Trane RTAA User Manual

™

Air-Cooled Series R
Rotary Liquid Chiller

Model RTAA
70 to 125 Tons

Built for the Industrial and Commercial Markets

RLC-PRC016-ENAugust 2002

Features and
Benefits

Yo u…

Like its chillers, Trane wants its
relationships with customers to last.
Trane is interested in maintaining long
term, loyal relationships. This
perspective means the point in time that
a customer purchases a chiller is the
beginning of a relationship, not the end.
Your business is important, but your
satisfaction is paramount.

Designed by Customers….

Trane’s RTAA 70-125 was designed with
the end user’s requirements in mind.
Reliability, efficiency, sound, and
physical size were primary design
concerns in expanding the RTAA product
line down to 70 tons. The result is a
reliable chiller that will help you achieve
your bottom line goals.

© 2002 American Standard Inc. All rights reserved.

RLC-PRC016-EN2

Contents

Features and Benefits

Model Number Description

General Data

Selection Procedure

Application Considerations

Performance Adjustment Factors

Performance Data

Electrical Data

Jobsite Connections

Controls

Dimensional Data

Weights

2

13

14

15

16

20

22

29

30

32

40

41

The standard ARI rating condition
(54/44°F and 95°F) and IPLV are ARI
certified. All other ratings, including the
following, are outside the scope of the
certification program and are excluded:

• Glycol.

• 50 Hz.

• Remote evaporator models.

RLC-PRC016-EN

Options

Typical Wiring Diagrams

Features Summary

Mechanical Specifications

Water Chiller

42

43

45

46

Systems Business Unit

3

Features and
Benefits

Improvements

The RTAA 70-125 offers the same high
reliability of its larger predecessor
coupled with lowered sound levels,
increased energy efficiency, and reduced
physical footprint, all due to its advanced
design, low speed/direct drive
compressor and proven Series R
performance.

Some of the major advantages of the
Model RTAA 70-125 vs its larger
predecessor are:

• Higher energy efficiency

• Lower sound levels

• Smaller physical footprint

The Series R
industrial grade design built for both the
industrial and commercial markets. It is
ideal for schools, hospitals, retailers,
office buildings, Internet service
providers and industrials.

ASHRAE Standard 90.1 and RTAA 70­125 World Class Energy Efficiency…

The importance of energy efficiency
cannot be understated. Fortunately,
ASHRAE has created a guideline
emphasizing its importance.
Nonetheless, energy is often dismissed
as an operational cost over which the
owner has little control. That perception
results in missed opportunities for
energy efficiency, reduced utility bills,
and higher profits. Lower utility bills
directly affect profitability. Every dollar
saved in energy goes directly to the
bottom line. Trane’s RTAA 70-125 is one
way to maximize your profits.

™

Model RTAA 70-125 is an

™

ASHRAE Standard 90.1 & Executive
Order

- New technology applied to the

design, controls, and manufacturing
have created superior efficiency levels in
the RTAA 70-125 that are unmatched in
the industry. All Trane air-cooled chillers
meet the new efficiency levels mandated
by ASHRAE Standard 90.1. This new
standard requires higher efficiencies
than past technologies can deliver. The
US Federal Government has adopted
standard 90.1 and, in some cases,
requires even higher efficiencies.
Federal Executive Order mandates
energy consuming devices procured
must be in the top 25% of their class or

be at least 10% better than any product
standard for that product. In the case of
chillers, that product standard is
ASHRAE 90.1. Trane’s RTAA 70-125
meets and exceeds the efficiency
requirements of 90.1, with some units
meeting the “stretch goals” of Executive
Order.

Risk.

The US Federal Government has
adopted ASHRAE 90.1, and it’s expected
to be adopted domestically, if not
globally, in the future. Domestic
acceptance has already begun. Make
sure that your chillers as well as your
entire HVAC system complies, or you
may be caught retrofitting your project
with new equipment and paying extra
design dollars if the code is adopted
during construction.

Precise Capacity Control.

patented unloading system allows the
compressor to modulate infinitely and
exactly match building loads. At the
same time chilled water temperatures
will be maintained within +/- 1/2ºF of

Trane’s

setpoint, potentially eliminating the need
for external considerations to maintain
temperatures. Reciprocating and screw
chillers with stepped capacity control do
well to maintain chilled water
temperatures within 2ºF of setpoint.
Stepped control also results in
overcooling or undercooling your space
because rarely does the capacity of the
machine match the building load. The
result can be 10% higher energy bills.
Trane’s RTAA optimizes the part load
performance of your machine for energy
efficiency, precise temperature control
for all modes of operation, and your
personal comfort regardless of changing
conditions.

