Toshiba MMY-MAP0804HT8-E Installation Manual page 16

29-EN
SMMS-i
NOTE
However, if the environmental temperature changes from the moment of applying pressure to 24 hours after that, the pressure
will change by about 0.01MPa (0.1kg/cm²G) per 1°C. Consider the pressure change when checking the test result.
REQUIREMENT
When pressure decrease is detected in steps 1-3, check the leakage at the connecting points.
Check the leakage using a foaming agent or other measures and seal the leak with re-brazing, flare retightening or other
methods. After sealing, execute an airtight test again.
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Installation Manual
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Vacuum drying
• Be sure to perform vacuuming from both liquid and gas sides.
• Be sure to use a vacuum pump equipped with the counter-flow prevention function so that oil in the pump will
not flow back into piping for air conditioners. (If oil in the vacuum pump enters in the air conditioner with R410A
refrigerant, a problem may be caused in the refrigerating cycle.)
After finishing the airtight test and discharging nitrogen gas, connect the gauge manifold to the service ports of the liquid side,
gas side, and balance pipe side and connect a vacuum pump as shown in the figure below. Be sure to perform vacuuming for
the liquid, gas, and balance pipe sides.
To gauge manifold
Liquid-side service port
Liquid-side valve
Balance
service port
Balance
valve
Piping at site
• Use a vacuum pump with a high vacuuming degree [-100.7kPa (5Torr, -755mmHg)] and large exhaust gas
amount (40L/minute or larger).
• Perform vacuuming for 2 or 3 hours, though the time differs depending on the pipe length. Check that all the
packed valves at the liquid side, gas side, and balance pipe side are fully closed.
• If the pressure does not reach -100.7kPa or less, continue vacuuming for 1 hour or more. If the pressure does
not reach -100.7kPa after 3 hours of vacuuming, stop vacuuming and check for air leakage.
• If the pressure reaches -100.7kPa or less after vacuuming for 2 hours or more, close the valves VL and VH on
the gauge manifold fully and stop the vacuum pump. Leave it as it is for 1 hour to confirm that the vacuuming
degree does not change.
If the degree of vacuum loss is large, moisture may remain in the pipes. In that case, inject dry nitrogen gas and
apply pressure to 0.05MPa and perform vacuuming again.
• After finishing the above procedure of vacuuming, exchange the vacuum pump with a refrigerant canister and
advance to the additional charging of refrigerant.
Connected to indoor unit
Packed valve fully closed
Main pipe
(gas side)
Brazed
Packed valve details
To outdoor unit
To Fully
Gas-side valve
outdoor closed
unit
To
outdoor
Gas-side
unit
service port
Fully
Piping at site
closed
Piping at site
Follower units
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Installation Manual
Low pressure High pressure
gauge gauge
Gauge
V V
L H
manifold
Header outdoor unit
Service port
P
Service port
Vacuum pump
Packed valve fully closed
(liquid side)
Service port
Packed valve fully closed
(balance)