McQuay ACZ 010A Installation Manual
Installation, Operation and Maintenance Manual
IOMM ACZ1-3
Air-Cooled Scroll Condensing Units
ACZ 010A – ACZ 039A
10 to 43 Tons, 35 to 150 kW
R-22, R-407C
60 Hertz
Software Version: ACZSU0102B
Group: Chiller
Part Number: 331373901
Effective: December 2005
Supersedes: IOMM ACZ1-2
Table of Contents
Vintage
Nominal Tons
Introduction ....................................... 3
General Description ......................................... 3
Inspection......................................................... 3
Installation ....................................................... 3
Handling .......................................................... 3
Location ........................................................... 4
Service Access ................................................. 4
Vibration Isolators............................................ 6
Chilled Water System....................................... 7
Refrigerant Piping............................................ 9
Unit Component Location.............................. 13
Control Layout and Operation ...... 13
Control Center................................................ 13
R-407C Units.................................... 14
Start-up and Shutdown................... 16
Pre Start-up .................................................... 16
Start-up .......................................................... 16
Sequence of Operation ................................... 16
Physical Data.................................... 18
R-22 ............................................................... 18
R-407C........................................................... 20
Electrical Data ................................. 21
Field Wiring................................................... 21
R-22 ............................................................... 21
Dimensional Data ............................ 29
System Maintenance........................ 30
General........................................................... 30
Lubrication..................................................... 30
Electrical Terminals ....................................... 30
Condensers..................................................... 30
Refrigerant Sight glass................................... 30
Standard MicroTech II Controller. 31
Table of Contents........................................... 31
Overview........................................................ 32
General Description ....................................... 32
Automatic Adjusted Limits ............................ 34
Dynamic Default Values ................................ 35
Control Functions and Definitions ................. 36
Unit Enable .................................................... 37
Unit Mode...................................................... 38
Power Up Start Delay .................................... 38
Unit State ....................................................... 38
Evaporator Fan State Control......................... 39
Condenser Fans.............................................. 39
Low OAT Start............................................... 40
Capacity Overrides ........................................ 40
Low Ambient Lockout ................................... 41
Compressor Control....................................... 41
Normal Shutdown .......................................... 42
Rapid Shutdown............................................. 42
Liquid Line Solenoid ..................................... 42
Using the Controller....................................... 43
Service .............................................. 54
Thermostatic Expansion Valve....................... 54
Filter-Driers ................................................... 54
Liquid Line Solenoid ..................................... 54
Optional Controls........................................... 55
Troubleshooting Chart ................................... 57
MODEL CODE
A C Z XXX A
Scroll Compressor
2 ACZ 010A through 039A IOMM ACZ1-3
Air-Cooled
Condensing
"McQuay" is a registered trademark of McQuay International
Illustrations and data cover the McQuay International products at the time of publication
and we reserve the right to make changes in design and construction at anytime without notice.
2005 McQuay International
Introduction
General Description
McQuay air-cooled condensing units are complete, self-contained automatic refrigerating units.
Every unit is completely assembled, factory wired, and tested. Each unit consists of an air-cooled
condenser, Copeland Compliant Scroll hermetic compressor, and internal refrigerant piping,
ready to be piped to a field supplied low side.
The electrical control center includes all equipment protection and operating controls necessary
for automatic operation except for the staging control for the steps of capacity in the unit.
Condenser fan motors are three-phase (except single-phase on No.1 fan with SpeedTrol option)
and started by their own contactors with inherent overload protection. The compressor has solidstate motor protection for inherent thermal overload protection except Models ACZ 010 and 013
that have internal line breakage.
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 to be sure it agrees with the power supply available. Units are shipped FOB factory
and McQuay is not responsible for physical damage after the unit leaves the factory.
Note: Unit shipping and operating weights are listed on pages 18 and 19.
Installation
Note: Installation is to be performed by qualified personnel who are familiar with local
codes and regulations, especially concerning refrigerant release to the atmosphere.
WARNING
Sharp edges and coil surfaces can cause personal injury.
Wear protective gear and avoid contact with them.
Handling
Be careful to avoid rough handling of the unit. Do not push or pull the unit from anything other
than the base. Block the pushing vehicle away from the unit to prevent damage to the sheet-metal
cabinet and end frame (see Figure 1).
To lift the unit, lifting slots are provided in the base of the unit. Arrange spreader bars and cables
to prevent damage to the condenser coils or cabinet (see Figure 2).
IOMM ACZ1-3 ACZ 010A through 039A 3
Figure 1, Suggested Pushing Arrangement
BLOCKING REQUIRED
ACROSS FULL WIDTH
SPREADER BAR (2)
PIPE SLUNG THRU
OPENINGS IN LEGS (2)
Figure 2, Suggested Lifting Arrangement
NOTE:: The fork lift slots can be used for
lifting by inserting sufficiently strong pipe
through them as shown in Figure 2.
