McQuay Air-Cooled Global Water Chillers are complete, self-contained automatic
refrigerating units. Every unit is completely assembled, factory wired, charged, and
tested. Each unit consists of twin air-cooled condensers with integral subcooler
sections, two tandem or triple scroll compressors, brazed-plate or replaceable tube, dual
circuit shell-and-tube evaporator, and complete refrigerant piping. Liquid line
components include manual liquid line shutoff valves, sight-glass/moisture indicators,
solenoid valves, and thermal expansion valves. Other features include compressor
crankcase heaters, an evaporator heater for chilled water freeze protection, limited
pumpdown during “on” or “off” periods, automatic compressor lead-lag to alternate the
compressor starting sequence, and sequenced starting of compressors.
The electrical control center includes all equipment protection and operating controls
necessary for dependable automatic operation. Condenser fan motors are protected in
all three phases and started by their own three-pole contactors.
Manuals
This manual covers the installation, maintenance and service for dual circuit, AGZ
packaged scroll compressor chillers. Information on remote evaporator units is in IMM
ACZ/AGZ-4. Operating information is contained in the operating manual OM AGZ-1.
Inspection
Check all items carefully against the bill of lading. Inspect all units for damage upon
arrival. Report shipping damage and file a claim with the carrier. Check the unit
nameplate before unloading, making certain it agrees with the power supply available.
McQuay is not responsible for physical damage after the unit leaves the factory.
Note: Unit shipping and operating weights are available in the Physical Data
tables beginning on page 31.
Nomenclature
A G Z - XXX B S
Scroll Compressor
Air-Cooled
Global
Application
S= Standard Ambient, Packaged
M= Standard Ambient, Remote
H= High Ambient, Packaged
B= High Ambient, Remote
Design Vi ntage
Model Size
(Nominal Tons)
IMM AGZ-8 AGZ 026B through 130B 3
Installation
Note: Installation is to be performed by qualified personnel who are familiar
with local codes and regulations.
WARNING
Sharp edges on unit and coil surfaces are a potential hazard to personal safety.
Avoid contact with them.
Handling
Be careful to avoid rough handling of the unit. Do not push or pull the unit from
anything other than the base. Block the pushing vehicle away from the unit to prevent
damage to the sheet metal cabinet and end frame (see
To lift the unit, 2 1/2" (64mm) diameter lifting tabs are provided on the base of the unit.
Arrange spreader bars and cables to prevent damage to the condenser coils or cabinet
Figure 2).
(see
Figure 1, Suggested Pushing Arrangement
Blocking is required
across full width
Figure 1).
Figure 2, Suggested Lifting Arrangement
Number of fans may vary
from this diagram. The lifting
Spreader bars
Spreader bars
required
required
(use caution)
(use caution)
method will remain the same.
All rigging locations
must be used.
4 AGZ 026B through 130B IMM AGZ-8
Location
Unit Placement
AGZ units are for outdoor applications and
can be mounted either on a roof or at ground
level. For roof mounted applications, install
Figure 3, Clearances
SEE ATTACHED TABLE
DIMENSION “A”
the unit on a steel channel or I-beam frame to
support the unit above the roof. For ground
level applications, install the unit on a
substantial base that will not settle. A one-
4 FT. (1220mm)
CLEARANCE FOR
SERVICE ACCESS
4 FT. (1220)
CLEARANCE FOR
SERVICE ACCESS
piece concrete slab with footings extended
below the frost line is recommended. Be sure
the foundation is level within 1/2" (13mm)
over its length and width. It is recommended
SEE ATTACHED TABLE
DIMENSION “A”
that the unit be raised a few inches with
suitable supports, located at least under the
mounting locations, to allow water to drain
from under the unit and to facilitate cleaning under it. The foundation must be strong enough to
support the weights listed in the Physical Data Tables beginning on page
Do not block the flow of air to and
from the condenser coil. Restricting
airflow or allowing air recirculation
AIR
DISCHARGE
will result in a decrease in unit
performance and efficiency because
discharge pressures are increased.
There must be no obstruction above
AIR FLOWAIR FLOW
AIR FLOW
“B”
the unit that would deflect discharge
air downward where it could be
recirculated back to the inlet of the
The recommended minimum side clearance between two units
is dimension “B’ in table on this page.
condenser coil. The condenser fans
are propeller type and will not
operate with ductwork.
AIR FLOWAIR FLOW
AIR
DISCHARGE
Install the unit with enough side
clearance for air to enter the coil and
for servicing. Provide service access
to the evaporator, compressors,
“C”“C”
electrical control panel and piping
components.
