This manual covers two similar product lines:
AGZ-BM, Packaged chiller with the evaporator shipped separately for remote installation, field
piping to the outdoor unit, and interconnection of wiring. The refrigeration specialties are shipped
from the factory for field installation.
Operating instructions are contained in operating manual OM AGZ.
ACZ-BC, Condensing unit with no evaporator included. For use with customer supplied low side
(usually an air-handling unit), field piped and wired to the condensing unit.
Operating instructions are contained in operating manual OM ACZ.
These McQuay air-cooled units are complete, self-contained, automatic refrigerating units. Every
unit is completely assembled, factory wired, tested and provided with a holding charge. Each unit
consists of two air-cooled condenser sections with integral subcooler sections, two tandem or triple
scroll compressors, (brazed-plate or replaceable tube, dual circuit shell-and-tube evaporator and
liquid line components including manual, sight-glass/moisture indicators, solenoid valves, and
thermal expansion valves on AGZ-BM only). Other features include compressor crankcase heaters,
an evaporator heater for chilled water freeze protection (on AGZ-BM only), one-time pumpdown
during “on” or “off” periods, and automatic compressor lead-lag to alternate the compressor starting
sequence.
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. Model ACZ condensing units require a field-supplied multi-step
thermostat wired to the outdoor unit.
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 unit leaves the factory.
Note: Unit shipping and operating weights are available in the Physical Data tables
beginning on page 28.
Nomenclature
A G Z - XXX B M
C=Condensing Unit
Scroll Compressor
Air-Cooled
G=Global Chiller
Application
C= Condensing Unit
M= Remote Evaporator
Design Vi ntage
Model Size
(Nominal Tons)
IMM ACZ/AGZ-4 ACZ / AGZ-BM 3
Page 4
Installation
Note: Installation is to be performed by qualified personnel who are familiar with local
codes and regulations.
Sharp edges on unit and coil surfaces are a potential hazard to personal safety. Avoid
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 (see
Figure 1, Suggested Pushing Arrangement
WARNING
contact with them.
Figure 1).
Figure 2).
Blocking is required
across full width
Figure 2, Suggested Lifting Arrangement
Spreader bars
Spreader bars
required
required
(use caution)
(use caution)
Number of fans may vary
from this diagram. The lifting
method will remain the same.
All rigging locations
must be used.
4 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 5
Location
Unit Placement
ACZ/AGZ units are for outdoor applications and can
be mounted either on a roof or at ground level. For
Figure 3, Clearances
SEE TABLE BELOW
DIMENSION “A”
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. A one-piece
4 FT. (1220mm)
CLEARANCE FOR
SERVICE ACCESS
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. The
foundation must be strong enough to support the
SEE TABLE BELOW
DIMENSION “A”
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
will result in a decrease in unit
performance and efficiency because
discharge pressures are increased.
There must be no obstruction above
the unit that would deflect discharge
air downward where it could be
recirculated back to the inlet of the
condenser coil. The condenser fans are
propeller type and will not operate
with ductwork.
AIR FLOWAIR FLOW
The recommended minimum side clearance between two units
is dimension “B’ in table on this page.
AIR
DISCHARGE
AIR FLOW
“B”
ft. (m)
4 FT. (1220)
CLEARANCE FOR
SERVICE ACCESS
AIR
DISCHARGE
Install the unit with enough side
clearance for air entrance to the coil
AIR FLOWAIR FLOW
AIR
DISCHARGE
and for servicing. Provide service
access to the evaporator, compressors,
electrical control panel and piping
components.
Do not allow debris to accumulate
“C”“C”
near the unit where it could be drawn
into the condenser coil. Keep
condenser coils and fan discharge free
of snow or other obstructions to permit
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.
adequate airflow for proper operation.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 5
Page 6
Restricted Air Flow
General
The clearances required for design-life operation of ACZ/AGZ air-cooled units 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.
The McQuay ACZ/AGZ units have several features that can mitigate the problems attributable to
restricted airflow.
• The condenser section is configured as shown below. This configuration 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 ACZ 030 to 045 and 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 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 7
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 unit 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.
When close to a wall, place chillers on the north or east-side of them. 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
D
Figure 6, Adjustment Factors
3.0
2.0
1.0
.5
ACZ
090-155
AGZ
075-130
4.5 ft.
(1.4m)
6 ft.
(1.8m)
8 ft.
(2.4m)
ACZ
030-080
AGZ
026-070
3.5 ft.
(1.0m)
4 ft.
(1.2m)
6 ft.
(1.8m)
4.0
3.0
2.0
ACZ
ACZ
030-080
090-155
AGZ
AGZ
026-070
075-130
4.5 ft.
3.5 ft.
(1.4m)
(1.0m)
6 ft.
8 ft.
4 ft.
(1.2m)
6 ft.
(1.8m)
(1.8m)
(2.4m)
0
0
IMM ACZ/AGZ-4 ACZ / AGZ-BM 7
Page 8
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
ACZ 090-155
AGZ 026-070
ACZ 030-080
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
ACZ 090-155
AGZ 026-070
ACZ 030-080
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 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 9
Case 3, Three or More Units Side By Side
When three or more units are side by side, the outside units (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
Chiller 1Chiller 2Chiller 3
Figure 10, Adjustment Factor
4.0
3.0
2.0
1.0
0
AGZ 075-130
ACZ 090-155
AGZ 026-070
ACZ 030-080
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
ACZ 090-155
AGZ 026-070
ACZ 030-080
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 ACZ/AGZ-4 ACZ / AGZ-BM 9
Page 10
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 must 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
ACZ 030-080
4
(1.2)
3.5
(1.0)
3.0
(0.9)
2.5
(0.7)
AGZ 075-130
ACZ 090-155
6
(1.8)
5
(2.0)
4
(1.2)
3
(0.9)
01020304050
10 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 11
Case 5, Pit/Solid Wall Installation
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 for air-flow characteristics. The installation design engineer
must approve the work to avoid an unreasonable risk of accident and is responsible for final design
criteria.
Figure 13, Pit Installation
Figure 14, Adjustment Factor
AGZ 026-070
ACZ 030-080
AGZ 075-130
ACZ 090-155
D=4
(1.4)
D=6
(1.8)
D=5
(2.0)
D=8
(2.4)
AGZ
075-130
ACZ
090-155
D=10
(3.1)
AGZ
026-070
ACZ
030-080
D=7
(2.1)
D=4
AGZ 026-070
ACZ 030-080
AGZ 075-130
ACZ 090-155
(1.4)
D=6
(1.8)
D=5
(2.0)
D=8
(2.4)
AGZ
075-130
ACZ
090-155
D=10
(3.1)
AGZ
026-070
ACZ
030-080
D=7
(2.1)
IMM ACZ/AGZ-4 ACZ / AGZ-BM 11
Page 12
Sound Isolation
The low sound level of the ACZ/AGZ units 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 can be objectionable. Reduce
structurally transmitted sound by isolating refrigerant lines, electrical conduit and the unit itself. Use
wall sleeves and rubber isolated piping hangers to reduce transmission of water, refrigerant, 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 isolator springs are recommended for all roof-mounted installations, or wherever vibration
transmission is a consideration. Some form of isolator is also recommended for slab installations,
primarily to keep the unit base from resting its entire length directly on the slab.
Table 2 and Table 3 list isolator point loads for all unit sizes. Figure 15 and 16 shows isolator
locations. See Dimensional Data for detailed mounting hole location.
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, RP-4, Neoprene-in-Shear Isolators CP-2, Spring Isolators
Figure 16, Isolator Locations,
4/6 FAN UNIT8 FAN UNIT
34
45
6
CONTROL
PANEL
12
12ACZ / AGZ-BM IMM ACZ/AGZ-4
CONTROL
PANEL
12
3
Page 13
Table 2, Isolator Loads At Each Mounting Location (With Aluminum Fins)
ACZ-B
Model
ACZ 030 AGZ 026
ACZ 035 AGZ 030
ACZ 040 AGZ 035
ACZ 045 AGZ 040
ACZ 050 AGZ 045
ACZ 055 AGZ 050
ACZ 060 AGZ 055
ACZ 065 AGZ 060
ACZ 070 AGZ 065
ACZ 080 AGZ 070
AGZ-BM
Model
Shipping
lbs 3550 3600 1227 901 849 623 3600 72
kg 1608 1631 556 408 385 282 1631 32
lbs 3550 3600 1227 901 849 623 3600 72
kg 1608 1631 556 408 385 282 1631 32
lbs 3550 3600 1227 901 849 623 3600 72
kg 1608 1631 556 408 385 282 1631 32
lbs 3550 3610 1261 872 873 604 3610 72
kg 1608 1635 571 395 395 274 1635 32
lbs 3590 3650 1275 881 883 611 3650 72
kg 1626 1653 578 399 400 277 1653 32
lbs 3730 3800 1295 951 896 658 3800 119
kg 1690 1721 587 431 406 298 1721 54
lbs 3780 3850 1303 1016 860 671 3850 119
kg 1712 1744 590 460 390 304 1744 54
lbs 3820 4040 1367 1066 903 704 4040 142
kg 1730 1830 619 483 409 319 1830 65
lbs 3970 4070 1305 1146 862 757 4070 142
kg 1798 1844 591 519 390 343 1844 65
lbs 4080 4180 1278 1192 885 825 4180 217
kg 1848 1894 579 540 401 374 1894 99
Wt
Operating.
Wt
Loc. 1 Loc. 2 Loc. 3 Loc. 4 Total
NOTE (1): Additional weight for copper coils is per mounting location.
(1) Add’l for
Copper Fins
Table 3, Isolator Loads At Each Mounting Location (With Aluminum Fins)
ACZ
Model
ACZ090 AGZ 075
ACZ100 AGZ 085
ACZ110 AGZ 090
ACZ120 AGZ 100
ACZ130 AGZ 110
ACZ140 AGZ 120
ACZ155 AGZ 130
NOTE (1): Additional weight for copper coils is per mounting location.
3600 1631 Black Gray Gray Green- - Orange Purple Red Orange
3600 1631 Black Gray Gray Green- - Orange Purple Red Orange- 3600 1631 Black Gray Gray Green- - Orange Purple Red 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 BlackGray Gray - - Orange Purple Purple Red - 4180 1894 Black BlackGray Gray - - Orange Orange Purple Red - 5630 2550 Red BlackRed Black - - Green Orange Green Orange- 5790 2623 Red BlackRed Black - - Green Orange Green Orange- 5950 2695 Red BlackRed 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 Temperature and Water Flow Limitations
ACZ/AGZ units are designed to operate in ambient temperatures as shown in the following table.
Table 6, Unit Maximum Operating Ambient Temperature
Unit Model Standard Controls
AGZ 026B – 130B
ACZ 030B – 155B
115°F 105°F 125°F
w/ Low Ambient VFD
Control Option
The VFD Low Ambient Control Option imposes an additional heat load on the control panel limiting
operation to 105°F ambient temperature. The addition of the High Ambient Panel Option allows
operation to 125°F ambient temperature.