The slots are centered around the unit enter-ofgravity.
Location
Unit Placement
ACZ units are for outdoor applications and can be mounted on a roof or at ground level. Set units
on a solid and level foundation. For roof-mounted applications, install the unit on a steel channel
or I-beam frame to support the unit above the roof. For ground level applications, install the unit
on a substantial base that will not settle. A one-piece concrete slab with footings extended below
the frost line is recommended. Be sure the foundation is level (within 1/2” [13 mm] over its
length and width). The foundation must support the operating weights listed in the Physical Data
Tables on pages 18 and 19.
Since its operation is affected by wind, the unit should be located so that its length is parallel with
the prevailing wind. If this is not practical, field fabricated wind deflectors may be required.
Service Access
Each end of the unit must be accessible after installation for periodic service. Compressors, filterdriers, and liquid line solenoid valve are accessible from the end of the unit. Motor protector
controls are on the compressor. Most operating, equipment protection, and starting controls are
located in the unit control box.
The fan deck with the condenser fans and motors can be removed from the top of the unit.
4 ACZ 010A through 039A IOMM ACZ1-3
Clearances
4 Ft.
Clearance for Air Inlet
Clearance for Air Inlet
The recommended minimum side clearance between two units
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
unit is 6 feet (1828mm) when installed in a pit. The pit cannot
The flow of air to and from the
condenser coil must not be limited.
Restricting airflow or allowing air
recirculation will result in a decrease
in unit performance and efficiency.
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 on the fan outlet.
Figure 3, Clearance requirements
4 Ft. (1220mm)
(1220mm)
Clearance for
Service Access
4 Ft. (1220mm)
4 Ft.
(1220mm)
Clearance for
Service Access
Install the unit with enough side
clearance for air entrance to the coil
and for servicing. Provide service
access to the compressors, electrical
control panel and piping components as
shown in Figure 3. Do not block
access to the unit with piping or
conduit.
Do not allow debris to accumulate near
the unit. Air movement can draw
debris into the condenser coil causing
air starvation. Give special
consideration to low ambient operation
where snow can accumulate. Keep
condenser coils and fan discharge free
of snow or other obstructions to permit
adequate airflow.
Sound Isolation
The low sound levels of the ACZ units
are suitable for most applications.
When additional sound reduction is
necessary, locate the unit away from
sound sensitive areas. Avoid locations
beneath windows or between structures
where normal-operating sounds may be
objectionable. Reduce structurally
transmitted sound by isolating
electrical conduit and the unit itself.
Use wall sleeves and rubber isolated
refrigerant piping hangers to reduce
transmission of noise into occupied
spaces. Use flexible electrical conduit
to isolate sound through electrical
conduit. Spring isolators are effective
in reducing the low amplitude sound
generated by the compressors and for
unit isolation in sound-sensitive areas.
is 8 feet (2440mm).
is provided. The minimum clearance on each side of the
be deeper than the unit.
The minimum clearance to a side wall or building taller than
the unit height is 6 feet (1828mm) provided no solid wall
above 6 feet (1828mm) tall is closer than 12 feet (3658mm)
to the opposite side of the unit.
IOMM ACZ1-3 ACZ 010A through 039A 5
Vibration Isolators
Vibration isolators are recommended for all roof-mounted installations or wherever vibration
transmission is a consideration.
The unit should be initially on shims or blocks at the listed free height. When all piping, wiring,
flushing, charging, etc. is completed, the springs are adjusted upward to loosen the blocks or
shims that are then removed.
A rubber anti-skid pad is part of the isolator. Installation of spring isolators requires flexible
piping connections and at least three feet of flexible conduit to avoid straining the piping and
transmitting vibration and noise. These units cannot be bolted to isolators.
Table 1, Recommended Vibration Isolators
Neoprene-in-Shear
Model RF LF RB LB
010, 013,016,020,025,028 RP-3 Red RP-3 Red RP-3 Black RP-3 Black 350014859
033, 039 RP-3 Green RP-3 Green RP-3 Red RP-3 Red 350014857
Spring
Model RF LF RB LB
010, 013 CP 1-24 Brown CP 1-24 Brown CP 1-24 Brown CP 1-24 Brown 35 00 14831
016, 020 CP 1-25 Red CP 1-25 Red CP 1-24 Brown CP 1-24 Brown 3 50014830
025, 028 CP1-26 Purple CP1 -2 6 Purple CP 1-24 Brown CP 1 -24 Brown 350014829
033 CP1-27 Orange CP1 -26 Purple CP 1- 24 Brown CP 1-24 Brown 350014836
039 CP1-27 Orange CP1-27 Orange CP 1-24 Brown CP 1-24 B ro wn 350014828
Note
: See dimension drawing for location of isolators
Kit P/N
Kit P/N
Corner Operating Weights
ACZ
Unit
Model
010 259 257 243 241 1000
013 259 257 243 241 1000
016 353 360 251 256 1220
020 377 383 288 292 1340
025 498 505 232 235 1470
028 508 515 232 235 1490
033 605 567 304 284 1760
039 712 649 313 286 1960
RF LF RB LB Total
RP-3, Neoprene-in Shear Isolator CP-1, Spring Isolator
R BI
L BI
R FI
Control
Panel
L FI
6 ACZ 010A through 039A IOMM ACZ1-3
Chilled Water System
Air
Flow
Switch
Vibration
Eliminators
Drain
Isolation
Strainer
Water Piping (Applicable when the Unit is Field Connected to a Water Type
Evaporator)
Local authorities can supply the installer with the proper building and safety codes required for
proper installation.
