Trane RAUS 160-400 Owner's manual

Co
Installation
Operation
Maintenance
RAUS/RAUX condensing units
Air cooled chiller
s and heat pumps condensing units with scroll
compressors
RAUS 160
– 400 Cooling capacity 56.3-140 kW
RAUX 150
– 350 Cooling capacity 52.4-122.1 kW
Heating capacity 55.8-130.9 kW
July 2021CG-SVX053A-GB
Original instructions

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INDEX
1OVERVIEW ....................................................................................................................................................................3
2SAFETY REGULATIONS...............................................................................................................................................3
3OPERATING LIMITS......................................................................................................................................................6
4INSTALLATION..............................................................................................................................................................9
5ACOUSTIC PROTECTION ......................................................................................................................................... 11
6ELECTRICAL POWER SUPPLY ................................................................................................................................ 11
7HOW TO SIZE REFRIGERANT LINES ...................................................................................................................... 12
8LIQUID RECEIVER ..................................................................................................................................................... 21
9REMOTE TERMINALS CONTROL AND EXPANSION VALVE ................................................................................. 24
10 ELECTRICAL PANEL............................................................................................................................................ 25
11 OPERATOR RESPONSABILITIES ....................................................................................................................... 26
12 START-UP PRELIMINARY PROCEDURES......................................................................................................... 26
13 CHECK LIST – MANDATORY OPERATION CONTROL BEFORE START-UP .................................................. 27
14 MAINTENANCE..................................................................................................................................................... 31
15 RECOMMENDED SPARE PARTS ....................................................................................................................... 34
16 TROUBLESHOOTING........................................................................................................................................... 35
17 IMPROPER USES................................................................................................................................................. 38

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1OVERVIEW
1.1 FOREWORD
These instructions are given as a guide to good practice in the installation, start-up, operation, and maintenance by the
user of RAUS / RAUX units. They do not contain full service procedures necessary for the continued
successful operation of this equipment. The services of a qualified technician should be employed through the medium of
a maintenance contract with a reputable service company. Read this manual thoroughly before unit start-up.
1.2 WARRANTY
A. The warranty for Trane machines is 12 months from the date the machine is operated for the first time but no more than 18
months from the date of the invoice. The warranty is reduced to 6 months from the start up date for units running continuously,
that is more than 12 hours a day. The date the machine is operated for the first time means the date reported in the “1st start up
form” contained into the “machine log book”. This form should be filled in and sent, within 8 days from the start up, to Trane.
B. The warranty is valid if all the installation regulations have been adhered to (both those which may have come from Trane
and those coming from current practice), if the “1st start up form” has been filled in and sent to the Trane after sales
department.
C. The warranty is subject to any faults or defects being reported within eight days from their discovery. The warranty will only
be applied if and when the purchaser suspends use of the equipment as soon as a defect has been found.
Replacement items are to be considered always ex TRANE factory. Labour costs to replace failed items either under warranty
or not, will be not of TRANE care.
D. The warranty is valid if the first running of the machine is carried out by a Trane authorised assistance centre.
E. The warranty is subject to regular maintenance of the unit which is appropriately indicated in the “machine log
book” located inside the electrical panel.
F. The warranty is automatically over in case of payments not fulfilled, non-performance of the contract and even if the units
show tampering without TRANE writing approvals.
G. Non observance of the above mentioned rules and of all the indications written on this manual, will cause the immediate
loss of warranty, getting free TRANE from any responsibility for the unit and any damages to persons or things.
1.3 RECEIVING THE UNIT
On receiving the unit, it is up to the customer to check that there is no obvious damage or pieces missing. If this is so, an
immediate complaint must be made to the carrier for damage or for not-delivery and the Receiving Card to be found inside the
unit electrical panel must be filled in. Photographic evidence must be provided for macroscopic damage. The card must be sent
to Trane within 8 days of receiving the goods: if it is not sent back or delayed, the complaint will not be accepted.
1.4 FACTORY INSPECTION
Trane units are inspected into the factory, in appropriate areas, in accordance with internal procedures. Each performance test
carried out on the unit is possible only if the same conditions are reproduced and maintained (charge consistency, constant
temperature and evaporation - condensation and recovery capacity, quality and tolerance of the measuring instruments etc.) in
the test rooms.
The inspection conditions are those indicated by the customer in the ordering phase: if not otherwise specified, reference
should be made to the nominal performance indicated in the technical bulletin in force at the date of the Confirmation of the
Order.
2SAFETY REGULATIONS
All Trane units are designed, built and inspected in compliance with Pressure Equipment Directive (PED97/23/EC or
2014/68/EU and Machinery Directive 2006/42/EC.
2.1 ACCESS TO DANGEROUS AREA
The access to the unit dangerous areas is usually obstructed through protection panels, which are removable, by using a tool.
Axial fans are protected with accident prevention grilles.
For all the units which allow access to the cooling piping without security gratings (optional) or closing panelling, the following
precautions must be taken:
-mark the areas with contact risks.
-apply warning signs.
The danger zone must be of a suitable size to avoid any contact, even accidental contact.
Trane declines any responsibility for damage to things and unauthorized personnel in case of absence of clear and static
limiting systems of the risk areas and of the relevant warning and danger signs.