Compressor loading and unloading is adaptively determined by system load, ambient air temperature,
and other inputs to the MicroTech control algorithms. An optional low ambient fan VFD option allows
operation down to 0°F (-18°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.
Evaporator flow rates can be found on page
25. Operation 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.
w/ Low Ambient VFD Control
Plus High Ambient Panel Option
Water Piping (Model AGZ-BM)
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:
14 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 15
1. Vibration eliminators to reduce vibration and noise transmission to the building.
2. Shutoff valves are required to isolate the unit from the piping system 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 system 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
be installed. Place the strainer far enough upstream to prevent cavitation at the pump
must
inlet (consult pump manufacturer for recommendations). The use of a strainer will prolong
pump life and keep system performance up.
7. A strainer must
be installed in the water line before the inlet of the evaporator. This will help
prevent foreign material from entering and decreasing the evaporator performance.
8. 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.
9. 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.
10. 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 controller will automatically reset the available range for the
Leaving Water Temperature, Freezestat and Evaporator Pressure settings.
Reset the freezestat setting to approximately 4 to 5 degrees F (2.3 to 2.8 degrees C) below the
leaving chilled water setpoint temperature. See the section titled “Glycol Solutions” for
additional information concerning glycol.
11. Perform a preliminary leak check before insulating the piping and filling the system.
12. Piping insulation should include a vapor barrier to prevent condensation and possible damage
to the building structure from water dripping.
Figure 17, AGZ 075BM – AGZ 130BM, Typical Field Evaporator Water Piping
THERMOWELL
T
INLET
T
IMM ACZ/AGZ-4 ACZ / AGZ-BM 15
Page 16
Figure 18, AGZ 026BM - AGZ 070BM, Typical Field Evaporator Water Piping
Air
T
Inlet
Outlet
T
Thermowell
Vent
P
Drain
Vibration
Eliminators
Strainer
Isolation
Valves
Flow
Switch
Flow Switch (Model AGZ-BM)
Mount a water flow switch in the leaving water line of the remote water chiller 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 flow switch is available from McQuay (part number 017503300). It is a “paddle” type switch and
adaptable to any pipe size from 2” (51 mm) to 6” (152 mm) nominal. Certain minimum flow rates
are required to close the switch and are listed in
19. 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.
NOTE: Differential pressure switches are not recommended for outdoor installation.
Table 7. Installation should be as shown in Figure
Note: See pressure drop table on page 25 for minimum and maximum flow through the evaporator.
Minimum Required Flow To
Activate Switch - gpm (l/m)
Maximum Flow Rate
gpm (l/m)
Figure 19, Flow Switch Installation
Flow direction marked on switch
1" (25mm) NPT flow switch connection
Tee
Water Connections
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.
16 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 17
Variable Speed Pumping
Variable water flow involves lowering 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 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 between the minimum and maximum values listed on
25. If flow drops below the minimum allowable, large reductions in heat transfer can occur. If
page
the flow exceeds the maximum rate, excessive pressure drop and tube erosion can occur.
System Water Volume Considerations
All chillers need adequate time to recognize a load change, respond to the change and stabilize
without short cycling the compressor. The water volume in the system and the size of the piping
loop is a critical consideration. Good engineering practice is to have a minimum water volume of
four times the flow rate (GPM) for comfort cooling applications. For process applications where the
load can change quickly, contact the local McQuay sales office for recommendations. A water
storage tank (provided by others) can be required to increase the system water volume in some
systems.
Since there are many other factors that can influence performance, systems can successfully operate
below these suggestions. However, as the water volume decreases below these suggestions, the
possibility of problems increases. We believe that these guidelines should be an industry standard
and not just recommendations from McQuay.
Glycol Solutions
The use of a glycol/water mixture in the evaporator to prevent freezing will reduce system capacity
and efficiency and increase pressure drop. The system capacity, required glycol solution flow rate,
and pressure drop with glycol can be calculated using the following formulas and tables.
1. Capacity – Multiply the capacity based on water by the Capacity correction factor from
through
2. Flow – Multiply the water evaporator flow by the Flow correction factor from
Table 11.
Table 8 through
Table 8
Table 11 to determine the increased evaporator flow due to glycol.
If the flow is unknown, it can be calculated from the following equation:
(gpm) Flow Glycol
−
TDelta
×
=
3. Pressure drop -- Multiply the water pressure drop from page
factor from
Table 8 through Table 11. High concentrations of propylene glycol at low
)(24
glycolCapacityTons
×
FactorCorrectionFlow
25 by Pressure Drop correction
temperatures can cause unacceptably high-pressure drops.
4. Power -- Multiply the water system power by Power correction factor from
Table 8 through
Table 11.
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.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 17
Page 18
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 8, Ethylene Glycol Factors for Models AGZ 026BM to 070BM
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 12 or Table 13.
18 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 19
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 degree F to 16 degree F (3.3
degree C to 8.9 degree C) are found in
Table 12 and Table 13. Ranges outside these temperatures
can affect the control system's capability to maintain acceptable control and must not be used.
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 12 and Table 13. 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.
Table 12, Capacity and Power Derates, Models AGZ 026 to 070
All ACZ units have two circuits, each with either two compressors, or three compressors on models
ACZ 120 through 155. These circuits must be kept separated throughout the entire refrigerant piping
system. Each unit refrigerant circuit must be piped to a separate coil or to a separate air handler
(with a single coil).
Temperature control for each evaporator coil is provided by the installer through field-supplied and
wired temperature controllers. The field-supplied staging signals are field-wired to the Microtech II
controller that correspondingly activates and deactivates the scroll compressors. The MicroTech II
controller has a menu screen (See operating manual OM AGZ) that allows selection between “Unit’
and “Circuit”.
Select “Unit” for a single air handler with row control where it does not matter which circuit starts
first. When the controller gets a signal to start Stage 1 of cooling, it will start the compressor, on
either circuit, with the fewest number of starts, so either circuit can start first. Energizing stage 2
will start the compressor with the fewest starts on the other circuit. Further staging requests will
continue to start alternate compressors between the two circuits.
For applications where the staging must be associated with a particular circuit (face-split coils or
separate air handlers), select “Circuit”. In this mode, stages 1, 2, and 3 are connected to refrigerant
circuit #1 and stages 4, 5,and 6 to refrigerant circuit #2. As the thermostat for coil #1 stages up, the
microprocessor will start the compressors on circuit # 1 (compressors 1, 3 and 5). Compressors 5
and 6 are found only on the six compressor units.
The field supplied temperature controller is required to close normally open 24-volt contacts on a
demand for cooling. These closure signals are field wired to the terminal strip (TB3) in the
condensing unit. Refer to the field wiring diagram (page
staging is required:
51) for details. The following control
Condensing Unit Model
ACZ-030B through 110B 4 4
ACZ-120B through 155B 6 6
Number of
Capacity Steps
Number of Required
Contact Closure Signals
In summary:
• Evaporator coil #1 must be piped to the condensing unit circuit #1. See dimension drawings
beginning on page
dimension drawings beginning on page
52. Evaporator coil #2 must be piped to the condensing unit circuit #2. See
52 for circuit locations.
• Evaporator staging thermostat for coil #1 must be wired to the unit terminal board TB3, stages 1,
and 2 (and 3 on models 120 through 155). Evaporator staging thermostat for coil #222 must be
wired to the unit terminal board TB3, stages 4, and 5 (and 6 on models 120 through 155).
AGZ-BM Remote Evaporator Chillers: Refrigerant specialties including the expansion valves,
solenoid valves, filter-drier and sight glasses for use with the AGZ-BM remote evaporator models are
supplied by McQuay but require field installation. The remaining components including fittings and
Schrader valves are provided and piped by the installer.
The hot gas bypass valve with solenoid valve option can be provided as a field-installed or factory
installed option.
ACZ-B Condensing Units:
variety of evaporator types, other than a water chiller as shown in the above diagram, may be used.
Very often these may be air handlers with multiple-circuited coils. If multiple evaporator circuits and
expansion valves are used, they must be piped so that only two circuits end up being piped back to
the condensing unit, matching the unit’s two refrigerant circuits. Each circuit must have a solenoid
valve with a filter-drier installed ahead of it installed close to the evaporator.
The hot gas bypass valve with solenoid valve option can be provided as a field-installed or factory
installed option.
Unit-Mounted Valves:
valve and a suction shutoff valve factory mounted as standard.
No Refrigerant specialties are furnished on the ACZ condensing units. A
Both the ACZ-B and the AGZ-BM outdoor sections have a liquid line shutoff
22 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 23
Refrigerant Piping
All field piping, wiring, and procedures must be performed in accordance with ASHRAE, EPA, and
industry standards. Proper refrigerant piping can make the difference between a reliable system and
an inefficient, problematic system.
The primary concerns related to piping are refrigerant pressure drop, a solid liquid feed to the
expansion valves, continuous oil return and properly sized refrigerant specialties.
Insulate the suction line to reduce excessive superheat build-up. Insulate the liquid line, where
located in areas above ambient temperature, to prevent loss of subcooling and consequent liquid
flashing.
A holding charge of R-22 is provided for the evaporator (AGZ-BM) and the outdoor section. The
installer must properly evacuate the piping system and provide the operating charge of R22. Refer to
the piping schematic drawing on page
The recommended source for refrigerant piping techniques and sizing is the ASHRAE 2002
Refrigeration Handbook, chapter 2.
Although conflicting piping recommendations can be found in different sources, McQuay offers the
following recommendations for these controversial issues.
The use of double risers for vertical gas risers is generally not required and should be used only as a
last resort to maintain the minimum refrigerant flow to carry oil up the vertical risers. Slightly
downsizing the vertical riser is a preferable option to providing double risers.
Slope the refrigerant lines 1” per 10 feet of horizontal run in the direction of refrigerant flow to assist
oil return.
22 for additional details.
Resist using hot gas bypass for applications when operation in ambient temperature below 40
degrees is expected. This recommendation helps to maintain adequate condensing pressures and
liquid refrigerant at the expansion valve when condenser capacities are at their maximum.
Pressure drops in the refrigerant lines should be maintained at or below the ASHRAE
recommendations and line lengths should be made as short as possible. Exceeding these
recommendations will decrease performance and could impact reliability.
Small traps should be provided at the base of each major vertical gas riser to assist in the collection
of oil. If vertical risers exceed more than 25 feet, install a small trap at the midpoint and at a
maximum of 20 foot intervals.
Use caution in sizing the liquid line in applications where the evaporator is above the outdoor
section. The weight of the liquid refrigerant in the vertical column will decrease the pressure at the
top of the riser (approximately 0.5 psi per foot of vertical rise) allowing some of the refrigerant to
flash to a gas. Adequate refrigerant subcooling is needed at the outdoor section to prevent large
volumes of refrigerant gas at the expansion valve.
