Trane Rtaaiom3 Manual

							71RTAA-IOM-3
Alarm/Running/Maximum
Capacity Indicator Wiring
If the optional remote Alarm/Running/
Maximum Capacity contacts are used,
provide electrical power, 115 VAC
(contact load not to exceed 1150 VA
inrush, 115 VA sealed), with fused-
disconnect to a customer-furnished
remote device. Also provide proper
remote device ground connection.
To install the available remote running
and alarm indication, the installer must
provide leads 525 thru 532 from the
panel to the proper terminals of
terminal strip 1U1TB4 on the UCM, as
shown in Figures 31 thru 32. Refer to
the field diagrams which are shipped
with the unit.
Low Voltage Wiring
The remote devices described below
require low voltage wiring. All wiring to
and from these remote input devices to
the UCM must be made with shielded,
twisted pair conductors. Be sure to
ground the shielding only at the UCM.
See Figures 34 thru 36 for the
recommended conductor sizes.
Caution: To prevent control
malfunctions, do not run low
voltage wiring (
						

							72RTAA-IOM-3
External Chilled Water
Setpoint (CWS):
Remote Resistor/Potentiometer,
Voltage Source 2-10 VDC, or
Current Source 4-20 mA
This option allows the external setting
of the Chilled Water Setpoint,
independent of the Front Panel Chilled
Water Setpoint, by one of three means:
1. A remote resistor/potentiometer
input (fixed or adjustable)2. An isolated voltage input 2-10 VDC
3. An isolated current loop input
4-20 mA
Methods 2 and 3 are usually used in
interfacing with a Generic BAS or a
process controller to the chiller.
To enable external setpoint operation,
Item 30 of Menu 3, “External Chilled
Water Setpoint d/E”, should be set to
“E” using the Front Panel Operator
Interface.1. Remote Resistor/Potentiometer Input
(fixed or adjustable)
Connect the remote resistor and/or
potentiometer to terminals TB1 -3
and TB1 -5 of Options Module 1U2,
as shown in Figure 38.
For units with 40 F to 60 F LCWS
range, a field-furnished 25 Kohm
linear taper potentiometer (±10%)
and a fixed 5.6 Kohm (±10%) 1/4 watt
resistor should be used.
For units with 20 F to 39 F LCWS
range, a field-furnished 25 Kohm
linear taper potentiometer (±1 0%)
and a fixed 15 Kohm (±1 0%) 1/4 watt
resistor should be used.
If the potentiometer is to be remotely
mounted, it and the resistor must be
connected to the UCM prior to
mounting. Then, with the UCM
display in Menu 0 and the display
advanced to “Active Chilled Water
Setpoint”, the UCM can be used to
calibrate the positions of the
potentiometer to correspond with
the desired settings for the leaving
water temperature. External resistor
input values for various chilled water
setpoints are shown in Table 13.
Table 13
Input Values Vs. External Chilled Water Setpoint
InputsResulting Chilled
Resistance (Ohms) Current (mA) Voltage (Vdc) Water Setpoint (F)
94433 4.0 2.0 0.0
68609 5.2 2.6 5.0
52946 6.5 3.2 10.0
42434 7.7 3.9 15.0
34889 8.9 4.5 20.0
29212 10.2 5.1 25.0
24785 11.4 5.7 30.0
21236 12.6 6.3 35.0
18327 13.8 6.9 40.0
15900 15.1 7.6 45.0
13844 16.3 8.2 50.0
12080 17.5 8.8 55.0
10549 18.8 9.4 60.0
9050 20.0 10.0 65.0
Figure 38
Resistor and Potentiometer
Arrangement for External Chilled
Water Setpoint 
						