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2.2 GENERAL PRECAUTIONS
The operator must only intervene on the unit commands; he or she must not open any panels except for the one which gives
access to the command module.
The installer must only intervene on the connections between the plant and the machine; he or she must not open any machine
panels nor carry out any commands.
The following precautions should be made when approaching or working on the unit:
• Do not wear jewelry, baggy clothes or any other accessory which can get caught up.
• Use appropriate protection (gloves, glasses etc.) when using an open flame (welding) or compressed air.
• If the unit is located in a closed environment, wear hearing protection.
• Before disconnecting, removing tubes, filters, joints or other line parts intercept the connection tubes, empty them until the
pressure reaches that of the atmosphere.
• Do not use your hands to check for possible pressure losses.
• Always use tools which are in good condition; make sure the instructions have been fully understood before usingthem.
• Make sure that any tools, electrical cables or other loose objects have been removed before closing the unit and starting it
up again.
2.3 PRECAUTIONS AGAINST RISKS DUE TO THE REFRIGERANT
Refer to refrigerant safety data sheet.
2.4 PRECAUTIONS AGAINST RESIDUAL RISKS
Prevention from risks due to the command system
• make sure the instructions for use have been understood before carrying out any work on the controlpanel.
• always keep the instruction manual close at hand when working on the control panel.
• start up the unit only after having certified that it is correctly connected to the plant.
• inform the technician promptly of any alarms which appear on the unit.
• do not reset the alarms to manual restart without having first identified the cause and removed it.
2.5 PREVENTION AGAINST RESIDUAL MECHANICAL RISKS
• install the unit in accordance with the provisions of the following manual.
• carry out all the maintenance operations provided for by this manual regularly.
• wear a protective helmet before entering inside the unit.
• before opening a machine panel make sure that it is firmly connected by means of a hinge.
• do not touch the air condensation batteries without having first put on protective gloves.
• do not remove the protections to the moving parts while the unit is running.
• before restarting the unit make sure that the moving part protections are in the correct position.
2.6 PREVENTION AGAINST RESIDUAL ELECTRICAL RISKS
• connect the unit to the mains in accordance with the provisions of this manual.
• carry out all maintenance operations regularly.
• before opening the control panel or access any electrical component installed on the unit disconnect the unit from the mains
by means of the main switch.
• check that the unit has been earthen correctly before starting it up.
• control all the electrical connections and the connection cables paying particular attention to the state of isolation; replace
the cables which are clearly worn or damaged.
• carry out periodic checks of the wiring inside the panel.
• do not use cables with an inappropriate section or flying connections not even for a limited period or in anemergency.
2.7 PREVENTION AGAINST RESIDUAL RISKS OF A DIFFERENT NATURE
• the residual risks due to pressure are mainly coming from a failure of the safety devices. To prevent them it is necessary to
check and replace them when required.
• the RAUS units are equipped with a high pressure safety valve which may relieve high pressure and high
temperature refrigerant in close vicinity of the unit in case of an abnormal overpressure event. In order to prevent
harm to people who might find themselves close to the unit, the installer should convey the escaped refrigerant by
means of piping. The safety valve installed in the unit is equipped with a threaded connection that makes conveying
easier. No safety valve is installed on RAUX units.
If a piping aimed at conveying refrigerant from safety valves, as described above, has not been installed by the installer, in
order to protect from safety devices exhausting it is not allowed to remove the protections while the unit is in operation and to
approach the unit without wearing the right protections. In case of accidental contact with refrigerant due to the safety valves
exhaust it is necessary to follow the above indicated.
• carry out the plant connections to the unit by following the indications reported on the following manual and on the panels of