RLC-PRC016-EN4

Excellent Reliability

A building environment is expected to
be comfortable. When it is, no one says
a word. If it’s not… that’s a different
story. The same is true with chillers. No
one ever talks about chillers, yet alone
compressors, until they fail, and tenets
are uncomfortable and productivity is
lost. Trane’s helical rotary compressors
have a first year reliability rate of over
99%, which means our chillers stay
running when you need them.

Screw compressors were designed to
replace the inherent design flaws of a
reciprocating compressor. Trane’s helical
rotary compressor has successfully
achieved this goal, proven by the over
99% reliability rating of our compressor
in the first year of operation. A good
design like Trane’s should maintain this
level of reliability for several years of
chiller operation. Not all screw
compressors maintain a high reliability
and Trane is the only manufacturer that
will publish a reliability number. The
point is to make sure that you are getting
a reliable screw chiller design so that you
don’t end up with the downtime and lost
earnings that the industry is trying to

Features and
Benefits

avoid by getting away from
reciprocating technology.

Fewer moving parts.

rotary compressors have only two major
rotating parts: the male and female rotor.
A reciprocating compressor can have
more than 15 times that number of
critical parts. Multiples of pistons,
valves, crankshafts, and connecting rods
in a reciprocating unit all represent
different failure paths for the
compressor. In fact, reciprocating
compressors can easily have a failure
rate four times that of a helical rotor.
Combine this with two to three
reciprocating compressors for each
helical rotary compressor on chillers of
equal tonnage, and statistics tell you it’s

Trane’s helical

a matter of time before you lose a
reciprocating compressor.

Robust parts.

compressors are precisely machined
using state of the art processes from
solid metal bar stock. Tolerances are
maintained within a micron or less than
a tenth of the diameter of a human hair.
The resulting compressor is a robust yet
highly sophisticated assembly capable of
ingesting liquid refrigerant without risk
of damage. Contrast this to a
reciprocating compressor, which can be
destroyed by a single slug of liquid.

Series R

• Direct-drive, low speed for high
efficiency and reliability.

• Simple design with only four moving
parts, resulting in high reliability and
low maintenance.

• Field serviceable compressor for easy
maintenance.

• Precise rotor tip clearance for optimal
efficiency.

• Suction gas-cooled motor, resulting in
lower operating temperatures for
increased motor life, and giving the
capability for:

• Five-minute start-to-start/two minute
stop-to-start capability, which allows
for closer water loop temperature
control.

Helical rotary

™

Compressor Highlights

RLC-PRC016-EN

5

Features and
Benefits

RTAA 70-125 Chiller Highlights

• High Reliability, with over 99%
compressor reliability rate in the first
year of operation, and Adaptive
Controls to keep the chiller on line
producing cold water during adverse
conditions.

• High Efficiency (all units exceed
ASHRAE 90.1 efficiency standard).

• Low sound levels.

• Small footprint, with smallest required

application space (operating footprint)
in the industry.

• Years of research, testing, and
successful applications. The Trane
helical rotary compressor has amassed
thousands of hours of testing, much of
it at severe operating conditions. Not
to mention the successful application
of RTAA chillers for over 11 years, with
a developed reputation as the industry
standard.

• Trouble free startup through factory
testing of compressor and completed
chiller and factory installation of chiller
accessories.

• +/- ½°F leaving water temperature
control, resulting from PID feed­forward controls, and linear load
matching, also allowing for 10% flow
rate change per minute while
maintaining ± ½°F leaving water
temperature control.

Trane helical rotary screw compressor
component parts versus reciprocating
compressor components.

RLC-PRC016-EN6

Features and

Optimum

Benefits

Superior Full Load Efficiency

Precise Rotor Tip Clearances

Higher energy efficiency in a helical
rotary compressor is obtained by
reducing the rotor tip clearances. This
reduces the leakage between high and
low pressure cavities during
compression. Precise rotor tip clearance
is achieved with the latest manufacturing
and machining technology. Trane is the
first helical rotary compressor
manufacturer to electronically check
compressor parts machining accuracy as
part of the standard production process.