Do not allow debris to accumulate
near the unit where it could be drawn
The unit must not be installed in a pit or enclosure that is
deeper or taller than the height of the unit unless extra space
is provided. The minimum clearance on each
side of the unit is dimension “C” in table on this page.
into the condenser coil. Keep
condenser coils and fan discharge free of snow or other obstructions to permit adequate airflow
for proper operation.
AIR
DISCHARGE
IMM AGZ-8 AGZ 026B through 130B 5
Restricted Air Flow
General
The clearances required for design-life operation of AGZ air-cooled condensers are
described in the previous section. Occasionally, these clearances cannot be maintained
due to site restrictions such as units being too close together or a fence or wall
restricting airflow, or both.
Fortunately, the McQuay AGZ chillers have several features that can mitigate the
problems attributable to restricted airflow.
• The condenser section is shaped as shown
Figure 4. This allows inlet air for these
coils to come in from either side. A vertical coil and its adjacent angled coil are
manifolded together to serve one refrigerant circuit.
• The MicroTech II® control is proactive in response to “off-design conditions”. In
the case of single or compounded influences restricting airflow to the unit, the
microprocessor will act to keep the compressor(s) running (possibly at reduced
capacity) rather than allowing a shut-off on high discharge pressure.
• The MicroTech II® control can be programmed to sequence the compressors in the
most advantageous way. For example, in the diagram shown below, it might be
desirable to program circuit #1 to be the lag circuit (last circuit to reach full load)
during periods of high ambient temperatures.
Figure 4, Coil and Fan Arrangement
Building
Circuit #1Circuit #2
NOTE: Models AGZ 026 to 035 do not have an interior slanted coil.
The following sections discuss the most common situations of condenser air restriction
and give capacity and power adjustment factors for each. Note that in unusually severe
conditions, the MicroTech II® controller would adjust the unit operation to remain
online until a less severe condition is reached.
6 AGZ 026B through 130B IMM AGZ-8
Case 1, Building or Wall on One Side of One Unit
The existence of a screening wall or the wall of a building in close proximity to an air-cooled
chiller is common in both rooftop and ground level applications. Hot air recirculation on the
coils adjoining the wall will increase compressor discharge pressure, decreasing capacity and
increasing power consumption. Only the compressor(s) connected to these coils will be
affected. Circuits opposite the wall are unaffected.
When close to a wall, it is desirable to place chillers on the north or east side of them. It is also
desirable to have prevailing winds blowing parallel to the unit’s long axis. The worst case is to
have wind blowing hot discharge air into the wall.
Figure 5, Unit Adjacent to Wall
H
Figure 6, Adjustment Factors
3.0
2.0
1.0
.5
D
AGZ
075-130
4.5 ft.
(1.4m)
6 ft.
(1.8m)
8 ft.
(2.4m)
AGZ
026-070
3.5 ft.
(1.0m)
4 ft.
(1.2m)
6 ft.
(1.8m)
4.0
3.0
2.0
AGZ
6 ft.
8 ft.
AGZ
026-070
3.5 ft.
(1.0m)
4 ft.
(1.2m)
6 ft.
(1.8m)
075-130
4.5 ft.
(1.4m)
(1.8m)
(2.4m)
0
0
IMM AGZ-8 AGZ 026B through 130B 7
Case 2, Two Units Side By Side
Two or more units sited side by side are common. If spaced closer than 12 feet (3.7 meters) or
8 feet (2.5meters) depending on size, it is necessary to adjust the performance of each unit;
circuits adjoining each other are affected. NOTE: This case applies only to two units side by
side. See Case 3 for three or more parallel units. If one of the two units also has a wall
adjoining it, see Case 1. Add the two adjustment factors together and apply to the unit located
between the wall and the other unit.
Mounting units end to end will not necessitate adjusting performance. Depending on the
actual arrangement, sufficient space must be left between the units for access to the control
panel door opening and/or evaporator tube removal. See “Clearance” section of this guide for
requirements for specific units.
Figure 7, Two Units Side by Side
Figure 8, Adjustment Factor
3.0
2.0
1.0
0
AGZ 075-130
AGZ 026-070
9
(2.7)
6.5
(2.0)
10
(3.0)
7
(2.1)
11
(3.3)
7.5
(2.2)
12
(3.6)
8
(2.4)
AGZ 075-130
AGZ 026-070
6.0
4.0
2.0
0
9
(2.7)
6.5
(2.0)
10
(3.0)
7
(2.1)
11
(3.3)
7.5
(2.2)
12
(3.6)
8
(2.4)
8 AGZ 026B through 130B IMM AGZ-8
Case 3, Three or More Units Side By Side
When three or more units are side by side, the outside chillers (1 and 3 in this case) are
influenced by the middle unit only on their inside circuits. Their adjustment factors will be the
same as Case 2. All inside units (only number 2 in this case) are influenced on both sides and
must be adjusted by the factors shown below.
