Midea MTA-76C(H)RN1 Technical Manual page 80

Midea R410A T3 Top-discharge Split Type Series 50Hz

All connections between indoor unit and outdoor unit are copper-to copper and should be brazed
with a phosphorous-copper alloy material such as Silfos-5 or equivalent. Do not use soft solder.
The outdoor units have reusable valves on both the liquid and vapor connections. The total
system refrigerant charge is retained within the outdoor unit during shipping and installation. The
reusable valves are provided to evacuate and charge per the instruction.

Dry nitrogen should always be supplied through the tubing while it is being brazed, because the
temperature required is high enough to cause oxidation of the copper unless an inert
atmosphere is provided. The flow of dry nitrogen should continue until the joint has cooled.
Always use a pressure regulator and safety valve to insure that only low pressure dry nitrogen is
introduced into the tubing. Only a small flow is necessary to displace air and prevent oxidation.

Install the connective pipe only after fixing the indoor unit and outdoor unit. Keep dry when
installing the connective pipe. Do not let moist intrude into the pipeline system.

Allowed length of refrigerant pipe and height difference.
Max. actual length of pipe (L)
Max. height difference between indoor
and outdoor unit
Max. number of bends

Do not increase or decrease piping sizes.

As shown in following picture, when brazing the indoor and outdoor connective lines, pad a
sheet metal under the valve avoids the flame burning the chassis.
79
Outdoor unit (upper)
Outdoor unit lower (lower)
MCAC-UTSM-201501
Allowed value
50m
25m
30m
15