Optimized Compressor Parts Profiles

Rotor and slide valves are unique
designs, optimized for the air
conditioning application. The rotors are
designed for the pressure ranges in the
air conditioning application. The unloader
valve has a unique profile that resulted
from computer performance modeling in
typical part-load situations.

Advanced Heat Transfer Surfaces

Condenser and evaporator tubes use the
latest heat transfer technology for
increased efficiency.

Efficiencies

Great Part Load Efficiency
With Trane Helical Rotary
Screw Compressors and
Electronic Expansion Valve

Trane Helical Rotary Screw Compressor
Means Superior Part Load Performance

The air-cooled Series R
part-load performance. The combination
patented unloading system on the
“general purpose” compressor utilizes
the variable unloading valve for the
majority of the unloading function
similar to that of the slide valve. The
“general purpose” compressor also
uses a step unloader valve which is a
single unloading step to achieve the
minimum unloading point of the
compressor. The result of both of these
designs is optimized part-load
performance far superior to single
reciprocating compressors.

™

chiller has great

RLC-PRC016-EN

7

Features and
Benefits

Electronic Expansion Valve

When coupled with Trane’s Adaptive

™

Control
expansion valve significantly improves
part-load performance of the Series R
chiller by minimizing superheat in the
evaporator and allowing the chiller to
run at reduced condensing
temperatures. Chillers which use
conventional TXV’s must run at higher
head pressures and consume more
power than necessary at part-loads.
Additionally, the electronic expansion
valve and its controls allow much better
stability and control over dynamic load
and head changes. Under these
conditions a conventional TXV may
never achieve control stability and
extended periods of TXV “hunting” and
liquid slugging are common.

Capacity Control and Load Matching

Infinitely variable compressor
modulation allows the compressor
capacity to exactly match the building
cooling load. Reciprocating and screw
chillers that rely on stepped capacity
control must run at a capacity equal to or
greater than the load. Much of this
excess capacity is lost because
overcooling goes toward building latent
heat removal, causing the building to be
dried beyond normal comfort
requirements. The result is an increase in
chiller energy costs, particularly at the
part-load conditions at which the chiller
operates most of the time.

microprocessor, our electronic

™

PID Chilled Water Setpoint
Control Through Slide Valve
Modulation

Maintain Chilled Water Supply Within

1

±

/2°F of Setpoint

Chillers that have step capacity control
typically can only maintain water
temperature to around ± 2°F. With the
air-cooled Series R™ chiller, maintaining
temperature control has never been so
accurate.

Reduce Compressor Cycling

Modulating capacity control offers better
compressor reliability. Compressor
cycling, typical of reciprocating
compressors, will decrease compressor
component life. Parts like motors and
valves do not stand up well to excessive
compressor cycling.

Cutaway view of Trane’s electronic expansion valve.

RLC-PRC016-EN8

Features and
Benefits

Trouble-Free Installation,
Start-Up and Operation

Adaptive Control™ Microprocessor

The RTAA 70-125 chiller offers advanced
microprocessor control and features the
Adaptive Control microprocessor. So
what is the Adaptive Control
microprocessor? Adaptive Control
means the Unit Control Module (UCM)
directly senses the control variables that
govern operation of the chiller: motor
current draw, evaporator temperature,
condenser temperature, etc.

When any of the variables approaches a
limit condition where the unit may be
damaged or shut down on a safety, the
UCM takes corrective action to avoid

shutdown and keep the chiller operating.
It does this through combined actions of
compressor slide valve modulation,
electronic expansion valve modulation
and fan staging. Additionally, the UCM
optimizes total unit power consumption
during normal operating conditions. No
other chiller control system in the
marketplace duplicates this
performance.

The End Of Most Nuisance Trip-Outs
And Unnecessary Service Calls?

Unnecessary service calls and unhappy
tenants are reduced. Only when the
UCM has exhausted the corrective
actions it can take and the unit is still
violating an operating limit will the unit
shut down. CONTROLS ON OTHER

CHILLERS TYPICALLY SHUT DOWN THE
CHILLER, QUITE PROBABLY JUST
WHEN IT IS NEEDED THE MOST.

For example:
A typical five-year-old chiller with dirty
coils might trip-out on high pressure
cutout on a 100°F day in August. A hot
day is just when comfort cooling is
needed the most. In contrast, the air­cooled Series R™ chiller with an Adaptive
Control microprocessor will stage fans
on, modulate electronic expansion valve,
and modulate slide valve as it
approaches a high pressure cutout.
Thereby KEEPING THE CHILLER ON­LINE JUST WHEN YOU NEED IT THE
MOST.

