Oil Management - Danfoss ADAP-KOOL AK-HP 780 Design Manual

Oil management

Principle
The controller turns on the oil flow for e.g. 1 second. The system
then pauses while the oil once again settles. This is repeated a
certain number of times, which will be determined by the plant
and control principles.
The pulse time, pause time and number of pulses can be adjusted.
The system can be controlled by signal from:
• Level switch on compressor
• Level switch on oil separator
• Level switch on oil receiver
• Pressure transmitter on oil receiver
• In special circumstances the pulse counter can also be used to
control, but this is not energy efficient.
Examples of oil circuits
One oil separator and
one oil receiver
One oil separator
One oil separator per
compressor
One oil separator per
compressor and
common oil receiver
90 Heat pump controller RS8GF202 © Danfoss 2015-08
Safety relays
The controller can manage the oil supply to the compressors
during normal regulation. However if the compressors are force
controlled, this will be done outside the normal regulation. To
avoid compressor damages, a safety relay can be incorporated in
the control circuit so the controller can cutout the compressor if
the oil supply is absent during forced control.
The function "Safety relay" can be selected under setup and wiring
should be done as shown.
Control principle for compressor
A compressor that is shut down does not receive any oil.
When the compressor is in operation, a signal from the compres-
sors oil-level switch is expected. When the signal is given, the
following process is carried out:
- Delay time, re-started in case of chatter.
- Oil injection commences after delay time sequence.
- The solenoid valve follows the pulse process and the oil is
injected. Pulse time, period time and the total number of pulses
are set for the current plant.
- After the defined number of pulses, the oil injection is stopped
again. If the level switch registers a stable oil signal before the
sequence of the defined number of pulses finishes, the remain-
ing pulses are omitted.
- If the level switch registers a lack of oil when the last pulse has
stopped, the compressor will be shut down and an alarm will be
given. If the oil level is deemed to be OK again, the alarm will be
cancelled and the compressor can restart.
If an OK on oil level is absent, the compressor will stop and can
then only be manually started using the reset function.
The safety relay is connected during
normal operating conditions
AK-HP 780