							73RTAA-IOM-3
2. Isolated 2-10 VDC Voltage Source
Input
Set DIP Switch SW1-1 of Options
Module 1U2 to “OFF”. Connect the
voltage source to terminals TB1 -4 (+)
and TB1 -5 (-) on Options Module
1U2. CWS is now based on the
following equation:
CW Setpoint 0 F = (VDC x 8.125) -
16.25
Sample values for CWS vs. VDC
signals are shown in Table 13.
Minimum setpoint
= 0 F (2.0 VDC input)
Maximum setpoint
= 65 F (9.4 VDC input)
Maximum continuous input voltage
= 15 VDC
Input impedance = 40.1 Kohms
SW1 -1 off)
3. Isolated 4-20 mA Current Source
Input
Set DIP Switch SW1-1 of Options
Module 1U2 to “ON”. Connect the
current source to terminals TB1-4
(+)and TB1-5 (-). CWS is now based
on the following equation:
Setpoint °F = (mA x 4.0625) - 16.25
Sample values for CWS vs. mA
signals are shown in Table 13.
Minimum setpoint = 0 F (4.0 mA)
Maximum setpoint = 65 F (18.8 mA)
Maximum continuous = 30 mA
input current
Input impedance = 499 ohms
SW1 -1 on)
Note: The negative terminal TB1 -5 is
referenced to the UCM chassis ground.
To assure correct operation, 2-10 VDC
or 4-20 mA signals must be isolated or
“floating” with respect to the UCM
chassis ground. See Figures 34 thru 36.External Current Limit Setpoint
(CLS): Remote Resistor/
Potentiometer, Voltage Source 2-10
VDC or Current Source 4-20 mA
This option allows the external setting
of the Current Limit Setpoint,
independent of the Front Panel Current
Limit Setpoint, by one of three means:
1. A remote resistor/potentiometer
input (fixed or adjustable)
2. An isolated voltage input 2-10 VDC
3. An isolated current loop input 4-20
mA
Methods 2 and 3 are usually used in
interfacing with a Generic BAS.To enable external Current Limit
Setpoint operation, Item 31 of Menu 3,
“External Current Limit Setpoint WE”,
should be set to “E” using the Front
Panel Operator Interface.
1. Remote Resistor/Potentiometer Input
 To cover the entire range of Current
Limit Setpoints; (40 to 120%), a field
furnished 50 Kohm log taper
potentiometer (±10%) and a fixed
820 ohm (±1 0%) 1/4 Waft resistor
should be wired in series and
connected to terminals TB1 -6 and
TB1 -8, of options module 1U2, as
shown in Figure 39.
Table 14
Input Values Vs. External Current Limit Setpoint
InputsResulting Current
Resistance  (Ohms) Current (mA) Voltage (Vdc) Limit Setpoint (% RLA)
49000 4.0 2.0 40
29000 6.0 3.0 50
19000 8.0 4.0 60
13000 10.0 5.0 70
9000 12.0 6.0 80
6143 14.0 7.0 90
4010 16.0 8.0 100
2333 18.0 9.0 110
1000 20.0 10.0 120
Figure 39
Resistor and Potentiometer
Arrangement for External
Current Limit Setpoint 
						

							74RTAA-IOM-3
If the potentiometer is to be remotely
mounted, it and the resistor must be
connected to the UCM prior to
mounting. Then, with the UCM display
in Menu 0 and the display advanced to
“Active Current Limit Setpoint”, the
UCM can be used to calibrate the
positions of the potentiometer to
correspond with the desired settings
for the current limits. External resistor
input values for various current limit
setpoints are shown in Table 14.
2. 2-10 VDC Voltage Source Input
Set DIP Switch SW1-2 of Options
Module 1U2 to “OFF”. Connect the
voltage source to terminals TB1 -7 (+)
and TB1 -8 (-) of Options
Module 1U2. CLS is now based on the
following equation:
CL Setpoint % = (VDC x 10) + 20
Sample values for CLS vs. VDC signals
are shown below:
Minimum setpoint
= 40% (2.0 VDC input)
Maximum setpoint
= 120% (10.0 VDC input)
Maximum continuous input voltage
= 15 VDC
Input impedance = 40.1 Kohms
(SW1 -2 off)3. 4-20 mA Current Source Input
Set DIP Switch SW1-2 of Options
Module 1U2 to “ON”. Connect the
current source to terminals TB1 -7 (+)
and TB1 -8 (-) of Options Module 1U2.
CLS is now based on the following
equation:
CL Setpoint % = (mA x 5) + 20
Sample values for CLS vs. mA signals
are shown in Table 14.
Minimum setpoint = 40% (4.0 mA)
Maximum setpoint = 120% (20.0 mA)
Maximum continuous input current
= 30 mA
Input impedance = 499 ohms
(SW1 - 2 on)
Note: The negative terminal TB1 -8 is
referenced to the UCM chassis ground.
To assure correct operation, 2-10 VDC
or 4-20 mA signals must be isolated or
“floating” with respect to the UCM
chassis ground. See Figures 31 thru 32.
Optional Bidirectional
Communications Link (BCL)
This option allows the UCM in the
control panel to exchange information
(e.g. operating setpoints and Auto/
Standby commands) with a higher
level control device, such as a Tracer, a
multiple-machine controller or a
remote display panel. A shielded,
twisted-pair connection establishes the
bidirectional communications link
between the unit control panel and the
Tracer, multiple-machine controller or
remote display panel.
Note: The shielded, twisted-pair
conductors must run in a separate
conduit.
Caution: To prevent control
malfunctions, do not run low
voltage wiring (
						

