Start sequence
Frequency inverters are inherently soft starting. When starting the compressor, the inverter should be set to a very low speed/frequency, increasing it until the nominal operating speed of the compressor is achieved. This must not happen too fast ‒ otherwise, the high inrush current to the motor may damage the inverter. Usually, the starting process can be programmed with control over the ascending ramp and starting voltage boost.
Risk of compressor damage due to lack of oil!
With FI operation, observe the recommended speed ramps in order to avoid a delayed internal lubrication to the compressor.
Recommended start sequence
Bitzer suggests adhering to the following start sequence, i.e. ascending to 50 .. 60 Hz. This can be programmed in the frequency inverter (with VARIPACK: "Hold frequency") or must be implemented with the superior control. Individual applications may allow for a lower "start dwell speed” with approval by Bitzer.
Start sequence for ELV21 see operating instructions, for ELV52 on request.
Acceleration during ascending ramp: 17 .. 30 Hz / sec
Nominal operating frequency: 50 .. 60 Hz
Time at nominal operating frequency: ≥ 60 sec
For EL.7, a minimum running time of 3 min has to be observed - please contact Bitzer for operation of EL.7 with frequency inverter.
This start sequence is intended only to manage oil delivery within the compressor itself. It is not intended to address oil migration or oil return from the system. System oil return issues should also be addressed and may require extended time at nominal operating frequency to return any oil potentially pumped out at start-up, if lower operating frequencies and mass flows are expected.
There is no specific stop sequence for scroll compressors with frequency inverter – the procedure is the same as without frequency inverter, but special care should be taken to maintain a sufficient oil level.
During operation, frequency changes should be much slower than during start and stop (Configuration of the frequency inverter).
For work on the compressor once it has been commissioned:
WARNING
The compressor is under pressure!
Serious injuries are possible.
Depressurise the compressor!
Wear safety goggles!
CAUTION
Surface temperatures of more than 60°C or below 0°C.
Risk of burns or frostbite.
Close off accessible areas and mark them.
Before performing any work on the compressor: switch it off and let it cool down or warm up.
Risk of compressor failure!
Operate the compressor only in the intended rotation direction!