Mitsubishi Electric Mr.SLIM PUZ-A42NHA5-BS Service Manual page 19

1. Refrigerant collecting (pump down)
Perform the following procedures to collect the refrigerant when moving the indoor unit or the outdoor unit.
1 Supply power (circuit breaker).
* When power is supplied, make sure that "CENTRALLY CONTROLLED" is not displayed on the remote controller. If "CENTRALLY
CONTROLLED" is displayed, the refrigerant collecting (pump down) cannot be completed normally.
* Start-up of the indoor-outdoor communication takes about 3 minutes after the power (circuit breaker) is turned on. Start the pump-down
operation 3 to 4 minutes after the power (circuit breaker) is turned ON.
2 After the liquid stop valve is closed, set SW1-1 on the control board of the outdoor unit to ON. The compressor (outdoor unit) and ventilators
(indoor and outdoor units) start operating and refrigerant collecting operation begins. LED1 and LED2 on the control board of the outdoor
unit are lit.
* Only set SW1-1 to ON if the unit is stopped. However, even if the unit is stopped and SW1-1 is set to ON less than three minutes after
the compressor stops, the refrigerant collecting operation cannot be performed. Wait until compressor has been stopped for three minutes
and then set SW1-1 to ON again.
3 Because the unit automatically stops in about two to three minutes when the refrigerant collecting operation is completed (LED1 off, LED2
lit), be sure to quickly close the gas stop valve. If LED1 is lit and LED2 is off and the outdoor unit is stopped, refrigerant collection is not
properly performed. Open the liquid stop valve completely, and then repeat step 2 after three minutes have passed.
* If the refrigerant collecting operation has been completed normally (LED1 off, LED2 lit), the unit will remain stopped until the power supply
is turned off.
4 Turn off the power supply (circuit breaker).
* Note that when the extension piping is very long with large refrigerant amount, it may not be possible to perform a pump-down operation.
Warning:
When pumping down the refrigerant, stop the compressor before disconnecting the refrigerant pipes. The compressor may burst if
air etc. get into it.
2. 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 D.
(2) Do not add pressure to the specified pressure all at once; add pressure little by little.
1 Pressurize to 0.5 MPa (5 kgf/cm²G), wait 5 minutes, and make sure the pressure does not decrease.
2 Pressurize to 1.5 MPa (15 kgf/cm²G), wait 5 minutes, and make sure the pressure does not decrease.
3 Pressurize to 4.15 MPa (41.5 kgf/cm²G) 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, the pressure will change by about 0.03 MPa (0.3 kgf/cm²G). 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.
Stop valve <Liquid side>
Stop valve <Gas side>
Service port
Open/Close section
3. Start and finish of test run
• Operation from the indoor unit
Execute the test run using the installation manual for the indoor unit.
• Operation from the outdoor unit
By using the DIP switch SW4 on the control board of outdoor unit, test run can be started and finished, and its operation
mode (cooling/heating) can be set up.
1 Set the operation mode (cooling/heating) using SW4-2.
2 Turn on SW4-1 to start test run with the operation mode set by SW4-2.
3 Turn off SW4-1 to finish the test run.
• There may be a faint knocking sound around the machine room after power is supplied, but this is
not a problem with the product because the linear expansion valve is just moving to adjust opening pulse.
• There may be a knocking sound around the machine room for several seconds after compressor
starts operating. But this is not a problem with product because the check valve itself generates
the sound because pressure difference is small in the refrigerant circuit.
Note:
The operation mode cannot be changed by SW4-2 during test run. (To change test run mode, stop the unit by SW4-1,
change the operation mode and restart the test run by SW4-1.)
OCH512
Local pipe
Sealed, same way for gas side
Pipe cover
Do not use a wrench here.
Refrigerant leakage may result.
Use 2 wrenches here.
19
<SW4>
ON
OFF
1 2
Stop Operation
Cooling Heating
(PUZ only)