Compressor Control; Maximum Discharge Gas Temperature; Liquid Injection Into Economizer Port; High/Low Pressure Monitoring - Danfoss Optyma Plus User Manual

Compressor control

The compressor is controlled by a signal at the DI1 input.
The compressor will start once the input is connected.
Three restrictions have been implemented to avoid frequent start/
stops:
- One for minimum ON time
- One for minimum OFF time
- One for how much time must elapse between two starts.
These three restrictions have the highest priority during
regulation, and the other functions will wait until they are
complete before regulation can continue. When the compressor is
'locked' by a restriction, this can be seen in a status notification.
If the DI3 input is used as a safety stop for the compressor, an
insufficient input signal will immediately stop the compressor.
The compressor can be speed-controlled with a voltage signal at
the AO2 output.
If the compressor has been running for a long period at low speed,
the speed is increased for a short moment for the purpose of oil-
return.

Maximum discharge gas temperature

The temperature is recorded by sensor Td.
If variable speed control is chosen for the compressor, this control
will initially reduce the compressor capacity if the Td temperature
approaches the set maximum value.
If a higher temperature is detected than the set max. temperature,
the fan's speed will be set to 100%. If this does not cause the
temperature to drop, and if the temperature remains high
after the set delay time, the compressor will be stopped. The
compressor will only be re-started once the temperature is
10 K lower than the set value. The above mentioned re-start
restrictions must also be complete before the compressor can
start once again.
If the delay time is set to '0' , the function will not stop the
compressor. The Td sensor can be deactivated (o63).

Liquid injection into economizer port

The controller can activate the liquid injection into economizer
port if the discharge temperature is approaching the maximum
allowable temperature.
Note: Liquid injection function use the Aux Relay.
High pressure monitoring
During regulation, the internal high pressure monitoring function
is able to detect an over the limit condensing pressure so that the
regulation can continue.
However, if the C73 setting is exceeded, the compressor will be
stopped.
If, on the other hand, the signal comes from the interrupted safety
circuit connected to DI3, the compressor will immediately be
stopped and the fan will be set to 100%.
When the signal is once again 'OK' at the DI3 input, the regulation
will resume.
Low pressure monitoring
During regulation, the internal low pressure monitoring function
will cut out the compressor upon detecting a suction pressure that
falls below the lower limit, but only once the minimum ON time
is exceeded. An alarm will be issued. This function will be time
delayed, if the compressor starts at low ambient temperature.
Pump down limit
The compressor will be stopped if a suction pressure that falls
below the set value is registered, but only once the minimum ON
time is exceeded.
4 User Guide RS8GD602 © Danfoss 2015-10 Optyma Plus
TM