Install piping with minimum bends and changes in elevation to minimize pressure drop. Consider
the following when installing water piping:
1. Vibration eliminators to reduce vibration and noise transmission to the building.
2. Shutoff valves 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. Install drains at the
lowest points in the system.
4. A means of maintaining adequate system water pressure (expansion tank or regulating valve).
5. Temperature and pressure indicators located at the unit to aid in unit servicing. Pressure
gauge taps must be installed in the chilled water inlet and outlet piping or as shown in Figure
4.
6. A strainer or other means of removing foreign matter from the water before it enters the pump.
Place the strainer far enough upstream to prevent cavitation at the pump inlet (consult pump
manufacturer for recommendations). The use of a strainer will help prolong pump life and
keep system performance up.
7. A 40-mesh strainer is required in the water line just before the inlet of the evaporator. This
will help prevent foreign material from entering and decreasing the performance of the
evaporator.
8. If the unit is used as a replacement chiller on a previously existing piping system, flush the
system thoroughly before unit installation. Regular water analysis and chemical water
treatment on the evaporator is recommended immediately at equipment start-up.
9. 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. Reset the freezestat and low
leaving water alarm temperatures. The freezestat is factory set to default at 38°F (3.3°C).
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.
10. Perform a preliminary leak check before insulating the piping and filling the system.
11. Piping insulation should include a vapor barrier to prevent condensation and possible damage
to the building structure.
Figure 4, Typical Field Evaporator Water Piping
Vent
Inlet
P
Outlet
Valves
IOMM ACZ1-3 ACZ 010A through 039A 7
System Volume
It is important to have adequate water volume in the system to provide an opportunity for the
chiller to sense a load change, adjust to the change and stabilize. As the expected load change
becomes more rapid, a greater water volume is needed. The system water volume is the total
amount of water in the evaporator, air handling products and associated piping. If the water
volume is too low, operational problems can occur, including rapid compressor cycling, rapid
loading and unloading of compressors, erratic refrigerant flow in the chiller, improper motor
cooling, shortened equipment life and other undesirable occurrences.
For normal comfort cooling applications, where the cooling load changes relatively slowly, we
recommend a minimum system volume of five minutes times the flow rate (gpm). For example, if
the design chiller flow rate is 50 gpm, we recommend a minimum system volume of 250 gallons
(50 gpm x 5 minutes).
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.
Variable Chilled Water flow
Variable chilled water flow systems are not recommended for this class of equipment due to
limited unloading capability.
Flow Switch
Mount a water flow switch in the
leaving water line to shut down the unit
when water flow is interrupted.
Figure 5, Flow Switch Installation
A flow switch is available from
McQuay (part number 017503300). It
is a “paddle” type switch and adaptable
to pipe sizes down to 1 1/4” (32mm)
nominal. Certain minimum flow rates
are required to close the switch and are
listed in Table 2. Install the switch as
shown in Figure 5. Connect the
normally open contacts of the flow
switch in the unit control center at
terminals 4 and 5. 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. Follow installation instructions provided
with the flow switch. Calibrate the flow switch to open at one-half of nominal flow rate.
Differential pressure switches are not recommended for outdoor installation.
They are subject to freezing-up at low ambient temperatures.
CAUTION
:
8 ACZ 010A through 039A IOMM ACZ1-3
Table 2, Flow Switch Settings
(NOTE !)
Min.
Adjst.
Max.
Adjst.
