Tandem and trio operation

Inverter driven Orbit scroll compressors may be connected in tandem and trio arrangements (ESH7: tandems only, EL.7: single application only). In these cases, however, observe the respective maximum range of frequencies (see tables below): They are necessary to ensure adequate lubrication resp. oil return from the system when compression capacity is reduced. Whether by staging or inverter operation, capacity reduction reduces the refrigerant mass flow rate in the system. Special care must be taken to avoid oil traps and ensure that at low loads and low ambient temperatures, the flow velocity is sufficient to return oil from evaporators and any suction accumulators.

Individual rather than common drive operation

Equipping each compressor with a frequency inverter (= individual drive operation) allows individual compressors to be stopped or started independently of the others ‒ within certain ranges, which are listed in detail in the tables below. With BITZER Advanced Header Technology (BAHT), it is possible to combine fixed and variable speed Orbit compressors with the same pipes as used for conventional on/off operation. For ESH7, only the standard piping system is available.

In contrast, it is not recommended to use one inverter for several compressors (= common drive operation), because e.g.:

Compound systems of 2 or 3 Orbit scroll compressors utilizing BAHT

Risk of compressor damage if speed/frequency limits are not observed!

Risk of compressor damage if speed/frequency limits are not observed!

In compound systems with frequency inverter on one compressor: Observe the limitations in speed/frequency for this compressor! They vary with compressor type and supply frequency (50 or 60 Hz).

In compound systems with frequency inverter on each compressor: All compressors must operate at the same speed/frequency when running simultaenously! If only one compressor is actually running, it may operate at any frequency of 35 .. 75 Hz.

Due to the pressure difference necessary to achieve oil distribution, the variable speed options are limited to speeds that will achieve the pressure differentials for proper functioning of the oil management system.

Relevant parameters for possible combinations of Orbit compressors are:

After selecting the compressors in the Bitzer Software according to the required refrigerating capacity, possible combinations of fixed and variable speed drives can be checked in the following tables.