Danfoss ADAP-KOOL AK-HP 780 Design Manual page 91

Control principle for emptying the oil separator in the receiver
The system can be controlled by a signal from a high level switch
or it can be controlled by a signal from both a high and a low level
switch.
- In the case of a high level switch, the solenoid valve is opened
and the oil is emptied into the receiver in user defined a pulse
process. The system determines the pulse length, period time
and number of pulses.
- If a low level switch is installed and it registers a low level of oil
before the number of pulses has finished, the pulses stop and
the emptying process is terminated.
If the high level switch is still registering oil after the total number
of pulses has finished, an alarm is given for high oil level in the
separator.
If the low level switch is still registering oil after the total number
of pulses is finished, an alarm is given for remaining oil in the
separator.
An alarm for signal failure is also given if the high level switch
registers oil while a low level switch does not register oil.
If either the high or low level switch is activated in the set time
interval, a "no oil separated" alarm is given.
If an oil separator has been fitted for each compressor, it is the
level switch in the compressor, that determines the emptying
process of oil into the compressor. The level switch in the separa-
tor can be used for monitoring.
If "partial shared oil separators" have been fitted, the distribution
from compressor 1 and up will be as follows: The order cannot
be changed but the number of compressors that belong to the
individual separators need to be set.
AK-HP 780 Heat pump controller RS8GF202 © Danfoss 2015-08
Control principle for pressure in the receiver
Pressostat
- In the case of lack of pressure difference to fill the HT compres-
sors, the solenoid valve is opened in user defined pulses and the
pressure is taken from the oil separator. The pulse length and
the period time between the pulses is determined by the system
and are the same as those set for the oil separator.
- When the pressure transmitter registers the required pressure,
the pulses are stopped.
- Alarm limits and texts for maximum and minimum pressure,
respectively, can be set.
Pulse counter
Here, the controller uses a pulse count to determine the pressure
build-up in the receiver.
Basis: The controller has counted the number of the set pulses
in a period time for all compressors. This value is divided by the
number of compressors.
Reading: The controller registers the number of pulses sending oil
to the compressors.
Action: When the measured number of pulses reaches a percent-
age of the basis (factory setting = 50%), the pulse sequence is
started from the separator to the receiver.
Level signal
High and low level signals can also be received from the receiver.
These signals are only used for monitoring and alarms.
Miscellaneous
All oil valves are closed when the "Main switch" is off.
If you wish to carry out a manual oil injection, this can be done via
the function "Manual operation". Here, you can send one or more
pulses. The length of the pulse can be set in milliseconds.
If a compressor falls out due to lack of oil, it can only be recon-
nected manually in the plant itself. This can be done via a pulse
pressure on a defined input. There is one reset and this applies to
all compressors. Upon reset, all the counters are reset.
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