NOTES:
1. A segmented 3-inch paddle (1, 2, and 3 inches) is furnished mounted, plus a 6-inch paddle loose.
2. Flow rates for a 2-inch paddle trimmed to fit the pipe.
3. Flow rates for a 3-inch paddle trimmed to fit the pipe.
4. Flow rates for a 3-inch paddle.
5. Flow rates for a 6-inch paddle
Flow
Flow Lpm 0.8 1.1 2.2 2.8 4.3 11.4 22.9 35.9 38.6
Flow
Flow Lpm 2.8 4.1 6.1 7.3 11.4 27.7 53.4 81.8 90.8
inch 1 1/4 1 1/2 2 2 1/2 3 4 5 6 8 Pipe Size
mm 32 (2) 38 (2) 51 63 (3) 76 102 (4) 127 (4) 153 (4) 204 (5)
gpm 5.8 7.5 13.7 18.0 27.5 65.0 125.0 190.0 205.0
Lpm 1.3 1.7 3.1 4.1 6.2 14.8 28.4 43.2 46.6
gpm 3.7 5.0 9.5 12.5 19.0 50.0 101.0 158.0 170.0
No
gpm 13.3 19.2 29.0 34.5 53.0 128.0 245.0 375.0 415.0
Lpm 3.0 4.4 6.6 7.8 12.0 29.1 55.6 85.2 94.3
gpm 12.5 18.0 27.0 32.0 50.0 122.0 235.0 360.0 400.0
No
Refrigerant Piping
Introduction
NOTE: All field piping, wiring, and procedures must be performed in accordance with ASHRAE,
EPA, and industry standards. Proper refrigerant piping can represent the difference between a
reliable, trouble free system and months or years of inefficient, problematic performance.
System concerns related to piping are:
1. Refrigerant pressure drop
2. Solid liquid feed to the expansion valve(s)
3. Continuous oil return
The most important and least understood is number 3. “Continuous oil return”. The failure of oil
to return at or close to the rate of displacement from the compressor can result in oil trapping and
ultimate compressor failure.
On the other hand, the instantaneous return of a large volume of compressor oil (slug) can be
equally damaging to a compressor.
All compressors displace some oil during operation. Oil is carried into the compressor with
suction gas; and that same gas entrains oil present on the compressor walls as it is being
compressed. The sum of the two is then pumped into the discharge piping.
More oil is displaced at compressor start-up than during the normal running periods. If a
compressor experiences excessive starts because of recycling pumpdown control, the oil can be
pumped out and trapped in the condenser with the refrigerant charge. This oil can not return
regardless of the adequacy of the piping system.
A similar problem to a lesser extent occurs when the equipment is oversized for the available
cooling load.
In short, extreme care should be exercised to assure that both piping and controls are suitable for
the application such that displaced oil is returned to the compressor moderately. Note that oil loss
to the system can be due to a hang up in the evaporator, as well as in the piping.
Suction Lines
McQuay recommends the use of ASHRAE for guidelines in sizing and routing piping with one
exception. See the 1998 ASHRAE Handbook Refrigeration Edition, Chapter 2 for tables and
guidelines. The single exception is to the piping of direct expansion cooling coils located above
the compressors. In all cases, regardless of whether the equipment has pumpdown control or not,
IOMM ACZ1-3 ACZ 010A through 039A 9
a trap in the suction line equal to the height of the coil section is recommended. In its absence,
upon a power failure, all of the liquid in the coil will fall by gravity to the compressor below.
Suction line gas velocities can range between 900 and 4000 feet per minute. Consideration should
be given to the possibility of objectionable noise in or adjacent to occupied space. Where this is a
concern, gas velocities on the low side are recommended.
Routing must also take into account the requirement established in the latest ANSI/ASHRAE 15.
To size the suction line, determine:
a. The maximum tons for the circuit
b. The actual length in feet
c. The equivalent length contributed by elbows, fittings, valves or other refrigerant
specialties. ASHRAE Tables 2-10, 11 & 12
d. If a vertical riser exists including the trap at the coil, determine the minimum tons for the
circuit.
Add b and c above to obtain the total equivalent feet. Use the ASHRAE table for R22. Suction
line selections are based upon the pressure equivalent of a 2ºF loss per 100 equivalent feet.
Select a line size that displays an equal or slightly larger tons then that determined in a) above.
To determine the actual line loss:
1. Modify the table tons by the value for the design condensing temperature.
2. Use the formula in the notes to calculate the line loss in terms of the saturation temperature.
3. Convert the saturation temperature loss calculated to a pressure drop equivalent using the
(Delta) listed in the table for the comparable delta temperature.
NOTE: Excessive pressure drop is undesirable because:
• It reduces available compressor capacity.
• It increases power consumed for the net tons realized.
• It can affect the performance of both the evaporator and the expansion valve previously
selected for the application.
The line loss calculated, expressed in temperature, or PSID pressure drop will be used to establish
the temperature required at the evaporator to produce the required cooling, as well as, the suction
pressure that the compressor must operate at to deliver the required capacity.
Having selected the suction line size, based upon total equivalent length and maximum tons,
verify the line size selected will maintain entrainment of the lubricating oil up any vertical risers
at the minimum tons for the circuit. See d) above, and ASHRAE Tables.