The piping systems should always extend above the highest component in the refrigeration system
before dropping down to make the final refrigerant connections to components. This practice will
hinder the draining of condensed refrigerant to the lower component when normal shutdown
procedures do not occur (such as a power failure).
NOTE: Do not run refrigerant piping underground.
Pumpdown
The pumpdown capacity of ACZ/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 the unit’s
pumpdown capacity. The AGZ-BM remote evaporators have an insignificant operating charge.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 23
Page 24
Chilled Water Flow Switch
A water flow switch must be mounted in the leaving chilled water line to prove that there is adequate
water flow to the evaporator before the unit can start. It also serves to shut down the unit in the
event that water flow is interrupted in order to guard against evaporator freeze-up.
A flow switch is available from McQuay under ordering number 017503300. It is a paddle-type
switch and adaptable to any pipe size from 1" (25mm) to 8" (203mm) nominal.
NOTE: Minimum and maximum flows are established to ensure the Delta-T for each unit size falls within the 6 - 16°F range for
Inch-Pound S.I. Inch-Pound S.I. Inch-Pound S.I.
gpm DP ft. lps DP kpagpm DP ft. lps DP kpa gpm DP ft. lps DP kpa
proper unit control. The unit must operate within these values.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 25
Minimum Nominal Maximum
Page 26
Wind Baffles and Hail Guards
CO
A
Wind Baffles/Hail Guards are a field-installed option that is used to stabilize unit operation in high wind
areas and to assist in operation at low ambient temperatures.
assembly on an ACZ/AGZ unit. The actual number of panels and parts will vary by model size. The parts
are shown in the table below and referenced by balloon numbers.
Figure 22, Installation Sequence
Rib Attachment (First)
Figure 22 is a sketch of a typical panel
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
Front Panel Attachment (Second)
PLACE FRONT "A" AND
FASTEN TO BOTH SIDES
I
L
C
O
A
L
R
I
T
C
E
V
N
I
T
U
C
B
2
1
A
3
ATTACH ALL RIBS TO
IL VERTICAL CHANNELS.
E
D
PLACE FRONT "B" BY LAPPING
OVER "A" AND REPEAT
ATTACHMENT PROCEDURE.
Top Panel Attachment (Last)
E
TTACH TOP "A" AT HORIZONTAL COIL CHANNEL FIRST.
26ACZ / AGZ-BM IMM ACZ/AGZ-4
THIS WILL SQUARE THE P ANEL.
OVERLAP THE FRONT P ANEL FLANGE.
T
I
E
R
I
N
T
V
U
A
Table 15, Packing List
Description Part Number Bubble Number
D
I
L
O
C
A
L
C
C
B
ATTACH LEFT SIDE SECOND.
OVERLAP PANEL "B" OVER P ANEL "A"
AND REPEAT ATTACHMENT PROCEDURE.
Page 27
Vertical Support Rib 074758501 1
O
Top Cover 330409401 2
¼ - 20 x ½” Screw (Place in Poly Bag) 046093807
Front Panel 330409501 3
Figure 23, 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 ACZ/AGZ-4 ACZ / AGZ-BM 27
Page 28
Physical Data
Table 16, ACZ 030B - 040B, AGZ 026BM – 035BM
BASIC DATA Ckt.1 Ckt.2 Ckt.1 Ckt.2 Ckt.1 Ckt.2
Number Of Refrigerant Circuits 2 2 2
Unit Operating Charge, R-22, Lbs. 22 22 22 27 27 27
Unit Operating Charge, R-22, kg 10 10 10 12 12 12
Cabinet Dimensions, LxWxH, In. 94.4 x 88.0 x 100.4 94.4 x 88.0 x 100.4 94.4 x 88.0 x 100.4
Cabinet Dimensions, LxWxH, (mm) 2398 x 2235 x 2550 2398 x 2235 x 2550 2398 x 2235 x 2550
Unit Operating Weight, Lb (kg) 3600 (1634) 3600 (1634) 3600 (1634)
Unit Shipping Weight, Lb (kg) 3550 (1612) 3550 (1612) 3550 (1612)
Add'l. Weight If Copper Finned Coils, Lb. (kg)284 (129) 284 (129) 284 (129)
COMPRESSORS
Type Tandem Scrolls Tandem Scrolls Tandem Scrolls
Nominal tonnage of each Compressor 7.5 7.5 7.5 9.0 9.0 9.0
Number Of Compressors per Circuit 2 2 2 2 2 2
Oil Charge Per Compressor, Oz. 140 140 140 140 140 140
Oil Charge Per Compressor, (g) (496) (496) (496) (496) (496) (496)
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Staging, 4 Stages, Circuit #1 in Lead 0-25-50-75-100 0-23-50-73-100 0-25-50-75-100
Staging, 4 Stages, Circuit #2 in Lead 0-25-50-75-100 0-27-50-77-100 0-25-50-75-100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area Sq. Ft. 26.3 26.3 26.3 26.3 26.3 26.3
Coil Face Area, (M2) 2.4 2.4 2.4 2.4 2.4 2.4
Finned Height x Finned Length, In. 50x75.6 50x75.6 50x75.6 50x75.6 50x75.6 50x75.6
Finned Height x Finned Length, (mm)
Fins Per Inch x Rows Deep 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3
Number Of Fans - Fan Diameter, In. (mm) 4 – 30 (762) 4 – 30 (762) 4 – 30 (762)
Number Of Motors - HP (kW) (2) 4 – 1.0 4 – 1.0 4 – 1.0
Fan And Motor RPM, 60Hz 1140 1140 1140
60 Hz Fan Tip Speed, FPM (M/Sec) 8950 (4224) 8950 (4224) 8950 (4224)
60 Hz Total Unit Airflow, CFM (M3/sec) 24,316 (11,478) 24,316 (11,478) 24,316 (11,478)
REMOTE EVAPORATOR - BRAZED PLATE (AGZ-BM ONLY)
Number of Evaporators 1 1 1
Number of Refrigerant Circuits 2 2 2
Water Volume, Gallons, (L) 4.3 (16.4) 5.0 (18.9) 5.7 (21.4)
Maximum Water Pressure, psig (kPa) 363 (2503) 363 (2503) 363 (2503)
Max. Refrig. Working Pressure, psig (kPa) 450 (3102) 450 (3102) 450 (3102)
Water Inlet / Outlet Victaulic Conn. In. (mm) 3 (76) 3 (76) 3 (76)
Drain - NPT int., In. (mm) Field Field Field
Vent - NPT int., In. (mm) Field Field Field
NOTES:
1. Nominal capacity based on 95°F ambient air and 50°F SST.
2. Except for 380V/60 & 575V/60, HP = 2.0
PHYSICAL DATA
ACZ 030B,
AGZ 026BM
1270 x
1920
450
(3103)
1270 x
1920
450
(3103)
MODEL NUMBER
ACZ 035B
AGZ 030BM
1270 x
1920
450
(3103)
1270 x
1920
450
(3103)
ACZ 040B
AGZ 035BM
1270 x
1920
450
(3103)
1270 x
1920
450
(3103)
28ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 29
Table 17, ACZ 045B - 060B, AGZ 040BM – 055BM
PHYSICAL DATA
BASIC DATA Ckt.1 Ckt.1 Ckt.2 Ckt.1 Ckt.2 Ckt.1 Ckt.2 Ckt.2
Number Of Refrigerant Circuits 2 2 2 2
Unit Operating Charge, R-22, lbs. 31 31 37 37 37 37 44 44
Unit Operating Charge, R-22, kg 14 14 17 17 17 17 20 20
Cabinet Dimensions, LxWxH, in. 94.4 x 88.0 x 100.4 94.4 x 88.0 x 100.4 94.4 x 88.0 x 100.4 94.4 x 88.0 x 100.4
Type Tandem Scrolls Tandem Scrolls Tandem Scrolls Tandem Scrolls
Nominal tonnage of each Compressor 10.0 10.0 10.0 13.0 13.0 13.0 13.0 15.0
Number Of Compressors per Circuit 2 2 2 2 2 2 2 2
Oil Charge Per Compressor, oz. 140 140 140 140 140 140 140 140
Oil Charge Per Compressor, (g) (496) (496) (496) (496) (496) (496) (496) (496)
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Staging, 4 Stages, Circuit #1 in Lead 0-25-50-75-100 0-22-50-46-100 0-25-50-75-100 0-25-50-75-100
Staging, 4 Stages, Circuit #2 in Lead 0-25-50-75-100 0-28-50-85-100 0-25-50-75-100 0-25-50-75-100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area, sq. ft. (Note 1) 26.3 26.3 44.1 44.1 44.1 44.1 44.1 44.1
Coil Face Area (sq. M) 2.4 2.4 4.1 4.1 4.1 4.1 4.1 4.1
Finned Height x Finned Length, in. 50x75.6 50x75.6 42x75.6 42x75.6 42x75.6 42x75.6 42x75.6 42x75.6
Finned Height x Finned Length, (mm)
Fins Per Inch x Rows Deep 16 x 3 16 x 3 16 x 2 16 x 2 16 x 2 16 x 2 16 x 3 16 x 3
Number Of Fans - Fan Diameter, in. (mm) 4 – 30 (762) 4 – 30 (762) 4 – 30 (762) 4 – 30 (762)
Number Of Motors - HP (kW) (Note 2)) 4 – 1.5 4 – 1.5 4 – 1.5 4 – 1.5
Fan And Motor RPM, 60Hz 1140 1140 1140 1140
60 Hz Fan Tip Speed, FPM (m/sec) 8950 (4224) 8950 (4224) 8950 (4224) 8950 (4224)
60 Hz Total Unit Airflow, CFM (m3/sec) 39,600 (18,692) 39,600 (18,692) 37,228 (17,572) 37,228 (17,572)
REMOTE EVAPORATOR - BRAZED PLATE (AGZ-BM ONLY)
Number of Evaporators 1 1 1 1
Number of Refrigerant Circuits 2 2 2 2
Water Volume, Gallons, (L) 6.3 (23.9) 7.2 (27.3) 8.1 (30.7) 9.2 (34.9)
Maximum Water Pressure, psig (kPa) 363 (2503) 363 (2503) 363 (2503) 363 (2503)
Maximum Refrigerant Working Pressure, psig
(kPa)
Water Inlet / Outlet Victaulic Conn., in. (mm) 3 (76) 3 (76) 3 (76) 3 (76)
Drain - NPT int., in. (mm) Field Field Field Field
Vent - NPT int., in. (mm) Field Field Field Field
NOTES:
1. The AGZ 040 condenser is the same as the AGZ 045.
2. Except for 380V/60 & 575V/60, HP = 2.0
ACZ 045B
AGZ 040BM
2398 x 2235 x
2250
1270 x
1920
450
(3103)
1270 x
1920
450
(3103)
450 (3102) 450 (3102) 450 (3102) 450 (3102)
1067 x
(3103)
MODEL NUMBER
ACZ 050B
AGZ 045BM
2398 x 2235 x
2250
1920
450
1067 x
1920
450
(3103)
ACZ 055B
AGZ 050BM
2398 x 2235 x
2250
1067 x
1920
450
(3103)
1067 x
1920
450
(3103)
ACZ 060B
AGZ 055BM
2398 x 2235 x
2250
1067 x
1920
450
(3103)
1067 x
1920
450
(3103)
IMM ACZ/AGZ-4 ACZ / AGZ-BM 29
Page 30
Table 18, ACZ 065B - 080B, AGZ 060BM – 070BM
PHYSICAL DATA
BASIC DATA Ckt.1 Ckt.2 Ckt.1 Ckt.2 Ckt.1 Ckt.2
Number Of Refrigerant Circuits 2 2 2
Unit Operating Charge, R-22, lbs. 44 44 50 57 57 57
Unit Operating Charge, R-22, kg 20 20 23 26 26 26
Cabinet Dimensions, LxWxH, in. 94.4 x 88.0 x 100.4 94.4 x 88.0 x 100.4 94.4 x 88.0 x 100.4
Type Tandem Scrolls Tandem Scrolls Tandem Scrolls
Nominal tonnage of each Compressor 15.0 15.0 15.0 15 / 20 15 / 20 15 / 20
Number Of Compressors per Circuit 2 2 2 2 2 2
Oil Charge Per Compressor, oz. 140 140 140 140 /148 140 /148 140 /148
Oil Charge Per Compressor, (g) (496) (496) (496) 496/ 525 496/ 525 496/ 525
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Staging, 4 Stages, Circuit #1 in Lead 0-25-50-75-100 0-23-46-77-100 0-25-50-75-100
Staging, 4 Stages, Circuit #2 in Lead 0-25-50-75-100 0-31-46-69-100 0-25-50-75-100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area, sq. ft. 44.1 44.1 52.6 52.6 52.6 52.6
Coil Face Area, (m2) 4.1 4.1 4.9 4.9 4.9 4.9
Finned Height x Finned Length, in. 42x75.6 42x75.6 50x75.6 50x75.6 50x75.6 50x75.6
Finned Height x Finned Length, (mm)
Fins Per Inch x Rows Deep 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3
Number Of Fans - Fan Diameter, in. (mm) 4 – 30 (762) 4 – 30 (762) 4 – 30 (762)
Number Of Motors - HP (kW) (1) 4 – 1.5 4 – 2.0 4 – 2.0
Fan And Motor RPM, 60Hz 1140 1140 1140
60 Hz Fan Tip Speed, FPM (m/sec) 8950 (4224) 8950 (4224) 8950 (4224)
60 Hz Total Unit Airflow, CFM (m3/sec) 37,228 (17,572 43,452 (20,510) 43,452 (20,510)
REMOTE EVAPORATOR - BRAZED PLATE (AGZ-BM ONLY)
Number of Evaporators 1 1 1
Number of Refrigerant Circuits 2 2 2
Water Volume, Gallons, (L) 9.2 (34.9) 11.2 (42.5) 11.2 (42.5)
Maximum Water Pressure, psig (kPa) 363 (2503) 363 (2503) 363 (2503)
Maximum Refrigerant Working Press., psig (kPa) 450 (3102) 450 (3102) 450 (3102)
Water Inlet / Outlet Victaulic Conn., in. (mm) 3 (76) 3 (76) 3 (76)
Drain - NPT int, in. (mm) Field Field Field
Vent - NPT int, in. (mm) Field Field Field
NOTE: Except for 380V/60 & 575V/60, HP = 2.0
ACZ 065B
AGZ 060BM
2398 x 2235 x
2550
1067 x
1920
450
(3103)
1067 x
(3103)
MODEL NUMBER
1920
450
ACZ 070B
AGZ 065BM
2398 x 2235 x
2550
1270 x
1920
450
(3103)
1270 x
1920
450
(3103)
ACZ 080B
AGZ 070BM
2398 x 2235 x
2550
1270 x
1920
450
(3103)
1270 x
1920
450
(3103)
30ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 31
Table 19, ACZ 090B - 110B, AGZ 075BM – 090BM
PHYSICAL DATA
BASIC DATA Ckt.1 Ckt.2 Ckt.1 Ckt.2 Ckt.1 Ckt.2
Number Of Refrigerant Circuits 2 2 2
Unit Operating Charge, R-22, lbs. 56 56 56 66 66 66
Unit Operating Charge, R-22, (kg) 25 25 25 30 30 30
Cabinet Dimensions, LxWxH, in. 134.9 x 88.0 x 100.4 134.9 x 88.0 x 100.4 134.9 x 88.0 x 100.4
Cabinet Dimensions, LxWxH, (mm) 3426 x 2235 x 2550 3426 x 2235 x 2550 3426 x 2235 x 2550
Unit Operating Weight, Lbs. (kg) 5630 (2556) 5790 (2629) 5950 (2701)
Unit Shipping Weight, Lbs. (kg) 5510 (2502) 5670 (2574) 5830 (2647)
Add'l Weight If Copper Finned Coils, lbs. (kg) 870 (395) 870 (395) 870 (395)
COMPRESSORS
Type Tandem Scrolls Tandem Scrolls Tandem Scrolls
Nominal tonnage of each Compressor 20.0 20.0 20.0 25.0 25.0 25.0
Number Of Compressors per Circuit 2 2 2 2 2 2
Oil Charge Per Compressor, oz. 148 148 148 200 200 200
Oil Charge Per Compressor, (g) (525) (525) (525) (709) (709) (709)
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Staging, 4 Stages, Circuit #1 in Lead 0-25-50-75-100 0-22-50-72-100 0-25-50-75-100
Staging, 4 Stages, Circuit #2 in Lead 0-25-50-75-100 0-28-50-78-100 0-25-50-75-100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area, sq. ft. 78.8 78.8 78.8 78.8 78.8 78.8
Coil Face Area, (m2) 7.3 7.3 7.3 7.3 7.3 7.3
Finned Height x Finned Length, in. 50 x113.4 50 x113.4 50 x113.4 50 x113.4 50 x113.4 50 x113.4
Finned Height x Finned Length, (mm)
Fins Per Inch x Rows Deep 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3
Number Of Fans - Fan Diameter, in. (mm) 6 – 30 (762) 6 – 30 (762) 6 – 30 (762)
Number Of Motors - HP (kW) 6 – 2.0 6 – 2.0 6 – 2.0
Fan And Motor RPM, 60Hz 1140 1140 1140
60 Hz Fan Tip Speed, FPM (m/sec) 8950 (4224) 8950 (4224) 8950 (4224)
60 Hz Total Unit Airflow, CFM (m3/sec) 65,178 (30,765) 65,178 (30,765) 65,178 (30,765)
REMOTE EVAPORATOR - SHELL AND TUBE (AGZ-BM ONLY)
Number of Evaporators 1 1 1
Number of Refrigerant Circuits 2 2 2
Diameter, in. - Length, ft. 14.0 x 5.2 14.0 x 5.2 14.0 x 5.2
Diameter, (mm) – Length, (mm) 356 x 1585 356 x 1585 356 x 1585
Water Volume, Gallons, (L) 25 (95) 25 (95) 25 (95)
Maximum Water Pressure, psig (kPa) 152 (1047) 152 (1047) 152 (1047)
Maximum Refrigerant Working Pressure, psig (kPa) 300 (2066) 300 (2066) 300 (2066)
Water Inlet / Outlet Victaulic Connections, in. (mm) 5 (127) 5 (127) 5 (127)
Drain - NPT int, in. (mm) 0.5 (12.7) 0.5 (12.7) 0.5 (12.7)
Vent - NPT int, in. (mm) 0.5 (12.7) 0.5 (12.7) 0.5 (12.7)
ACZ 090B
AGZ 075BM
1270 x
2880
450
(3103)
1270 x
2880
450
(3103)
MODEL NUMBER
ACZ 100B
AGZ 085BM
1270 x
2880
450
(3103)
1270 x
2880
450
(3103)
ACZ 110B
AGZ 090BM
1270 x
2880
450
(3103)
1270 x
2880
450
(3103)
IMM ACZ/AGZ-4 ACZ / AGZ-BM 31
Page 32
Table 20, ACZ 120B - 155B, AGZ 100BM – 130BM
PHYSICAL DATA
BASIC DATA Ckt.1 Ckt.2 Ckt.1 Ckt.2 Ckt.1 Ckt.2 Ckt.1 Ckt.2
Number Of Refrigerant Circuits 2 2 2 2
Unit Operating Charge, R-22, lbs. 72 82 82 82 82 99 99 99
Unit Operating Charge, R-22, (kg) 33 37 37 37 37 45 45 45
Cabinet Dimensions, LxWxH, in. 173.1 x 88.0 x 100.4 173.1 x 88.0 x 100.4 173.1 x 88.0 x 100.4 173.1 x 88.0 x 100.4
Cabinet Dimensions, LxWxH, (mm) 4397 x 2235 x 2550 4397 x 2235 x 2550 4397 x 2235 x 2550 4397 x 2235 x 2550
Unit Operating Weight, Lbs. (kg) 6970 (3164 7230 (3282) 7480 (3396) 7760 (3523)
Unit Shipping Weight, Lbs. (kg) 6820 (3096) 7080 (3214) 7360 (3341) 7640 (3469)
Add'l. Weight If Copper Finned Coils, lbs. (kg) 1155 (524) 1155 (524) 1155 (524) 1155 (524)
COMPRESSORS
Type Trio Scrolls Trio Scrolls Trio Scrolls Trio Scrolls
Nominal tonnage of each Compressor 15.0 20.0 20.0 20.0 20.0 25.0 25.0 25.0
Number Of Compressors per Circuit 3 3 3 3 3 3 3 3
Oil Charge Per Compressor, oz. 140 148 148 148 148 200 200 200
Oil Charge Per Compressor, (g) (496) (525) (525) (525) (525) (709) (709) (709)
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Staging, 6 Stages, Circuit #1 in Lead 0-14-33-48-67-81-100 0-17-33-50-67-83-100 0-15-33-48-67-81-100 0-17-33-50-67-83-100
Staging, 6 Stages, Circuit #2 in Lead 0-19-33-52-67-86-100 0-17-33-50-67-83-100 0-19-33-52-67-86-100 0-17-33-50-67-83-100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area, sq. ft. 105.3 105.3 105.3 105.3 105.3 105.3 105.3 105.3
Coil Face Area, (m2) 9.8 9.8 9.8 9.8 9.8 9.8 9.8 9.8
Finned Height x Finned Length, in. 50 x151.6 50 x151.6 50 x151.6 50 x151.6 50 x151.6 50 x151.6 50 x151.6 50 x151.6
Finned Height x Finned Length, (mm)
Fins Per Inch x Rows Deep 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3 16 x 3
Notes for “Electrical Data Single- and Multi-Point” Power:
1. Unit wire size ampacity (MCA) is equal to 125% of the largest compressor-motor RLA
plus 100% of RLA of all other loads in the circuit including the control transformer.
