McQuay AC 40A, AC 50A, AC 58A, AC 75B, AC100B Applications Manual
...
AM - MAC
Contents
Introduction .............................................................................................................. 1 - 3
1. Chiller Mounting ................................................................................................... 4 - 8
2. Water Pipe Circuit............................................................................................... 9 - 27
3. Water Pipe and Fittings ................................................................................... 28 - 66
4. Pipe and Fitting Size ....................................................................................... 67 - 72
5. Water Pump ..................................................................................................... 73 - 86
6. Water Storage Tank and Expansion Tank ..................................................... 87 - 93
7. Insulation Material ......................................................................................... 94 - 106
8. Pipe Support ......................................................................................................... 107
9. Water Side Treatment .................................................................................. 108 - 114
10. Heating Operation ...................................................................................... 115 - 120
11. Electrical Wiring Control ............................................................................ 121 - 140
12. Flow Switch................................................................................................. 141 - 145
13. System Balancing....................................................................................... 146 - 148
14. Chiller Shut Down....................................................................................... 149 - 150
Appendix (Appendix 1-19) ...............................................................................37 Pages
Copyright©2003 by McQuay International. All rights reserved. This publication is strictly confidential and
is meant for DISTRIBUTORS of McQuay International only. No part of this publication may be reproduced
or distributed in any form or by any means, or stored in a data base or retrieval system, without the prior
written permission of McQuay International.
Introduction
The air-cooled mini chillers form part of a complete integrated water hydronic system with the
chiller water fan coil units. The range of capacity from 30,000 Btu/hr to 150,000 Btu/hr (8.79 –
43.96 KW) makes them suitable for various applications:
- Office Rooms
- Private Houses
- Business Rooms
- Club, Pubs, Coffee Houses
- Hotels
- Restaurants
- Process Cooling
The advantages of using these chillers are:
1. Due to its compact design, the mini-chillers require a smaller space for installation.
The design also allows for flexibility in design to meet various types of application
requirements.
2. The amount of refrigerant used is small compared with other split and multi-split direct
expansion systems, i.e. they are more environmental friendly.
3. There is no necessity to use cooling towers.
4. No refrigerant is used in the occupied space.
5. The usage of water as the cooling medium allows for excellent load variability with minimal
system complexity as against equivalent VRV systems.
6. Ability to have long piping distances.
A water hydronic system can be classified as a close
or open system.
Definition
: A close water system is one with no more than one point of interface with a
compressible gas or surface. [ASHRAE handbook: 1996 System & Equip.]
The basic design of the mini-chiller is for a close system. However, a modification for an open
system is possible.
The close hydronic system will consist of the following fundamental components:
a. Source
b. Load
c. Expansion Tank
d. Pump
e. Distribution System
Introduction Page 1
Schematic diagram of the basic close hydronic system:
Expansion
tank
Heat Pump Heat
Distribution system
SOURCE LOAD
In the mini chiller, the source will comprise of the refrigeration circuit, i.e. compressor, expansion
device, condenser and evaporator. A brazed plate heat exchanger (BPHE) is used as the
evaporator to produce the chilled water.
A built-in water tank is also provided in the mini chiller to act as a buffer storage. See next page.
For integration, both the expansion tank and pump are incorporated together into the mini chiller.
Hence, the schematic diagram of the system becomes as follows:
Introduction Page 2
If both chilled water and hot water are required in the system, a mini chiller with a reverse
cycle operation will be used. The unit will have an additional 4-way valve and accumulator for
this purpose.
It is by such integration of components of the hydronic system that the mini chiller becomes
compact. Installation of the chiller will thus only involve:
1. The chiller mounting
2. Indoor fan coil unit installation
3. Water piping installation between the chiller and fan coil unit
4. Electrical wiring connection
This manual is written with the purpose of providing guidelines as to the installation and operation
of the hydronic system; i.e. both the chiller and fan coil unit. Application design guidelines will also
be discussed. Selection criteria of piping, valve, pump and other equipment are also given.