If the line size selected will not maintain satisfactory oil return in a suction riser, the following
options are available:
• The vertical length can be sized smaller to accommodate the lower circuit tons at reduced
load.
• Hot gas bypass can be introduced at the distributor to the evaporator, increasing the volume of
gas available in the suction line to entrain the oil.
• An oil separator can be installed in the discharge line.
Note:
In horizontal refrigerant gas lines, oil return to compressors is provided by sizing lines at a
velocity above the minimum recommended and pitching the lines in the direction of refrigerant
flow.
10 ACZ 010A through 039A IOMM ACZ1-3
Underground Refrigerant Lines
Expansion Valve
Fittings Permit
Expansion Valve
Expansion Valve
Fittings Permit
Expansion Valve
McQuay does not recommend the installation of suction lines underground. If job conditions
require that they be located below ground, a suitable sized suction accumulator must be installed
ahead of the compressor to interrupt liquid refrigerant slugs at start-up.
Long Vertical Riser Installation
Where job conditions require refrigerant gas lifts of more than 25 feet, McQuay recommends the
installation of a short trap half-way up the riser or at not more than 20 feet intervals. These traps
are required to capture and hold small quantities of oil during off cycles.
Figure 6, DX Coil Piping
Condensing Unit Above Coil
n
o
i
t
c
r
u
o
s
S
s
Liquid
to Coil
h
c
t
i
p
P
m
o
C
o
T
Suction Trap
Short as
e
r
Hot gas bypass valve
and solenoid
valve located as
close to condensing
unit as possible.
n
o
i
t
c
r
u
o
s
S
s
h
c
re
t
i
p
P
m
o
C
o
Liquid
to Coil
T
G
H
l
i
o
C
o
t
P
B
A
i
r
F
A
i
r
F
l
o
w
Control Bulb
Strap To Line
and Insulate
l
o
w
Condensing Unit Below Coil
Hot gas bypass valve
and solenoid
valve located as
close to condensing
unit as possible.
Liquid
to Coil
t
c
Su
h
c
re
t
p
Pi
m
o
C
o
T
l
i
o
C
o
t
P
B
G
H
n
o
i
s
s
S
h
c
t
i
P
o
C
o
T
Suction Trap
Short as
r
o
n
o
i
t
c
r
u
o
s
s
e
r
p
m
A
i
r
F
l
o
w
Control Bulb
Strap To Line
and Insulate
A
i
r
F
l
o
w
Liquid
Suction Trap
Short as
Fittings Permit
Control Bulb
Strap To Line
and Insulate
to Coil
Suction Trap
Short as
Fittings Permit
Control Bulb
Strap To Line
and Insulate
IOMM ACZ1-3 ACZ 010A through 039A 11
Liquid Lines
Liquid lines are generally sized for 1 to 2 degree F line losses or their equivalent in pressure
drop. Actual selection can vary based upon the pressure drop expected from refrigerant
specialties such as solenoids, refrigerant driers, valves, etc. piping lifts or risers and the
amount of condenser sub-cooling expected.
The principal concern in sizing and routing liquid lines is assurance that liquid is present in
the line at start-up of the compressor, and that liquid and not vapor is available at the inlet
to the expansion valve during system operation.
Liquid can not be available in a liquid line at start-up if:
1. The solenoid valve is located adjacent to the condenser or condensing unit, remote
from the expansion valve.
2. An excessive length of liquid line is located in a heated ambient and the application
permits migration of the refrigerant to a cold air-cooled condenser.
3. Liquid refrigerant is permitted to gravitate from the liquid line to the condenser because
of the relative location of components.
In the event 2) or 3) above are possible, the application should include a check valve at the
condenser end of the liquid line. The check valve should be a low-pressure drop valve.
The line between the check valve and the solenoid valve can be comparable to a pressure
vessel and as the line becomes heated refrigerant trapped in the confined space will
increase in pressure. The check valve should include a pressure relief devise, relieving
from the line side to the condenser side of the circuit. The relief can be sized for a pressure
differential from 80 to 180 psi, but not more than 180 psi, and should be auto-resetting as
the pressure is relieved.
Liquid line solenoid valves should be located adjacent to the expansion valve with possibly
only a sight glass interposing the two.
If liquid lines are short, they may be of smaller diameter than the size indicated in the
current ASHRAE Refrigerant Handbook. As indicated above, the designer must size the
liquid line to assure that pure liquid will reach the inlet of the expansion valve. If the
condenser is sized to produce 10ºF of subcooling, and each degree represents 3.05 psi with
R-22, the liquid line and its refrigerant specialties can have pressure losses totaling 10 x
3.05 psi (or 10 x 2.2) and still satisfy the objective of delivering pure liquid to the
expansion valve.
