The AGZ-D family of air-cooled scroll chillers offers a wide
selection of units from 25 to 190 tons with dual refrigerant
circuits and either two or three scroll compressors per circuit.
The AGZ series of air-cooled scroll chillers continues
McQuay's legacy of high quality, high efficiency, latest
technology and quiet operation. These features make the AGZ
family the best overall value in air-cooled packaged chillers
available today.
Efficient Operation
The AGZ units utilize environmentally acceptable R-410A
refrigerant and meet the performance requirements of
ASHRAE Standard 90.1 for efficiency. Excellent part-load
performance is achieved with four or six scroll compressors.
High overall efficiency = lower annual energy costs
Latest Control Technology
These units have the latest control technology through
utilization of McQuay's MicroTech III® microprocessor.
Integrating with your building automation system is easy with
the Open Choice™ feature using LonTalk®, BACnet® or
Modbus® network communication, via field mounting of a
small communication module to the unit controller.
Compact Size
Our reputation for compact designs with small footprints to
minimize space requirements continues to be a primary
feature. The coil design and canted fan deck allow close
spacing to walls and other units. These attributes can lower
installation cost and are excellent for replacement/retrofit jobs.
Quiet Operation
The AGZ units further enhance McQuay's reputation for low
operating sound levels to make these chillers "neighborhood
friendly".
LEED® Points
Developed by the U.S. Green Building Council (USGBC) in
1998, Leadership in Energy and Environmental Design
(LEED®) is an internationally recognized certification
program and intends to provide building owners and operators
a consistent structure for identifying and implementing
practical and measurable green building design, construction,
operations and maintenance solutions.
For building owners who want to pursue LEED Green
Building Certification, the AGZ-D series of air-cooled chillers
can qualify for the Energy and Atmosphere Credit 4, Enhanced
Refrigerant Management worth 2 points.
CAT 6113
Features and Benefits
A
G Z XXX D H
Air-Cooled
Global Design
Scroll Compressor
Nominal Tons
Application
Design Vintage
H = Standard Packaged
Chiller Nomenclature
Features and Benefits
Unit Design Features
McQuay AGZ air-cooled Chillers are a product of the McQuay
commitment to offer quiet, reliable, energy efficient
equipment, incorporating high quality compressors, state-ofthe-art coil design, and innovative packaging.
Construction
AGZ chillers are factory-assembled and mounted on a heavygauge steel base. The base rails, supports and cabinetry are
powder-coat painted for long life. The base distributes the unit
weight for roof loading. Their small footprint allows smaller
mounting pads or support structures and is a plus for retrofit or
replacement applications.
Compressors
Reliable hermetic scroll compressors with cast iron scrolls and
three Teflon® impregnated bearings are used on the AGZ-D
chillers to promote longevity.
Each model has four to six steps of capacity modulation
depending on model size. One to six compressors can run,
depending on the load of the system, resulting in excellent
part-load efficiency and reduced annual operating costs.
Evaporator
Models AGZ-025 through AGZ-130
The evaporator is a compact, high efficiency, dual circuit,
brazed plate-to-plate type heat exchanger consisting of parallel
stainless steel plates. These heat exchangers provide excellent
heat exchange efficiency in a compact footprint and are
especially attractive for smaller capacity units.
Condenser Coils
Condenser coils have internally enhanced seamless copper
tubes arranged in a staggered row pattern. The coils are
mechanically expanded into McQuay lanced and rippled
aluminum fins with full fin collars. A variety of optional coil
material and coatings are available so that the unit can be
constructed to meet almost any environment. Options include
copper fins, black fin and ElectroFin® coating; see page 73 for
description of options.
Condenser Fans and Motors
Multiple direct-drive, dynamically balanced propeller fans
operate in formed venturi openings at low tip speeds for
maximum efficiency and minimum noise and vibration. A
heavy-gauge vinyl-coated fan guard protects each fan.
Each condenser fan motor (including the optional VFD fan
motor) is Totally Enclosed Air Over (TEAO), heavy-duty, 3phase with permanently lubricated ball bearings and inherent
overload protection. These motors are designed specifically for
outdoor use.