2. The control transformer is furnished on the unit and no separate 115V power is required.
For both single- and multi-point power connections, the control transformer is in circuit
#1 with control power wired from there to circuit #2. In multi-point power,
disconnecting power to circuit will disconnect all control power to the unit.
3. If a separate 115V power supply is used for the control circuit, then the wire sizing amps
is 10 amps for all unit sizes.
4. Recommended power lead wire sizes for 3 conductors per conduit are based on 100%
conductor ampacity in accordance with NEC. Voltage drop has not been included.
Therefore, it is recommended that power leads be kept short. All terminal block
connections must be made with copper (type THW) wire.
5. “Recommended Fuse Sizes” are selected at approximately 150% to 175% of the largest
compressor RLA, plus 100% of all other loads in the circuit.
6. “Maximum Fuse or HACR breaker size” is selected at approximately 225% of the
largest compressor RLA, plus 100% of all other loads in the circuit.
7. The recommended power lead wire sizes are based on an ambient temperature of 86°F
(30°C). Ampacity correction factors must be applied for other ambient temperatures.
Refer to the National Electrical Code Handbook.
8. Must be electrically grounded according to national and local electrical codes.
Voltage Limitations:
Within ± 10 percent of nameplate rating.
Notes for “Compressor and Condenser Fan Amp Draw”:
1. Compressor RLA values are for wiring sizing purposes only but do not reflect normal
operating current draw at rated capacity.
Notes for “Field Wiring Data”
1. Requires a single disconnect to supply electrical power to the unit. This power supply
must either be fused or use an HACR type circuit breaker.
2. All field wiring to unit power block or optional non-fused disconnect switch must be
copper.
3. All field wire size values given in table apply to 75°C rated wire per NEC.
Circuit Breakers
Factory installed circuit breakers are standard on units with single point power supply only. This
option provides unit installed compressor short circuit protection and makes servicing easier.
Connection Type Power Block
Single Point (Standard) Std Opt. Std Opt
Multi-Point (Optional) Std Opt. Not Avail. Opt.
Disconnect
Swt.
Circuit
Breakers
High Short
Circuit Current
IMM ACZ/AGZ-4 ACZ / AGZ-BM 49
Page 50
Figure 24, AGZ-BM, Typical Field Wiring Diagram
SCO
DI
3 PHASE
POWER
NNECT
(BY OTHERS)
UNIT MAIN
TERMINAL BLOCK
GND LUG
TO COMPRESSOR(S)
AND FAN MOTORS
NOTE: ALL FIELD WIRING TO BE
INSTALLED AS NEC CLASS 1
WIRING SYSTEM WITH CONDUCTOR
RATED 600 VOLTS
FIELD SUPPLIED
REMOTE STOP SWITCH
(BY OTHERS)
ICE MODE SWITCH
(BY OTHERS)
ALARM BELL
OPTION
CHW FLOW SWITCH
---MANDATORY–(BY OTHERS)
OPTION
CONTROL POWER
N
120VAC
FACTORY SUPPLIED ALARM
FIELD WIRED
ALARM BELL RELAY
TIME
CLOCK
FUSED CONTROL
CIRCUIT TRANSFORMER
DISCONNECT
(BY OTHERS)
10A
FUSE
(BY OTHERS)
CHW PUMP RELAY
120 VAC 1.0 AMP MAX
OFF
AUTO
ON
MANUAL
OFF
AUTO
ON
MANUAL
(BY OTHERS)
120 VAC
CONTROLLER
TB1
TB2
TB1-20
1
2
35
33
34
CONTROL
CIRCUIT
FUSE
120 VAC
N
120 VAC
32
GND
IF REMOTE STOP
52
72
43
83
54
CONTROL IS USED,
585
REMOVE LEAD 585
FROM TERM. 52
TO 72.
BELL
12
ALARM BELL OPTION
ALARM BELL
RELAY
COM NO
74
NOR. OPEN PUMP AUX.
CONTACTS (OPTIONAL)
44
61
4-20MA FOR
EVAP. WATER RESET
(BY OTHERS)
4-20MA FOR
DEMAND LIMIT
(BY OTHERS)
DWG. 330423101 REV.0A
+
-
+
-
LESS EVAPORATOR ONLY
LIQUID LINE #1 SOLENOID
24 VAC 1.5 AMP MAX
LIQUID LINE #2 SOLENOID
24 VAC 1.5 AMP MAX
68
69
70
71
GND
91
93
92
93
24 VAC
N
24 VAC
N
50ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 51
Figure 25, ACZ-B, Typical Field Wiring Diagram
SCO
A
A
A
UNIT MAIN
TERMINAL BLOCK
3 PHASE
POWER
DI
NNECT
(BY OTHERS)
GND LUG
TO COMPRESSOR(S)
AND FAN MOTORS
NOTE 1:
LL FIELD WIRING TO BE
INSTALLED AS NEC CLASS 1
WIRING SYSTEM WITH CONDUCTOR
RATED 600 VOLTS
FIELD SUPPLIED
OPTION
CONTROL POWER
OPTION
CLOCK
TIME
FACTORY SUPPLIED ALARM
REMOTE STOP SWITCH
(BY OTHERS)
ALARM BELL
EVAP FLOW SWITCH
---MANDATORY–(BY OTHERS)
(SEE NOTE 2)
NOTE 2:
EVAP. AIR FLOW SWITCH OR
FAN AUX. CONTACT FOR
CIRCUIT #2 FAN WHEN UNIT IS
SET FOR CIRCUIT SEQUENCING
MODE.
NOTE 3:
WHEN CONNECTED TO
EVAPORATORS USING
OPTIONAL CIRCUIT CONTROL,
STAGES 1-3 ACTIVATE
COMPRESSORS FOR
CONDENSING UNIT CIRCUIT #1
AND STAGES 4-6 ACTIVATE
COMPRESSORS FOR
CONDENSING UNIT CIRCUIT #2.
LABEL DWG. 330423201 REV.0D
CIRCUIT TRANSFORMER
DISCONNECT
(BY OTHERS)
N
120VAC
FIELD WIRED
ALARM BELL RELAY
AUTO
OFF
ON
MANUAL
NOR. OPEN PUMP AUX.
CONTACTS (OPTIONAL)
4-20MA FOR
DEMAND LIMIT
(BY OTHERS)
STAGING OPERATION IN UNIT
+
-
LESS EVAPORATOR ONLY
SEQUENCING SETTING
STAGE 1
ST
COMPR. - EITHER CIRCUIT
1
STAGE 2
1STCOMPR. - OPPOSITE CIRCUIT
STAGE 3
ND
2
COMPR. - INITIAL CIRCUIT
STAGE 4
ND
2
COMPR. - OPPOSITE CIRCUIT
STAGE 5
RD
3
COMPR. - INITIAL CIRCUIT
STAGE 6
RD
3
COMPR. - OPPOSITE CIRCUIT
FUSED CONTROL
10A
FUSE
(BY OTHERS)
DX EVAP FAN RELAY
(BY OTHERS)
120 VAC 1.0 AMP MAX
LIQUID LINE #1 SOLENOID
24 VAC 1.5 AMP MAX.
LIQUID LINE #2 SOLENOID
24 VAC 1.5 AMP MAX.
HOT GAS BYPASS #1 SOLENOID
24 VAC 1.0 AMP MAX.
HOT GAS BYPASS #2 SOLENOID
24 VAC 1.0 AMP MAX.
TB3
120 VAC
TB1-20
TB1
1
2
35
33
CONTROLLER
34
32
TB2
52
72
43
83
44
61
54
J20-ID18
70
71
91
93
92
93
95
97
96
97
101
102
103
104
105
106
107
108
109
110
111
112
CONTROL
CIRCUIT
FUSE
120 VAC
N
120 VAC
GND
IF REMOTE STOP
585
CONTROL IS USED,
REMOVE LEAD 585
FROM TERM. 52 TO 72.
12
GND
24 VAC
N
24 VAC
N
24 VAC
N
24 VAC
N
STAGING OPERATION IN CIRCUIT
SEQUENCING SETTING
STAGE 1
ST
1
COMPR. - CIRCUIT #1
STAGE 2
2ND COMPR. - CIRCUIT #1
STAGE 3
RD
3
COMPR. - CIRCUIT #1
STAGE 4
ST
COMPR. - CIRCUIT #2
1
STAGE 5
ND
2
COMPR. - CIRCUIT #2
STAGE 6
RD
COMPR. - CIRCUIT #3
3
TB3
LARM BELL
RELAY
COM NO
LARM BELL OPTION
(SEE NOTE 3)
101
102
103
104
105
106
107
108
109
110
111
112
UNIT
CIRCUIT #1
UNIT
CIRCUIT #2
IMM ACZ/AGZ-4 ACZ / AGZ-BM 51
Page 52
Dimensional Data
Figure 26, Dimensions: ACZ 030B - 080B
AGZ 026BM – 070BM
13.3 (338)
ISOLATOR LOCATIONS ON BOTTOM OF RAIL
51.2 (1301)
19.9
(506)
67.8 (1721)
COMPRESSOR
CIRCUIT #2
25.0
(636)
HOT GAS
CONN.
94.4 (2397)
COMPRESSOR
CIRCUIT #1
8.9 (226)
LIQUID
CONN.
Z
19.9
(507)
13.3 (338)
2.0
(51)
CONTROL
PANEL
SUCTION
CONN.
16.7
424)
9.1
(231)
FIELD CONTROL
CONNECTION
Y
25.8
(656)
REFRIGERANT CONNECTIONS
SUCTION
LINE #2
HOT GAS
BYPASS #1
LIQUID
LINE #1
CONTROL
PANEL
25.1
(637)
88.0 (2335)
6.4 (162)
SUCTION
LINE #1
HOT GAS
BYPASS #2
LIQUID
LINE #2
POWER
ENTRY
POINT
0.875
KNOCK OUT
43.8
(1111)
X
14.3 (364)
DWG. #3305196-R03
100.4
(2550)
NOTES:
1. Hail and wind guards add 20 inches to the width of each side.
2. Be sure that the expansion valves’ sensing bulb and capillary are attached to the correct suction line.
Any of the following options can be included on a unit:
Controls
Hot Gas Bypass
Hot gas bypass permits unit operation down to 10% of full load capacity. This option includes a
factory-mounted hot gas bypass valve, solenoid valve, and manual shutoff valve for each circuit.
Head Pressure Control
Fan VFD low ambient control allows unit operation down to 0°F (-18°C). (Not available on 380
volt, 60 Hertz units.)