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the unit itself.
• if a part is disassembled, make sure that it is correctly reassembled before restarting the unit.
• do not touch the discharge line of the compressor, the compressor itself or any other tube or component which is inside the
machine without putting on protective gloves.
• keep a fire extinguisher which is able to put out fires on electrical equipment near the machine.
• in the event of fire either if it originates on the unit or near it make sure the power supply to the unit is promptly cut and that
any person who might be near the unit at that moment is moved to a secure location
• on units installed inside, connect the refrigerant circuit shut off valve to a network of tubes which are able to lead the
possible spillage of refrigerating fluid outside.
• eliminate any fluid loss inside or outside the unit.
• collect the discharge liquid and clean up any possible oil leakage.
• periodically clean the compressor casing of the accumulated dirt deposits.
• do not keep inflammable liquids near the unit.
• do not dispose of the refrigerant fluid and the lubricating oil in the environment.
• welding should only be carried out on empty tubes; do not approach the tubes containing refrigerant fluid with flames or
other sources of heat.
• do not bend or strike tubes containing pressurized fluids.
2.8 PRECAUTIONS TO BE OBSERVED DURING MAINTENANCE OPERATIONS
Only authorised technicians may carry out maintenance operations. Before carrying out any maintenance the following must be
performed:
• isolate the unit from the mains electricity by using the external knife switch.
• place a notice on the external knife switch which says “do not use - maintenance in progress”.
• make sure that any possible on-off commands are disabled.
• use appropriate safety equipment (helmet, isolating gloves, protective glasses, safety shoes etc.).
If measurements or controls must be carried out which require the machine to be running the following observations must be
followed:
• operate with the electrical panel open for as short a time as is possible.
• close the electrical panel as soon as the individual measurement or control has been carried out.
• for units which are located outside, do not carry out interventions in dangerous atmospheric conditions such as rain, snow,
fog etc.
The following precautions should also be taken at all times:
• never dispose of fluids contained in the refrigerant circuit into the environment.
• when replacing the electronic card always use appropriate equipment (extractor, anti-static bracelet, etc.).
• if a compressor, the condensation batteries or any other heavy part is to be replaced, make sure that the lifting equipment
matches the weight to be lifted.
• if the unit has an independent compressor compartment, do not open the ventilator compartment without having first
isolated the machine using the knife switch on the side of the panel and only after having placed a sign which says “do not use -
maintenance in progress”.
• if modifications must be carried out to the cooling, hydraulic or electrical circuit of the unit, as well as to its command logic,
contact Trane.
• if particularly complicated assembly or disassembly operations are to be carried out contact Trane.
• always use original spare parts bought directly from Trane or from official dealers of the companies reported in the list of
recommended spare parts.
• if the unit is to be moved after a year of being in the site or if it has to be dismantled contact Trane.
VERY IMPORTANT
No refrigerant high pressure safety valve is installed on RAUX (RAUS mounts a refrigerant safety valve instead).
The unit fail safe is assured by the cut-out of the electrical power supply to the coils of the compressors
contactors. The cut-out action is carried out by the electrical contact of the unit high pressure switch (regarding
its position in the refrigerant circuit of RAUX refer to the par.2 INSTALLATION DIAGRAM AND PLACING OF THE
LIQUID RECEIVER).
No Shrader valve is installed in the port the unit high pressure switch is plugged into.
This implies that following instruction must be observed:
2.9 MANUAL ALARM RESET
If there is an alarm the unit must not be manually reset before having located and eliminated the cause of the fault. Repeated
manual resets may cause the warranty to be void.
DO NOT PULL OUT THE HIGH PRESSURE SWITCHES HP IF THE UNIT IS NOT COMPLETELY VOID OF
REFRIGERANT. FAILURE TO FOLLOW THIS INSTRUCTION COULD RESULT IN DEATH OR SERIOUS
INJURY