RLC-PRC016-EN

9

Features and
Benefits

Close Spacing Of Chiller

The air-cooled Series R
tightest recommended side clearance in
the industry, four feet, but that is not all.
In situations where equipment must be
installed with less clearance than
recommended, such as frequently
occurs in retrofit and rooftop
applications, restricted air flow is
common. Conventional chillers may not
work at all. However, the air-cooled
Series R
microprocessor will simply make as
much chilled water as it can given the
actual installed conditions, stay on line
during any unforeseen abnormal
conditions, and optimize its
performance. Consult your Trane sales
engineer for more details.

Lower Service Expense

Nuisance service calls are avoided.
When there is a real problem that must
be corrected, the UCM’s extensive
diagnostics help assure that the problem
is quickly identified. Down time and
service expense are minimized. And with
the ability to communicate with the
Trane Integrated Comfort™ system or a
remote display panel, service problems
can be identified and diagnosed remote
to the installation.

™

chiller with Adaptive Control

™

chiller has the

™

Factory Testing Means Trouble-Free
Start-Up

All air-cooled Series R
a complete functional test at the factory.
This computer-based test program
completely checks the sensors, wiring,
electrical components, microprocessor
function, communication capability,
expansion valve performance and fans.
In addition, each compressor is run
tested to verify capacity and power
consumption. The end result of this test
program is that the chiller arrives at the
jobsite fully tested and ready to go to
work.

™

chillers are given

Factory Installed And Tested Controls/
Options Speed Installation

All Series R™ chiller options, including
control power transformer, starter
disconnect, low ambient control,
ambient temperature sensor, low
ambient lockout, communication
interface and ice making controls are
factory installed and tested. Some
manufacturers send options in pieces to
be field installed. With Trane, the
customer saves on installation expense
and has assurance that ALL chiller
controls/options have been tested and
will function as expected.

RLC-PRC016-EN10

Features and
Benefits

Superior Control

Unit Control Module

Trane’s Adaptive Control
microprocessor control system enhances
the air-cooled Series R™ chiller by
providing the very latest chiller control
technology.

State-of-the-Art Equipment

The 70 to 125 ton air-cooled chillers offer
the exclusive Trane Adaptive Control
logic with the Clear Language Display
(UCM). The Clear Language Display has
various functions that allow the operator
to read unit information and adjust
setpoints. The Clear Language Display
panel has 16 keys, the readout screen is a
two-line, 40 character liquid crystal with a
backlight. The backlight allows the
operator to read the display in low-light
conditions.

™

Unit Control Module Features

Equal Compressor Sequencing

Trane maximizes both compressor and
motor life by equalizing both the number
of starts and the operating hours. The
UCM will start the compressor with the
least number of starts and turn off the
compressor with the most operating
hours. Conventional “auto” lead-lag
control will equalize starts, but running
hours will typically be unequal.
Equalizing both starts and running hours
will provide equal compressor wear.

Internal “Built-In” Chiller Flow
Protection

The UCM automatically detects a no
waterflow condition. An external flow
switch is not required, which lowers
costs versus typical chillers. Built-in flow
protection also eliminates nuisance flow
switch problems.

RLC-PRC016-EN

Remote Clear Language Display Panel
for 70 to 125-ton air-cooled chillers.

11

Features and
Benefits

Easy Chiller System Logging

The UCM displays data required to log
the chiller system. The following
information is available either as
standard or as an option with the Air­Cooled Series R

• Entering and leaving chilled water
temperatures

• Ambient air temperature

• Evaporator and condenser refrigerant

temperatures and pressures

• Compressor suction temperature

• Percent RLA for each compressor

• Percent line voltage

• Compressor starts and running hours

• Active setpoints:

chilled water setpoint
current limit setpoint
ice termination setpoint
low ambient lockout setpoint

• Over 90 diagnostic and operating
conditions

• Part failure diagnostics:
water temperature sensors
refrigerant temperature sensors
compressor contactors

Remote Display Panel

Trane air-cooled Series R
chillers are available with a twisted pair
connection to an optional remote display
panel. Chiller operation can be controlled
similarly to the control interface on the
chiller itself. Through a twisted pair of
wires the unit can be turned on or off,
change the chilled water setpoint, and
display over 90 operating and diagnostic
conditions. The remote display panel can
be mounted indoors so access to chiller
information is just steps away,
eliminating any need to go outdoors or
on the roof.