Figure 1: AGZ130D with Optional Full Louver Package
The water side working pressure is 653 psig (4502 kPa).
Evaporators are designed and constructed according to, and
listed by, Underwriters Laboratories (UL).
Models AGZ-140 through AGZ-190
The evaporator is direct-expansion, U-tube type with water
flowing in the baffled shell side and refrigerant flowing
through the tubes. Two independent refrigerant circuits within
the evaporator serve the unit's dual refrigerant circuits. The
water side working pressure is 152 psig (1048 kPa). Each
evaporator is designed, constructed, inspected, and stamped
according to the requirements of the ASME Boiler and
Pressure Vessel Code. Double thickness insulation is available
as an option.
4CAT 611
Fan Deck
The fan deck is canted inward and directs discharge air toward
the center of the unit, reducing the tendency to spill over the
sides and into the coil, reducing capacity. This feature, combined with the coil design allows closer unit spacing than most
competitors. The result is a smaller installation footprint and
reduced first cost. The external condenser coils are fitted with
a standard wire mesh guards to protect the coil from damage.
Optional louvers create an attractive appearance that can
eliminate the need for screening walls
1. Evaporator is brazed-plate on AGZ 025-130 and shell-and-tube on AGZ 140-190.
2. Hot gas bypass (shown in dotted lines) is an option. The controls are factory installed.
3. Models 025 to 045 have TXV valves only, Models 140 to 190 have EXV valves only, Models 050 to 130 have TXV as
standard with EXV available as an option.
Features and Benefits
VALVE
DRIE
HOT G AS
SH UT-OFF
DI SCHA RGE
OIL
SIG H T
GLASS
SO LENOI D
HGBP
VALVE
SUC TIO N
TEMP. SENSOR
LEAVIN G WATER
(ON O PPOSITE SIDE)
Control System
The MicroTech III advanced DDC chiller controller surpasses
all other microprocessor-based chiller control systems
available today. This powerful, user-friendly control system
provides the flexibility and performance needed for either
stand-alone unit operation or the controller can be easily tied
into your building automation system of choice using
McQuay's Open Choices feature. Open Choices allows you to
choose from open standard protocols such as BACnet®,
Modbus and LonWorks® to communicate easily with the
building automation system that best meets your facility
requirements. These optional communications modules are
available factory installed or can be easily field installed.
The MicroTech III controller's state-of-the-art design will not
only permit the chiller to run more efficiently, but will also
simplify troubleshooting if a system failure occurs. Every
MicroTech III controller is programmed and tested prior to
shipment to help provide a trouble-free start-up.
Operator-friendly
The MicroTech III control menu structure is separated into
four distinct categories that provide the operator or service
technician with a full description of current unit status, control
parameters, and alarms. Security protection helps prevent
unauthorized changing of the setpoints and unit control
parameters.
CAT 6115
Features and Benefits
MicroTech III control continuously performs important selfdiagnostic checks while monitoring system temperatures,
pressures and protection devices. It will automatically
shutdown a compressor, a refrigerant circuit or the entire unit
if a fault occurs. The cause of the shutdown will be retained in
memory and can be easily displayed in plain English or metric
units for operator review. In addition to displaying alarm
diagnostics, the MicroTech III chiller controller also provides
the operator with a warning of pre-alarm conditions. Alarm
notification data can also be passed to a BAS through an
optional communication module.
Staging
The scroll compressors are staged on and off as a function of
leaving chilled water temperature. Lead/lag is automatic and
switched based on starts and operating hours.
Equipment Protection
The unit is protected in three ways:
1 alarms that shut the unit down and require manual reset
to restore unit operation,
2 alarms that shut the unit down and then restart
automatically (do notrequire manual restart), and
3 limit alarms that reduce unit capacity in response to
some out-of-limit condition. Shut down alarms activate
an alarm signal that can be exported to a remote location.
Limit alarms activate a light on the controller and do not
trigger a remote alarm.
Building Automation System (BAS) Interface
The following BAS protocols are supported:
•BACnet/IP
• BACnet MS/TP
• LonWorks (FTT-10A)
• Modbus
• All operating conditions, system alarms, control parameters and schedules are monitored.