Figure 9, Three or More Units
AGZ 075-130
AGZ 026-070
Chiller 1Chiller 2Chiller 3
Figure 10, Adjustment Factor
4.0
3.0
2.0
1.0
0
15
(4.6)
11
(3.3)
16
(4.9)
12
(3.7)
17
(5.2)
13
(4.0)
18
(5.5)
14
(4.3)
AGZ 075-130
AGZ 026-070
8.0
6.0
4.0
2.0
0
15
(4.6)
11
(3.3)
16
(4.9)
12
(3.7)
17
(5.2)
13
(4.0)
18
(5.5)
14
(4.3)
IMM AGZ-8 AGZ 026B through 130B 9
Case 4, Open Screening Walls
Decorative screening walls are often used to help conceal a unit either on grade or on a rooftop.
These walls should be designed such that the combination of their open area and distance from
the unit do not require performance adjustment. It is assumed that the wall height is equal to or
less than the unit height when mounted on its base support. This is usually satisfactory for
concealment. If the wall height is greater than the unit height, see Case 5, Pit Installation.
The distance from the ends of the unit to the end walls should be sufficient for service, opening
control panel doors, and pulling evaporator tubes, as applicable.
If each side wall is a different distance from the unit, the distances can be averaged providing
either wall is not less than 8 feet (2.4 meters) from the unit. For example, do not average 4 feet
and 20 feet to equal 12 feet.
Figure 11, Open Screening Walls
Figure 12, Wall Free Area vs Distance
AGZ
026-070
4
(1.2)
3.5
(1.0)
3.0
(0.9)
2.5
(0.7)
AGZ
075-130
6
(1.8)
5
(2.0)
4
(1.2)
3
(0.9)
01020304050
10 AGZ 026B through 130B IMM AGZ-8
Case 5, Pit/Solid Wall Installation
A
A
A
A
A
A
A
Pit installations can cause operating problems and great care should be exercised if they are
to be used on an installation. Recirculation and restriction can both occur. A solid wall
surrounding a unit is substantially the same as a pit and the data presented here should be
used.
Steel grating is sometimes used to cover a pit to prevent accidental falls or trips into the pit.
The grating material and installation design must be strong enough to prevent such accidents,
yet provide abundant open area or serious recirculation problems will occur. Have any pit
installation reviewed by McQuay application engineers prior to installation to make sure it
has sufficient air-flow characteristics. The installation design engineer must approve the
work to avoid the risk of accident.
Figure 13, Pit Installation
Figure 14, Adjustment Factor
D=4
(1.4)
D=6
(1.8)
D=5
(2.0)
D=8
(2.4)
075-130
GZ
026-070
AGZ
075-130
GZ
D=10
(3.1)
GZ
026-070
D=7
(2.1)
D=4
(1.4)
D=6
(1.8)
D=5
(2.0)
D=8
(2.4)
GZ
075-130
D=10
(3.1)
GZ
026-070
D=7
(2.1)
GZ
026-070
GZ
075-130
IMM AGZ-8 AGZ 026B through 130B 11
Sound Isolation
The low sound level of the AGZ chiller is suitable for most applications. When additional
sound reduction is necessary, locate the unit away from sound sensitive areas. Avoid
locations beneath windows or between structures where normal operating sounds may be
objectionable. Reduce structurally transmitted sound by isolating water lines, electrical
conduit and the unit itself. Use wall sleeves and rubber isolated piping hangers to reduce
transmission of water or pump noise into occupied spaces. Use flexible electrical conduit to
isolate sound transmission through electrical conduit. Spring isolators are effective in
reducing the low amplitude sound generated by scroll compressors and for unit isolation in
sound sensitive areas.
Vibration Isolators
Vibration isolators are recommended for all roof-mounted installations or wherever
vibration transmission is a consideration.
Table 2 lists isolator loads for all unit sizes.
RP-4, Neoprene-in-Shear Dimensions
CP-2, Spring Isolator Dimensions
Figure 15 shows isolator locations. See Dimensional Data starting on page 41 for detailed
mounting hole locations.
Isolators are also recommended for slab installations, primarily to keep the unit base from
resting its entire length directly on the slab.