In calculating the pressure losses, or gains, note that each foot of rise in a liquid line results
in an approximate 0.5 psi loss. Thus a 10 foot rise represent 5 pounds per square inch loss
in refrigerant pressure, or the equivalent of 1.6ºF subcooling with R-22. Total line losses
will include values for line friction, equivalents for valves and elbows and pressure losses
from manufacturers’ catalogs for driers, solenoids, sight glasses, etc.
When calculating condenser subcooling, note that saturated condensing pressure should be
read at the same point in the system where the liquid refrigerant temperature is obtained.
12 ACZ 010A through 039A IOMM ACZ1-2
Unit Component Location
MicroTech II
Compressors
Connection
Optional Hot Gas Bypass Valve
Control Panel
Removable Panel in
This Area to Facilitate
Field Piping
Suction
Connection
Tandem Scroll
Liquid
Control Layout and Operation
Control Center
All electrical controls are enclosed in a weather resistant control center with tool-locked,
hinged access doors. The left-hand section contains the microprocessor controller and
control input and output terminals. All high-voltage components are located on the right
Control
Transformer
ON/OFF Switch
SpeedTrol Location
Field Connection
Terminals
side of the panel.
24-Volt Trans.
Non-Fused Disc.
or
Power Block
Fan
Contactors
Fan
Protection
Compressor Contactors
IOMM ACZ1-2 ACZ 010A through 039A 13
R-407C Units
AGZ chillers are available with R-407C refrigerant as non-ARI certified units. R-407C is a
zeotropic blend of three compounds, and as such exhibits the characteristic of glide. It does not
behave as one substance like R-22 does. Glide is the difference (in degrees F) between the
beginning and end phase-change process in either the evaporator or condenser. During these
processes, different ratios of the refrigerant’s components change phase from the beginning to the
end of the process. The following functions, conditions and settings will differ from units
charged with R-22.
1. Different physical data and electrical data
2. Polyolester lubricants are used instead of mineral oil.
3. The saturated pressure/temperature relationship
4. Control and alarm settings
5. Charging procedures
1. Lubrication. The units are factory-charged with polyoester (POE) lubricant and one of
the following lubricants must be used if lubricant is to be added to the system:
POEs are very hygroscopic and will quickly absorb moisture if exposed to air. Pump the
lubricant into the unit through a closed transfer system. Avoid overcharging the unit.
Copeland Ultra 22 CC
Mobil EAL Arctic 22 CC
ICI EMKARATE RL RL 32CF
2. Pressure/temperature relationship. See Table 3 on page 15 for the saturated pressuretemperature chart. Due to refrigerant glide, use the following procedures for superheat and
subcooling measurement.
To determine superheat, only vapor must be present at the point of measurement, no liquid.
Use the temperature reading, the pressure reading and the Saturated P/T Chart. If the
pressure is measured at 78 psig, the chart shows the saturated vapor temperature to be
50.6°F. If the temperature is measured at 60°F, the superheat is 9.4 degrees F.
To determine subcooling, only liquid must be present, no vapor. Use the temperature
reading, the pressure reading and the Saturated P/T Chart. If the pressure is measured at
250 psig, the chart shows the saturated liquid temperature to be 108.2°F. If the temperature
is measured at 98°F, the subcooling is 10.2 degrees F.
The P/T relationship between R-407C and R-22 is similar enough to allow the use of R-22
expansion valves. The valves may be marked as “R-22’ or “R-22/R-407C”.
3. Control and alarm settings. The software that controls the operation of the unit is
factory-set for operation with R-407C, taking into account that the pressure/temperature
relationship differs from R-22. The software functionality is the same for either refrigerant.
4. Charging procedure. The units are factory-charged with R-407C. Use the following
procedure if recharging in the field is necessary:
Whether topping off a charge or replacing the circuit’s entire charge, always remove the
refrigerant from the charging vessel as a liquid. Many of the cylinders for the newer
refrigerants have a dip tube so that liquid is drawn off when the cylinder is in the upright
position. Do not vapor charge out of a cylinder unless the entire contents will be charged
into the system.
With the system in a 250-micron or lower vacuum, liquid can be charged into the high side.
Initially charge about 80 percent of the system total charge.
14 ACZ 010A through 039A IOMM ACZ1-2
Start the system and observe operation. Use standard charging procedures (liquid only) to
top off the charge.
It may be necessary to add refrigerant through the compressor suction. Because the
refrigerant leaving the cylinder must be a liquid, exercise care to avoid damage to the
compressor. A sight glass can be connected between the charging hose and the compressor.
It can be adjusted to have liquid leave the cylinder and vapor enter the compressor.