Examples of such complete installations are as shown in the following pages. This manual will
give some technical information and details on how such installations are designed and done
at site.
In general, there are three series of mini chillers available:
a) A series (from 30,000 Btu/hr [8.79 kW] to 50,000 Btu/hr [14.65 kW])
- double stack design, with built-in buffer tank
b) B series (from 75,000 Btu/hr [21.98 kW] to 125,000 Btu/hr [36.64 kW])
- double stack design, with built-in buffer tank
c) C series (from 80,000 Btu/hr [23.45 kW] to 150,000 Btu/hr [43.96 kW])
- monoblock design, without buffer tank
This manual must be used in conjunction with the Technical Manual and Installation and
Operation Manual (IOM) of the mini chillers and chilled water fan coil units.
Introduction Page 3
Section 1: Chiller Mounting
Care must be taken to locate the air-cooled chiller at the proper place. Ensure sufficient
clearance around the unit to allow proper air flow and to facilitate access for maintenance.
Location of the units must also prevent short-circuiting of the discharge air. Do not block any air
passage in and out of the units.
Please refer to the corresponding Technical Manual for further information.
The chiller unit must be placed on a firm surface, e.g. concrete flooring, slab or plinth. Due
to space consideration, the chiller may be mounted onto a steel bracket which is secured to
a firm surface, e.g. brick wall, concrete wall or a steel structure.
concrete flooring
Series B Chiller
Plinth
Wall
Steel bracket
Plinth
Section 1 Page 4
Such brackets must have sufficient strength to carry the weight of the chiller unit. It is
recommended that angle bars (e.g. 38mm*38mm*3mm
t
) or hollow section bars (e.g. 25mm*
50m*2mm
t
) to be used for fabricating these brackets.
These brackets must also allow clearance for removal of service panels for maintenance
purposes.
In any case, it is vital that the chiller unit is secured firmly onto the concrete floor/slab or steel
bracket by using studs, wall plugs or bolts/nuts at the four (4) mounting holes located at the base
plate of the chiller. The weight of the chiller unit and the water pipe connections are not sufficient
to prevent unit movement should any sudden impact or strong vibrations occur in the unit. Failure
to do so may cause the water pipes to deform and break.
It is further recommended that rubber isolation pads (1/2" thick) to be placed beneath each
mounting hole to prevent excessive vibration and noise. If necessary, isolating springs can
also be mounted.
The following pages are examples of these isolation pads and springs.
Section 1 Page 5
Special installation:
The A and B series mini chiller units have been designed with the refrigerant circuit located in the
top compartment and the hydraulic kit in the bottom compartment:
A-series B-series
Hydraulic kit
Piping
connection
Refrigerant
Water
B-series
A
-series
In some special installations whereby the available space (especially the height) is not
sufficient to install the chiller, it is possible to to detach these two compartments and install
them side by side. This is especially useful when there are multiple units which are stacked
together with a steel bracket.
Bracket
Hydraulic kit
Water
pip
es
Refrigerant pipe
connection
Hydraulic kit
Water pipes
Section 1 Page 6
For the A-series type of mini chiller, the inter-connecting pipes between the two
compartments are the refrigerant pipes. For the B-series type, there is a water pipe in
between the two compartments.
Therefore, the detached installation of the A-series mini chillers is very similar to the
installation of a split type air-conditioning unit.
Note:
Gas line to be insulated with
tube insulation. Use the
correct size for each pipe, thickness
¼
”
Refrig. Pipe size
Liquid Gas
AC 040A
3/8” ¾”
AC 050A
3/8” ¾”
AC 058A
½” ¾”
Take care of the following items [for detached A-series installations]:
Maximum pipe length,m
AC 040C
20
AC 050C
20
AC 058C
20
a) Do not allow excessive refrigerant pipe
length between the two compartments.
Always choose the shortest path.
