Mitsubishi Electric CITY MULTI PUMY-P NKMU Series Installation Manual page 7

4. Installing the refrigerant piping
D
A Front piping cover
B Piping cover
C Stop valve
D Service panel
E Bend radius : 100 mm - 150 mm
Fig. 4-4
A
C
D
E
F
G
A Stop valve <Liquid side>
B Stop valve <Gas side>
C Service port
D Open/Close section
E Local pipe
Fig. 4-5
(1)
B
B
A
A
D
J
G
G
E
E
Type A Type B
Fig. 4-6
(2) 1
B
G
D
H
E
Fig. 4-7
C
A E
B
H
I
C
F Sealed, same way for gas side
G Pipe cover
H Do not use a wrench here.
Refrigerant leakage may result.
I Use two wrenches here.
C
D
F
G
2
I
4.3. Refrigerant piping (Fig. 4-4)
Remove the service panel D (three screws) and the front piping cover A (two screws)
and rear piping cover B (two screws).
1 Perform refrigerant piping connections for the indoor/outdoor unit when the outdoor
unit's stop valve is completely closed.
2 Vacuum-purge air from the indoor unit and the connection piping.
Evacuation
Evacuate with the valve of the outdoor unit closed and evacuate both the connection
piping and the indoor unit from the service port provided on the valve of the outdoor
unit using a vacuum pump. (Always evacuate from the service port of both liquid pipe
and gas pipe.) After the vacuum reaches 650 Pa [abs] [0.0943 psi/5 Torr], continue
evacuation for at least one hour or more. Then, stop the vacuum pump and leave it for
1 hour. Ensure the degree of vacuum has not increased. (If the degree of vacuum
B
increase is larger than 130 Pa [0.01886 psi/1.0 Torr], water might have entered.
Apply pressure to dry nitrogen gas up to 0.05 MPa [7.25 psi] and vacuum again.)
Finally, seal in with the liquid refrigerant through the liquid pipe, and adjust the gas
piping to obtain an appropriate amount of the refrigerant during operation.
* Never perform air purging using refrigerant.
3 After connecting the refrigerant pipes, check the connected pipes and the indoor
unit for gas leaks. (Refer to 4.4 Refrigerant pipe airtight testing method)
4 Vacuumize the refrigerant lines through the service port of the liquid and gas stop
valves. And then open the stop valves completely (for both the liquid and gas stop
valves). This will completely connect the refrigerant lines of the indoor and outdoor
units.
• If the stop valves are left closed and the unit is operated, the compressor and
control valves will be damaged.
• Use a leak detector or soapy water to check for gas leaks at the pipe connec-
tion sections of the outdoor unit.
• Do not use the refrigerant from the unit to purge air from the refrigerant
lines.
• After the valve work is completed, tighten the valve caps to the correct torque:
20 to 25 N·m [14 to 18 ft·lbs] (200 to 250 kgf·cm).
Failure to replace and tighten the caps may result in refrigerant leakage. In
addition, do not damage the insides of the valve caps as they act as a seal to
prevent refrigerant leakage.
5 Use sealant to seal the ends of the thermal insulation around the pipe connection
sections to prevent water from entering the thermal insulation.
Note:
<Triple Evacuation>
• Evacuate the system to 4,000 microns from both service valves. System
manifold gauges must not be used to measure vacuum. A micron gauge must
be used at all times.
- Break the vacuum with Nitrogen (N2) into the discharge service valve to 0 PSIG.
• Evacuate the system to 1,500 microns from the suction service valve.
- Break the vacuum with Nitrogen (N2) into the discharge service valve to 0 PSIG.
• Evacuate the system to 500 microns. System must hold the vacuum at 500
microns for a minimum of 1 hour.
• Conduct a rise test for a minimum of 30 minutes.
4.4. Refrigerant pipe airtight testing method
(1) Connect the testing tools.
• Make sure the stop valves A B are closed and do not open them.
• Add pressure to the refrigerant lines through the service port C of the liquid
stop valve A and the gas stop valve B.
(2) Do not add pressure to the specified pressure all at once; add pressure little by little.
1 Pressurize to 0.5 MPa [73 PSIG], wait five minutes, and make sure the
pressure does not decrease.
2 Pressurize to 1.5 MPa [218 PSIG], wait five minutes, and make sure the pres-
sure does not decrease.
3 Pressurize to 4.15 MPa [601 PSIG] and measure the surrounding temperature
and refrigerant pressure.
(3) If the specified pressure holds for about one day and does not decrease, the pipes
have passed the test and there are no leaks.
• If the surrounding temperature changes by 1°C [1.8°F], the pressure will change
by about 0.01 MPa [1.5 PSIG]. Make the necessary corrections.
(4) If the pressure decreases in steps (2) or (3), there is a gas leak. Look for the source
of the gas leak.
4.5. Stop valve opening method
(1) Gas side (Fig. 4-6)
Type A
1 Remove the cap, then turn one-quarter rotation counter-clockwise with a flat-bladed
screwdriver to complete open.
2 Check that the valves are fully open, then return the cap to its original state and
tighten it down.
Type B
1 Remove the cap, pull the handle toward you and rotate 1/4 turn in a counterclock-
wise direction to open.
2 Make sure that the stop valve is open completely, push in the handle and rotate
the cap back to its original position.
(2) Liquid side (Fig. 4-7)
1 Remove the cap and turn the valve rod counterclockwise as far as it will go with
the use of a 4 mm [5/32 inch] hexagonal wrench. Stop turning when it hits the
stopper.
(ø6.35 [1/4 inch]: Approximately 4.5 revolutions) (ø9.52 [3/8 inch]: Approximately
10 revolutions)
2 Make sure that the stop valve is open completely, push in the handle and rotate
the cap back to its original position.
A Valve
B Unit side
C Handle
D Cap
E Local pipe side
F Open position side
G Service port
H Wrench hole
I Refrigerant flow direction
J Operation section
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