Pump-Down Method For Replacing The Compressor - Hitachi RAS-2-HVNP Service Manual

12. Maintenance notes

12.6 Pump-down method for replacing the compressor

No.
1 Turn off the main switch of the outdoor unit.
Remove the covers the thermistor the crankcase heater the power
2
wirings and other items according to the chapter 10.
Attach the manifold to the check joint of the high pressure side and
3
the low-pressure side of the outdoor unit.
4 Turn on the main switch of the outdoor unit.
Set the exclusion of the compressor by setting the DSW so that a
5 broken compressor will not work. You can set the exclusion of the
compressor by setting the DSW1-4 in ON position.
The compressor replacing mode is performed:
6
• The DSW1-4 on the outdoor unit PCB→ON (The cooling is
run).
The operation finishes when one of the following conditions occurs:
1 Ten minutes have passed and STP is displayed in seven seg-
ments.
7
2 "08" is displayed in seven segments.
3 When Ps< 0.1 MPa is continued for one minute in ten minutes
STP is displayed in seven seconds and the operation finishes.
8 Close the liquid stop valve completely.
Check for a leakage of the check valve on the discharge gas side:
• DSW4-4 (enforced stoppage of the compressor) → ON so that
the compressor will not run although the running command is
sent from the remote control switch.
9
• Check that variation of Ps on the outdoor unit PCB is 17 se-
conds. Make sure that the Ps increase is within 0.03 Mpa in two
minutes after the Ps increase at the stoppage (during approxi-
mately five minutes). Also make sure that Pd > Ps.
Collect the refrigerant by means of the refrigerant collection:
• Perform either A or B depending on the process 10.
- The leak rate at the process 10 is within the specification
10
→Collect the refrigerant only at the low-pressure side.
- The leak rate at the process 10 is greater than the
specification → Collect all the refrigerant of the outdoor
unit side by means of the machine.
After collecting the refrigerant remove the change hose (collector
11 side) of the low-pressure side so that the low-pressure side of the
refrigerant cycle will be the atmosphere pressure.
12 Turn OFF the main switch of the outdoor unit.
Perform the replacement of the compressor and the change of the
13
refrigerant oil according to the section "replacing the compressor".
14 Perform the vacuum from the check joint of the low-pressure side.
Open the liquid stop valve and the gas stop valve completely when
15
you finish the vacuum.
Make sure that the power is turned OFF and attach the following
16 items: the power supply wire the thermistor the crankcase heater
the 63H wiring the panel and the nut).
Set the DSW back to the original setting. Make sure that all the
17
wirings to the compressor are connected correctly.
Recharge the refrigerant that is collected in the process by the stop
18
valve of the liquid side during the cooling at the TEST RUN mode.
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SMGB0079 rev.0 - 01/2013
Procedure Remarks
Make sure that the terminal part of the detached power supply
wires is not exposed by the winding insulation tape and other items.
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• This operation is performed for up to a maximum of ten minutes.
• If the inverter compressor is excluded the operation starts after
three minutes.
• The operation may finished when any of the conditions 1) to
3) occurs.
To avoid the spillage of all the refrigerant if the check valve is
broken.
• When you stop the compressor for replacing:
• You can check the leakage of the check valve by means of the
Ps variation because the SVA opens so that the discharge gas
side of the inverter compressor can connect to the low-pressure
side.
• 0.03 MPa/2 minutes is within the permissible limits for the check
valve on the discharge gas side.
• The leakage of the check valve may cause an incorrect brazing
due to the gas pressure at the brazing of the discharge piping.
• If the compressor-replacing mode is performed again set the
DSW4-4 to OFF and keep the DSW4-4 at the OFF side during
ten minutes. Then start according to the procedure No. 6.
• The discharge of the refrigerant in the atmosphere is strictly
forbidden. Make sure that the refrigerant is collected by the co-
llector.
• Keep a note of the quantity of the collected refrigerant.
• Make sure that there is no pressure increase of the low-pressu-
re sides after collecting the refrigerant.
• Make sure that the refrigerant cycle is the atmosphere pressure.
Otherwise problems such as the blowing of gas and the suction
of the cutting material) may occur when you are removing the
compressors.
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Make sure that you follow the instructions.
If you collect the refrigerant only on the low-pressure side (A in 11).
You cannot perform the vacuum of the refrigerant from the check
joint of the high-pressure side.
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If the replacement of the compressor takes more than two hours an
additional change of the refrigerant is necessary. Additional change
= (replacing time – 2 hours) x 0.5 kg.