Isolator Installation
The unit should be initially installed on shims or blocks at the listed free height. When all
piping, wiring, flushing, charging, etc. is completed, adjust the springs upward to load them
and to provide clearance to remove the shims or blocks.
Installation of spring isolators requires flexible piping connections and at least three feet of
conduit flex tie-ins. Piping and conduit must be supported independently of the unit.
Bolting: if the chiller base is to be bolted to the isolators, it is recommended that the short
threaded studs usually found on isolators be replaced with eight-inch threaded rod that can
extend through the holes on the top of the base and then be bolted. Washers will be
required.
Figure 15, Isolator Locations
4 or 6 FAN U N IT8 FAN UN IT
34
45
6
CONTROL
PANEL
12
12AGZ 026B through 130B IMM AGZ-8
CONTROL
PANEL
12
3
Table 2, AGZ-BS/BH, Packaged, Isolator Loads At Each Mounting Location
Black Gray Gray Gray - - Orange Purple Purple Red - Black Gray Gray Gray - - Orange Purple Purple Red - Black Gray Gray Gray - - Orange Purple Purple Red - Black Gray Black Gray - - Orange Purple Purple Red - Black Gray Black Gray - - Orange Purple Purple Red - Black Gray Black Gray - - Orange Purple Purple Red - Black Black Black Gray - - Orange Purple Purple Purple- Black Black Black Gray - - Orange Purple Orange Purple- Black Black Black Black - - Orange Orange Orange Purple- Black Black Black Black - - Orange Orange Orange Purple- -
Red Black Red Black - - Gray Orange Gray Orange- Red Black Red Black - - Gray Orange Gray Orange- Red Black Red Black - - Gray Orange Gray Orange- -
Black Black Black Black Black Black Orange Orange Orange Orange Orange Orange
Red Black Black Red Black Black Green Orange Orange Green Orange Orange
Red Red Black Red Red Black Green Green Orange Green Green Orange
Red Red Black Red Red Black Green Green Orange Green Green Orange
NOTE (1): Position #4 is a CP-1, single spring isolator for ACZ 030 to 065 and AGZ 026 to 060. All others are CP-2, two
Operating
Weight
lbs kg 1 2 3 4 5 6 1 2 3 4 (1) 5 6
3600 1631 Black Gray Gray Green- - Orange PurpleRed Orange
3600 1631 Black Gray Gray Green- - Orange PurpleRed Orange - 3600 1631 Black Gray Gray Green- - Orange PurpleRed Orange - 3610 1635 Black Gray Gray Green- - Orange Purple Purple Orange - 3650 1653 Black Gray Gray Green- - Orange Purple Purple Orange - 3800 1721 Black Gray Gray Green- - Orange Purple Purple Orange - 3850 1744 Black Gray Gray Green- - Orange Purple Purple Orange - 4040 1830 Black Gray Gray Green- - Orange Purple Purple Orange - 4070 1844 Black Black Gray Gray - - Orange Purple Purple Red - 4180 1894 Black Black Gray Gray - - Orange Orange Purple Red - 5630 2550 Red Black Red Black - - Green Orange Green Orange - 5790 2623 Red Black Red Black - - Green Orange Green Orange - 5950 2695 Red Black Red Black - - Green Orange Green Orange - 6970 3157 Black Black Black Black Black Black Orange Orange Purple Orange Orange Purple
7230 3275 Black Black Black Black Black Black Orange Orange Purple Orange Orange Purple
7480 3388 Red Black BlackRed Black Black Green Orange Purple Green Orange Purple
7760 3515 Red Black BlackRed Black Black Green Orange Purple Green Orange Purple
spring.
Neoprene-In-Shear Mountings Spring-Flex Mountings
Ambient Air Temperature Limitations
Standard/High Ambient Panels
Models AGZ-B (26 to 130 tons, two circuit) have electrical data and subsequent field wiring
requirements that are tailored to individual applications.
There are many installations where the expected summer ambient air temperatures will be at
105°F (40.1°C) or less, resulting in smaller unit electrical requirements compared to operation at
106°F (41.1) and above. In these lower temperature cases, there can be considerable installation
cost savings by using smaller and more appropriate electrical service.
Therefore, the AGZ electrical data is divided into two classifications based on the design ambient
temperature where the unit will operate. Standard Ambient unit electrical data (BS and BM
models) is for operation in ambient temperatures of 105°F (40.1°C) or less. Units with the High
Ambient designation (BH and BB models) are for use above 105°F (40.1°C) to 125°F (51.7°C).
The AGZ-B units for high ambient operation require the addition of the High Ambient Control
Panel Option, which includes the addition of a small fan with a filter in the air intake to cool the
control panel, and a unit nameplate that lists the larger electrical requirements.
