Danfoss VZH052 Manual page 40

Control logic
Oil management logic
40
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CDS303 integrates oil return management(ORM)
function together with compressor oil boost
function.
3600rpm
Decrease ORM
time
2400rpm
Increase ORM
time
2811-ORM Low Speed
Running time expire
• 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,
ID Name
2810 Oil Return Management
2811 Low Speed Running Time
2812 Fixed Boost Interval
2813 Boost Duration
Oil management related parameters, 28-11, 28-
12, 28-13 could also be programmed by OEM.
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.
2812-boost interval
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.
Factory Setup
Enable
120
24
60
Considering oil return risk, a split system
with more than 10 m piping length requires
mandatory application approval by Danfoss
application specialists.
Unit Customer Access
R/W
min R/W
h R/W
s R/W