Daikin FTX25JVEA9, Service Manual

Page: 133 / 410

System control Si18-201
120 Main Functions
3.7 Oil Return Operation
Purpose of the
Function To collect refrigerating machine oil that adheres on the internal connection pipe wall during
regular operation and send it to the compressor.
Outline The oil recovery operation is conducted in the cooling cycle in both heating and cooling modes.
The oil recovery operation collects oil dissolved in liquid refrigerant from High Hz and Low Hz
(two types in both cooling and heating) and the section between Refnet joint and branch unit if
there is a non-operating branch unit during cooling operation.
Oil recovery function in cooling operation
The opening of bypass motorized valve in branch unit shall be 450 pulses during oil recovery
operation.
Oil recovery function in heating operation
Similar to the reverse cycle defrost, oil is collected by the cooling cycle.
The opening of bypass motorized valve in branch unit shall be 100 pulses during oil recovery
operation.
The oil recovery interval setting timer is set to 3 hours.
Details Oil recovery operation in cooling mode
In cooling operation, two types of oil recovery operations are conducted. One type of operation
collects refrigerating machine oil adhered on the main pipe wall and sends it to the compressor.
The other type, called non-operating BP oil recovery operation, collects refrigerating machine oil
seeping into non-cooling room units.
The intervals of operations to recover oil from the main pipe become shorter when the operating
frequency exceeds the specified frequency.
Main pipe oil recovery operation
When the operating frequency exceeds 75 Hz even once after an oil recovery operation, the oil
recovery operation interval becomes 5 hours. When the operating frequency does not exceed
75 Hz, the operation interval is 8 hours.
The minimum time of main pipe oil recovery operation time is 2 minutes. The maximum time is
5 minutes when High Hz appears. Under normal Hz, the operation time is 5 minutes.
During a main pipe oil recovery operation, the opening of the EVHs of BP units are set to 450
pulses when High Hz appears, but under normal Hz the opening are set to 450 pulses.
Non-operating BP oil recovery operation
When a BP unit with non-operating room units remain in that condition for 90 minutes while
room units of other BP units are operating, an oil recovery operation is activated to collect oil
from non-operating room units.
The opening of the EVHs of BPs for which the non-operating BP oil recovery operation is
conducted are set to 450 pulses.
The opening of the EVHs of BPs for which the non-operating room unit oil recovery operation is
conducted are set to 450 pulses.
The minimum and maximum times of non-operating BP oil recovery operation are 2 minutes
and 5 minutes, respectively.
Integral Timer Oil Recovery Time
Oil recovery from non-operating
branch unit TRAC1 1.5 hours TRBC1 2 minutes
Oil recovery during High Hz appearing TRAC2 5 hours TRBC2 2 minutes
Oil recovery during Low Hz operation TRAC3 8 hours TRBC3 2 minutes