							75RTAA-IOM-3
Installation Check List
Complete this checklist as the unit is
installed, to verify that all
recommended procedures are
accomplished before the unit is started.
This checklist does not replace the
detailed Instructions given in the
“Installation -Mechanical” and
“Installation -Electrical” sections of this
manual. Read both sections
completely, to become familiar with the
installation procedures, prior to
beginning the work.
Receiving
[  ] Verify that the unit nameplate data
corresponds to the ordering
information.
[  ] Inspect the unit for shipping
damage and any shortages of
materials. Report any damage or
shortage to the carder.
Unit Location and Mounting
[  ] Inspect the location desired for
installation and verify adequate
service access clearances.
[  ] Provide drainage for evaporator
water.
[  ] Remove and discard all shipping
materials (cartons, etc.)
[  ] Install optional spring isolators, if
required.
[  ] Level the unit and secure it to the
mounting surface.
Unit Piping
[  ] Flush all unit water piping before
making final connections to the unit.
Caution: If using an acidic
commercial flushing solution,
construct a temporary bypass
around the unit to prevent damage
to internal components of the
evaporator.
Caution: To avoid possible
equipment damage, do not use
untreated or improperly treated
system water.
[  ] Connect the chilled water piping to
the evaporator.
[  ] Install pressure gauges and shutoff
valves on the chilled water inlet and
outlet to the evaporator.
[  ] Install a water strainer in the
entering chilled water line.
[  ] Install a balancing valve and flow
switch (discretionary) in the leaving
chilled water line.
[  ] Install a drain with shutoff valve or a
drain plug on the evaporator.
[  ] Vent the chilled water system at
high points in the system piping.
[  ] Apply heat tape and insulation, as
necessary, to protect all exposed
piping from freeze-up.
Electrical Wiring
WARNING: To prevent injury or
death, disconnect electrical
power source before completing
wiring connections to the unit.
Caution: To avoid corrosion and
overheating at terminal
connections, use copper
conductors only.
[  ] Connect the unit power supply
wiring with fused-disconnect to the
terminal block (or unit-mounted
disconnect) in the power section of
the control panel.
[  ] Connect the control power supply
wiring with fused-disconnect to the
terminal strip in the power section
of the control panel.
[  ] Connect power supply wiring to the
evaporator heat tape. Connect leads
551 and 552 to terminals 11 and 12
of terminal strip 1TB3.
[  ] Connect power supply wiring to the
chilled water pump.
[  ] Connect power supply wiring to any
auxiliary heat tapes.
[  ] Connect the auxiliary contact of the
chilled water pump (5K1) in series
with the optional flow switch, if
installed, and then connect to the
proper terminals.
[  ] For the External Start/Stop function,
install wiring from remote contacts
(5K5, 5K21) to the proper terminals
on terminal strip 1U1TB3.
Caution: Information in
Interconnecting Wiring: Chilled
Water Pump Interlock and External
Auto/Stop must be adhered to or
equipment damage may occur.
[  ] If the remote alarm/running/
maximum capacity contacts are
used, install leads 525 thru 532 from
the panel to the proper terminals on
terminal strip 1U1TB4.
[  ] If the emergency stop function is
used, install low voltage leads 513
and 514 to terminals 3 and 4 of
1U1TB1.
[  ] If indoor zone temperature is to be
used, install leads 501 and 502 on
6RT4 to the proper terminals on
1U2TB1.
[  ] If the ice making-option is used,
install leads 501 and 502 on 5K20 to
the proper terminals on 1U2TB1. 
						