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3OPERATING LIMITS
3.1 STORAGE
The units can be stored within the following environmental conditions:
Min ambient temperature : -10°C
Max ambient temperature : 53°C
Max relative humidity : 95% not condensable
CAUTION: The storage in a very high humidity space (condensation) can damage electronic components.
3.2 OPERATING LIMITS
RAUS / RAUX unit operation is permitted within the limits indicated in the diagram provided in 3.3.
CAUTION: The operation outside the limits specified may cause the activation of the protections and disrupt the operation of
the unit and, in extreme cases, damage the unit.
In case of doubt, consult the factory.
These operating limits apply to unit operating at full load.
3.3 OPERATING RANGE
OAT
= Outdoor Air Temperature [°C]
ET = Evaporating Temperature [°C]
RAUS 160-400 –COOLING MODE

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OAT
= Outdoor Air Temperature [°C]
ET = Evaporating Temperature [°C]
RAUX 150-350 –CHILLER MODE

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OAT = Outdoor Air Temperature [°C]
CT = Condensing Temperature [°C]
RAUX 150-350 –HEAT PUMP MODE

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4INSTALLATION
4.1 MOVING AND POSITIONING THE UNIT
The units have been designed to be lifted from above by means of eyebolts and holes in the base members.
Use retractor bars to keep the lifting wires or chains away from the unit.
Lifting procedures provided with the unit have to be respected.
CAUTION
Do not use forklift trucks to lift the unit from below. If equipment for lifting from above is not available, using rollers may move the
unit. The surface on which the unit is placed must be flat and strong enough to withstand the weight of the unit while running. In
order to reduce the transmission of vibrations to the supporting structures, fit shock absorbers in every fastening point. Rubber
shock absorbers are recommended for units installed on the ground, spring shock absorbers for units installed on roofs. Open
spaces around the unit must be provided for in order to allow for the passage of necessary airflow and in order to allow normal
maintenance to be carried out (as shown on general catalogues).
IMPORTANT: Make sure that during transport the RAUS / RAUX unit ALWAYS remains in the correct position!
In example horizontal positioning of the unit can lead to irreversible damage to the compressors.
Damage arising from incorrect transport will not be under warranty by the manufacturer.
Immediately report an incorrect receipt of goods.
An arrow positioned upward indicates the vertical position of the unit.
Correct lifting procedure
Figure 1

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4.2 MINIMUM SPACE REQUIREMENTS
Dimensional drawing shall be respected to avoid:
• Noise
• Incorrect heat exchange and ventilation
• Difficult maintenance or inaccessibility to components
It is fundamental to respect minimum distances on all RAUS / RAUX units, in order to ensure optimum ventilation for
the condenser coils. Limited installation space could reduce the normal air flow, thus significantly reducing
the unit performance and considerably increasing consumption of electrical energy.
CAUTION:in case two stand-alone units have to be installed side by side, the distance of respect must
be doubled.
4.3 PRECAUTIONS FOR DOMINANT WINDS
Avoid obstacles on suction and discharge sides of the units. Respect the safety distances as shown on the units
dimensional drawings.
In case of presence of dominant winds in the installation area it is strictly necessary to avoid (for units with horizontal flow
fans) that such winds blow in front of the unit (fans discharge side). In case of unit with vertical flow fans it is strictly
necessary to avoid installations where the dominant winds could cause rejected hot air to come back to the condensing
coils.
4.4 PRECAUTIONS AGAINST DIRECT SUNSHINE
Direct solar radiation can raise the temperature of condensation until it causes the unit shutdown or failure start-up of the
same by action of the high pressure switch.
4.5 PRECAUTIONS AGAINST THE PRESENCE OF FIREPLACES AND EXHAUST HOT AIR
Avoid installation of the machines downwind of chimneys, smokestacks and different effluent discharges.
minimum space requirements [mm]
Figure 2