Features
• Can be wired up to 1,000 feet (308 meters) from the unit
for flexibility in placing each remote user interface
within your building.
Benefits
• Allows you to access the user interface for each unit
from one location, inside the building.
• Users need to learn one format because the remote user
interface is identical to the unit-mounted version.
• No additional field commissioning is required for the
remote user interface.
• Can be retrofit after unit installation.
• Is fully compatible with the optional BAS communication modules.
Cable and Wiring Recommendations
Communications: Belden 9841 or equal AWG 22 twisted pair.
See McQuay manual IM1005 for wiring and installation
information.
Figure 3: Remote Interface Panel
Optional Remote Interface Panel
In addition to the unit-mounted user interface provided with
MicroTech III controls, the AGZ chillers can be individually
equipped with a remote user interface. It provides convenient
access to unit diagnostics and control adjustments, without
having to access a rooftop or outdoor location. One remote
panel can be connected to up to eight chillers.
Each remote user interface is similar to its unit-mounted
counterpart and offers the same functionality and display,
including:
• Three buttons and a navigating wheel with a 8 line by
30-character display format.
• Digital display of messages in English language.
6CAT 611
Application Considerations
Full Load Capacity Reduction (AGZ110-130)
0.0
1.0
2.0
0812162024
Wall He ight (ft)
Distance = 4ftDistance = 5f t
Power Increase (AGZ110-130)
0.0
1.0
2.0
0812162024
Wall Height (ft)
% Power Increase
Distance = 4ftDistance = 5ft
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 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. Use a one-piece concrete slab with footings extended
below the frost line. Be sure the foundation is level within 0.5”
(13mm) over its length and width. The foundation must be
strong enough to support the weights listed in the Physical
Data Tables beginning on page 39.
Service Clearance
Sides: Minimum of 4 feet (1.22 m)
Control panel end: Minimum of 4 feet
Opposite control panel:
• Minimum 4 feet on models 025 to 130;
• 12 feet on models 140-190 (allows clearance to remove
the evaporator ).
Application Considerations
Case 1: Wall on One Side
In this case a solid wall up to 24-feet is considered. (For walls
higher than 24 ft., use the 24-foot values.) Also use these
charts for an adjacent building. For perforated screening walls,
use Case 4. Spacing is differentiated by unit size families.
Figure 4: Wall on One Side of Unit
Note: Maintain a minimum of 4-feet on all sides; except models
140-190, which require 12-feet opposite the control
panel to remove the evaporator.
For models AGZ 025-100: use 4 feet from any height wall. For
models 110-190, use Performance Adjustment curves below.
Figure 5: Case 1 Adjustment Factors (AGZ110D-130D)
Air Clearance
McQuay's advanced “W” coil design and open air-passage
ends allow very close unit spacing and a small installation
footprint. The AGZ-D fans are canted inward and reduce
recirculation by directing discharge air to the center of the unit,
reducing the tendency to flow outward and spill over into the
coil inlet.
Sufficient clearance must be maintained between the unit and
adjacent walls or other units to allow the required unit air flow
to reach the coils. Failure to do so will result in a capacity
reduction and an increase in power consumption. No
obstructions are allowed above the unit at any height.
Spacing Requirements
In general, with a small performance penalty in some cases,
AGZ-D units can be spaced at four feet from other units or a
wall. Curves on the following pages give the minimum
clearance for different types of installations and also capacity
reduction and power increase if closer spacing is used.