The clear language display for chiller
sizes of 70-125 tons has the ability to
control multiple units. In a multiple unit
configuration, the Remote Clear
Language Display Panel has the
capability to communicate with up to
four units. Each unit requires a separate
communication link with the Remote
Display Panel.

™

Chiller microprocessor:

™

70-125 ton

Easy Interface To The Building
Management System

Controlling the air-cooled Series R
chiller with building management
systems is state-of-the-art yet simple.

Chiller inputs include:

• Chiller enable/disable

• Circuit enable/disable

• Chilled water setpoint

• Current limit setpoint

• Ice making enable

Chiller outputs include:

• Compressor running indication

• Alarm indication (CKt 1/CKt2)

• Maximum capacity

™

Trane Chiller Plant Manager/ICS

The Tracer
Building Management System
provides building automation and
energy management functions
through stand- alone control. The
Chiller Plant Manager is capable of
monitoring and controlling your entire
chiller plant system.

Application software available:

• Time-of-day scheduling

• Duty cycle

• Demand limiting

• Chiller sequencing

• Process control language

• Boolean processing

• Zone control

• Reports and logs

• Custom messages

• Run time and maintenance

• Trend log

• Totalizing

• PID control loops

And of course, Trane’s Chiller Plant
Manager Panel can be used on a
stand- alone basis or tied into a
complete building automation
system.

™

Chiller Plant Manager

RLC-PRC016-EN12

Model Number
Description

Model Nomenclature Digit Number

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

70-125 Tons

Digits 1,2 — Unit Model

RT = Rotary Chiller

Digit 3 — Unit Type

A = Air Cooled

Digit 4 — Development Sequence

A = First Sequence

Digit 5, 6 & 7 — Nominal Capacity

070 = 70 tons
080 = 80 tons
090 = 90 tons
100 = 100 tons
110 = 110 tons
125 = 125 tons

Digit 8 — Unit Voltage

A = 200/60/3
C = 230/60/3
D = 380/60/3
4 = 460/60/3
5 = 575/60/3
S = Special

Digit 9 — Compressor Starter Type

Y = Y-Delta Closed Transition
X = X-Line (Across the Line)
S = Special

Digit 10, 11 — Design Sequence

** = Factory Input

Digit 12 — Evaporator Leaving Temperature

1 = Standard 40 to 65°F
2 = Low 0 to 39°F
3 = Ice-Making 20 to 65°F
S = Special

Digit 13 — Condenser Coil Fin Material

A = Aluminum
S = Special
2 = Copper Fins
4 = CompleteCoat

Digit 14 — Agency Listing

0 = No Agency Listing
3 = C/UL Listing

Digit 15 — Control Interface

C = Deluxe without Communication
D = Deluxe with Communication

Digit 16 — Chilled Water Reset

0 = No Chilled Water Reset
1 = Based on Return Water Temperature
2 = Based on Outside Air Temperature

Digit 17 — Miscellaneous Factory Installed

Options

A = Architectural Louvered Panels
B = Control Power Transformer
C = Convenience Outlet
D = Low Ambient Lockout Sensor
F = Mech. Disconnect Switch
G = Low Ambient Operation
K = Coil Protection
M = Access Guard
P = Circuit Breaker (Single Point Power)
Z = Circuit Breaker (Dual Point Power)

Field Installed Options

Q = Spring Isolators
N = Neoprene Isolators
R = Remote Display Panel
3 = 5 Year Compressor Warranty
8 = Architectural Louvered Panels
9 = Coil Protection
0 = Access Guard
J = Remote Evaporator
H = Sound Attenuator

RLC-PRC016-EN

13

General Data

Table G-1 — General Data RTAA — 70-125 Ton

Size 70 80 90 100 110 125
Compressor
Quantity 2 2 2 2 2 2
Nominal Size (1) (Tons) 35/35 40/40 50/40 50/50 60/50 60/60
Evaporator
Water Storage (Gallons) 39.8 37.3 34.4 32.1 53.4 45.8