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4.6 PRECAUTIONS AGAINST THE PRESENCE OF FOLIAGE AND FOREIGN BODIES
Avoid installing the unit in the immediate vicinity of plants that can prevent proper intake and discharge air.
4.7 CONTROL OF COMPRESSOR FASTENING
The compressors are fitted on shock absorbers. For fixing through spring anti-vibration mounts, it is necessary to remove
blockages put to fasten the compressors, as indicated on the label on compressors body.
5ACOUSTIC PROTECTION
When the sound level must be checked in particular, it is necessary to pay maximum WARNING in isolation
from the base of the unit properly applying the anti-vibration mounts (provided optionally). Also, install flexible
joints on water connections.
6ELECTRICAL POWER SUPPLY
The mains power supply characteristics have to match the unit’s absorption. The mains power supply tension must
correspond to the nominal value ± 10%, with a maximum difference between the phases of 2%.
All power supply wiring must be sized and selected accordingly by the project engineer in accordance with standard IEC
60364. All wiring must comply with local code.
6.1 POWER CONNECTIONS
Protect the unit electric box power supply circuit with protection devices (not included in the supplied
equipment). Connect the line terminals with a three-core cable of a section which is appropriate to the machine
absorption. The switch and the fuses like all the power connections must comply with the regulations in force.
6.2 IMBALANCE BETWEEN THE SUPPLY TENSION PHASES
Do not run the electrical motors when the voltage unbalance between the phases is more than
2%. Use the following formula to check:
% Imbalance = [(Vx – Vave) x 100/Vave]
Vave = (V1 + V2 + V3)/3
Vx = phase with greatest difference from Vave (without
regard to the sign)
IMPORTANT: If the mains voltage has an imbalance of above 2%, contact the company, which distributes the electrical
energy. If the unit functions with a unit voltage imbalance between the phases of above 2% the warranty is invalid.
6.3 UNIT VOLTAGE PHASING
It is important that proper rotation of the compressors be established before the unit is started. Proper motor
rotation requires confirmation of the electrical phase sequence of the power supply. The motor is internally
connected for clockwise rotation with the incoming power supply phases A-B-C.

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7HOW TO SIZE REFRIGERANT LINES
In the dimensioning of refrigerant lines of air conditioning systems equipped with two sections, the designer has to take into account
that, due to the pressure loss of the refrigerant circuits, cooling capacity decrease and compressors power input increase may
occur. It is also necessary to consider that the fluid changes its state when circulating within the plant.
Another common problem is related to the oil: this, in fact, is highly miscible to the refrigerant and consequently it is easily dragged
into the circuit; obviously, it is necessary to make sure that this lubricant is able to entirely come back to the compressor. Finally,
the following basic conditions, typical of each refrigerant circuit, must be respected: cleaning of the pipes and total absence of liquid
to the compressor's inlet.
In order to avoid all the above mentioned problems, the connection lines must be properly sized.
7.1 DIAMETER
The pipes diameter is one of the most critical feature in sizing the refrigerant lines. The refrigerant speed inside the pipes
and the pressure drop depend on the diameter.
Although it is advisable to limit as much as possible the pressure drop (to reduce the loss of cooling capacity) is important
to ensure a velocity in the pipe to allow the oil carryover.
Generally the dimensioning of the suction line is made in order to maintain a speed higher than 4 m/s to the minimum
load (minimum step of capacity) and lower than 20 m/s at full load.
The tables below show the standard diameters for machines RAUS and RAUX. These diameters shall be considered
approximate and must be verified for each installation.
RAUS STANDARD DIAMETERS
SIZE
Suction
diameter
[mm]
Liquid
diameter
[mm]
160
42
22
180
42
22
190
42
22
200
42
22
210
42
22
230
42
22
240
42
22
300
54
28
340
54
28
370
54
28
400
54
28
RAUS connection kit includes: solenoid valve, mechanical expansion valve, filter dryer, liquid sight and safety valve.
RAUX STANDARD DIAMETERS
SIZE
Suction diameter
[mm]
Liquid
diameter
[mm]
Balancing
diameter
[mm]
150
35
22
22
170
35
22
22
180
35
22
22
190
35
22
22
200
35
22
22
210
35
22
22
230
35
28
28
270
42
28
28
300
42
28
28
320
42
28
28
350
42
28
28