All units with the optional VFD low ambient fan control automatically include the High Ambient
Control Panel Option. Operation of the VFD generates a quantity of panel heat best removed by
use of a control panel fan.
IMM AGZ-8 AGZ 026B through 130B 15
Winter Operation Temperatures
0°F to 34°F 35°F and Above
Fan Control Optional VFD (1) Standard FanTrol (2)
Design Ambient Air Temperature
Electrical Data (3)
≤105°F >106°F ≤105°F >106°F
Standard
Ambient
High
Ambient
Standard
Ambient
High
Ambient
Panel Fan Required (4) Yes Yes No Yes
Model Designator (5)
1. VFD is variable speed, fan control through the MicroTech II controller.
2. FanTrol is fan cycling off discharge pressure.
3. Standard Ambient electrical data begins on page
4. The VFD option automatically includes the factory-installed panel fan and filter set
5. The designator is the last two characters in the model number, i.e. AGZ 100BS.
41, High Ambient data begins on page 51.
Panel Ratings
Vo ltage
208-230
240
380-460
575
Standard
Standard Options
Panel
Optional
VFD
High Short Circuit
Panel (kA)
High Interrupt Panel w/
Disconnect Swt. (kA)
35 5 120 120
35 5 100 100
35 5 65 65
5 5 25 25
Water Flow Limitations, Constant Flow
The evaporator flow rates and pressure drops shown on page 25 are for full load design
purposes. The maximum flow rate and pressure drop are based on a 6-degree
temperature drop. Avoid higher flow rates with resulting lower temperature drops to
prevent potential control problems resulting from very small control bands and limited
start up/shut off temperature changes.
The minimum flow and pressure drop is based on a full load evaporator temperature
drop of 16-degrees.
Evaporator flow rates below the minimum values can result in laminar flow causing
freeze-up problems, scaling and poor control. Flow rates above the maximum values
will result in unacceptable pressure drops and can cause excessive erosion, potentially
leading to failure.
Water Flow Limitations, Variable Flow
The full load, minimum flow limitation for constant flow is not to be confused with the
part load minimum flow rate that must be maintained for chillers operating in primary
variable flow pumping systems. As chiller capacity drops, the flow rate for this
pumping system will reduce proportionally. See the following table for the part load
minimum flo w rates.
Other design practices for variable flow systems requiring a range of evaporator flow
rates can be found below.
These minimum flow rates assume that flow will be reduced proportionally to the
cooling load.
16 AGZ 026B through 130B IMM AGZ-8
Table 9, Minimum Part Load Flow Rates
AGZ Model 034 026 030 035 040 045 050 055 060
Minimum Part
Load Flow (GPM)
AGZ Model 065 070 075 085 090 100 110 120 130
Minimum Part
Load Flow (GPM)
33 26 29 32 37 41 45 50 55
59 63 71 119 128 146 161 180 194
Variable Speed Pumping
Variable water flow involves changing the water flow through the evaporator as the
load changes. McQuay chillers are designed for this duty provided that the rate of
change in water flow is slow and the minimum and maximum flow rates for the vessel
are not exceeded.
The recommended maximum change in water flow is 10 percent of the change per
minute.
The water flow through the vessel must remain above the values listed on
Table 9. If
flow drops below the minimum allowable, large reductions in heat transfer can occur.
Drain Valves at Start-up
Model sizes AGZ 075 and larger have shell-and-tube evaporators. They are drained of
water in the factory and shipped with evaporator drain plugs removed and stored in the
control panel or with an open ball valve in the drain holes. The drain is located on the
bottom of the vessel. Be sure to replace plugs or close the valves prior to filling the
vessel with fluid.
Water Piping
Local authorities can supply the installer with the proper building and safety codes
required for safe and proper installation.
Install piping with minimum bends and changes in elevation to minimize pressure drop.
The following issues must be considered when designing and installing water piping:
1. Vibration eliminators to reduce vibration and noise transmission to the building.
2. Shutoff valves are required to isolate the unit from the piping during unit servicing.
3. Manual or automatic air vent valves at the high points of the system. Drains must
be installed at the lowest points in the system.
4. Adequate water pressure must be maintained (expansion tank or regulating valve).
5. Temperature and pressure indicators located at the unit are required to aid in unit
servicing.
6. A strainer or other means of removing foreign matter from the water before it enters
the pump must
cavitation at the pump inlet (consult pump manufacturer for recommendations).
The use of a strainer will prolong pump life and keep system performance up.
