Low Ambient Dampers; Compressor Crankcase Heaters - Trane RAUJ-C20 Installation, Operation And Maintenance Manual

O O p p e e r r a a t t i i n n g g P P r r i i n n c c i i p p l l e e s s
Table 27. RAUJ condenser fan sequencing data: 20 to 60 ton units
Controlling Device
Interlock Circuit 1
Interlock Circuit 2
Fan Temperature Switch
Fan Pressure Switch
(a) Fan used on 40, 50 and 60 ton units only.
(b) 1S36 and 1S37 normally-closed contacts open on ambient temperature drop to 30°F. Contacts reclose on ambient temperature rise to 30°F and 33°.
(c) Fan used on 25, 30, 50 and 60 ton units only.
(d) Fan used on 50 and 60 ton units only.
80 to 120 Ton Specs
Condenser fan cycling is accomplished through
interlocking the fan operation with compressor
operation (1K1 & 1K4), liquid line pressure switches
(4S7 & 4S8). Table 28, p. 92
sequencing data. See "Condenser Fans," p. 86
condenser fan locations and designators.
Table 28. RAUJ condenser fan sequencing data: 80 to 120 ton units
Controlling Device
Interlock Circuit 1
Interlock Circuit 1
Interlock Circuit 2
Interlock Circuit 2
Fan Pressure Switch
(a) Fan used on 100 and 120 ton units only.

Low Ambient Dampers

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
0ºF without hot gas bypass or 10ºF 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
92
Fan "ON"
1K1 Closed
1K3 Closed
33°F
(b)
33°F
444 psig
444 psig
lists the condenser fan
for
Fan ON
1K1 Closed
1K1, 1K2 Closed
1K4 Closed
1K3, 1K4 Closed
444 psig
444 psig
Fan "OFF"
1K1 Open
1K3 Open
1S36
30°F
1S37
30°F
4S11
255 psig
4S12
255 psig
When a cooling command has been initiated, the first
compressor for circuit 1 is energized. An auxiliary
contact on the compressor contactor is closed,
energizing contactor 1K9 and turning on fan 4B2. When
the liquid line pressure exceeds 255 psig the fan
pressure switch (4S7) will close and energize contactor
1K7, turning on fans 4B1 and 4B4.
Fan OFF
1K1 Open
1K1, 1K2 Open
1K4 Open
1K3, 1K4 Open
4S7
255 psig
4S8
255 psig
temperatures can be maintained as the ambient
temperatures change.
The low ambient damper actuator controls damper
modulation for each refrigerant circuit in response to
saturated condensing temperature.

Compressor Crankcase Heaters

Each compressor is equipped with a crankcase heater
and is controlled by a 600 volt auxiliary switch on the
compressor contactor. The proper operation of the
crankcase heater is important to maintain an elevated
compressor oil temperature during the "Off" cycle to
Fan Identification
2B2
2B5 (a)
2B3 (c)
2B6 (d)
2B1
2B4 (a)
Fan Identification
4B2, 4B6
(a)
4B2, 4B5, 4B6 (a)
5B2, 5B6 (a)
5B2, 5B5, 5B6 (a)
4B1, 4B4, 4B3 (a)
5B1, 5B4, 5B3 (a)
SS-SVX11K-EN