GENER
AL INFORMA
TION
PR
ODUC
T INFORMA
TION
SY
STEM DESIGN
INTEGR
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ORDERING INFORMA
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Control logic
CDS303 integrates oil return management(ORM)
function together with compressor oil boost
function.
• Oil boost function: If compressor runs below
2400 rpm for more than 120 minutes (low speed
running time, 28-11), in case oil get trapped
in system and compressor inner part cannot
get lubricated, CDS303 oil boost function will
accelerate compressor speed to 3600 rpm for 1
minute (minimum duration, includes ramp up
time, 28-13) to take the oil back from system.
In case of slow acceleration condition, please
make sure compressor maintain minimum speed
3600rpm for at least 1 minute running.
* Please note for oil boost function, it is enabled
by parameter 28-10 as default setting. Please
notice when hands on mode is selected, oil
return management will not work even if
parameter 28-10 (oil return management) is set
to on. During hands on mode, if compressor
runs below 2400rpm for more than 120 minutes,
oil return fault alarm (A208) will report on
LCP and stop the compressor. Please select
hands on mode carefully and only select hands
on mode if the OEM has implemented oil
return management in the system controller
and qualified oil management. Under such
conditions, the compressor could run below
2400rpm continually and meanwhile drive oil
return management 28-10 will get by passed..
• Oil return function: To double ensure oil
return from system, compressor speed will
boost to 3600 rpm at a fixed time intervals (as
programmed in parameter 28-12, default 24 hrs)
any way.
Oil management related parameters, 28-11, 28-
12, 28-13 could also be programmed by OEM.
Considering oil return risk, a split system
with more than 10 m piping length requires
mandatory application approval by Danfoss
application specialists.
Oil management logic
2400rpm
3600rpm
2811-ORM Low Speed
Running time expire
2812-boost interval
Decrease ORM
time
Increase ORM
time
ID
Name
Factory Setup
Unit
Customer Access
2810
Oil Return Management
Enable
R/W
2811
Low Speed Running Time
120
min
R/W
2812
Fixed Boost Interval
24
h
R/W
2813
Boost Duration
60
s
R/W
This function uses a timer.
The timer is set at parameter low speed running
time 28.11, 120min.
When actual compressor speed is below 40rps,
the timer is increasing. When compressor speed
is above 40rps timer is decreasing.
When time counter reaches 120min the oil return
boost is started.
When the boost is terminated, the compressor
speed goes back to run on reference (speed
setpoint) and the time counter is reset and
restarting from zero.
SY
STEM DESIGN
40
AB237586440343en-000601