Mitsubishi Electric MXZ-8B48NA Installation Manual page 9

5. Installing the refrigerant piping
'
® Front piping cover
Piping cover
© Stop valve
© Service panel
© Bend radius : 100 mm - 150 mm [3-15/16" - 5-7/8"]
Fig. 5-7
Fig. 5-8
Fig. 5-9
5.6. Refrigerant piping (Fig. 5-7)
Remove the service panei © (3 screws) and the front piping cover ® (2 screws)
and rear piping cover © (2 screws).
Refrigerant pipes are protectively wrapped
'The pipes can be protectively wrapped up to a diameter of 290 mm (3-9/16") be-
fore or after connecting the pipes. Cut out the knockout in the pipe cover following
the groove and wrap the pipes.
Pipe inlet gap
* Use putty or sealant to seal the pipe inlet around the pipes so that no gaps re-
main.
(lf the gaps are not closed, noise may be emitted or water and dust will enter the
unit and breakdown may result.)
5.7. Caution for piping connection/valve operation
* Conduct piping connection and valve operation accurately by following the figure
below.
* Apply sealer along the insulator to prevent water entering the insulator covering
the refrigerant pipe joints.
« After evacuation and refrigerant charge, ensure that the handle is fully open. If
operating with the valve closed, abnormal pressure will be imparted to the high- or
low-pressure side of the refrigerant circuit, giving damage to the compressor, etc.
* Determine the amount of additional refrigerant charge (refer "5.3. Addition of re-
frigerant"), and charge refrigerant additionally through the service port after com-
pleting piping connection work.
« After completing work, tighten the service port (12 - 15 N-m) [9 - 11 ft-lbs] and cap
(20 - 25 N-m) [14 - 18 ft-lbs] securely to prevent gas leak.
*4 Nem 10 kgf-cm
Method of completely opening the stop valve
The stop valve opening method varies according to the outdoor unit model. Use the
appropriate method to open the stop valves.
(1) Gas side (Fig. 5-8)
@ Remove the cap, pull the handle toward you and rotate 1/4 tum in a counter-
clockwise direction to open.
@ Make sure that the stop vaive is open completely, push in the handle and rotate
the cap back to its original position.
(2) Liquid side (Fig. 5-9)
@ Remove the cap and turn the valve rod counterclockwise as far as it will go
with the use of a 4 mm [3/16"] hexagonal wrench. Stop turning when it hits the
stopper.
@® Make sure that the stop vaive is open completely and rotate the cap back to its
original position.
® Valve © Completely closed
Unit side © Completely open
© Service port ® Refrigerant piping side (On-site installation)
© Handie © Direction the refrigerant flows in
© Cap @ Wrench hole
5.8. Airtight test and evacuation
© Airtight test (Fig. 5-10)
Airtight test should be made by pressurizing nitrogen gas. For the test method, re-
fer to the following figure.
(1) Connecting the testing tool. Make a test with the stop valve closed. Be also sure
to pressurize both liquid or high-pressure pipe and gas or low pressure pipe.
(2) Do not add pressure to the specified pressure all at once; add pressure little by
little.
@® Pressurize to 0.5 MPa [73 PSIG], wait five minutes, and make sure the pres-
sure does not decrease.
@® Pressurize to 1.5 MPa [218 PSIG], wait five minutes, and make sure the pres-
sure does not decrease.
@® Pressurize to 3.8 MPa [550 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.
® Nitrogen gas © Outdoor unit
System analyzer © Stop valve
© Lo-knob ® Liquid pipe or high-pressure pipe
© Hi-knob @® Gas pipe or low-pressure pipe
® To branch box ® Service port