5. Oil
equation
control
This control function is aimed at preventing compressors of the outdoor unit from
running out of oil, and is basically performed by opening/closing solenoid valve
SV3D. There are t
hree
control patterns as described below.
• Oil accumulated in the oil
separator is returned to the
compressor.
1.
Preparatory control
If the oil level judgment result in the memory continues to be “low” for 30 seconds,
SV3D turned on and off intermittently.
2. Oil recovery control
This control function is performed if the oil level judgment result continues to be
"low" for 15 minutes. ( Item 6.)
3.
Oil depletion protection control
This control function is performed if oil
recovery
control fails to achieve an optimum
oil level. In concrete terms, if a low oil level situation continues for
45
minutes, the unit
is brought to a protective shutdown, followed by a restart 2 minutes and 30 seconds
later. If protective shutdown is repeated three times, the
trouble
is confirmed as
final.(There will be no more restarts.) The
check
code is “H07”.
• This protective control is
performed when a
prolonged low oil level is
detected.
6.
Refrigerant/
oil recovery
control
• Control duration is about 2 to
5 minutes, though it varies
according to the operating
conditions of the system.
1.
Cooling oil (refrigerant) recovery control
Performed during cooling, this control function aims to: collect any
refrigerating oil
condensate that has built up in inter-unit gas pipes and indoor units
and return it to
outdoor unit when the compressor operation command is
inadequate; and prevent
the accumulation of refrigerant in outdoor heat exchangers
while cooling operation
is in progress under low outside air temperature conditions.
1)
Control commencement conditions
•
During cooling, when the oil level judgment result continued to be "low" for
15 minutes
.
2)
Control details
• All compressors currently in operation are operated at the minimum speed, with those
currently not in operation turned on.
• Indoor units are set to the cooling oil (refrigerant) recovery control mode, with their
indoor PMVs opened to a certain degree.
• Compressors are operated at the target speed.
• After recovery control is performed for a specified period of time, it is terminated, and
normal cooling operation resumes.
2.
Heating refrigerant (oil) recovery control
Performed during heating, this control function aims to recover any liquid refrigerant
trapped inside indoor units that have been turned off. It also serves the additional
purposes of recovering indoor/outdoor refrigerant after defrosting and recovering oil
present in outdoor heat exchangers during heating overload operation.
1)
Control commencement conditions
• When heating operation has started (compressors have just been turned on)
• When heating takes over upon completion of defrosting
2)
Control details
• All compressors currently in operation are operated at the minimum speed, with those
currently not in operation turned on.
• Indoor units are set to the heating refrigerant (oil) recovery control mode, with their
indoor PMVs opened to a certain degree.
• Compressors are operated at the target speed.
• Upon completion of refrigerant recovery for all the indoor units, normal cooling
operation resumes.
• Control duration is about 2 to
10 minutes, though it varies
according to loading
conditions.
• Compressor rotational
speed varies with control
conditions, indoor unit
capacity, and outdoor unit
specification.
Item
Description of operation, numerical data, and other information
Remarks
- 42 -