Min. Flow (GPM) 84 96 108 120 132 150

Max. Flow (GPM) 252 288 324 360 396 450

Condenser
Qty of Coils 4 4 4 4 4 4
Coil Length (In) 156/156 156/156 168/156 168/168 204/168 204/204
Coil Height (In) 42 42 42 42 42 42
Fins/Ft. 192 192 192 192 192 192
Number of Rows 2 2 2 2 2 2
Condenser Fans
Quantity (1) 4/4 4/4 5/4 5/5 5/5 5/5
Diameter (In) 30 30 30 30 30 30
Total Airflow (CFM) 71750 71750 77640 83530 87505 91480
Nominal RPM 850 850 850 850 850 850
Tip Speed (Ft/Min) 6675 6675 6675 6675 6675 6675
Motor HP (Ea) 1.0 1.0 1.0 1.0 1.0 1.0
Min Starting/Oper Ambient (2)
Std Unit (Deg F) 25 25 25 25 25 25
Low Ambient (Deg F) -10 -10 -10 -10 -10 -10
General Unit
Refrigerant HCFC-22 HCFC-22 HCFC-22 HCFC-22 HCFC-22 HCFC-22
No. of Independent
Refrigerant Circuits 2 2 2 2 2 2
% Min. Load (3) 15 15 15 15 15 15
Refrigerant Charge (1) (Lb) 58/58 61/61 73/61 73/73 98/73 98/98

Oil Charge (1) (Gallons) 2.5/2.5 2.5/2.5 3/2.5 3/3 3/3 3/3

1. Data containing information on two circuits shown as follows: ckt 1/ckt2.

2. Minimum start-up/operating ambient based on a 5 mph wind across the condenser.

3. Percent minimum load is for total machine at 50°F ambient and 44°F LWT, not each individual circuit.

(Liters) 150.6 143.1 130.2 121.5 202.11 173.4

(L/Sec) 5.3 6.1 6.8 7.6 8.3 9.5

(L/Sec) 15.9 18.2 20.4 22.7 25.0 28.4

(Kg) 26/26 28/28 34/28 34/34 44/34 44/44

(Liters) 10.6/10.6 10.6/10.6 12.7/10.6 12.7/12.7 12.7/12.7 12.7/12.7

RLC-PRC016-EN14

Selection
Procedure

The chiller capacity tables, P-1 through
P-12, cover the most frequently
encountered leaving water
temperatures. The tables reflect a 10°F
(6°C) temperature drop through the
evaporator. For temperature drops other
than 10°F (6°C), refer to Table F-1, and
apply the appropriate Performance Data
Adjustment Factors. For chilled brine
selections, refer to Figures F-2 and 3 for
Ethylene and Propylene Glycol
Adjustment Factors.

To select a Trane air-cooled Series R
chiller, the following information is
required:

1. Design load in tons of refrigeration

2. Design chilled water temperature drop

3. Design leaving chilled water
temperature

4. Design ambient temperature

Evaporator flow rates can be determined
by using the following formulas:

GPM =

OR L/S =

NOTE: Flow rates must fall within the
limits specified in Table G-1 (for GPM or
for l/s).

Tons x 24

Temperature Drop (Degrees F)

kW (Capacity) x .239
Temperature Drop (Degrees C)

™

Selection Example

Given:

Required System Load = 115 Tons
Leaving Chilled Water Temperature
(LCWT) = 44°F Chilled Water
Temperature Drop = 10°F Design
Ambient Temperature = 95°F
Evaporator Fouling Factor = 0.0001

1. To calculate the required chilled water
flow rate we use the formula given
below:

GPM =

2. From Table P-6 (RTAA Performance
Data), an RTAA 125 at the given
conditions will produce 120.1 tons
with a compressor power input of

136.3 kW and a unit EER of 9.8.

3. To determine the evaporator pressure
drop we use the flow rate (GPM) and
the evaporator water pressure drop
curves, Figure F-1. Entering the curve
at 276 GPM, the pressure drop for a
nominal 125 ton evaporator is 18 feet.

4. For selection of chilled brine units or
applications where the altitude is
significantly greater than sea level or
the temperature drop is different than
10°F, the performance adjustment
factors from Tables F-1, F-2, and/or F-3
should be applied at this point.

