Tandem and trio operation

Orbit compressors are particularly suitable for parallel operation (tandems and trios). With respect to oil balance in such arrangements, Bitzer has developed the Bitzer Advanced Header Technology (BAHT). The BAHT headers reduce the pressure drop variations of the refrigerant circuit and the impact they can have on oil equalisation between the compressors: It will be maintained regardless of operating sequence, as long as the oil quantity in the system is sufficient for tandem resp. trio compounds.

Further advantages of the compound systems:

extension of capacity compared to single compressors
wide range of compressor combinations for full and part load capacity and efficiency optimization
optimum capacity adjustment with low power consumption in part load range (combination of identical or different compressor sizes, possibly with external frequency inverter, see Technical Information EST-420)
optimum oil distribution
low load on electrical supply during start
high degree of operational safety
simple and cost-effective installation

For further information see the Bitzer Software as well as:

ESP-130: Brochure Hermetic Scroll Compressors ORBIT, ORBIT+, ORBIT FIT
EST-420: Bitzer scroll compressors with external frequency inverters

There are multiple tandem and trio arrangements using BAHT, the following figures show some examples. Please contact Bitzer for dimensional drawings and further information.

In each tandem or trio, one compressor is the primary compressor. This should be the compressor with the lowest displacement in the tandem, because it is the first to receive oil from the BAHT header:

In case of a vertical BAHT header (ORBIT 6 tandem and trio, mixed tandem), the primary compressor is the compressor connected to the bottom part of the BAHT.
In case of a horizontal BAHT header (ORBIT 8 tandem), the primary compressor is the compressor connected next to the closed end.

Orbit 6 tandem

Example of an even or uneven tandem arrangement of ORBIT 6 compressors with BITZER Advanced Header Technology (vertical BAHT header)SL: Suction gas lineDL: Discharge gas line#1 .. #2: Compressors no. 1 .. 2. Compressor no. 1 is the primary compressor.4: Sight glass5: Oil maintenance connection6: Oil equalizing line7: Mounting position for vibration dampers8: Mounting position for tandem and trio fixing rails — Example of an even or uneven tandem arrangement of ORBIT 6 compressors with BITZER Advanced Header Technology (vertical BAHT header)
SL: Suction gas line
DL: Discharge gas line
#1 .. #2: Compressors no. 1 .. 2.
Compressor no. 1 is the primary compressor.
4: Sight glass
5: Oil maintenance connection
6: Oil equalizing line
7: Mounting position for vibration dampers
8: Mounting position for tandem and trio fixing rails

Orbit 8 tandem

Example of an even or uneven tandem arrangement of ORBIT 8 compressors with BITZER Advanced Header Technology (horizontal BAHT header).
SL: Suction gas line
DL: Discharge gas line
#1 .. #2: Compressors no. 1 .. 2.
Compressor no. 1 is the primary compressor.

Orbit 6 / Orbit 8 tandem

Example of a mixed tandem arrangement of ORBIT 6 and ORBIT 8 compressors with BITZER Advanced Header Technology (vertical BAHT header)
SL: Suction gas line
DL: Discharge gas line
#1 .. #2: Compressors no. 1 .. 2
Compressor no. 1 is the primary compressor.

Orbit 6 trio

Example of an even trio arrangement of ORBIT 6 compressors with BITZER Advanced Header Technology (vertical BAHT header)SL: Suction gas lineDL: Discharge gas line#1 .. #3: Compressors no. 1 .. 3Compressor no. 2 is the primary compressor.4: Sight glass5: Oil maintenance connection6: Oil equalizing line7: Mounting position for vibration dampers8: Mounting position for tandem and trio fixing rails — Example of an even trio arrangement of ORBIT 6 compressors with BITZER Advanced Header Technology (vertical BAHT header)
SL: Suction gas line
DL: Discharge gas line
#1 .. #3: Compressors no. 1 .. 3
Compressor no. 2 is the primary compressor.
4: Sight glass
5: Oil maintenance connection
6: Oil equalizing line
7: Mounting position for vibration dampers
8: Mounting position for tandem and trio fixing rails

Exchanging comressors in a tandem or trio

When replacing a compressor in a tandem or trio consisting of ORBIT compressors with design variable 1 (to be identified by the last digit of the motor code, e.g. GSU80295VAB431), most ORBIT compressors with design variable 2 are backwards compatible. One exception is compressor GSD80485V.2: If this model is implemented into a tandem or trio of compressors with design variable 1, a washer must be mounted into the suction port of the GSD80485V.2:

Washer in the suction connection in case of implementing a GSD80485V.2 compressor into a tandem or trio of compressors with design variable 1.