Water Flow Switch (AGZ-BM only)
(P/N 017503300) A water flow switch is available for field installation in the chilled water piping to
avoid evaporator freeze-up under low or no flow conditions. Terminals are provided in the unit
control center for field hook-up of the water flow switch. If this option is not ordered with the unit,
then a field supplied water flow switch must be installed.
Alarm Bell
Field-installed and wired to the control panel to provide remote indication of unit alarm condition.
See Field Wiring Diagram for connection locations.
BAS Interface (Protocol Selectability™ Feature)
Connection to Chiller
Connection to the chiller for all Building Automation System (BAS) protocols will be at the unit
controller. An interface card, depending on the protocol being used, can be factory -installed in the
unit controller (or it can be field-installed).
Protocols Supported
Table 37, Standard Protocol Data
Protocol Physical Layer Data Rate Controller Other
BACnet®/IP or
BACnet/Ethernet
BACnet MSTP RS-485 (TBD)
LONWORKS®
Modbus RTU? RS-485or RS-232 (TBD)
Ethernet 10 Base-T 10 Megabits/sec
FTT-10A 78kbits/sec
2
pCO
Unit Controller
2
pCO
Unit Controller
2
pCO
Unit Controller
2
Unit Controller
pCO
Reference ED 15057:
BACnet PICS
Reference ED 15057:
L
Functional Profile
BACnet PICS
ONMARK
®
Chiller
Note: For additional information on the protocol data available through the BACnet or
LONWORKS communications modules reference ED 15062, MicroTech II Chiller Unit Controller
Protocol Information.
Modbus – When selected, the ident number and baud rate can also be changed to suit the application.
ONWORKS – When selected, the ident number and baud rate setpoints are not available. Baud rate
L
is locked at 4800.
BACnet – When selected, the ident number and baud rate setpoints are not available. Baud rate is
locked at 19200.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 57
Page 58
The interface kits on the MicroTech II™ controller are as follows:
• Modbus RTU
The following functions are available through the BAS where possible. Exact capabilities can vary
depending on the protocol in use.
• Enable/Disable chiller operation by setting the Unit Enable setpoint.
• Select the operating mode by setting the Unit Mode setpoint.
• Set the Cool LWT and Ice LWT setpoints.
• Read all digital and analog I/O values.
• Read Enable status of chiller.
• Read current operating mode and status (state) of chiller.
• Send a description of each alarm when it occurs.
Reference documents ED 15057, ED 15062 and ED 15063 can be obtained from the local McQuay
sales office, or they can also be found on
type) > Control Integration.
®™ The following are trademarks or registered trademarks of their respective companies: BACnet
from the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., LonTalk,
LONMARK and LONWORKS from Echelon Corporation, and Modbus from Schneider Electric.
www.mcquay.com under Product Information > (chiller
Unit
Vibration Isolators
Spring or neoprene-in-shear vibration isolators are available for field installation to reduce vibration
transmission through the unit base. See page
Protective Base Guards
Optional factory installed vinyl-coated welded wire base guards provide all-around lower unit
protection on ground level installations. Coil guards are standard.
Copper Fin Condenser Coils
Copper fin condenser coils are available as an option on all models.
Black Fin Coils
Aluminum fin stock precoated with a phenolic coating with 1000 hour salt spray resistance (ASTM
B117-90).
Coated Fins
Copper or aluminum fins coated with ElectroFin® baked epoxy protective coating with 3000+ hour
salt spray resistance (ASTM B117-90).
Evaporator Insulation (AGZ-BM only)
Double insulation thickness (total of 1 ½ inch) for high humidity areas or low fluid temperatures.
Sound Reduction
Acoustical blankets are factory-installed on each compressor.
12 for detailed information on their installation.
Hail and Wind Guards
A field-mounted option shipped as a kit including panels, fasteners, and instructions. See page 26 for
further information.
58 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 59
Refrigerant Specialties Kit
Required on AGZ-BM Remote Evaporator units consisting of thermal expansion valve, solenoid
valve, sight glass and filter-drier (sealed on Models 026 to 070, replaceable core on Models 075 to
130).
Electrical
Multi-Point Electrical Connection
Provides a power connection to each of the unit’s two electrical circuits.
Disconnect Switch with Through-the-Door Handle
A factory or field-installed option for service use, nonfused disconnect switch (mounted inside the
power section of the control box) with a through-the-door handle is available with single and multipoint power supply.
Phase Loss/Voltage Protection
Phase loss with under/over voltage protection and multiple LED indication of fault type is available
as a factory-installed option to guard against compressor motor burnout.
Convenience Outlet
10.0 amp, 115 volt outlet located in control panel to provide power for servicing unit.
Ground Fault Protection
Protects equipment from damage from line-to-ground fault currents less than those required for
conductor protection.
High Short Circuit Current Protection
Provides control panel protection against short circuit currents per following table:
Voltage 208 240 460 600
Current (kA) 120 100 65 25
High Ambient Control Panel
Consists of exhaust fan with rain hood, two inlet screens with filters, necessary controls and wiring
to allow operation to 125°F. The option can be factory or field-installed as a kit. Must be used for:
• Ambient temperatures above 105°F (40°C) with fan VFD (low ambient option)
• Ambient temperatures above 115°F (46°C) with standard FanTrol control.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 59
Page 60
Start-up
Pre Start-up
The unit must be inspected to see that no components became loose or damaged during shipping or
installation.
Start-Up
There should be adequate building load (at least 50 percent of the unit full load capacity) to properly
check the operation of the unit’s refrigerant circuits.
Record all operating parameters required by the “Compressorized Equipment Warranty Form”.
Return this information within 10 working days to McQuay International as instructed on the form to
register the start-up date with the McQuay Warranty Department.
1. Verify chilled water or air-flow.
2. Verify that the remote start / stop or time clock has requested the chiller to start.
3. Set the thermostat setpoint to required temperature. For AGZ-AM units, the system water
4. Put both pumpdown switches (PS1 and PS2) to the ON position.
5. Put system switch (S1) to ON position.
6. There can be a delay of 2 minutes after closing S1. The time delay is due to the compressor
7. After the chiller has been operating for a period of time and has become stable, check the
8. Complete the “Compressorized Equipment Warranty Form”.
temperature must be greater than the total of the leaving water temperature setpoint plus 1/2 the
control band before the MicroTech II controller will stage on cooling. Set the Evap Delta T and
the Start Delta T as a starting point.
Switch
PS1, PS2,
Pumpdown
Switches
S1,
System Switch
ON OFF
Circuits will operate in the
normal automatic mode
Unit will operate in the
normal automatic mode
Switch Position
Circuit will go through the
normal pumpdown cycle and
shut off.
Unit will shut off immediately
without pumping down
(emergency stop)
inherent motor protection or the Stage Up Timer counting. This should only occur on initial
start-up or when power to the chiller has been turned off and back on. More than one
compressor will not start at the same time.
following:
Compressor oil level. (Some scroll compressors do not have oil sight glasses)
Refrigerant sight glass for flashing.
Rotation of condenser fans.
60 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 61
Shutdown
Temporary
1. Put both circuit switches to the OFF position (Pumpdown and Stop).
2. After compressors have stopped, put System Switch (S1) to OFF (emergency stop).
3. Turn off chilled water pump or air handler if applicable. Chilled water pump to operate while
compressors are pumping down.
To start the chiller after a temporary shutdown, follow the start-up instructions.
Extended
1. Front seat both condenser liquid line service valves.
2. Put both circuit switches to the OFF position (Pumpdown and Stop position.)
3. After the compressors have stopped, put System Switch (S1) to the OFF position (emergency
stop).
4. Front seat both refrigerant circuit discharge valves (if applicable).
5. If electrical power is on to unit, the compressor crankcase heaters will keep the liquid refrigerant
out of the compressor oil. This will minimize start-up time when putting the unit back into
service. The evaporator heater will be able to function.
6. If electrical power is off, tag all opened electrical disconnect switches to warn against start-up
before the refrigerant valves are in the correct operating position. When starting the unit,
electrical power must be on for 24 hours before starting the chiller.
To start the chiller after an extended shutdown, follow the prestart-up and start-up instructions.
Water Piping Checkout
1. Check the pump operation and vent all air from the system.
2. Circulate evaporator water checking for proper system pressure and pressure drop across the
chiller barrel. Compare the pressure drop to the evaporator water pressure drop curve.
3. Clean all water strainers before placing the unit into service.
Refrigerant Piping Checkout
1. Check all exposed brazed joints on the unit, as well as any field-installed piping, for evidence of
leaks. Joints can have been damaged during shipping or when the unit was installed.
2. Check that all refrigerant valves are either opened or closed as required for proper operation of
the unit.
3. A thorough leak test must be done using an approved electronic leak detector. Check all valve
stem packing for leaks. Replace all refrigerant valve caps and tighten.
4. Check all refrigerant lines to see that they will not vibrate against each other or against other unit
components and are properly supported.
5. Check all flare connections and all refrigerant threaded connectors.
6. Look for any signs of refrigerant leaks around the condenser coils and for damage during
shipping or installation.
7. Leak detector is applied externally to refrigerant joints at the factory. Do not confuse this residue
with an oil leak.
8. Connect refrigerant service gauges to each refrigerant circuit before starting unit.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 61
Page 62
Electrical Check Out
CAUTION
Electrical power must be applied to the compressor crankcase heaters
24 hours before starting unit to drive off refrigerant from the
oil or compressor damage can occur.
1. Open all electrical disconnects and check all power wiring connections. Start at the power block
and check all connections through all components to and including the compressor terminals.
These should be checked again after 3 months of operation and at least annually thereafter.
2. Check all control wiring by pulling on the wire at the spade connections and tighten all screw
connections. Check plug-in relays for proper seating and that retaining clips are installed.
3. Put System Switch (S1) to the Emergency Stop position.
4. Put both circuit #1 & #2 switches to the Pumpdown and Stop position.
5. Apply power to the unit. The panel Alarm Light will stay on until S1 is closed. Ignore the
Alarm Light for the checkout period. If you have the optional Alarm Bell, you can disconnect it.
6. Check at the power block or disconnect for the proper voltage and for the proper voltage
between phases. Check power for proper phasing using a phase sequence meter before starting
unit.
7. Check for 120Vac at the control transformer and at TB-2 terminal #1 and the neutral block (NB).
8. Check between TB-2 terminal #7 and NB for 120Vac supply for transformer #2.
9. Check between TB-2 terminal #2 and NB for 120Vac control voltage. This supplies the
compressor crank case heaters.
10. Check between TB-3 terminal #17 and #27 for 24Vac control voltage.
Operation
Hot Gas Bypass (Optional)
This option allows the system to operate at lower loads without excessive on/off compressor cycling.
The hot gas bypass option is required to be on both refrigerant circuits because of the lead / lag
feature of the controller.
This option allows passage of discharge gas into the evaporator inlet (between the TX valve and the
evaporator) which generates a false load to supplement the actual chilled water or air handler load.