7. Flush the system water piping thoroughly before making connections to the unit
evaporator. Be sure to install a strainer (40-mesh for models AGZ 010 through 070
and 20-mesh for AGZ 075 through 130) in the return water line before the inlet to
the chiller. Design the water piping so the chilled water circulating pump discharges
into the evaporator inlet.
8. The unit’s evaporator has a thermostat and heater to prevent freeze-up down to -
20°F (-29°C). The heating cable can be wired to a separate 115V supply circuit.
As shipped from the factory, the heating cable is wired to the control circuit. All
water piping to the unit must also be protected to prevent freezing.
be installed. Place the strainer far enough upstream to prevent
IMM AGZ-8 AGZ 026B through 130B 17
CAUTION
If separate disconnect is used for the 115V supply to the evaporator heating
cable, mark the disconnect clearly to ensure the disconnect is not accidentally
shut off during cold seasons causing a possible damaging evaporator freeze-up.
9. If the unit is used as a replacement chiller, flush the system thoroughly before unit
installation. Regular water analysis and chemical water treatment for the
evaporator loop is recommended immediately at equipment start-up.
10. The total water volume in the system should be sufficient to prevent frequent “on-
off” cycling. Turnover rate should not be less than 4 minutes for normal variable
cooling loads.
11. When glycol is added to the water system for freeze protection, the refrigerant
suction pressure will be lower, cooling performance less, and water side pressure
drop greater. If the percentage of glycol is high, or if propylene is used instead of
ethylene glycol, the added pressure drop and loss of performance could be
substantial. When Glycol or Ice are selected as Unit Mode, the MicroTech II will
automatically reset the available range for the Leaving Water Temperature,
Freezestat and Evaporator Pressure settings.
12. Reset the freezestat setting to 6 degrees F (3.3 degrees C) below the leaving chilled
water setpoint temperature. See the section titled “Glycol Solutions” for additional
information concerning glycol.
13. Perform a preliminary leak check before insulating the piping and filling the
system.
14. Piping insulation should include a vapor barrier to prevent condensation and
possible damage to the building structure.
Figure 16, AGZ 075 – AGZ 130, Typical Field Evaporator Water Piping
THERMOWELL
T
INLET
T
18 AGZ 026B through 130B IMM AGZ-8
Figure 17, AGZ 026 - AGZ 070, Typical Field Evaporator Water Piping
Air
T
Inlet
Outlet
T
Thermowell
Vent
P
Drain
Vibration
Eliminators
40-Mesh
Strainer
Isolation
Valves
Flow
Switch
NOTE: Outdoor piping must be protected if freezing temperatures are a possibility.
Flow Switch
Mount a water flow switch in the leaving water line to shut down the unit when water
flow is interrupted. A flow switch is an equipment protection control and should never
be used to cycle a unit.
A “paddle” type flow switch is available from McQuay (part number 017503300).
Certain flow rates are required to open the switch and are listed in
Wire from switch terminals Y and R to the unit control panel terminals shown on the
field wiring diagram (page
Installation should be as shown in
70).
Figure 18. Connect the normally open contacts of
the flow switch in the unit control center at terminals 44 and 61. There is also a set of
normally closed contacts on the switch that can be used for an indicator light or an
alarm to indicate when a “no flow” condition exists. Freeze protect any flow switch
that is installed outdoors. Manufacturer’s instructions included with the switch should
be followed.
Table 10 on page 19.
NOTE: Differential pressure switches are not recommended for outdoor installation.
They can freeze and not indicate a no-flow condition.
Bring water piping to the evaporator through the side between the vertical supports.
Provide taps for the connection of pressure gauges and thermometers in the inlet and
outlet lines. Check the inlet and outlet labels on the unit against the certified drawings
supplied on the job and be sure the water piping is hooked up correctly. Contact the
McQuay sales office if any discrepancies exist.
System Water Volume Considerations
All chilled water systems need adequate time to recognize a load change, respond to
that load change and stabilize, without undesirable short cycling of the compressors or
loss of control. In air conditioning systems, the potential for short cycling usually
exists when the building load falls below the minimum chiller plant capacity or on
close-coupled systems with very small water volumes.
Some of the things the designer should consider when looking at water volume are the
minimum cooling load, the minimum chiller plant capacity during the low load period
and the desired cycle time for the compressors.
Assuming that there are no sudden load changes and that the chiller plant has
reasonable turndown, a rule of thumb of “gallons of water volume equal to two to three
times the chilled water gpm flow rate” is often used.
A properly designed storage tank should be added if the system components do not
provide sufficient water volume.
