Emerson Copeland Scroll Introduction Manual page 39

Alternative methods using the sight glass connections for oil equalisation connections have been shown to work on specific systems.
Notes are given below on some possible methods, but because of wide variations in system design and operating conditions, these
methods cannot be given general approval by Emerson Climate Technologies. The user has to verify operation in each system type.
4.2 Gas and oil equalization tube at sight glass position
Emerson Climate Technologies has conducted tests to prove the satisfactory operation of up to three compressors in parallel using
a gas and oil equalising tube. The configuration of suction line and equalization line should be as described below (see sections 4.3
and 4.4).
This method can be used for:
• Two or three ZF, ZS, ZB refrigeration Scroll compressors
• They must all be the same model, not uneven sizes
• All voltages
• Refrigerants R404A, R507, R22
• Same operating envelope as single compressor with injection where required
• Adequate liquid floodback protection must be provided
• Any sequence of compressors is allowed
Figure 1: Scrolls in parallel
Compressor models approved
Low temperature Medium temperature
ZF09K* to ZF48K* ZB15K* to ZB114K* ZS21K* to ZS11M*
Table 2: Model applicability
4.3 Suction line configuration
An adequately sized suction header providing equal distribution of returning
refrigerant and oil to each individual compressor must be used. The non-
symmetrical design as shown below is acceptable and does not create oil level
problems between the compressors.
Figure 2: Oil return Figure 3: Suction line configuration
36