Long piping will cause high pressure
drops and reduces the capacity of the
system. Use the following
recommendations:
Maximum elevation, m
AC 040A
10
AC 050A
10
AC 058A
10
b) It is possible to have the hydraulic kit
higher or lower than the refrigerant
compartment. Do not allow excessive
elevation between these two
compartments. Use the following
recommendations:
If the elevation exceeds the above recommendations, care must be taken to ensure sufficient oil
return to the compressor. Use oil traps (one every 30ft height interval) or oil separators, if
necessary.
c) The longer pipe lengths will require more refrigerant charge for optimum
performance.
Recommendation: Additional 50g (R-22) for every 1 meter of connecting pipe length.
Similarly, additional refrigerant oil charge may be required.
Section 1 Page 7
d) Use as few bends as possible in the pipe run. Each bend will cause extra pressure drop and
reduces the capacity of the system. Do not use more than 10 bends. For both A and B series chillers, locating the hydraulic kit at a far distance will also mean having a longer
water pipe length. This will incur a higher pressure head to the water pump in the chiller
unit. If not careful, this will reduce the water flow rate through the system and may cause
system failure, e.g. water freezing, compressor tripping.
Furthermore, the longer pipe will increase the cost of installation.
Always look for the closest possible locations for these two compartments.
External drain pan
In some instances, it is necessary to install an external drain pan beneath the unit to collect
any condensate water from the chiller unit. This is especially so for the heat pump versions
,where water will condense on the heat exchanger coil during the heating mode. Further more,
a lot of water will flow out during the defrost cycle.
Such external drain pans are needed when the chiller units are installed inside a plant
room where it is not appropriate for the floor to be wet. (Note A)
It is recommended that the drain pan to be fabricated out of galvanised iron (GI) sheet
metal, at least 0.8 mm in thickness. Allow the drain pan depth of about 20mm.
This external drain pan should be laid out on the floor first before placing the entire chiller
unit on top of it. It is recommended that the chiller unit to be raised up by 20 - 30mm from
the drain pan so as to prevent rusting of the chiller base pan.
Note A: Caution! Please ensure adequate ventilation in the plant room else the
chiller unit may trip.
Section 1 Page 8
Section 2: Water Pipe Circuit
We have seen that the mini chiller has an integrated buffer storage tank, expansion tank and
water pump together as one unit. Henceforth, we will represent the unit as such:
MINI CHILLER UNIT
In this section, we will look at the various piping circuits which we can use to connect the chiller
unit with the load fan coil units.
There are many different piping circuit configurations which can be used, depending on:
a) the geometry of the building
b) the available space for installation (e.g. the dimensions of the plant room)
c) the economics of installation
d) loading capability requirements
The general rule of thumb in designing and determining the piping circuit network is:
KEEP IT SIMPLE!
The more extensive a pipe network is, the more complex it is and it becomes more difficult to
analyse and control.
In general, there are 4 types of this pipe configuration:
1. Series
2. Diverting
3. Parallel direct return
4. Parallel reverse return
Series Circuit:
Note: For C-series, the buffer tank is not
applicable but the fundamentals of water piping
circuitry is still the same
Water out
Water in
LOAD
FCU 1
LOAD
FCU 4
LOAD
FCU 3
LOAD
FCU 2
Section 2 Page 9
Advantages:
i. Lower piping cost
ii. High water temperature drops
Disadvantages:
i. Each fan coil loading cannot be controlled separately
Diverting Circuit:
LOAD
FCU 3
LOAD
FCU 1
LOAD
FCU 2
LOAD
FCU 4
Advantages:
i. Allows individual control to each fan coil unit
Disadvantages:
i. Only fan coil units with low pressure drops can be used
ii. Due to low water velocity in each fan coil, an air vent is required for
each fan coil
iii. Higher installation cost
iv. Water entering temperature for each fan coil is different, i.e. it gets
higher further away from the source
However, both the series and diverting circuits are seldom used in hydronic systems. The
more commonly used are the parallel circuits because they allow the same water
temperature to be available to all fan coil units.
It is recommended that the parallel circuits to be used in the installation of the mini chillers
with the fan coil units.