Note: The hot gas bypass valve cannot generate a 100% false load.
The valve that is supplied can provide a load of approximately 10 tons. The system load added to the
ten tons of the hot gas bypass valve has to exceed the compressor capacity for stage 1 compressors to
produce stable system operation. This requires 3-6 tons of system load.
The MicroTech II controls solenoid valves in the hot gas bypass lines that are energized whenever
their circuit is operating with only one compressor running. The hot gas valve is regulated by the
evaporator pressure and the remote adjustable bulb. The pressure regulating valve is factory set to
begin opening at 58 psig (32°F for R-22).
WARNING
The hot gas line can become hot enough to cause injury.
Be careful during valve checkout.
62 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 63
VFD Low Ambient Control (Optional)
The optional VFD fan control is used for unit operation below 35°F (2°C) down to a minimum of
0°F (-17°C). The control looks at the saturated discharge temperature and varies the fan speed to
hold the temperature (pressure) at the “target” temperature. This temperature is established as an
input to a setpoint screen labeled “Sat Condenser Temp Target”.
Filter-Driers (AGZ-BM)
A full flow filter-drier (AGZ 026 – 070) or a replaceable core type filter-drier (AGZ 075 – 130) for
each refrigerant circuit is shipped loose for field mounting. The core assembly of the replaceable
core drier consists of a filter core held tightly in the shell to allow full flow without bypass.
Pressure drop across the filter-drier at full load conditions must not exceed 10 psig at full load. See
Table 38 for pressure drop at other load points. Replace the filter-drier if the pressure drop exceeds
maximum.
WARNING
Pump out refrigerant before removing end flange for replacement of core(s).
Lowering refrigerant pressure will help prevent accidental blow-off of cover
causing possible bodily injury. EPA recovery regulations apply to this procedure.
A condenser liquid line service valve is provided for isolating the charge in the condenser, but also
serves as the point from which the liquid line can be pumped out. With the line free of refrigerant,
the filter-drier core(s) can be easily replaced.
System Adjustment
To maintain peak performance at full load operation, the system superheat and liquid subcooling can
require adjustment. Read the following subsections closely to determine if adjustment is required.
Liquid Line Sight Glass and Moisture Indicator
The color of the moisture indicator is an indication of the dryness of the system and is extremely
important when the system has been serviced. Immediately after the system has been opened for
service, the element can indicate a wet condition. It is recommended that the equipment operate for
about 12 hours to allow the system to reach equilibrium before deciding if the system requires a
change of drier cores.
Bubbles in the sight glass at constant full load indicates a shortage of refrigerant, a plugged filterdrier, or a restriction in the liquid line. However, it is not unusual to see bubbles in the sight glass
during changing load conditions.
Refrigerant Charging
Liquid line subcooling at the liquid shut-off valve should be between 15 and 20 degrees F at full
load. If the unit is at steady full load operation and bubbles are visible in the sight glass, then check
liquid subcooling.
Thermostatic Expansion Valve
The expansion valve performs one specific function. It keeps the evaporator supplied with the
proper amount of refrigerant to satisfy the load conditions.
The sensing bulb of the expansion valve is installed in the closest straight run of suction line from
the evaporator. The bulb is held on by clamps around the suction line and is insulated to reduce the
effect of surrounding ambient temperatures. In case the bulb must be removed, simply slit the
insulation on each side of the bulb, remove the clamps and then remove the capillary tubing that runs
along the suction line from the valve.
The power element is removable from the valve body without removing the valve from the line.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 63
Page 64
NOTE: Before adjusting superheat, check that unit charge is correct and liquid line sight
glass is full with no bubbles and that the circuit is operating under stable, full load
conditions.
The suction superheat for the suction leaving the evaporator is set at the factory for 8 to 12 degrees F
at full load. To have full rated unit performance, the superheat must be about 8 degrees F at 95°F
outdoor ambient temperature.
Crankcase Heaters
The scroll compressors are equipped with externally mounted band heaters located at the oil sump
level. The function of the heater is to keep the temperature in the crankcase high enough to prevent
refrigerant from migrating to the crankcase and condensing in the oil during off-cycle.
NOTE: Power must be supplied to the heaters 24 hours before starting the compressors.
Evaporator
Models AGZ 026 through 070
The evaporator is a compact, high efficiency, dual circuit, brazed plate-to-plate type heat exchanger
consisting of parallel stainless steel plates.
The evaporator is protected with an electric resistance heater and insulated with 3/4" (19mm) thick
closed-cell polyurethane insulation. This provides freeze protection down to -20°F (-29°C) ambient
air temperature.
The water side working pressure is 363 psig (2503 kPa). Evaporators are designed and constructed
according to, and listed by, Underwriters Laboratories (UL).
Models AGZ 075 through 130
The evaporator is direct expansion, shell-and-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 evaporator has a carbon steel shell and seamless high efficiency copper tubes, roller expanded
into a carbon steel tube sheet.
3/8" (10mm) vent and drain plugs are provided on the top and bottom of the shell.
The evaporator is wrapped with an electric resistance heater cable and insulated with 3/4" (19mm)
thick vinyl nitrate polymer sheet insulation, protecting against water freeze-up at ambient air
temperatures to -20°F (-29°C). An ambient air thermostat controls the heater cable. The fitted and
glued-in-place insulation has a K factor of 0.28 Btu in/hr ft
The refrigerant (tube) side maximum working pressure is 300 psig (2068 kPa). 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.
2
at 75°F.
64 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 65
Unit Maintenance
General
On initial start-up and periodically during operation, it will be necessary to perform certain routine
service checks. Among these are checking the liquid line sight glasses, taking condensing and
suction pressure readings, and checking to see that the unit has normal superheat and subcooling
readings. A recommended maintenance schedule is located at the end of this section.
Compressor Maintenance
The scroll compressors are fully hermetic and require no maintenance.
Lubrication
No routine lubrication is required on AGZ units. The fan motor bearings are permanently lubricated
and no further lubrication is required. Excessive fan motor bearing noise is an indication of a
potential bearing failure.
Compressor oil should be standard refrigeration mineral oil such as Suniso 3GS.
Electrical Terminals
Electric shock hazard. Disconnect all power before continuing with following
DANGER
service.
Condensers
The condensers are air-cooled and constructed of 3/8" (9.5mm) O.D. internally finned copper tubes,
bonded in a staggered pattern into louvered aluminum fins. Maintenance consists of routine removal
of dirt and debris from the outside surface of the fins. McQuay recommends the use of foaming coil
cleaners available at most air conditioning supply outlets. Use caution when applying such cleaners
as they can contain potentially harmful chemicals. Care should be taken not to damage the fins
during cleaning. The coils should be thoroughly rinsed to remove any cleaner residue.
If the service technician determines that the refrigerant circuit contains noncondensables, recovery
can be required, strictly following Clean Air Act regulations governing refrigerant discharge to the
atmosphere. The Schrader purge valves are located on the vertical coil headers on both sides of the
unit, at the end opposite from the control box. Decorative panels cover the coil headers and must be
removed for servicing. Recover with the unit off, after a shutdown of 15 minutes or longer, to allow
air to collect at the top of the coil. Restart and run the unit for a brief period. If necessary, shut unit
off and repeat the procedure. Follow accepted environmentally sound practices when removing
refrigerant from the unit.
Refrigerant Sight Glass
The refrigerant sight glasses should be observed periodically. (A weekly observation should be
adequate.) A clear glass of liquid indicates that there is normal subcooled refrigerant in the system.
Bubbling refrigerant in the sight glass, during stable run conditions, indicates that the system can be
short of refrigerant charge. Refrigerant gas flashing in the sight glass could also indicate an
excessive pressure drop in the liquid line, possibly due to a clogged filter-drier or a restriction
elsewhere in the liquid line. See
low, add charge to clear the sight glass. If subcooling is normal (15 to 20 degrees F) and flashing is
visible in the sight glass, check the pressure drop across the filter-drier. Subcooling should be
checked at full load with at least 70°F (21.1°C) outdoor air temperature, stable conditions, and all
fans running.
Table 38 for maximum allowable pressure drops. If subcooling is
IMM ACZ/AGZ-4 ACZ / AGZ-BM 65
Page 66
An element inside the sight glass indicates the moisture condition corresponding to a given element
color. If the sight glass does not indicate a dry condition after about 12 hours of operation, the
circuit should be pumped down and the filter-drier changed; or verify system condition by
performing an acid test on the compressor oil.
Preventive Maintenance Schedule
OPERATION WEEKLY
General
Complete unit log and review (Note 3) X
Visually inspect unit for loose or damaged components X
Inspect thermal insulation for integrity X
Clean and paint as required X
Electrical
Check terminals for tightness, tighten as necessary X
Clean control panel interior X
Visually inspect components for signs of overheating X
Verify compressor heater operation X
Test and calibrate equipment protection and operating controls X
Megger compressor motor * X
Refrigeration
Leak test X
Check sight glasses for clear flow X
Check filter-drier pressure drop (see manual for spec) X
Perform compressor vibration test X
Acid test oil sample X
Condenser (air-cooled)
Clean condenser coils (Note 4) X
Check fan blades for tightness on shaft (Note 5) X
Check fans for loose rivets and cracks X
Check coil fins for damage X
MONTHLY
(Note 1)
Notes:
1. Monthly operations include all weekly operations.
2. Annual (or spring start-up) operations includes all weekly and monthly operations.
3. Log readings can be taken daily for a higher level of unit observation.
4. Coil cleaning can be required more frequently in areas with a high level of airborne particles.
5. Be sure fan motors are electrically locked out.
* Never Megger motors while they are in a vacuum.
ANNUAL
(Note 2)
66 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 67
Service
Service on this equipment is to be performed by qualified refrigeration personnel
familiar with equipment operation, maintenance, correct servicing procedures, and
Anyone servicing this equipment shall comply with the requirements set forth by
Filter-Driers
A replacement of the filter-drier is recommended any time excessive pressure drop is read across the
filter-drier and/or when bubbles occur in the sight glass with normal subcooling. The maximum
recommended pressure drop across the filter-drier is as follows:
Table 38, Filter-Drier Pressure Drop
PERCENT CIRCUIT
CAUTION
the safety hazards inherent in this work. Causes for repeated tripping of
equipment protection controls must be investigated and corrected.
Disconnect all power before doing any service inside the unit.
the EPA in regards to refrigerant reclamation and venting.
LOADING (%)
100% 10 (69)
75% 8 (55.2)
50% 5 (34.5)
25% 4 (27.6)
MAXIMUM RECOMMENDED PRESSURE
DROP ACROSS FILTER-DRIER PSIG (KPA)
The filter-drier should also be changed if the moisture indicating liquid line sight glass shows excess
moisture in the system.