CAT 6117
% Ca pacity Reduction
Application Considerations
Full Loa d Ca pa city Re ducti on (AGZ140-180)
0.0
1.0
2.0
0812162024
Wall Height (ft)
Distance = 4ftDistance = 6f t
Power Increase (AGZ140-180)
0.0
1.0
2.0
0812162024
Wall Height (ft)
% Power Increase
Distance = 4ftDistance = 6ft
Full Load Capacity Reduction (AGZ190)
0.0
1.0
2.0
0812162024
Wall Height (ft)
Dist ance = 4ftDistance = 5ftDistance = 7ft
Power Increase (AGZ190)
0.0
1.0
2.0
3.0
0812162024
Wall Height (ft)
% Power Increase
Distance = 4ftDis tan ce = 5 ftDistance = 7f t
Full Load Capacity Reduction
0.0
0.5
1.0
1.5
2.0
2.5
3.0
4568
Distance Be tw een Units (ft)
% Capacity Reducti on
AGZ075-100DAGZ110-130DAGZ140-180DAGZ190D
Power Increase
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
4568
Distance Between Units (ft)
% Power Increase
AGZ075-100DAGZ110-130DAGZ140-180D
D
Figure 6: Case 1 Adjustment Factors (AGZ140D-180D)
% Capacity Reduction
Case 2: Two Units, Side-by-Side
Maintain a minimum of 6-feet on all sides; except models 140190, which require 12-feet opposite the control panel to
remove the evaporator.
Figure 8: Case 2 - Two units side by side
For models AGZ 025-100: use 4 feet between units. For
models 110-190, use Performance Adjustment chart in
Figure 9.
Figure 9: Case 2 Adjustment Factors
Figure 7: Case 1 Adjustment Factors (AGZ190D)
% Capacity Reduction
8CAT 611
AGZ190
Application Considerations
Full Load Capacity Reduction
0
1
2
3
4
5
6
4568
Distance Betwe en Units
% Capacity Reduction
AGZ075-100DAGZ110-130DAGZ 14 0-1 8 0DAGZ190D
Power Incre ase
0
1
2
3
4
5
6
7
8
9
4568
Distance Between Units (ft)
% Power Increase
AGZ075-100DAGZ110-130DAGZ140-180DAGZ190D
Wall Free Area vs. Distance
0
1
2
3
4
5
6
7
8
0 1020304050
% Open Wall Area
Distance from Wall to Unit (ft)
AGZ025-070AGZ075-130AGZ140-190
Case 3: Three or More Units, Side-by-Side
Maintain a minimum of 6-feet on all sides; except models 140190, which require 12-feet opposite the control panel to
remove the evaporator. For more than three units, allow an
additional 2-feet clearance between units.
Figure 10: Case 3 - 3 units side by side
Data is for the middle unit - with a unit on each side. See Case
2, page 8 for Adjustment Factors for the two outside units.
Figure 11: Case 3 Adjustment Factors
Case 4: Open Screening Walls
Decorative screening walls are often used to help conceal a
unit either on grade or on a rooftop. Design these walls 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. If the wall height is greater than
the unit height, see Case 5, Pit Installation, page 10. The
distance from the sides of the unit to the side walls must be
sufficient for service, such as opening control panel doors. For
uneven wall spacing, the distance from the unit to each wall
can be averaged providing no distance is less than 4 feet.
Values are based on walls on all four-sides.
Figure 12: Case 4 Adjustment Factor
CAT 6119
Application Considerations
Full Load Capacity Reduction (AGZ025-07 0)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0810121314
Depth of Pit (ft)
% Capacity Red uction
Distance = 4 ftDistance = 5 ftDistance = 6 ft
Power Increase (AGZ025-070)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0810121314
Depth of Pit (ft)
% Power Increase
Distance = 4 ftDistance = 5 ftDistance = 6 ft
Full Load Capacity Reduction (AGZ075-130)
0
1
2
3
4
5
6
0810121314
Depth of Pit (ft)
% Capacity Reduction
Distance = 5 ftDistance = 6 ftDistance = 8 ft
Power Increase (AGZ075-130)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0810121314
Depth of Pit / Wall Height (ft)
% Power In crease
Distance = 5 ftDistance = 6 f tDis tance = 8 ft
Full Load Capacity Reduction (AGZ140-190)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0810121314
Depth of Pit (ft)
% Capacity Reduction
Distance = 6 ftDi sta nc e = 8 f tDis tan ce = 10 f t
Power Increase (AGZ140-190)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0810121314
Depth of Pit / Wall Height (ft)
% Power Increase
Distance = 6 ftDistance = 8 ftDistance = 10 ft
Case 5: Pit Installation
Pit installations can cause operating problems resulting from
recirculation and restriction, and require care that sufficient air
clearance is provided, safety requirements are met and service
access is provided. Pit covers must have abundant open area at
least equal to the chiller footprint.A solid wall surrounding a
unit is substantially a pit and this data 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 to avoid
recirculation problems. Have any pit installation reviewed by
the McQuay sales representative prior to installation to ensure
it has sufficient air-flow characteristics, and approved by the
installation design engineer avoid risk of accident.