Section 2 Page 10
Parallel Direct Return
Vertical installation
Fan coil
unit
Horizontal installation
The basis for the design is "First In - First Out".
In this system, the length of supply and return piping for each fan coil is unequal. This will
affect the water flow rate through each individual load. Proper balancing is required to
provide adequate water flow rate for each fan coil.
Nevertheless, the cost of installation is lower compared with the reverse return configuration
due to the shorter pipe length needed. Therefore, this method is more economical for
installation of fan coils with different pressure drops and balancing valves are used.
This method is also suitable for open system applications whereby the return from the
fan coil loads are discharged into a external tank.
Section 2 Page 11
Parallel Reverse Return
Horizontal Installation
Fan coil
unit
V
ertical Installation
The basis for the design is "First In - Last Out".
In this installation, the supply and return water pipes or of nearly equal lengths. Thus, it seldom
requires balancing of water flow rate for individual fan coil unit. If required, this balancing will be
easier.
This method is recommended if all the fan coil units have the same or nearly the same
pressure drops.
Another advantage of this reverse return system is a reduction of the working pressure drop
across any balancing valves used for the fan coil units.
However, such a system is not recommended for high-rise buildings because of the vertical
weight of the extra piping required. In such instances, it may be more practical to use direct
return systems.
The extra piping also does not give any advantage in open system applications because the
same atmospheric conditions exist at all open points of the system.
Section 2 Page 12
Parallel Reverse Return Header, Direct Supply Rise
This is a variation of both the direct and reverse return systems, whereby it is not feasible to
have a full reverse return piping.
Instead, only the return header is in reverse, whereas the supply to the individual fan coils are in
direct configuration.
direct supply
reverse
return
This method will have the advantage of lower installation cost with some benefits of a better
water balanced system.
Balancing valves are required for each fan coil unit for proper flow balancing.
Section 2 Page 13
Close System vs. Open System
The mini chiller has been designed with an application for a close water piping system.
However, it is still possible to use the unit with an open system by means of an additional
buffer tank.
In such a system, the chiller will discharge the chilled water into the tank while a secondary
external pump will then pump the water to the fan coil units.
It is recommended that the tank to have a baffle plate in between to isolate the two return
water from the chiller and fan coil load. This will prevent the hotter return water temperature
from the load mixing with the cold chilled water from the chiller.
Such a method is suitable for:
- multiple chillers operation
- multiple secondary pumps supplying chilled water to several zones
The water volume in the tank can also be sized to act as a storage to provide cold water to the fan
coil units. By doing so, the chiller may be cycled-off for longer periods of time, hence saving energy
costs.
However, since this is an open system, there is a higher chance of air entering the water.
Care must also be taken to ensure there are no leakages along the pump suction line else
air will enter the system. The air will be drawn into the buffer tank and accumulate there. This
may affect the water flow rate and trip the chiller unit. Always ensure the automatic air vent
on the buffer tank is operating properly to release any trapped air.
Supply to load
Return from load
Tank
Chiller Secondary pump
Check if this air
vent is OK or not!!
Buffer tank
*** See Page 25 for more information
Section 2 Page 14
Primary - Secondary Pump System
There may be instances when the integrated pump in the mini chiller is not able to deliver the
required head pressure to the load in a close piping system.
To overcome this problem:
1. Change the water pump with a higher head pressure capability.
Please consult with the factory as to the requirements. Calculate the required
head pressure and select suitable replacement pump.
2. Install a booster pump.
It is recommended that this booster pump to be installed as a primary - secondary
system; as follows:
A
B
Primary pump in
chiller unit
Secondary booster pump
Bypass loop
Load
More than one secondary pumps can be installed together, e.g to serve several zones.
There are two drawbacks to this system:
a) Cost - additional two or more pumps are required
b) The bypass chilled water is sent back to the chiller unused
Keep the bypass loop as short and large as practical possible. Do not put any valve in
this loop. This is to minimise the pressure loss between the entry and exit points of the
loop.