During the first few months of operation, filter-drier replacement can be necessary if the pressure
drop across the filter-drier exceeds the values listed in the paragraph above. Any residual particles
from the condenser tubing, compressor and miscellaneous components are swept by the refrigerant
into the liquid line and are caught by the filter-drier.
Liquid Line Solenoid Valve
The liquid line solenoid valves that shut off refrigerant flow in the event of a power failure do not
normally require any maintenance. The solenoids can, however, require replacement of the solenoid
coil or of the entire valve assembly.
The solenoid coil can be checked to see that the stem is magnetized when energized by touching a
screwdriver to the top of the stem. If there is no magnetization, either the coil is bad or there is no
power to the coil.
The solenoid coil can be removed from the valve body without opening the refrigerant piping after
pumpdown. Shut off and lock-out the unit power.
The coil can then be removed from the valve body by simply removing a nut or snap-ring located at
the top of the coil. The coil can then be slipped off its mounting stud for replacement.
To replace the entire solenoid valve follow the steps involved when changing a filter-drier.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 67
Page 68
Remote Evaporator (AGZ-BM Only)
The evaporator is the direct expansion, shell-and-tube type with refrigerant flowing through the tubes
and water flowing through the shell over the tubes. The tubes are internally finned to provide
extended surface as well as turbulent flow of refrigeration through the tubes. Models AGZ 070BM
or smaller have a stainless steel brazed-plate type evaporator. Other than cleaning and testing, no
service work should be required on the evaporator.
Refrigerant Charging
Units are shipped with a holding charge of refrigerant and the system must be charged at the job site.
Follow these recommendations when field charging. Refer to the unit operating charge found in the
Physical Data Tables.
Unit charging can be done at any steady load condition (preferably at 75 to 100% load), and at any
outdoor temperature (preferably higher than 70°F (21.1°C). Unit must be allowed to run 5 minutes
or longer so that the condenser fan staging is stabilized at normal operating discharge pressure. For
best results charge with two or more condenser fans operating on each refrigerant circuit.
The ACZ/AGZ units have a condenser coil design with approximately 15% of the coil tubes located
in a subcooler section of the coil. This results in liquid cooling to within 5°F (3°C) of the outdoor air
temperature when all condenser fans are operating. This is equal to about 15°F-20°F (8.3°C-11.1°C)
subcooling below the saturated condensing temperature when the pressure is read at the liquid valve
between the condenser coil and the liquid line filter-drier. Once the subcooler is filled, extra charge
will not lower the liquid temperature and does not help system capacity or efficiency.
One of the following three scenarios will be experienced with an undercharged unit:
1. If the unit is slightly undercharged, the unit will show bubbles in the sight glass. Recharge the
unit as described in the charging procedure below.
2. .If the unit is moderately undercharged, it will normally trip on freeze protection. Recharge the
unit as described in the charging procedure below. However, freezestat trips can also be an
indication of low flow or poor heat transfer in the system evaporator.
3. If the unit is severely undercharged, the unit will trip due to lack of liquid flow to the expansion
valve. In this case, either remove the remaining charge by means of a proper reclamation system
and recharge the unit with the proper amount of refrigerant as stamped on the unit nameplate, or
add refrigerant through the suction valve on the compressor. If the unit is severely undercharged,
the unit can nuisance trip during this charging procedure. If this happens, operate the unit at
minimum load, adding charge until the sight glass is clear. Once the unit has enough charge so
that it does not trip out, continue with step 2 of the charging procedure below.
Procedure to charge a moderately undercharged ACZ/AGZ unit:
1. If a unit is low on refrigerant, you must first determine the cause before attempting to recharge
the unit. Locate and repair any refrigerant leak. Evidence of oil is a good indicator of leakage,
however, oil can not be visible at all leaks. Liquid leak detector fluids work well to show
bubbles at medium sized leaks, but electronic leak detectors can be needed to locate small leaks.
2. Add the charge to the system through the suction shutoff valve or through the Schrader fitting on
the tube entering the evaporator between the compressor and the evaporator head.
3. The charge can be added at any load condition between 25-100% load per circuit but at least two
fans should be operating per refrigerant circuit if possible. The suction superheat should be in
the 8 to 12 degree F (4.4°C - 6.6°C) range.
4. Add sufficient charge to clear the liquid line sight glass and until all flashing stops in the sight
glass.
68 ACZ / AGZ-BM IMM ACZ/AGZ-4
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5. Check the unit subcooling value by reading the liquid line pressure and temperature at the liquid
line near the filter-drier. The subcooling values should be between 15 and 20 degrees F (8.3 and
11.1 degrees C).
6. With outdoor temperatures above 60°F (15.6°C) all condenser fans should be operating and the
liquid line temperature should be within 5°F-10°F (2.8°C-5.6°C) of the outdoor air temperature.
At 25-50% load the liquid line temperature should be within 5°F (2.8°C) of outdoor air
temperature with all fans on. At 75-100% load the liquid line temperature should be within 10°F
(5.6°C) of outdoor air temperature with all fans on.
7. Overcharging of refrigerant will raise the compressor discharge pressure due to filling of the
condenser tubes with excess refrigerant.
W arranty Statement
Limited Warranty
Consult your local McQuay Representative for warranty details. Refer to Form 933-43285Y. To find
your local McQuay Representative, go to www.mcquay.com.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 69
Page 70
ACZ/AGZ Troubleshooting Chart
PROBLEM POSSIBLE CAUSES POSSIBLE CORRECTIVE STEPS
1. Main Switch. 1. Close Switch.
2. Fuse Blown. Circuit breakers open 2. Check electrical circuits and motor windings
3. Thermal overloads tripped 3. Overloads are auto-reset Check unit closely
Compressor
Will Not Run
Compressor
Noisy Or
Vibrating
High Discharge
Pressure
Low Discharge
Pressure
High Suction
Pressure
Low Suction
Pressure
Continued next page.
4. Defective contactor or coil. 4. Repair or replace
5. System Shutdown by equipment protection
devices
6. No cooling required 6. None. Wait until unit class for cooling
7. Liquid line solenoid will not open 7. Repair or replace solenoid coil. Check wiring
8. Motor electrical trouble 8. Check motor for opens, shorts, or burnout
9. Loose wiring 9. Check all wire junctions. Tighten all terminal
1. Low or no refrigerant charge
2. Compressor running in reverse
3. Improper piping support on suction or
discharge
4. Worn compressor isolator bushing
5. Worn Compressor
1. Noncondensables in system 1. Extract the noncondensables with approved
2. System overcharged with refrigerant 2. Remove excess, check liquid subcooling
3. Optional discharge shutoff valve partially
closed
4. FanTrol wiring not correct 4. Check FanTrol wiring
5. Fan not running 5. Check electrical circuit, Check fan motor
6. Dirty condenser coil
7. Air recirculation
1. Refrigerant flood back 1. Correct
2. Wind blowing into coil at low ambient 2. Shield coil from direct wind
3. Faulty condenser temperature regulation 3. Check condenser control operation
4. Insufficient refrigerant in system
5. Low suction pressure
6. Only one compressor operating 6. See corrective steps for Compressor Will Not
1. Excessive water temperature 1. Check control settings
2. Excessive load 2. Reduce load or add additional equipment
4. Compressors running in reverse 4. Check for proper phasing
1. Rapid load swings 1. Stabilize load
2. Lack of refrigerant 2. Check for leaks, repair, add charge. Check
3. Clogged liquid line filter-drier 3. Check pressure drop across filter-drier.
4. Expansion valve malfunctioning 4. Check and reset for proper superheat
5. Condensing temperature to low 5. Check means for regulating condenser
6. Compressor will not unload 6. See corrective steps for Compressor Staging
7. Insufficient water flow 7. Adjust flow
8. Evaporator head ring gasket slippage 8. Take pressure drop across vessel and
9. Evaporator dirty
10. Rapid load swings
for shorts or grounds. Investigate for
possible overloading. Replace fuse or reset
breakers after fault is corrected. Check for
loose or corroded connections.
when unit comes back on line. Allow time for
auto-reset.
5. Determine type and cause of shutdown and
correct it before resetting equipment
protection switch
screws
1. Repair and recharge
2. Check unit and compressor for correct
phasing
3. Relocate, add, or remove hangers
4. Replace
5. Replace
procedures
3. Open valve
6. Clean coil
7. Correct
4. Check for leaks. Repair and add charge
5. See corrective steps for Low Suction
Pressure
Stage Up
liquid sight glass
Replace
temperature
Intervals Too Low
contact factory to obtain design pressure
drop for that vessel
9. Clean chemically
10. Stabilize load
70 ACZ / AGZ-BM IMM ACZ/AGZ-4
Page 71
PROBLEM POSSIBLE CAUSES POSSIBLE CORRECTIVE STEPS
Compressor
Will Not Stage
Up
Compressor
Staging
Intervals Too
Short
Compressor Oil
Level Too High
Or Too Low
Compressor
Loses Oil
Motor Overload
Relays Or
Circuit Breakers
Open
Compressor
Thermal
Protection
Switch Open
1. Defective capacity control 1. Replace
2. Faulty thermostat stage or broken wire 2. Replace
3. Stages not set for application 3. Reset thermostat setting for application
1. Thermostat control band not set properly 1. Set control band wider
2. Erratic water thermostat 2. Replace
3. Insufficient water flow
4. Rapid load swings
1. Oil hang-up in piping 1. Review refrigerant piping and correct
2. Low oil level 2. Check and add oil
3. Loose fitting on oil line 3. Check and tighten system
4. Level too high 4. Adjust thermal expansion valve
5. Insufficient water flow - Level too high 5. Adjust flow
6. Excessive liquid in crankcase - Level too high
7. Short cycling
1. Lack of refrigerant 1. Check for leaks and repair. Add refrigerant
2. Excessive compression ring blow-by 2. Replace compressor
4. Voltage range or imbalance 4. Check and correct
5. High superheat
6. Compressor bearing failure
3. Adjust flow
4. Stabilize load
6. Check crankcase heater. Reset expansion
valve for higher superheat. Check liquid line
solenoid valve operation.
7. Stabilize load or increase staging interval
3. Check all connections and tighten
4. See corrective steps for High Discharge
Pressure
5. Check supply voltage. Notify power
company. Do not start until fault is corrected.
1. Add facilities so conditions are within
allowable limits
2. Open valve
5. Adjust to correct superheat
6. Replace compressor
IMM ACZ/AGZ-4 ACZ / AGZ-BM 71
Page 72
72ACZ / AGZ-BM IMM ACZ/AGZ-4
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IMM ACZ/AGZ-4 ACZ / AGZ-BM 73
Page 74
This document contains the most current product information as of this printing. For the most up-todate product information, please go to www.mcquay.com. All McQuay equipment is sold pursuant to
McQuay’s Standard Terms and Condition of Sale and Limited Product Warranty.
(800) 432-1342 • www.mcquay.com
IMM ACZ/AGZ-4 (07/07)
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