System Start-Up; Sequence Of Operation - Trane CAUC-C80 Installation Operation & Maintenance

Sequence of Operation

Standard air cooled condensers function as the outdoor
condensing units for appropriately sized split refrigeration
systems. These units, operating in conjunction with a
matched indoor compressor/evaporator configuration, pro-
vide refrigerant condensing for these systems down to a
normal ambient temperature of 40
ent is possible with the addition of externally mounted low
ambient dampers.
All condenser fans are direct drive, 26 inch propeller type.
They are driven by 1 HP thermally protected motors.
Condenser fan cycling is accomplished through interlocking
the fan operation with compressor operation (6K1 & 6K2),
and ambient temperature thermostats (1S42 & 1S43) are
used to provide additional fan cycling control. Table 5-1 lists
the condenser fan sequencing data and Figure 5-1 illus-
trates the condenser fan locations with their respective fan
and relay designators.
When wired properly, the unit will start and operate satisfac-
torily as long as the operating temperature is above the
minimum operating temperature listed in Table 5-2.
The condensing unit operation starts and stops automati-
cally when the cooling demand is initiated and terminated
by the cooling circuit interlock relays illustrated in
Figure 5-2.
The control components are mounted in the various areas
of the unit as illustrated in Figure 5-3.
Table 5-1
Condenser Fan Sequencing Data
Controlling Fan
Device ON
Customer
Interlock 6K1
Circuit 1
Closed
Customer
Interlock 6K2
Circuit 2
Closed
Fan Stage 1
o
Temperature 53 F
Switch Stage 2
o
1S42 (2) 73 F
Fan Stage 1
o
Temperature 53 F
Switch Stage 2
o
1S43 (2) 73 F
Notes:
1. Bold fan identifies fans used on CAUC-D10 & D12 units
only.
2. 1S42 and 1S43 normally-closed contacts open on
ambient temperature drop to "OFF" setpoints.
Contacts reclose on ambient temperature rise
on "ON" setpoints.
o F. Operation to 0 o F ambi-
Fan Fan
OFF Identification
6K1 4B2, 4B5, 4B6 (1)
Open
6K2 5B2, 5B5, 5B6 (1)
Open
o
4B3 (1)
45 F
o
65 F 4B1, 4B4 (1)
o
5B3 (1)
45 F
o
65 F 5B1, 5B4

System Start-Up

Low Ambient Damper Operation
Low Ambient Dampers are available as a factory installed
option or can be field-installed. Dampers are used to extend
the operation of these units from the standard operational
temperatures to a minimum of 0
o
or 10 F with hot gas bypass. (These values apply when
wind speed across the condenser coil is less than 5 m.p.h.).
If typical wind speeds are higher than 5 m.p.h., a wind
screen around the unit may be required. By restricting the
airflow across the condenser coils, saturated condensing
temperatures can be maintained as the ambient tempera-
tures change.
The low ambient damper actuator controls damper modula-
tion for each refrigerant circuit in response to saturated con-
densing temperature.
Low Ambient Thermostat Operation
In addition to the low ambient dampers a two stage low am-
bient thermostat is installed to further restrict the airflow
across the condenser by cycling the 4B1 + 4B6, 5B1 + 5B6
on 100 & 120 Ton units. The final stage thermostats opens
when the ambient temperature approaches 65
at approximately 73 o F. The second stage opens when the
ambient temperature approaches 45
o
proximately 53 F.
24
o
F without hot gas bypass
o
F and closes
o F and closes at ap-