However, this length must be sufficient to prevent recirculation turbulence.
Section 2 Page 15
The temperature of water entering the load will depend very much on the sizing of the
secondary pump.
1. If the capacity of primary pump = secondary pump, there will be no flow in the bypass
loop. Hence, the water temperature entering the load will be equal to the water
temperature leaving the chiller.
2. If the capacity of primary pump > secondary pump, there will be a nett flow down the
loop and returned to the chiller unused. Therefore, tee A becomes a diverging tee and
tee B becomes a mixing tee. The water temperature entering the load will also be equal
to the water temperature leaving the chiller. However, the water temperature entering
the chiller will be colder due to mixing of the unused chilled water at tee B.
3. If the capacity of primary pump < secondary pump, there will be a nett flow up the loop
from B to A. Thus, tee A becomes a mixing tee and tee B becomes a diverging tee.
Then, the water temperature entering the load will be in between the water temperature
leaving the chiller and the water temperature entering the chiller.
There may be installations using pumps in series to boost the head pressure.
But this is not recommended due to a high chance of wrong pump sizing which can
cause damage to the pumps themselves.
Primary pump
Secondary pump in series
Load
For this to work properly, both the primary and secondary pumps must be of the
same capacity. Else, the greater capacity pump will overflow the lesser pump and
cause:
a. Cavitation problems to the lesser pump.
b. Excessive pressure drops across the pump itself.
c. The extra head pressure build-up may cause damage to some of the
components in the chiller itself.
Section 2 Page 16
Multiple Chiller Installation
In most cases, one single chiller will not be sufficient to provide the cooling load of a system.
Several chillers must be combined together to give the required loading.
Generally, these chillers will be installed together in parallel. There are several ways to do
this:
1) Common Supply and Return Headers
Check valve
CHILLER 3
CHILLER 2
CHILLER 1
Chiller water return
Chilled water supply
Supply header
R
etu
rn h
eade
r
This method is most preferred and commonly used because of the lower cost and ease
of installation.
Each chiller is normally set at different return water temperature to facilitate load staging.
As the temperature becomes colder, the chillers will switch off one by one.
Generally, the header pipe size is larger than the supply and return pipes, e.g. one or two
size larger. This is to have a low pressure drop along the header. Check valves are usually
located along each chiller supply pipe to prevent back flush of water once the chiller is
switched off. Such back flow may damage the water pump.
However, this method has several drawbacks:
a) Proper balancing of the water flow rate through each chiller is crucial.
b) If any one chiller is off, the water flow to the load will be affected. So much so
that during low load conditions, when the return water temperature is cold, and
all the chillers have cycled off, no water will be pumped to the load. To
overcome this problem, it is necessary to wire the chiller controls for continuous
pump running as long as one fan coil unit is in operation. See Section 11.
Section 2 Page 17
c) Since all the water is pumped into one supply line, there is less flexibility in zoning
the water distribution. The pump head may not be sufficient to deliver water to
zones of high pressure losses, e.g. at the furthest end of the pipe system.
Because of the importance of water flow balancing among all the parallel chillers,
the design of the header is very important.
Place the common pipe near the center of the header pipe. This will help to balance
the water distribution between the left and right sides of the header.
If the common pipe is at one end of the header, water from the branches at the
other end of the header will find more difficulty to flow into the common pipe.
Balancing valves must be installed at each supply branch to ensure adequate
water flow rate through each chiller unit.
2) Primary-Secondary System
header
Water will experience a higher
Resistance to flow to common pipe
From the furthest branches.
Secondary pumps
To load
Return from load
Bypass loop
CHILLER 1
CHILLER 2
CHILLER 3
Section 2 Page 18
In this method, the load side of the system is isolated from the chiller side. Chillers of different
capacities can be installed together without much balancing problems and effect on the supply
flow rate to the loading. It just requires individual balancing of the flow rate through each chiller by
using the balancing valves. Check valves and balancing valves are recommended to be installed
for each chiller supply pipe.
