Compressors; Compressor Cycling; Compressor Lead/Lag Operation; Compressor Stages - Trane IntelliPak Signature Series Installation, Owner, And Diagnostic Manual

Compressors

Units use two sizes of hermetic scroll
compressors, 10 and 15 hp, and can use
from two to four compressors. When
viewing the front of the unit, compressors
are identified A through D from left to
right. The second compressor from the
left, or B compressor, is always the first to
come on, unless locked out for a
malfunction or shut off on frost protection.
Refer to Table O-SO-1 for compressor
cycling stages and Table O-SO-3 on page
79 for percent cooling capacity by stage.
The control system logic permits com-
pressor operation only after the supply
fan is on. If the supply fan shuts down,
compressors will not operate. Units
without head pressure control (units with
intermediate piping packages) will lock
out mechanical cooling when the entering
condenser water temperature falls below
54 F . Mechanical cooling will resume
when the entering condenser water
temperature exceeds 58 F .
When there are more than two compres-
sors in an air cooled unit, the first two
Table O-SO-1. Compressor Stages.
Unit Refrigerant
Size Circuit Type
Model # Digit 5
SXWF 20, 22, 25 Independent
SXRF 20
SXWF 29, 32 Independent
SXRF 25, 29
SXWF 35, 38 Independent
SXRF 30, 35 Manifolded
SXWF 42, 46 Independent
SXRF 40 Manifolded
SXWF 52, 58 Independent
SXRF 50 Manifolded
SXWF 65, 72 Independent
SXWF 80 Independent
SXRF 60 Manifolded
78
Owner
compressors are manifolded together. If
there are four compressors, the second
two are manifolded.

Compressor Cycling

Compressors cycle to maintain the
operating state required by the
temperature controls. In the event of a
compressor failure, the next available
compressor turns on. Refer to Table O-
SO-1 for compressor cycling by unit
model and tons.
During normal conditions, compressors
will not shut off until they have been on
for at least three minutes and will not turn
on until they have been off for at least
three minutes. Normal operating condi-
tions are established on an individual
compressor basis. When a compressor
starts, its timer also starts. The compres-
sor evaporator circuit frost protection can
override the "minimum" timer and
reduce the five minute minimum re-
quired time period.
When the unit is powered up, or manually
reset there will be a three to eight minute
delay before the first compressor may be
Compressor HP Standard
by Stage Compressor
A B C D Staging
10 10 B/AB
15 10 B/A/AB
10 10 10 B/BC/ABC
10 10 10 B/BC/ABC
15 10 10 B/A/AC/ABC
15 10 10 B/A/AC/ABC
15 15 15 B/BC/ABC
15 15 15 B/BC/ABC
15 15 15 10 B/BD/ABD/ABCD
15 15 15 15 B/BD/ABD/ABCD
15 15 15 15 B/BD/ABD/ABCD
Sequence of
Operation
turned on as requested by the unit
temperature control algorithm.

Compressor Lead/Lag Operation

Compressor lead/lag is a user-selectable
feature at the HI panel and is available on
all units. After each request for
compressor operation, the lead
refrigeration circuit or compressor
switches, thereby causing a more
equitable or balanced run time among
compressors.
When lead/lag is enabled, each time the
system cycles, it will alternate between
the standard compressor staging and the
lead/lag staging. Using Table O-SO-1, a
SXWF 29-ton unit will first stage com-
pressor B then A, then AB for first cycle
and A, then AB for the second cycle.
Appropriate condenser valves (water-
cooled and condenser fans (air-cooled)
will stage with appropriate compressors
to maintain saturated condensing
temperature. Enabling lead/lag may drop
a cooling stage when compared to
standard staging. See Table O-SO-1 for
compressor staging.
Lead/Lag SCM
Compressor or
Staging MCM
A/AB MCM
A/AB MCM
A/AC/ABC MCM
A/AC/ABC MCM
C/AC/ABC MCM
C/AC/ABC MCM
A/AC/ABC MCM
A/AC/ABC MCM
A/AD/ACD/ABCD MCM
A/AC/ABC/ABCD MCM
A/AC/ABC/ABCD MCM
SCXF-SVX01B-EN