Figure 13: Case 5 - Pit Installation
Figure 15: Case 5 Adjustment Factors (AGZ075D-130D)
Figure 14: Case 5 Adjustment Factors (AGZ025D-070D)
10CAT 611
Figure 16: Case 5 Adjustment Factors (AGZ140D-190D)
Application Considerations
Chilled Water Piping
Follow all instructions and recommendations for Chilled Water
Piping in IM 1100, available on www.mcquay.com. Design the
water piping so the chilled water circulating pump discharges
into the evaporator inlet. A 40-mesh strainer must be installed
in the inlet pipe to the chiller to avoid debris entering the
evaporator. The strainer may be field-supplied, or is available
as field-installed kit. See Optional Inlet Strainer below for
more information.
A water flow switch must be installed in the horizontal piping
of the supply (evaporator outlet) water line to avoid evaporator
freeze-up under low or no flow conditions. The flow switch
may be ordered as a factory-installed option, a field-installed
kit, or may be supplied and installed in the field (See Options
and Accessories, page 73for more information).
Vibration eliminators are recommended in both the supply and
return water lines. Pressure gauges must be installed in the
inlet and outlet water lines to the evaporator.
Insulate chilled water piping to reduce heat loss and prevent
condensation. Chillers not running in the winter should have
their water systems thoroughly drained to protect against
freezing. If the chiller operates year-round, or if the system is
not drained for the winter, protect the chilled water piping
exposed to outdoor temperature against freezing. Wrap the
lines with a heater cable and add proper amount of glycol to
the system to further protect the system.
Optional Inlet Strainer
An inlet water strainer kit is available to be field-installed,
sized per Table 1 and with the pressure drop show in
Figure 17. This pressure drop must be accounted for in the
total system pressure drop. The kit consists of:
• (1) Y-type 40% open area strainer with 304 stainless
steel perforated basket, Victaulic pipe connections and
strainer cap
• (1) Extension pipe with (2) Schrader fittings that can be
used for a pressure gauge and thermal dispersion flow
switch. The pipe provides sufficient clearance from the
evaporator for strainer basket removal.
The evaporator flow rates and pressure drops shown on page
page 45 are for full load design purposes. The maximum flow
rate and pressure drop are based on a 6°F 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°F. 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.
Evaporator Variable Flow
Reducing evaporator flow in proportion to load can reduce
system power consumption. The rate of flow change should be
a maximum of 10 percent of the flow per minute. For example,
if the maximum design flow is 200 gpm and it will be reduced
to a flow of 140 gpm, the change in flow is 60 gpm. Ten
percent of 200 gpm equals 20 gpm change per minute, or a
minimum of three minutes to go from maximum to minimum.
Do not reduce flow lower than the minimum flows listed in the
evaporator pressure drop section, page 45. The water flow
through the vessel must remain between the minimum and
maximum values listed on page 45. If flow drops below the
minimum allowable, large reductions in heat transfer can
occur. If the flow exceeds the maximum rate, excessive
pressure drop and tube erosion can occur.
Figure 19: Typical Piping, Shell and Tube Evaporator (models AGZ140D-190D)
Typical Piping
Piping for units with brazed-plate evaporators must have a
drain and vent connection provided in the bottom of the lower
connection pipe and to the top of the upper connection pipe
respectively. These evaporators do not have drain or vent
connections due to their construction.
System Water Volume Considerations
All chilled water systems need adequate time to recognize a
load change, respond to the change and stabilize to avoid
undesirable short cycling of the compressors or loss of
temperature 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
12CAT 611
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 storage tank
may have to be added to the system to reach the recommended
system volume.