115 Tons x 24 = 276 GPM

10°F

For example:

Corrected Capacity = Capacity
(unadjusted) x Glycol Flow Rate
Adjustment Factor

5. The final unit selection is:

• QTY (1) RTAA 125

• Cooling Capacity = 120.1 tons

• Entering/Leaving Chilled Water
Temperatures = 54/44°F

• Chilled Water Flow Rate = 276 GPM

• Evaporator Water Pressure Drop = 18

feet

• Compressor Power Input = 136.3 kW

• Unit EER = 9.8

Minimum Leaving Chilled Water
Temperature Setpoint

The minimum leaving chilled water
temperature setpoint for water is 40°F.
For those applications requiring lower
setpoints, a glycol solution must be used.
Contact the local Trane sales engineer for
additional information.

RLC-PRC016-EN

15

Application
Considerations

Application Considerations

Certain application constraints should be
considered when sizing, selecting and
installing Trane air-cooled Series R

™

chillers. Unit and system reliability is
often dependent upon properly and
completely complying with these
considerations. Where the application
varies from the guidelines presented, it
should be reviewed with your local
Trane sales engineer.

Unit Sizing

Unit capacities are listed in the
performance data section. Intentionally
oversizing a unit to assure adequate
capacity is not recommended. Erratic
system operation and excessive
compressor cycling are often a direct
result of an oversized chiller. In addition,
an oversized unit is usually more
expensive to purchase, install, and
operate. If oversizing is desired, consider
using two units.

Unit Placement

1. Setting The Unit

A base or foundation is not required if
the selected unit location is level and the
base is strong enough to support the
unit’s operating weight as listed in Tables
W-1 and W-2.

2. Isolation and Sound Emission

The most effective form of isolation is to
locate the unit away from any sound­sensitive area. Structurally transmitted
sound can be reduced by
ELASTOMERIC vibration eliminators.
Spring isolators have proven to be of
little benefit on air-cooled Series R

™

chiller installations and are not
recommended. An acoustical engineer

should always be consulted in critical
sound applications.

For maximum isolation effect, water
lines and electrical conduit should also
be isolated. Wall sleeves and rubber
isolated piping hangers can be used to
reduce the sound transmitted through
water piping. To reduce the sound
transmitted through electrical conduit,
use flexible electrical conduit.

State and local codes on sound
emissions should always be considered.
Since the environment in which a sound
source is located affects sound pressure,
unit placement must be carefully
evaluated. Sound power levels for Trane
air-cooled Series R

™

chillers are available

on request.

3. Servicing

Adequate clearance for evaporator and
compressor servicing should be
provided. Recommended minimum
space envelopes for servicing are
located in the dimensional data section
and can serve as a guideline for
providing adequate clearance. The
minimum space envelopes also allow
for control panel swing and routine
maintenance requirements. Local code
requirements may take precedence.

4. Unit Location

a. General

Unobstructed flow of condenser air is
essential to maintain chiller capacity and
operating efficiency. When determining
unit placement, careful consideration
must be given to assuring a sufficient
flow of air across the condenser heat
transfer surface. Two detrimental
conditions are possible and must be
avoided if optimum performance is to be
achieved: warm air recirculation and coil
starvation.

Warm air recirculation occurs when
discharge air from the condenser fans is
recycled back to the condenser coil inlet.

Coil starvation occurs when free airflow
to (or from) the condenser is restricted.

Both warm air recirculation and coil
starvation cause reductions in unit
efficiency and capacity because of the
higher head pressures associated with
them. The air-cooled Series R

™

chiller
offers an advantage over competitive
equipment in these situations.
Performance is minimally affected in
many restricted air flow situations due to
its unique condensing coil geometry.
Also, through its advanced Adaptive

™

Control

microprocessor logic, the
chiller will attempt to stay on-line where
competitive chillers would usually shut
down.

Trane’s unique Adaptive Control
microprocessor has the ability to
understand the operating environment
of the chiller and adapt to it by first
optimizing its performance and second,
staying on line through abnormal
conditions. For example, high ambient
temperatures combined with a restricted
air flow situation will generally not cause
the air-cooled Series R

™

chiller to shut
down. Competitive chillers would
typically shut down on a high pressure
nuisance cut-out in these conditions.

Debris, trash, supplies, etc. should not be
allowed to accumulate in the vicinity of
the air-cooled Series R

™

chiller. Supply
air movement may draw debris into the
condenser coil, blocking spaces between
coil fins and causing coil starvation.

Special consideration should be given to
low ambient units. Condenser coils and
fan discharge must be kept free of
obstructions to permit adequate airflow
for satisfactory unit operation.

RLC-PRC016-EN16