							76RTAA-IOM-3 
						

							77RTAA-IOM-3
Operating
Principles –
Mechanical
General
This section describes the mechanical
operating principles of Series R air-
cooled chillers equipped with
microcomputer-based control systems.
The 130 thru 400-ton Model RTAA units
are dual-circuited, helical-rotary type
air-cooled liquid chillers. The basic
components of an RTAA unit are:
- Unit Control Module (UCM)
- Unit-mounted panel
- Helical-rotary compressor
- Direct Expansion evaporator
- Air-cooled condenser
- Oil supply system (hydraulic and
  lubrication)
- Interconnecting piping
Components of a typical RTAA unit are
identified in Figures 1 thru 6.
Refrigeration
(Cooling) Cycle
Cycle Description
Figures 40 and 41 represent the
refrigeration system and control
components. Vaporized refrigerant
leaves the evaporator and is drawn into
the compressor. Here it is compressed
and leaves the compressor as a
mixture of hot gas and oil (which was
injected during the compression cycle).
The mixture enters the oil separator at
the two in/out caps. The separated oil
flows to the bottom of the separator,
while the refrigerant gas flows out the
top and passes on to the tubes in the
condensing coils. Here circulating air
removes heat from the refrigerant and
condenses it.
The condensed refrigerant passes
through the electronic expansion valve
and into the tubes of the evaporator.
As the refrigerant vaporizes, it cools the
system water that surrounds the tubes
in the evaporator.
Compressor Description
The compressors used by the Model
RTAA Series “R” Air-cooled chiller
consists of two distinct components:
the motor and the rotors. Refer to
Figure 42.
Compressor Motor
A two-pole, hermetic, squirrel-cage
induction motor directly drives the
compressor rotors. The motor is cooled
by suction refrigerant gas from the
evaporator, entering the end of the
motor housing through the suction
line, as shown in Figures 40 and 41.
Compressor Rotors
The compressor is a semi-hermetic,
direct drive helical rotary type
compressor. Each compressor has only
three moving parts: Two rotors -
“male” and ‘female” - provide
compression, and a slide valve controls
capacity. See Figure 42. The male rotor
is attached to, and driven by, the motor,
and the female rotor is, in turn, driven
by the male rotor. Separately housed
bearing sets are provided at each end
of 
both rotors. The slide valve is located
above, and moves along, the top of the
rotors.
The helical rotary compressor is a
positive displacement device. The
refrigerant from the evaporator is
drawn into the suction opening at the
end of the motor barrel, through a
suction strainer screen, across the
motor, and into the intake of the
compressor rotor section. The gas is
then compressed and discharged
directly into the discharge line.
There is no physical contact between
the rotors and compressor housing.
The rotors contact each other at the
point where the driving action between
the male and female rotors occurs. Oil
is injected along the top of the
compressor rotor section, coating both
rotors and the compressor housing
interior. Although this oil does provide
rotor lubrication, its primary purpose is
to seal the clearance spaces between
the rotors and compressor housing.
A positive seal between these internal
parts enhances compressor efficiency
by limiting leakage between the high
pressure and low pressure cavities.Capacity control is accomplished by
means of a slide valve assembly
located in the rotor section of the
compressor. Positioned along the top
of the rotors, the slide valve is driven
by a piston/cylinder along an axis that
parallels those of the rotors.
Compressor load condition is dictated
by the position of the slide valve over
the rotors. When the slide valve is fully
extended over the rotors and away
from the discharge end, the
compressor is fully loaded. Unloading
occurs as the slide valve is drawn
towards the discharge end. Slide valve
unloading lowers refrigeration capacity
by reducing the compression surface of
the rotors.
Compressor Loading Sequence
When there is a call for chilled water,
the UCM will start the compressor
which has the least number of starts. If
the first compressor cannot satisfy the
demand, the UCM will start another
compressor and then balance the load
on all compressors by pulsing the load/
unload solenoids.
The load on the compressors will be
kept in balance, as load fluctuates, until
the demand for chilled water is reduced
to a level that can be handled by one
compressor. At this time, the UCM will
drop off the compressor that has the
greatest number of operating hours
and will adjust the load on the other
compressor, as required. 
						

							78RTAA-IOM-3
Figure 40
Refrigeration System and
Control Components
Single Circuit(Continued on Next Page) 
						

							79RTAA-IOM-3
Figure 40
(Continued from Previous Page)
1 Schrader valve
2 Suction temperature sensor*
3 Manufacturing process tube
4 Suction service valve (optional)
5 Motor winding thermostat*
6 Discharge temperature sensor*
7 Pressure relief valve (450 psi)
8 High pressure cutout (405 psi)*
9 Discharge check valve
10 Evaporator waterside vent
11 Discharge line shutoff valve
12 Oil separator in/out cap
13 Saturated condensing temperature
sensor*
14 Condenser header
15 Subcooler header
16 Liquid line shutoff valve17 25 micron filter/drier
18 Liquid line sight glass
19 Electronic expansion valve
20 Saturated evaporator temperature
sensor*
21 Evaporator waterside drain
22 Leaving water temperature sensor*
23 Leaving water connection
24 Entering water connection
25 Entering water temperature sensor*
26 Drain with Schrader valve
27 Oil line
28 Entering oil cooler header
29 Leaving oil cooler header
30 Schrader valve with stem depressor
31 Oil line shutoff valve
32 5 micron oil filter33 Master solenoid valve*
34 Oil line to load/unload slide valve
solenoids
35 Injection oil check valve
36 Heater
37 Slide valve solenoids and orifices*
38 Oil flow differential pressure switch*
39 Compressor Drain Plug
40 Domestic water heater (option)
41 Oil line thermostat (option,
Domestic Water Heater)
42 Oil line bypass solenoid valve
(option, Domestic Water Heater)
*UCM Input/Output Control 
						

							80RTAA-IOM-3
Figure 41
Refrigeration System and
Control Components
Duplex Circuit(Continued on Next Page)