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RAUX connection kit includes: nr.2 check valves, nr.1 mechanical expansion valve, nr.2 safety valves on liquid line.
Additional R410A refrigerant charge for a linear meter of pipe
Diameter (mm)
Gas (Kg/m)
Liquid (Kg/m)
6
0.0014
0.0133
10
0.005
0.051
12
0.008
0.079
16
0.014
0.139
18
0.019
0.182
22
0.029
0.285
28
0.045
0.445
35
0.074
0.729
42
0.111
1.082
54
0.182
1.779
64
0.281
2.721
67
0.289
2.825
76
0.377
3.689
7.2 LENGTH
The length of the suction line produces pressure losses higher than those ones found in the circuit of a machine with a single
section. Obviously consequently there is a lower pressure in the intake to the compressor. This may cause, as already mentioned,
a decrease of the output power and increase of that absorbed, with consequent reduction of the COP. A similar phenomenon
occurs in the discharge line: loss of load forces the compressor to work at a pressure that is higher than the actual condensation,
with effects equal to those previously analyzed. In the following table the pressure drops effects on the cooling capacity are shown,
expressed in terms of temperature drops [°C] on the suction and discharge lines:
Losses of load (°C)
Power output (%)
Power input (%)
0
100
100
1°C suction
95.7
103.5
1°C discharge
98.4
103.5
2°C suction
92.2
106.6
2°C discharge
96.8
106.6
High pressure drops, caused by considerable lengths, create another type of problem on the liquid line: known as "gas flashing".
It consists in the evaporation of part of the refrigerant, due to the heat developed by friction along the line and due to the pressure
drops. This may cause a malfunction of the thermostatic valve. A proper sizing of the refrigerant lines will avoid these problems. A
simple and rather accurate method has been suggested by ASHRAE (American Society of Heating, Refrigerating and Air-
Conditioning Engineers)and will be explained below.

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7.3 CALCULATION OF THE EQUIVALENT PRESSURE DROP
For a correct and quick dimensioning of refrigerant lines please refer to the following table, developed for R410A refrigerant.
Table 1: Cooling capacity corresponding to different tubes diameter referred to different pressure drops or speed values.
This table refers to the pressure drop values or speed values (for the liquid line) indicated in the column heading.
If different pressure drops are needed, the cooling capacity shall be corrected with the following formula:
Where:
Pf: cooling capacity
P : cooling capacity shown in table 1
Le : equivalent length of the table 1
Leff : actual equivalent length
ΔT : required pressure drop
ΔTtab: pressure drop shown in table 1
The equivalent length can be calculated as follows:
A fictitious length for each curve or branch or concentrated drop shall be added to the real lengths, corresponding to the linear tube
length that would give the same pressure drop caused by the curve or by the branch.