Table 3, R-407C Saturated Pressure/Temperature Chart
Pressure
(PSIG)
20 -10.7 1.5 150 74.8 84.9
22 -8.2 4.0 155 76.8 86.8
24 -5.7 6.4 160 78.7 88.7
26 -3.4 8.7 165 80.6 90.5
28 -1.1 11.0 170 82.5 92.3
30 1.1 13.1 175 84.3 94.0
32 3.2 15.2 180 86.1 95.8
34 5.3 17.2 185 87.8 97.5
36 7.3 19.2 190 89.6 99.1
38 9.2 21.0 195 91.3 100.7
40 11.1 22.9 200 92.9 102.3
42 12.9 24.7 205 94.6 103.9
44 14.7 26.4 210 96.2 105.4
46 16.4 28.1 215 97.7 107.0
48 18.1 29.7 220 99.3 108.4
50 19.7 31.3 225 100.8 109.9
52 21.3 32.9 230 102.3 111.4
54 22.9 34.4 235 103.8 112.8
56 24.4 35.9 240 105.3 114.2
58 25.9 37.4 245 106.7 115.6
60 27.4 38.8 250 108.2 116.9
62 28.8 40.2 255 109.6 118.2
64 30.2 41.6 260 111.0 119.6
66 31.6 43.0 265 112.3 120.9
68 33.0 44.3 270 113.7 122.1
70 34.3 45.6 275 115.0 123.4
72 35.6 46.9 280 116.3 124.7
74 36.9 48.1 285 117.6 125.9
76 38.2 49.3 290 118.9 127.1
78 39.4 50.6 295 120.2 128.3
80 40.6 51.8 300 121.4 129.5
82 41.9 52.9 305 122.7 130.7
84 43.0 54.1 310 123.9 131.8
86 44.2 55.2 315 125.1 133.0
88 45.4 56.3 320 126.3 134.1
90 46.5 57.4 325 127.5 135.2
92 47.6 58.5 330 128.7 136.3
94 48.7 59.6 335 129.8 137.4
96 49.8 60.7 340 131.0 138.5
98 50.9 61.7 345 132.1 139.6
100 51.9 62.7 350 133.2 140.6
105 54.5 65.2 355 134.3 141.7
110 57.0 67.7 360 135.4 142.7
115 59.5 70.0 365 136.5 143.7
120 61.8 72.3 370 137.6 144.7
125 64.1 74.6 375 138.7 145.7
130 66.4 76.7 380 139.8 146.7
135 68.5 78.8 385 140.8 147.7
140 70.7 80.9 390 141.8 148.7
145 72.8 82.9 395 142.9 149.6
Liquid Temp
(°F)
Vapor Temp
(°F)
Pressure
(PSIG)
Liquid Temp
(°F)
Vapor Temp
(°F)
IOMM ACZ1-2 ACZ 010A through 039A 15
Start-up and Shutdown
Pre Start-up
1. The chilled-water system should be flushed and cleaned or air filters checked for
cleanliness on DX systems.
2. Open all electric disconnects and check all electric connections for tightness.
3. Inspect all water piping for flow direction and correct connections at the evaporator or
ductwork for tightness and completeness.
4. Verify that thermostat connections for two stages of control have been connected to unit
terminals 23 / J5-ID7 and 28 / J5- ID-8.
5. Check compressor oil level. The oil level should be visible in the oil sightglass.
6. Check voltage of the unit power supply and make certain voltage is within ±10% of
nameplate rating. Check unit power supply wiring for proper ampacity and a minimum
insulation temperature of 75°C. Check for proper phasing using a phase sequence
meter.
7. Verify all mechanical and electrical inspections have been completed according to local
codes.
8. Open control stop switch S1(off). Turn on the main power and control disconnect
switches. This will energize crankcase heaters. Wait at least 24 hours before starting
up unit.
Start-up
1. Start auxiliary equipment by turning on the following: time clock (if present), ambient thermostat
and/or remote on/off switch, chilled water pump or air handler.
2. If the field supplied staging control calls for cooling, the unit will begin the start-up
sequence.
3. After running the unit for a short time, check the oil level in the compressor (1/4 to 1/3 of the
glass), rotation of fans, and flashing in refrigerant sight glass.
4. Verify superheat temperature is at the factory setting of 8 to 12 degrees F (4.4 to 6.7
degrees C).
5. After system performance has stabilized, complete the current ACZ Start-Up Form
(obtainable from the local McQuay sales office) to establish inception of warranty
benefits. Return the form to McQuay International through your sales representative.
Sequence of Operation
The following sequence of operation is typical for Models ACZ 010A through ACZ 039A.
It can vary depending upon options.
Start-Up
With the control circuit power on, 115V power is applied through the control circuit fuse F1
to the compressor crankcase heaters, the compressor motor protections and the primary of
the 24V control circuit transformer. The 24V transformer provides power to the
microprocessor controller.
If an optional remote time clock or remote manual switch is field wired to the unit
(terminals 25 and 35), it must be closed in order to start the unit. The operation of the unit
is then under the control of the field supplied staging thermostat. A water or air flow switch
is recommended across terminals 26 and 36 to prove flow before starting compressors. If
not used, a jumper is required across the terminals. The two compressors will start when
the normally open staging contacts close.
