Danfoss VZH Series - Page 77

Application guidelines
77FRCC.PC.023.A7.22
Manifold compressors
Oil management concept
A restrictor is used in suction line of either xed
speed or inverter to well balance the low side
pressure between Variable speed and xed
speed compressors when xed speed is ON and
inverter is running at 100 rps, which is sized to
make sure xed speed have reasonable oil level
at this condition. That means when inverter run
at any frequency below 100 rps, the xed speed
never has oil starvation while the inverter has the
possibility of oil loss.
An optical-electrical level sensor is xed in
Variable speed compressor. The oil level sensor
monitors the compressor internal oil level and
send oil level signal to OEM main controller. While
the oil level is below the limit of minimum oil
level, the OEM main controller will enter an oil
management action (refer to oil management
specication for hybrid manifolding system
for details) to ensure the normal oil level or
protection of system.
An TEKLAB LC-XN optical-electrical level sensor
is xed on the Variable speed compressor. The
oil level sensor monitors the compressor oil level
and sends oil level signal to an external relay
(provided by OEM ).
If OEM main controller receives “ON” signal, the
oil level stays above required minimum level.
ON the contrary, signal OFF indicates oil below
minimum required level and will trigger OEM
main controller to activate oil management
action (refer to document “oil management
specication for hybrid manifolding system”to
get details). Regarding this oil level signal, a
5±2 seconds delay is recommended to be used
to consider the oil level uctuation which may
trigger false alarms.
For customers who needs UL certicates, please
order 24V AC/DC sensor.
230VAC model
External
Load / Relay
1 2
3
Sensor
L1
L2
L3
N
24VAC model
1 2
3
Sensor
External
Load / Relay
24VAC
0VAC