Variable Speed Pumping
Variable water flow involves reducing the water flow through the evaporator as the load
decreases. McQuay chillers are designed for this duty provided that the rate of change
in water flow is not greater than 10 percent of the change per minute.
The water flow through the vessel must remain above the values shown on
17. If flow drops below the minimum allowable, large reductions in heat transfer
page
can occur.
Table 9 on
Glycol Solutions
The use of a glycol/water mixture in the evaporator to prevent freezing will reduce
system capacity and efficiency, as well as increase pressure drop. The system capacity,
required glycol solution flow rate, and pressure drop with glycol may be calculated
using the following formulas and tables.
1. Capacity – Multiply the capacity based on water by the Capacity correction factor
Table 11 through Table 14.
from
2. Flow – Multiply the water evaporator flow by the Flow correction factor from
Table 11 through Table 14 to determine the increased evaporator flow due to glycol.
20 AGZ 026B through 130B IMM AGZ-8
If the flow is unknown, it can be calculated from the following equation:
T
)(24
×
=
CapacitykW
Delta
18.4
−×
For Metric Applications
(gpm) Flow GlycolFactorCorrectionFlow
– Use the following equation for metric applications:
=
(l/s) Flow Glycol
3. Pressure drop -- Multiply the water pressure drop from page
correction factor from
Table 11 through Table 14. High concentrations of
glycolCapacityTons
TDelta
−
×
×
FactorCorrectionFlow
)
25 by Pressure Drop
propylene glycol at low temperatures may cause unacceptably high pressure drops.
4. Power -- Multiply the water system power by Power correction factor from
11 through
Table 14.
Table
Test coolant with a clean, accurate glycol solution hydrometer (similar to that found in
service stations) to determine the freezing point. Obtain percent glycol from the
freezing point table below. It is recommended that a minimum of 25% solution by
weight be used for protection against corrosion or that additional compatible inhibitors
be added.
Concentrations above 35 percent do not provide any additional burst protection and
should be carefully considered before using.
CAUTION
Do not use an automotive grade antifreeze. Industrial grade glycols must be
used. Automotive antifreeze contains inhibitors which will cause plating on the
copper tubes within the chiller evaporator. The type and handling of glycol used
must be consistent with local codes.
Table 11, Ethylene Glycol Factors for Models AGZ 026B to 070B
The pumpdown capacity of AGZ units is given in the Physical Data Tables. Care should be
exercised to include all equipment and lines when calculating the system charge relative to
pumpdown capacity on remote evaporator units. The AGZ remote evaporators have an insignificant
operating charge.
Altitude Correction Factors
Performance tables are based at sea level. Elevations other than sea level affect the performance of
the unit. The decreased air density will reduce condenser capacity consequently reducing the unit's
performance. For performance at elevations other than sea level, refer to
Evaporator Temperature Drop Factors
Performance tables are based on a 10-degree F (5-degree C) temperature drop through the
evaporator. Adjustment factors for applications with temperature ranges from 6 to 16-degree F (3.3
to 8.9-degree C) are in
Temperature drops outside this 6 to 16-degree F (3.3 to 8.9-degree C) range can affect the control
system's capability to maintain acceptable control and are not recommended.
The maximum water temperature that can be circulated through the evaporator in a non-operating
mode is 100°F (37.8°C).
Fouling Factor
Performance tables are based on water with a fouling factor of
As fouling is increased, performance decreases. For performance at other than 0.0001 (0.0176)
fouling factor, refer to
Table 15 and Table 16.
Foreign matter in the chilled water system will adversely affect the heat transfer capability of
the evaporator and could increase the pressure drop and reduce the water flow. Maintain
proper water treatment to provide optimum unit operation.
22
)/0176.0(/0001.0
kWCmorBTUFhrft°×°××per ARI 550/590-98.
22 AGZ 026B through 130B IMM AGZ-8
Table 15, Capacity and Power Derates, Models AGZ 026B to 070B
Evaporator freeze-up can be a concern in the application of air-cooled water chillers. To
protect against freeze-up, insulation and an electric heater cable are furnished with the unit.
This protects the evaporator down to -20°F (-29°C) ambient air temperature. Although the
evaporator is equipped with freeze protection, it does not protect water piping external to the
unit or the evaporator itself if there is a power failure or heater cable burnout. Consider the
following recommendations for additional protection.
1. If the unit will not be operated during the winter, drain evaporator and chilled water piping
and flush with glycol. Drain and vent connections are provided on the evaporator to ease
draining.
2. Add a glycol solution to the chilled water system to provide freeze protection. Freeze
point should be approximately ten degrees below minimum design ambient temperature.