Evaporator Freeze Protection
Evaporator freeze-up can be a concern in the application of aircooled water chillers. To protect against freeze-up, insulation
and electric heaters are furnished with the unit. Models 140
through 190 have immersion heaters with a thermostat; models
025 through 130 have an external plate heater and thermostat.
They protect 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
Application Considerations
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 10°F below minimum design ambient
temperature.
3 The addition of thermostatically controlled heat and
insulation to exposed piping.
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 to maximize unit protection, but it can be
supplied from the control circuit. Operation of the heaters is
automatic through the ambient sensing thermostat that
energizes the evaporator heaters for protection against freezeup. Unless the evaporator is drained in the winter or contains
an adequate concentration of anti-freeze, the disconnect switch
to the evaporator heater must not be open.
Temperature and Water Flow Limitations
Low Ambient Operation
Compressor staging is adaptively determined by system load,
ambient air temperature, and other inputs to the MicroTech III
control. A low ambient option with fan VFD allows operation
down to -10° F (-23° C). The minimum ambient temperature is
based on still conditions where the wind is not greater than
five mph. Greater wind velocities will result in reduced
discharge pressure, increasing the minimum operating ambient
temperature. Field installed hail/wind guards are available to
allow the chiller to operate effectively down to the ambient
temperature for which it was designed.
High Ambient Operation
AGZ-D units for high ambient operation (105ºF to 125 F, 40.1
C to 51.7 C) require the addition of the optional high ambient
package that includes a small fan with a filter in the air intake
to cool the control panel.
All units with the optional VFD low ambient fan control
automatically include the high ambient option.
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.
Operating and Standby Limits
Table 2: Operating Limits
Maximum standby ambient temperature130°F (55°C)
Maximum operating ambient temperature105°F (40°C)
-with optional high ambient package (see information under High Ambient Operation125°F (52°C)
Minimum operating ambient temperature (standard control)35°F (2°C)
Minimum operating ambient temperature (with optional low-ambient control)-10°F (-23°C)
Leaving chilled water temperature40°F to 60°F (2°C to 16°C)
Leaving chilled fluid temperatures (with anti-freeze) - Unloading is not permitted with fluid leaving
temperatures below 25°F (-4°C). When ambient air temperature is above 100º F, minimum leaving
chilled fluid temperature (with antifreeze) is 25°F (4°C)
Operating chilled water delta-T range6 to 16°F (-14 to -9°C)
Maximum evaporator operating inlet fluid temperature76°F (24°C)
Maximum evaporator non-operating inlet fluid temperature100°F (38°C)
15°F to 60°F (-9°C to 16°C)
CAT 61113
Selction Procedure
tons24
T F
-----------------------
gpm=
kW
4.18
T C
-------------------------------------
ls=
Selction Procedure
AGZ-D chillers are ideal for a wide range of applications and
operating conditions.
Selection with Inch-Pound (I-P) units
The performance tables beginning on page 16cover the range
of leaving evaporator water temperatures and outside ambient
temperatures included under AHRI Standard 550/590-2003.
The tables are based on a 10°F (5.5°C) temperature drop
through the evaporator.
Adjustment factors for applications having other than a 10°F
(5.5°C) drop can be found in Table 5, page 15. The minimum
leaving chilled water temperature setpoint without glycol is
40°F (4ºC). For brine selections, see Tab le 3 and Table 4 on
page 15 for glycol adjustment factors. Ratings are based on a
0.0001 ft
level operation. For other fouling factors, different Delta-Ts, or
altitude correction factors see Table 5, page 15. For
applications outside the catalog ratings, please contact your
local McQuay sales representative.
Selection example
Given:
2
x hr x ºF/Btu fouling factor in the evaporator at sea
• 50 tons minimum
• 95°F ambient temperature
• 120 gpm, 54ºF to 44°F chilled water
• 0.0001 evaporator fouling factor
1 From Table 6, page 16, an AGZ 055D at the given
conditions will produce 52 tons with a unit kW input of
61.9 and a unit EER of 10.0.
