1A
Ton
10 Ton
1B
Ton
1.6.1
Tandem Compressor Option
An optional four stage cooling configuration is
available which utilizes three compressors (two
small tandem compressors and one large
compressor). The two small tandem compressors
operate as circuit 1 and the large compressor
operates as circuit 2 (see Figure 4).
Figure 4 - Tandem Compressor Configuration
1.6.1.1
Four Stage Operation
In the example of a CFU/D-070 (20 ton, 240,000
BTU) A/C system configured with three
compressors, two small (5 ton) compressors are
paired together as one, tandem circuit with a shared
suction line and shared discharge line
.
The
compressor suction and discharge ports are
equipped with back pressure isolation valves so one
compressor may operate independently or both
may operate together as required by capacity
staging demands. One large (10 ton) compressor is
also provided as circuit two.
The controller manages operation of the three
compressors with a unique method of staging
which conserves energy by incrementally
matching compressor capacity against the load.
The three
compressors are turned on in various combinations
to provide a total of 4 stages of cooling as shown in
the table below:
Stage
Cut-in
Offset
Compressor(s)
Capacity
1
+2° F
1A
5 tons
2
+3° F
2
10 tons
3
+4° F
1B+2
15 tons
4
+5° F
1A+1B+2
20 tons
CyberAiR DX Floor Mounted IOM Manual
1.6.1.2 Four Stage Compressor Rotation
Compressors 1A and 1B rotate the lead role after each
run cycle in the cooling mode. That is, after compressor
1A has completed an operating cycle as the primary
compressor for stage 1, the next time cooling stage
1 is called for, the compressors switch roles and
compressor 1B becomes the primary compressor
for stage 1. When compressor 1B is the primary for
stage 1 cooling, compressor 1A’s role is switched to
operate with compressor 2 for the third stage of
cooling.
Compressor 2 is not involved in the cooling mode
rotation so it will always be used for cooling stages
2, 3 and 4.
For the dehumidification mode, compressor circuits
1 and 2 (see Figure 4) rotate the lead role after
each run cycle. The tandem compressors rotate as
a single, dual compressor circuit because a single
small compressor from the tandem set does not
have enough capacity to satisfy the dehumidification
load alone. In the dehumidification mode, after
circuit 1 (compressors 1A and 1B) has completed
an operating cycle as the lead, the next time
dehumidification stage 1 is called for the
compressor circuits switch roles and circuit 2
(compressor 2) becomes the primary compressor
circuit for dehumidification.
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