The secondary pump alone will handle the flow and pressure requirements of the loads.
Because of this secondary pump, the sequencing of the chillers will not affect the
water supply to the load when any of the primary pumps switches off. Several secondary
pumps can also be installed to the bypass loop to serve several zones. This creates
flexibility of installation.
The only drawback to this method is cost. The piping network is more extensive and
additional water pumps are required.
It is important that the bypass loop is located correctly. The following two are questionable
variations to the above method:
By pass loop
By pass
[A]
[B]
Secondary pump
Secondary pump
To load
To load
Return from load
Return from load
Section 2 Page 19
For both method [A] and [B], the return water temperature for the multiple chillers will not be the
same due to mixing. This will cause inefficiencies and energy wastages to the chiller operation.
3) Common Tank System
This method is for an open system.
CHILLERS
to load
Tank
return from load
As seen from the diagram, each chiller and secondary pump forms its own individual pipe
circuit. There is no cross flow among each of them. This has been achieved with the
common tank which acts as a buffer storage tank.
Therefore, there is no need of check valves. Normal globe valves will suffice to ensure
proper water flow through each chiller.
Usually, the tank is at a higher elevated position, to allow gravity feed of water to the chillers
and pumps.
This method is most expansive to install due to the additional piping and tank required for
the system.
Please refer to Page 14 for cautions during installation and operation.
Section 2 Page 20
4) In some instances, variation to method (1) have been used whereby common
headers are NOT installed to the multiple chillers. Instead, the chillers are connected
together with one supply and return pipe only.
This method is still possible but there will be higher pressure drops along the common
pipe lines. It is recommended that a larger pipe size to be used along this common line
to reduce the friction losses.
Water flow rate tends to be faster at the tee nearest to the main supply lines due to
lower friction. Therefore, proper balancing to ensure sufficient distribution to each
chiller is vital.
A First In - Last Out arrangement between the supply and return lines may be
useful to reduce the problem of distribution.
5) Another variation to the primary-secondary system mentioned in (2) above, is to use
an auxillary tank to replace the by-pass loop. By using this tank, we can ensure a
minimal pressure drop between the entry tee and exit tee of the secondary circuit.
This is not a common
header pipe
To load
Return from load
To load
Return from load
A
uxiliary tank
Section 2 Page 21
Multiple Chiller, Single Fan Coil Load With Multiple Circuits
There are instances where several chillers are used to supply the chilled water to a large
single fan coil unit. Each chiller will serve one of the multiple circuits of the heat exchanger coil
in the fan coil unit.
There are two ways to install the pipe circuits for this system:
a) Individual Circuiting
b) Common Header
CIRCUIT 1
CIRCUIT 2
CIRCUIT 3
CHILLER 1
CHILLER 2
CHILLER 3
CIRCUIT 1
CIRCUIT 2
Section 2 Page 22
The first method has more extensive pipe works. But the water side flow control is
easier and there is less pressure drop. Globe valves may be needed to ensure
sufficient flow rate. Check valves are not required.
Due to the header pipes in the second method, check valves are needed for each
chiller. Globe valves or balancing valves are also needed for each chiller for water
balancing. All the pumps will operate in parallel and a higher water pressure drop is
expected. Furthermore, balancing valves are also required in each circuit of the fan
coil unit for proper balancing of the entire coil.
Nevertheless, if any one of the chiller is OFF, the second method will always allow an
even water distribution to the whole heat exchanger in the fan coil unit. In the first
method, hot air will by-pass through the portion of the coil which the chiller is OFF.
Section 2 Page 23
Make Up Water Supply
The make up water supply is used to refill water back into the hydronic system in the event of:
a) Leakage in the system
b) Maintenance service
The supply is usually from the main domestic pipe and it is usually connected to the water return
pipe of the pump; due to the lower pressure which will assist in "sucking" in the water. However,
should the pressure in the main supply pipe is lower than the pressure in the return pipe, water will
not enter the system. Rather, switch off the pump and allow the mains pressure to fill the system.