2 Use the following formula to calculate any unknown
elements (water only):
Selection example using ethylene glycol
Given:
• 44 tons minimum
• 95°F ambient air temperature
• 54°F - 44°F chilled water temperature
• 0.0001 evaporator fouling factor
• Protect from freezing down to 0°F
1 From Table 3, page 15, select an ethylene glycol
concentration of 40% to protect against freezing at 0°F.
2 At 40% ethylene glycol, the adjustment factors are:
• Capacity = 0.980
• kW = 0.992
• GPM = 1.132
• Pressure Drop = 1.557
3 Select the AGZ 050D from Table 6, page 16 and correct
with 40% ethylene glycol factors.
4 Correct capacity = 0.980 X 48.1 tons = 47.1 tons
5 Correct kW = 0.992 X 57.1 kW = 56.6 kW
6 Calculate chilled water flow:
Water flow @ corrected capacity=
440. tons x 24 / 10 F = 105.6 gpm
Glycol flow (at 40% solution) =
1.132 x 105.6 gpm = 119.5 gpm
Determine the evaporator pressure drop. Using Figure 27,
page 45, enter at 106 gpm (water) and follow up to the
AGZ050 line intersect. Read horizontally to obtain an
evaporator pressure drop of 11 feet. Correct the pressure drop
for 40% solution = 1.557 x 11.3 feet = 17.6 feet for ethylene
glycol using Table 3, page 15.
3 Determine the evaporator pressure drop. Using
Figure 27, page 45, enter at about 124 gpm and follow
up to the AGZ 055 line intersect. Read horizontally to
obtain an evaporator pressure drop of 13 feet of water.
14CAT 611
Selection with SI units
Use the SI tables and the same procedures as with I-P units.
Use the following formula to calculate any missing elements
(water only):
Performance Data
Ethylene Glycol Factors for Models AGZ 025D to 130D
° F° C
10
26-3.30.9980.9981.0361.097
20
18-7.80.9930.9971.061.226
30
7-140.9870.9951.0921.369
40
-7-220.980.9921.1321.557
50
-28-330.9730.9911.1821.791
Ethylene Glycol Factors for Models AGZ 140D to 190D
° F° C
10
26-3.30.9940.9981.0381.101
20
18-7.80.9820.9951.0631.224
30
7-140.970.9921.0951.358
40
-7-220.9550.9871.1341.536
50
-28-330.9390.9831.1841.755
% E.G.
Point
FlowPDCapacityPow e r
FlowPD% E.G.
Point
CapacityPow e r
Propylene Glycol Factors for Models AGZ 025D to 130D
° F° C
10
26-3.30.9950.9971.0161.1
20
19-7.20.9870.9951.0321.211
30
9-130.9780.9921.0571.38
40
-5-210.9640.9871.0921.703
50
-27-330.9520.9831.142.251
Propylene Glycol Factors for Models AGZ 140D to 190D
° F° C
10
26-3.30.9880.9961.0191.097
20
19-7.20.9720.9921.0351.201
30
9-130.9510.9871.0591.351
40
-5-210.9260.9791.0951.598
50
-27-330.9060.9741.1422.039
Flo wPD% P.G.
Point
CapacityPow e r
Flo wPD% P.G.
Point
CapacityPow e r
Capacity and Power Derates, Models AGZ 025 to 130
°F°CCap. P ower C ap. Po wer Cap. P ower Cap. Power
Note: Due to different performance characteristics, the factors
shown in the following tables are separated into brazedplate evaporators (AGZ025D - 130D) and shell-and-tube
evaporators (AGZ140D - 190D).
Ethylene & Propylene Glycol Factors
AGZ units can operate with a leaving chilled fluid temperature
range of 20°F (-6°C) to 60°F (10°C). A glycol solution is
required when leaving chilled fluid temperature is below 40°F
(4.6°C). The use of glycol will reduce the performance of the
unit depending on concentration.
Note: Ethylene and propylene glycol ratings are outside the
scope of AHRI Standard 550/590-2003 certification
program.
Table 3: Ethylene Glycol Correction Factors
Performance Data
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 Table 5.