3. The addition of thermostatically controlled heat and insulation to exposed piping.
4. Continuous circulation of water through the chilled water piping and evaporator.
The evaporator heater cable is factory wired to the 115-volt circuit in the control box. This power
should be supplied from a separate source, but it can be supplied from the control circuit.
Operation of the heater cable is automatic through the ambient sensing thermostat that energizes the
evaporator heater cable for protection against freeze-up. Unless the evaporator is drained in the
winter, the disconnect switch to the evaporator heater must not be open.
Operating/Standby Limits
Maximum standby ambient air temperature, 130°F (55°C)
Maximum operating ambient air temperature
Standard Ambient Unit, 105°F (40.6°C) and below, Models BS and BM
High Ambient Unit, above 105°F (40.6°C) to 125°F 51.7°C), Models BH and BB
Minimum operating ambient temperature (standard), 35°F (2°C)
Minimum operating temperature (with optional low-ambient control), 0°F (-18°C)
Leaving chilled water temperature, R-22, 40ºF to 60°F (4.4°C to 15.6°C)
Leaving chilled water temperature, R-407C, 42°F to 60°F (5.5°C to 15.6°C)
Leaving chilled fluid temperatures (with anti-freeze), 20°F to 60°F (-7°C to 16°C)
Design chilled water Delta-T range, 6 to 16 degrees F (3.3 to 8.9 degrees C)
Part load minimum flow for variable flow systems; varies with unit size, see below
Maximum operating inlet fluid temperature, 76°F (24°C)
Maximum non-operating inlet fluid temperature, 100°F (38°C)
Electric power supply, see page
69
Evaporator Flow and Pressure Drop Water Flow
Limitations
The evaporator flow rates and pressure drops shown on page 25 are for full load, constant flow
design purposes.
See the page
systems requiring a range of evaporator flow rates can be found on page
24 AGZ 026B through 130B IMM AGZ-8
16 for the part load minimum flow rates. Other design practices for variable flow
20.
Figure 19, AGZ 026B – 130B, Evaporator Pressure Drop
Protection against negative effects from wind and protection against fin damage from hail
can be achieved from two separate options from McQuay. Factory or field installed louvers
are available as well as the box-type enclosures described below.
Wind Baffles/Hail Guards are a field installed option that are used to stabilize unit operation
in high wind areas and to assist in operation at low ambient temperatures.
sketch of a typical panel assembly on an AGZ unit. The actual number of panels and parts
will vary by model size, being one set per fan, on each side (see
Table 19 through Table 22
for number of fans. The parts are shown in the table below and referenced by balloon
numbers.
Figure 20, Installation Sequence
Rib Attachment (First)
RIB FLANGES ON THE END
MUST POINT TO CENTER
OF COIL TO HAVE A FINISHED
LOOK. INTERIOR RIB FLANGES
CAN POINT IN ANY DIRECTION.
U
V
T
N
I
E
R
C
T
I
C
A
O
L
L
I
Figure 20 is a
Front Panel Attachment (Second)
PLACE FRONT "A" AND
FASTEN TO BOTH SIDES
L
I
C
O
L
A
C
I
T
E
R
V
T
N
I
U
C
B
2
1
A
3
ATTACH ALL RIBS TO
IL VERTICAL CHANNELS.
E
D
PLACE FRONT "B" BY LAPPIN
OVER "A" AND REPEAT
ATTACHMENT PROCEDURE.
26 AGZ 026B through 130B IMM AGZ-8
Top Panel Attachment (Last)
A
.
O
TTACH TOP "A" AT HORIZONTAL COIL CHANNEL FIRST.
THIS WILL SQUARE THE PANEL.
OVERLAP THE FRONT PANEL FLANGE.
C
O
I
L
C
L
A
I
T
R
E
I
V
T
U
N
B
A
Table 17, Packing List
Description Part Number Bubble Number
Vertical Support Rib 074758501 1
Top Cover 330409401 2
¼ - 20 x ½” Screw (Place in Poly Bag) 046093807
Front Panel 330409501 3
E
D
C
ATTACH LEFT SIDE SECOND.
LAP PANEL "B" OVER PANEL "A"
AND REPEAT ATTACHMENT PROCEDURE
Figure 21, Components
Top Panel, Install Last
Overlap the Front panel
T
REAR (AGAINST UNIT)
VERTICAL SUPPORT RIBTOP COVERFRONT PANEL
P
Front Panel, Install Second
Rib, Install First
IMM AGZ-8 AGZ 026B through 130B 27
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