In view of this, it is necessary to install a check valve along the make up supply pipe to
prevent back flow out of the system.
Other equipment which can be installed (optional) along the make up supply pipe:
a) Pressure gauge
b) Safety relief valve - to prevent over filling [see Section 10]
c) Pressure regulating valve
d) Filter element [see Section 9]
e) Water meter
Domestic water supply
Pressure gauge
Check valve
CHILLER
Return
Section 2 Page 24
Loop Piping Installation
One of the main advantages of using mini chillers is the ability to have long water piping
installations. However, it is important to check that the water pump head pressure capability is
adequate to pump the water through the pipe network. The longer the pipe length is, the higher
is the pressure drop. If the pump head is insufficient, it may be necessary to change the water
pump itself. See Section 5.
With such installations, it is also important to check the condition of the automatic air vent valve.
A high pressure drop along such pipe network may result in the return water to have a negative
pressure (i.e. suction vacuum pressure in the buffer tank). Due to the mechanism of the air vent,
air will be drawn into the buffer tank itself! This in turn will cause the pump to be air-locked. A
symptom of such condition is that air will always be purged out of the tank when we manually
open the air vent.
The solution to this problem is to remove the automatic air vent and plug up the hole. Make
sure that all the air trapped are purged out of the system before plugging it. This can be done
by continuously filling up the system with water until no air bubbles comes out of the hole.
Section2 Page 25
Water Pipe Connections
All mini chiller units comes with ∅1-1/4” pipe connections.
1] A-Series
The pipe connections are on the right-hand side of the unit (when facing the fan blade).
2] B-Series
The pipe connections are on the same side as the control box compartment
Water inlet
Water outlet
Water inlet
Water outlet
Section 2 Page 26
3] C-Series
The pipes can be connected either from the left or right side of the unit (with
respect to the compartment doors).
Water inlet
Water outlet
Section 2 Page 27
Section 3: Water Pipe and Fittings
There are several types of pipe we can use for the water piping:
1. Black carbon steel pipe
2. Copper pipe
3. PVC pipe
Do not use galvanised iron (GI) steel pipe! This is because the zinc coating on the GI pipe will
have an electrolytic reaction with the copper components of the system, e.g. the brazed plate heat
exchanger and fan coil unit heat exchanger.
The zinc will be the sacrificial metal and deposit itself on the copper surfaces.
a) The pipe wall thickness will slowly eat away and cause leakages
b) The zinc deposit on the copper surfaces will retard heat transfer process. It may also
reduce the gap between plates in the BPHE and slows the water flow rate.
The mini chiller water piping connections is for a pipe size of 1-1/4". For a single run installation,
the recommended maximum pipe length is 150 meters, but this will depend very much on the
method of installation and the fittings used. The more complex the piping network is and the more
fittings there are, the higher will be the friction losses. This will limit the piping length available.
Always calculate the friction losses in the system and compare this with the capability of the water
pump in the chiller unit. See Section 4
1. Black Steel Pipes
The black steel pipes are the most commonly used in chiller installations. It is relatively cheap and
by far the strongest among the 3 types mentioned above.
However, these pipes are heavier and requires more extensive work to join and install.
The common pipe sizes are determined from the ASME (American Society of Mechanical
Engineers) standard B36.1 OM which specifies the pipe dimensions. See Appendix 1.
Generally, steel pipes are sold in lengths of 6 meters each. The dimensions of importance which
we need to know is the nominal pipe size (NIPS) and schedule number (wall thickness).
For pipes 14" (350mm) and larger, the nominal diameter is the same as the actual outside
diameter.
For pipes between 3" (80mm) to 12" (300mm), the nominal diameter is close to the actual inside
diameter.
However, for pipes smaller than that, the nominal value does not correspond to any actual
dimension.
Steel pipes are manufactured with different wall thickness. The ASME standard has defined
schedule numbers to identify these specifications. A pipe with a nominal pipe size may have
several schedule numbers. See also Appendix 1
Section 3 Page 28
Loading...