16 ACZ 010A through 039A IOMM ACZ1-2
Equipment Protection Alarms
The following conditions will shut down the unit and activate the alarm circuit:
• No water or air flow • Low evaporator pressure
• High condenser pressure • Motor protection system
• Phase voltage protection (Optional) • Outside ambient temperature
• Sensor failures
The following alarms will limit unit operation:
• Condenser pressure stage down, unloads unit at high discharge pressures
• Low ambient lockout, shuts off unit at low ambient temperatures
• Low evaporator pressure hold, holds stage #1 until pressure rises
• Low evaporator pressure unload, shuts off stage #2
Unit Enable Selection
Enables unit operation from local keypad, digital input, or Building Automation System.
Unit Mode Selection
Selects standard cooling or test operation mode. (Test is for service personnel only.)
Condenser Fan Control
Control of condenser fans is provided by the MicroTech II controller. The control steps
condenser fans based on discharge pressure.
Shutdown
As the Stage #2 external staging thermostat is satisfied, it will stage off the lag compressor
unloading the unit. The Stage #1 will de-energize the liquid line solenoid valve SV1 and
the lead compressor will pump down the unit and shut off on Low Suction Pressure at 40
psig. If the low pressure cutoff point cannot be reached in 120 seconds, the compressor
will time off. The compressor crankcase heaters will energize when the compressors shut
off, keeping the small amount of refrigerant in the plate heat exchanger from migrating to
the compressor. See page Error! Bookmark not defined. for detailed explanation of
compressor staging.
IOMM ACZ1-2 ACZ 010A through 039A 17
Physical Data
R-22
Table 4, Physical Data, ACZ 010A through 020A
PHYSICAL DATA
BASIC DATA
Number Of Refrigerant Circuits 1 1 1 1
Unit Operating Charge, R-22, Lb. (kg), Note 1 22.0 (10.0) 22.0 (10.0) 24.0 (10.9) 31.0 (14.1)
Cabinet Dimensions, LxWxH, In. 73.6 x 46.3 x 50.8 73.6 x 46.3 x 50.8 73.6 x 46.3 x 50.8 73.6 x 46.3 x 50.8
Cabinet Dimensions, LxWxH, (mm)
Unit Operating Weight, Lbs. (kg) 1000 (454) 1000 (454) 1220 (554) 1340 (608)
Unit Shipping Weight, Lbs. (kg) 1080 (490) 1080 (490) 1300 (590) 1420 (645)
Add'l Weight If Copper Finned Coils, Lb. (kg) 220 (99.7) 220 (99.7) 220 (99.7) 220 (99.7)
COMPRESSORS
Type Scroll Scroll Scroll Scroll
Nominal Horsepower 4.0 / 4.0 6.0 / 6.0 7.5 / 7.5 9.0 / 9.0
Oil Charge Per Compressor, Oz. (g) 57 (1616) 60 (1701) 140 (3969) 140 (3969)
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Standard Staging 0 – 50 – 100 0 – 50 – 100 0 – 50 – 100 0 – 50 – 100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area,Sq. Ft. (M2) 30.3 (2.8) 30.3 (2.8) 30.3 (2.8) 30.3 (2.8)
Finned Height x Finned Length, In. 84 x 52 84 x 52 84 x 52 84 x 52
Finned Height x Finned Length, (mm) (2134) x (1321) (2134) x (1321) (2134) x (1321) (2134) x (1321)
Fins Per Inch x Rows Deep 16 x 2 16 x 2 16 x 2 16 x 3
Pumpdown Capacity lb. (kg) 35.3 (16.0) 35.3 (16.0) 35.3 (16.0) 50.3 (22.8)
CONDENSER FANS - DIRECT DRIVE PROPELLER TYPE
Number Of Fans - Fan Diameter, In. (mm) 2 – 26 (660) 2 – 26 (660) 2 – 26 (660) 2 – 26 (660)
Number Of Motors - HP (kW) 2 – 1.0 (0.75) 2 – 1.0 (0.75) 2 – 1.0 (0.75) 2 – 1.0 (0.75)
Fan And Motor RPM, 60 Hz 1140 1140 1140 1140
Total Unit Airflow, CFM (l/s), 60 Hz 13950 (6584) 13950 (6584) 13950 (6584) 12000 (5664)
Not e: Operating charge is f or the condensi ng unit only. Refrigerant lin es and evaporator charge must be added.
010A 013A 016A 020A
(1869) x (1176) x
(1289)
ACZ MODEL NUMBER
(1869) x (1176) x
(1289)
(1869) x (1176) x
(1289)
(1869) x (1176) x
(1289)
18 ACZ 010A through 039A IOMM ACZ1-2
Loading...