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Those fictitious lengths are shown in the table 2 and shall be considered effective for fully open valves.
Table 2: Equivalent lengths (in meters) for concentrated drops.
The table1 is referred to a condensation temperature of 40°C.
In case of different condensation temperatures the following correcting values shall be applied to the cooling capacity.
Cond. Temp (°C)
20
30
40
50
K suction line
1.18
1.1
1
0.91
K discharge line
0.8
0.88
1
1.11
Table 2.a: Cooling capacity of the correction factors in function of the condensing temperature.
Using the table 1 and the suggested correction factors it is possible to choose the proper diameter in accordance to the requested
cooling capacity and the evaluated pressure drops.
Once the choice is taken a check shall be made by calculating the real pressure drop using the following formula.
with symbols having the same meaning as in formula [1]
In order to verify if the selected diameter could be correct the following maximum pressure drops shall be considered according to
ASHRAE:
Liquid line: ΔPmax = 0,5÷1 K
Suction line: ΔPmax = 1 K
Discharge line: ΔPmax = 1 K
Example:
How to choose the proper tube diameter.
Input data:
Equivalent length calculated: Leq=60 m
Saturated suction temperature: Tas=5°C
Condensing temperature: Tc=50°C
Cooling capacity at the evaporator: Pf=30 kW
Since the values of cooling capacity indicated in Table 1 are relative to pressure drop values equal to 0.02 K / m , first check the

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pressure drops that would occur on the line using the diameter corresponding to the cooling capacity of the unit. The equivalent
length is about 60 meters, then with a pressure drops of 0.02 K / m the total pressure drops are equal to: T = 60x0,02 = 1.2 K
These pressure drops are higher than the maximum specified by ASHRAE. To comply with the recommended value (K1) it is
necessary to reduce the pressure drops length down to 0.016 K / m, using the formula [1 ] .
Refer to Table 1 and to search in the discharge line column (with suction temperature equal to 5 ° C) a cooling capacity close to the
unit one.
P = 29.7 kW at line with Δext = 28 mm.
This capacity is relative to a condensing temperature of 40 ° C. To obtain the corresponding 50 ° C capacity, this value shall be
multiplied to a factor shown in the table 2a:
(discharge line, Tc = 50 ° C) factor = 1.11.
The cooling capacity delivered by the line with Δext = 28 mm (corresponding to pressure drops of 0.02 k/m) is therefore P = 29,7
x1, 11 = 32.97 kW.
In conclusion, the data we need to use the formula [1] are the following:
ΔT=0,016x60=0,96 K
ΔTtab=0,02 K
Le=1m
Leff=60m
P=32,97 kW
As a consequence:
The above value represents the cooling capacity for a line with Δext=28mm, at Tas=5°C e Tc=50°C and with a corresponding
pressure drop equal to 0,016 K/m.
Since this capacity is lower than the cooling capacity supplied by the unit (30 kW), the pipe diameter will be undersized.
The Δext=35 mm will then be chosen. In order to verify if the choice is correct, the total pressure drop must be calculated again by
using the formula [2]. Consequently, having chosen Δext=35 mm only the P value will change, as follows:
P=54,37x1,11=60,35 kW
And then:
As shown, the new total pressure drop is much smaller than the maximum value suggested by ASHRAE.
It should be noted that it’s important to verify that the compressor oil return on the suction line is ensured.
A small oil amount tends to escape towards the refrigerant circuit, and therefore it is fundamental that even this small oil amount
could flow through the pipes reaching the compressor through the suction line. In this section, the oil can flow by gravity if the pipe
is oriented downward otherwise it is carried by the refrigerant if the pipe is perfectly horizontal or even upward oriented.
To ensure a correct oil flowing the refrigerant speed shall not be lower than the minimum allowed value. This, however, shall also
be possible if the is working at partial load due to a reduced power demand from the plant.
In such cases, very common for unit of big capacity, it is necessary to size the plant according to the minimum compressor
capacity, and not in accordance to the full load capacity.
In Tables 3 and 4, the allowed capacities at partial load condition are shown, both for the suction and discharge lines.

