conventional charging procedures, the following requirements shall be followed. Ensure that
contamination of different refrigerants does not occur when using charging equipment. Hoses or lines shall
be as short as possible to minimize the amount of refrigerant contained in them. Cylinders shall be kept
in an appropriate position according to the instructions. Ensure that the refrigeration system is earthed
prior to charging the system with refrigerant. Label the system when charging is complete (if not already).
Extreme care shall be taken not to overfi ll the refrigeration system. Prior to recharging the system it shall
be pressure tested with OFN. The system shall be leak tested on completion of charging but prior to
commissioning. A follow up leak test shall be carried out prior to leaving the site.
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