Toshiba MMU-AP0091H Owner's Manual Installation And Operation page 42

5
REFRIGERANT PIPING
Airtight test
After the refrigerant piping has finished, execute an airtight test. For an airtight test, connect a nitrogen gas bomb as
shown in the figure below, and apply pressure.
• Be sure to apply pressure from the service ports of the packed valves (or ball valves) at liquid side, discharge gas
side, balance pipe and suction gas side.
• An air tight test can be only performed to the service ports at liquid side, discharge gas side, and suction gas side
of the outdoor unit.
• Close fully valves at liquid side, discharge gas side, balance pipe and suction gas side. As there is possibility that
nitrogen gas enters in the refrigerant cycle, re-tighten the valve rods before applying pressure.
(Re-tightening of the valve rods are unnecessary for valves at discharge gas side because they are ball valves.)
• For each refrigerant line, apply pressure gradually with steps at liquid side, discharge gas side, balance pipe and
suction gas side.
Be sure to apply pressure to suction gas side, discharge gas side, liquid side and balance pipe.
Never use "Oxygen", "Flammable gas" and "Noxious gas" in an airtight test.
Detailed drawing of packed valve
To gauge manifold
Discharge gas side
service port
Discharge gas side
ball valve
Liquid side
service port
Liquid side
packed valve
Piping at site
Piping at site
STEP 1 : Apply pressure 0.3MPa (3.0kg/cm
STEP 2 : Apply pressure 1.5MPa (15kg/cm
STEP 3 : Apply pressure 3.73MPa (38kg/cm
• Check pressure down.
No pressure down: Accepted

However, if there is difference of ambient temp. between when pressure has been applied and when

24 hours passed, pressure changes by approx. 0.01MPa (0.1kg/cm²G) per 1°C. Correct the pressure.
Leaked position check
When a pressure-down is detected in STEP 1, STEP 2, or STEP 3, check the leakage at the connecting points.
Check leakage with hearing sense, feeler, foaming agent, etc, and perform re-brazing or re-tightening of flare if
leakage is detected.
REQUIREMENT
Connected to indoor unit
Main pipe
Suction gas side
service port
Suction gas side
packed valve
To outdoor
unit
To
outdoor
unit
Piping
Piping
at site
at site
Balance pipe
service port
To outdoor unit
Balance pipe
packed valve
Connected to follower outdoor units
2
G) for 3 minutes or more.
2
G) for 3 minutes or more.
2 G) for approx. 24 hours.
Pressure down: Check the leaked position.
Packed valve fully closed
(Suction gas side)
Outdoor unit
Brazed
Service
Copper pipe
port
Fully
closed
Service port
Ball valve fully closed
(Discharge gas side)
Fully
closed
Packed valve fully closed
(Liquid side)
Fully
closed
Packed valve fully closed
(Balance pipe)

Available to detect a gross leakage

Available to detect slow leakage
39
Low- High-
pressure pressure
gauge gauge
Gauge
V V
L H
manifold
Reducing
valve
Ø6.4
Ø6.4
Copper
pipe
Nitrogen
gas