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Table 3: Minimum capacity (kW) ensuring the oil flowing in vertical sections of the suction line (R410a refrigerant).
The cooling capacity shown in table 3 refer to 40°C of condensing temperature: in case of different temperature values of the liquid
line, the capacities must be adjusted according to the following factors:
Liquid temperature (°C)
30
40
50
Correction factor
1.08
0.91
0.82
Table 3.a: Correction factors for different liquid temperature.
Table 4: Minimum capacity (kW) ensuring the oil flowing in vertical sections of the discharge line (R410a).
In this case also, the cooling capacity shown in table 4 refers to a saturated evaporating temperature equal to -5°C: for different
temperature values the capacity must be adjusted according to the following factors:
Saturated suction temperature (°C)
-20
+5
Correction factor
0.96
1.02
Table 4.a: Correction factors for different suction temperature

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It might be guessed that in order to guarantee the proper speed ensuring the correct oil flow, if the compressor is working at partial
loads, the diameter shall be reduced, therefore a too much high speed is obtained when the compressor is working at full load.
This is cause of excessive pressure drops.
Thus, the refrigerant line sizing, results often in a problem of balance between two opposite needs. In some cases (especially
when the suction line is upward oriented), this balance cannot be easily reached, and therefore it is necessary to use a precaution
on the plant, known as a "dual inclination".
The dual inclination consist in installing two parallel lines, one of each (marked as “A” in fig. 1) is sized in order to allow the oil
return at the minimum capacity, the other one (marked as “B”) is sized to ensure that the sum of the two sections is at least equal to
that of a single line dimensioned in accordance to the maximum cooling capacity.
Between the two vertical sections a sump is realized. The sump is sized in order to guarantee that at minimum loads, it will be filled
with oil closing the entrance to the line "B".
The sump, however, must not contain excessive amounts of oil, but it must have a minimum volumetric capacity. When the cooling
capacity grows, the greater flow creates a higher pressure allowing to overcome the oil cap and therefore also the line “B” works.
There are two other important precautions to be taken into account in making suction lines an oil trap 6 meters shall be created or a
small downward line inclination shall be installed in case of horizontal sections, to ensure a better oil flow.
If the circuit is equipped with two evaporators in parallel, one independent from each other, and one of the two evaporators is not
working, oil accumulation must be avoided anyway.
If the two evaporators are installed at the same level a downward line on both evaporators outlet shall be created, before joining the
common section.

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If the two evaporators are installed at different levels there are two possible solutions shown in figure2.
On the discharge line, there is the same problem due to the oil flow on the suction line. The solution to the problem is the same.
In this case, the most important issue could be the oil drop towards the compressor.
This issue can be solved using check valves and making oil taps if the condenser is mounted at a higher level than the compressor.
On the liquid line, it is important to avoid that non liquid refrigerant reaches the thermostatic valve.
This purpose is achieved by giving to the fluid a high subcooling in the condenser, but a proper sized liquid receiver shall be
installed upstream from the line in the case of high lengths (over 20 meters).
If the liquid temperature is lower than the outdoor temperature (it may happen for water cooled units) the line shall be properly
insulated.

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7.4 PRECAUTIONS FOR REFRIGERANT LINE SIZING
• Suction line must always be insulated to avoid condensate formation.
• The liquid line must be insulated if the outdoor temperature is higher than the liquid temperature. (approximately 5°C less than the
condensing temperature)
• The discharge line must be insulated only to prevent from burning danger (the temperature can reach up to 100°C)
• Special couplings or U-shaped or L-shaped sections can be used to compensate the copper pipe expansions. The expansion of
the pipe can be estimated using the following table:
Temperature (°C)
-20
0
25
50
75
100
125
Expansion (mm/mt)
0
0.4
0.7
1.1
1.5
1.9
2.3
These special couplings or U-shaped or L-shaped sections used to compensate the pipe expansion can be sized according to the
following sketch:
Since this type of components may cause significant pressure drops, their use must be carefully evaluated.
Supports shall be installed to support the pipes weight and shall be spaced according to the following prescriptions:
Pipe diameter (mm)
14-18
22-28
35-54
63
Max distance between the supports (m)
2
2.5
3
3.5
Curves and joints cause pressure drops. Large-radius curves are strongly recommended; in case of barriers to overcome 45°
curves are recommended if compared to 90°.
T joint shall be made in accordance with the following prescriptions: