McQuay | ACZ 045A | Unit installation | McQuay ACZ 045A Unit installation

Installation, Operation and Maintenance Manual
IOMM ACZ1-2
Group: Chiller
Part Number: 331373901
Effective: June 2005
Supersedes: IOMM ACZ1-1
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
Table of Contents
Introduction........................................3
Standard MicroTech II Controller. 25
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
Table of Contents ...........................................25
Overview........................................................26
General Description .......................................26
Automatic Adjusted Limits.............................28
Dynamic Default Values.................................29
Control Functions and Definitions .................30
Unit Enable ....................................................31
Unit Mode ......................................................32
Power Up Start Delay.....................................32
Unit State........................................................32
Evaporator Fan State Control.........................33
Condenser Fans ..............................................33
Low OAT Start ...............................................34
Capacity Overrides.........................................34
Low Ambient Lockout....................................35
Compressor Control .......................................35
Normal Shutdown ..........................................36
Rapid Shutdown .............................................36
Liquid Line Solenoid......................................36
Using the Controller .......................................37
Control Layout and Operation.......13
Control Center ................................................13
Start-up and Shutdown ...................14
Pre Start-up.....................................................14
Start-up...........................................................14
Sequence of Operation ...................................14
Physical Data....................................16
Electrical Data..................................18
Field Wiring ...................................................18
Dimensional Data.............................23
System Maintenance ........................24
General ...........................................................24
Lubrication .....................................................24
Electrical Terminals........................................24
Condensers .....................................................24
Refrigerant Sight glass ...................................24
Service............................................... 48
Thermostatic Expansion Valve .......................48
Filter-Driers....................................................48
Liquid Line Solenoid......................................48
Optional Controls ...........................................49
Troubleshooting Chart....................................51
MODEL CODE
A C Z XXX A
Air-Cooled
Vintage
Condensing
Nominal Tons
Scroll Compressor
"McQuay" is a registered trademark of McQuay International
©
2005 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.
2
ACZ 010A through 039A
IOMM ACZ1-2
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 16 and 17.
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 ACZ1-2
ACZ 010A through 039A
3
Figure 1, Suggested Pushing Arrangement
Blocking required
across full width
Figure 2, Suggested Lifting Arrangement
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 16 and 17.
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 ACZ1-2
Clearances
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)
Clearance for Air Inlet
4 Ft.
(1220mm)
Clearance for
Service Access
4 Ft.
(1220mm)
Clearance for
Service Access
4 Ft. (1220mm)
Clearance for Air Inlet
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.
The recommended minimum side clearance between two units
is 8 feet (2440mm).
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.
IOMM ACZ1-2
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 6 feet (1828mm) when installed in a pit. The pit cannot
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.
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
Model
010, 013,016,020,025,028
033, 039
Model
010, 013
016, 020
025, 028
033
039
Neoprene-in-Shear
RF
LF
RP-3 Red
RP-3 Red
RP-3 Green
RP-3 Green
Spring
LF
CP 1-24 Brown
CP 1-25 Red
CP1-26 Purple
CP1-26 Purple
CP1-27 Orange
RF
CP 1-24 Brown
CP 1-25 Red
CP1-26 Purple
CP1-27 Orange
CP1-27 Orange
CP
CP
CP
CP
CP
RB
RP-3 Black
RP-3 Red
RB
1-24 Brown
1-24 Brown
1-24 Brown
1-24 Brown
1-24 Brown
LB
RP-3 Black
RP-3 Red
CP
CP
CP
CP
CP
LB
1-24 Brown
1-24 Brown
1-24 Brown
1-24 Brown
1-24 Brown
Kit P/N
350014859
350014857
Kit P/N
350014831
350014830
350014829
350014836
350014828
Note: See dimension drawing for location of isolators
Corner Operating Weights
ACZ
Unit
Model
010
013
016
020
025
028
033
039
RIB
RF
LF
RB
LB
Total
259
259
353
377
498
508
605
712
257
257
360
383
505
515
567
649
243
243
251
288
232
232
304
313
241
241
256
292
235
235
284
286
1000
1000
1220
1340
1470
1490
1760
1960
RP-3, Neoprene-in Shear Isolator
6
ACZ 010A through 039A
RIF
Control
Panel
LIB
LIF
CP-1, Spring Isolator
IOMM ACZ1-2
Chilled Water System
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
Air
Vent
Strainer
Inlet
P
Isolation
Valves
Vibration
Eliminators
Outlet
Flow
Switch
Drain
IOMM ACZ1-2
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.
CAUTION:
Differential pressure switches are not recommended for outdoor installation.
They are subject to freezing-up at low ambient temperatures.
Table 2, Flow Switch Settings
Pipe Size
Minimum
8
Flow
inch
mm
gpm
1 1/4
32
4.8
1 1/2
38
6.3
ACZ 010A through 039A
2
51
9.9
2 1/2
63
15.3
3
76
24.4
4
102
33.3
IOMM ACZ1-2
Adjustment
No
Flow
Maximum
Adjustment
Flow
No
Flow
Lpm
gpm
Lpm
gpm
Lpm
gpm
Lpm
18.2
3.0
11.3
7.7
29.1
5.9
22.3
22.7
3.6
13.6
10.0
37.9
7.0
26.5
37.5
5.9
22.3
15.8
59.8
11.0
41.6
57.9
9.5
36.0
23.7
89.7
17.0
64.3
92.4
15.4
58.3
35.5
134.4
29.2
110.5
126.0
21.1
79.9
61.4
232.4
37.7
142.7
Refrigerant Piping
Introduction
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,
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
IOMM ACZ1-2
ACZ 010A through 039A
9
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.
CAUTION:
•
•
•
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.
Underground Refrigerant Lines
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.
10
ACZ 010A through 039A
IOMM ACZ1-2
Figure 6, DX Coil Piping
Condensing Unit Above Coil
Hot gas bypass valve
and solenoid
valve located as
close to condensing
unit as possible.
Condensing Unit Below Coil
n
ctio
Su essor
r
ch
Pit omp
C
To
n
ctio r
Su esso
r
ch
Pit omp
C
To
Liquid
to Coil
Air
Flo
w
Hot gas bypass valve
and solenoid
valve located as
close to condensing
unit as possible.
Air
F
Liquid
to Coil
ion
uct or
h S press
c
t
i
P om
C
To
BP
HG
to
ion
uct or
h S press
c
t
i
P om
C
To
il
Co
A ir
F lo
t
BP
HG
oil
oC
Air
F
w
Liquid
to Coil
low
Liquid
to Coil
Suction Trap
Short as
Fittings Permit
IOMM ACZ1-2
Expansion Valve
Control Bulb
Strap To Line
and Insulate
Suction Trap
Short as
Fittings Permit
Expansion Valve
Control Bulb
Strap To Line
and Insulate
Suction Trap
Short as
Fittings Permit
low
Expansion Valve
Control Bulb
Strap To Line
and Insulate
ACZ 010A through 039A
Suction Trap
Short as
Fittings Permit
Expansion Valve
Control Bulb
Strap To Line
and Insulate
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
Control Panel
Removable Panel in
This Area to Facilitate
Field Piping
Suction
Connection
Tandem Scroll
Compressors
Liquid
Connection
Optional Hot Gas Bypass Valve
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
side of the panel.
24-Volt Trans.
Transformer
ON/OFF Switch
Non-Fused Disc.
or
Power Block
MicroTech II
Fan
Contactors
SpeedTrol Location
Field Connection
Terminals
Fan
Protection
Compressor Contactors
IOMM ACZ1-2
ACZ 010A through 039A
13
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.
14
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
15
Physical Data
Table 3, Physical Data, ACZ 010A through 020A
ACZ MODEL NUMBER
PHYSICAL DATA
010A
013A
016A
020A
BASIC DATA
Number Of Refrigerant Circuits
1
1
1
1
22.0 (10.0)
22.0 (10.0)
24.0 (10.9)
31.0 (14.1)
Unit Operating Weight, Lbs. (kg)
73.6 x 46.3 x 50.8
(1869) x (1176) x
(1289)
1000 (454)
73.6 x 46.3 x 50.8
(1869) x (1176) x
(1289)
1000 (454)
73.6 x 46.3 x 50.8
(1869) x (1176) x
(1289)
1220 (554)
73.6 x 46.3 x 50.8
(1869) x (1176) x
(1289)
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)
Scroll
Scroll
Scroll
Scroll
Unit Operating Charge, R-22, Lb. (kg), Note 1
Cabinet Dimensions, LxWxH, In.
Cabinet Dimensions, LxWxH, (mm)
COMPRESSORS
Type
Nominal Horsepower
Oil Charge Per Compressor, Oz. (g)
4.0 / 4.0
6.0 / 6.0
7.5 / 7.5
9.0 / 9.0
57 (1616)
60 (1701)
140 (3969)
140 (3969)
0 – 50 – 100
0 – 50 – 100
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Standard Staging
0 – 50 – 100
0 – 50 – 100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area,Sq. Ft. (M2)
Finned Height x Finned Length, In.
Finned Height x Finned Length, (mm)
30.3 (2.8)
30.3 (2.8)
30.3 (2.8)
30.3 (2.8)
84 x 52
84 x 52
84 x 52
84 x 52
(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)
1140
1140
1140
1140
13950 (6584)
13950 (6584)
13950 (6584)
12000 (5664)
Fan And Motor RPM, 60 Hz
Total Unit Airflow, CFM (l/s), 60 Hz
Note: Operating charge is for the condensing unit only. Refrigerant lines and evaporator charge must be added.
16
ACZ 010A through 039A
IOMM ACZ1-2
Table 4, Physical Data, ACZ 025A through 039A
ACZ MODEL NUMBER
PHYSICAL DATA
025A
028A
033A
039A
BASIC DATA
Number Of Refrigerant Circuits
Unit Operating Charge, R-22, Lb. (kg), Note 1
Cabinet Dimensions, LxWxH, In.
Cabinet Dimensions, LxWxH, (mm)
Unit Operating Weight, Lbs. (kg)
1
1
1
1
34.0 (15.4)
36.0 (16.3)
47.0 (21.3)
50.0 (22.7)
106.2x 46.3 x 50.8 106.2x 46.3 x 50.8 106.2x 46.3 x 58.8 106.2x 46.3 x 58.8
(2697) x (1176) x (2697) x (1176) x
(2697) x (1176) x
(2697) x (1176) x
(1289)
(1289)
(1493)
(1493)
1470 (667)
1490 (676)
1760 (799)
1960 (890)
Unit Shipping Weight, Lbs. (kg)
1580 (717)
1600 (726)
1890 (858)
2090 (949)
Add'l Weight If Copper Finned Coils, Lb. (kg)
350 (159)
350 (159)
435 (197)
435 (197)
COMPRESSORS
Type
Scroll
Scroll
Scroll
Scroll
Nominal Horsepower
10.0 / 13.0
13.0 / 13.0
15.0 / 15.0
20.0 / 20.0
Oil Charge Per Compressor, Oz. (g)
140 (3969)
140 (3969)
140 (3969)
296 (8392)
0 – 50 – 100
0 – 50 – 100
CAPACITY REDUCTION STEPS - PERCENT OF COMPRESSOR DISPLACEMENT
Standard Staging
0 – 45 - 100
0 – 50 – 100
CONDENSERS - HIGH EFFICIENCY FIN AND TUBE TYPE WITH INTEGRAL SUBCOOLING
Coil Face Area,Sq. Ft. (M2)
Finned Height x Finned Length, In.
Finned Height x Finned Length, (mm)
49.0 (4.6)
49.0 (4.6)
58.3 (5.4)
84 x 84
84 x 84
100 x 84
58.3 (5.4)
100 x 84
(2134) x (2134)
(2134) x (2134)
(2545 ) x (2134)
(2545 ) x (2134)
Fins Per Inch x Rows Deep
16 x 2
16 x 2
16 x 3
16 x 3
Pumpdown Capacity lb. (kg)
53.1 (24.0)
53.1 (24.0)
90.7 (41.1)
92.8 (42.0)
CONDENSER FANS - DIRECT DRIVE PROPELLER TYPE
Number Of Fans - Fan Diameter, In. (mm)
3 – 26 (660)
3 – 26 (660)
3 – 26 (660)
3 – 26 (660)
Number Of Motors - HP (kW)
3 – 1.0 (0.75)
3 – 1.0 (0.75)
3 – 1.0 (0.75)
3 – 1.0 (0.75)
Fan And Motor RPM, 60 Hz
Total Unit Airflow, CFM (l/s), 60 Hz
1140
1140
1140
1140
20925 (9877)
20925 (9877)
19800 (9346)
19800 (9346)
Note: Operating charge is for the condensing unit only. Refrigerant lines and evaporator charge must be added.
IOMM ACZ1-2
ACZ 010A through 039A
17
Electrical Data
Field Wiring
Wiring must comply with all applicable codes and ordinances. Warranty is void if wiring is not
in accordance with specifications. Copper wire is required for all power lead terminations at the
unit.
ACZ 010A through ACZ 039A units have single-point power connection. A single field supplied
fused disconnect is required or it can be supplied as a factory-mounted option. The control
transformer is factory mounted.
Table 5, ACZ 010A – 039A, Electrical Data Single Point
Power Supply
ACZ
Unit
Size
Volts
Minimum
Circuit
Ampacity
(MCA)
Hub (Conduit
Connection)
Field Wire
Quantity
Wire
Gauge
75C
Quantity
Field Fuse Size
or HACR (Heating/AirConditioning/Refrigeration)
Breaker Size
Nominal
Size
Recommended
In. (mm)
Maximum
010A
208
230
460
575
45
45
22
18
3
3
3
3
8
8
10
10
1
1
1
1
1.00 (25)
1.00 (25)
1.00 (25)
1.00 (25)
50
50
25
20
50
50
25
20
013A
208
230
460
575
54
54
26
23
3
3
3
3
6
6
10
10
1
1
1
1
1.00 (25)
1.00 (25)
1.00 (25)
1.00 (25)
60
60
30
25
70
70
35
30
208
230
460
575
65
65
34
27
3
3
3
3
6
6
10
10
1
1
1
1
1.00 (25)
1.00 (25)
1.00 (25)
1.00 (25)
80
80
40
30
80
80
45
35
020A
208
230
460
575
79
79
41
33
3
3
3
3
4
4
8
10
1
1
1
1
1.00 (25)
1.00 (25)
1.00 (25)
1.00 (25)
90
90
45
40
100
100
50
40
025A
208
230
460
575
103
103
53
45
3
3
3
3
2
2
6
8
1
1
1
1
1.25 (32)
1.25 (32)
1.00 (25)
1.00 (25)
125
125
60
50
125
125
70
60
028A
208
230
460
575
110
110
58
48
3
3
3
3
2
2
6
8
1
1
1
1
1.25 (32)
1.25 (32)
1.00 (25)
1.00 (25)
125
125
70
60
150
150
80
60
033A
208
230
460
575
127
127
62
58
3
3
3
3
1
1
6
6
1
1
1
1
1.50 (38)
1.50 (38)
1.00 (25)
1.00 (25)
150
150
70
70
175
175
80
70
039A
208
230
460
575
182
182
79
63
3
3
3
3
3/0
3/0
4
6
1
1
1
1
1.50 (38)
1.50 (38)
1.00 (25)
1.00 (25)
225
225
90
80
250
250
100
80
016A
NOTES:
1. See page 21 for all Electrical Data notes.
2. HACR = Heating/Air-Conditioning/Refrigeration
18
ACZ 010A through 039A
IOMM ACZ1-2
Table 6, ACZ 010A – 039A Compressor and Condenser Fan Motor Amp Draw
Rated Load Amps
ACZ
Unit
Size
Volts
010A
208
230
460
575
013A
208
230
460
575
016A
208
230
460
575
020A
208
230
460
575
025A
208
230
460
575
028A
208
230
460
575
033A
208
230
460
575
039A
208
230
460
575
Compressors
Locked Rotor Amps
No. of
Fan
Mtrs
Compressors
Fan
Motor
(Each)
No. 1
No. 2
No. 1
No. 2
Fan
Motor
(Each)
60
14.8
14.8
7.1
5.8
14.8
14.8
7.1
5.8
5.8
5.8
2.8
2.5
2
2
2
2
23.7
21.4
10.7
11.0
91
91
50
37
91
91
50
37
60
18.6
18.6
9.1
7.4
18.6
18.6
9.1
7.4
5.8
5.8
2.8
2.5
2
2
2
2
23.7
21.4
10.7
11.0
156
156
75
54
156
156
75
54
60
23.7
23.7
12.5
9.1
23.7
23.7
12.5
9.1
5.8
5.8
2.8
2.5
2
2
2
2
23.7
21.4
10.7
11.0
189
189
99
74
189
189
99
74
60
29.9
29.9
15.3
11.6
29.9
29.9
15.3
11.6
5.8
5.8
2.8
2.5
2
2
2
2
23.7
21.4
10.7
11.0
232
232
125
100
232
232
125
100
60
33.6
33.6
16.5
13.7
41
41
21.8
17.3
5.8
5.8
2.8
2.5
3
3
3
3
23.7
21.4
10.7
11.0
278
278
127
100
350
350
158
125
60
41.0
41.0
21.8
17.3
41.0
41.0
21.8
17.3
5.8
5.8
2.8
2.5
3
3
3
3
23.7
21.4
10.7
11.0
350
350
158
125
350
350
158
125
60
48.5
48.5
23.7
21.7
48.5
48.5
23.7
21.7
5.8
5.8
2.8
2.5
3
3
3
3
23.7
21.4
10.7
11.0
425
425
187
148
425
425
187
148
60
73.1
73.1
31.0
24.4
73.1
73.1
31.0
24.4
5.8
5.8
2.8
2.5
3
3
3
3
23.7
21.4
10.7
11.0
505
505
225
180
505
505
225
180
Hz.
Across-The-Line
See page 21 for all Electrical Data notes.
IOMM ACZ1-2
ACZ 010A through 039A
19
Table 7, ACZ 010A – 039A Field Wiring Data, Single Point Power
Wiring to
Standard Power Block Terminal
ACZ
UNIT
SIZE
Volts
010A
208
230
460
575
013A
208
230
460
575
016A
208
230
460
575
020A
208
230
460
575
025A
208
230
460
575
028A
208
230
460
575
033A
208
230
460
575
039A
208
230
460
575
HZ.
Wiring to
Optional Disconnect Switch
Maximum
Terminal
Amps
Connector Wire Range
(Copper Wire Only)
Disconnect
Size
Connector Wire
Range
(Copper Wire Only)
60
175
175
175
175
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
100
100
63
63
#8-1/0
#8-1/0
#1-#14
#1-#14
60
175
175
175
175
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
100
100
63
63
#8-1/0
#8-1/0
#1-#14
#1-#14
60
175
175
175
175
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
100
100
63
63
#8-1/0
#8-1/0
#1-#14
#1-#14
60
175
175
175
175
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
100
100
63
63
#10-1/0
#10-1/0
#1-#14
#1-#14
60
175
175
175
175
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
225
225
100
100
#2-4/0
#2-4/0
#8-1/0
#10-1/0
60
175
175
175
175
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
225
225
100
100
#2-4/0
#2-4/0
#8-1/0
#10-1/0
60
175
175
175
175
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
14 GA – 2/0
225
225
100
100
#2-4/0
#2-4/0
#8-1/0
#10-1/0
60
335
335
175
175
6 GA – 400 kcmil
6 GA – 400 kcmil
14 GA – 2/0
14 GA – 2/0
225
225
125
100
#2-4/0
#2-4/0
#3-3/0
#10-1/0
See page 21 for all Electrical Data notes.
20
ACZ 010A through 039A
IOMM ACZ1-2
Notes for “Electrical Data”
1. Field Fuse Size for recommended and maximum is based on use of a time-delay fuse.
2. 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.
3. Since the control transformer is furnished, no separate 115V power is required.
4. If a separate 115V power supply is used for the control circuit, the wire sizing amps is
10 Amps.
5. Recommended power lead wire sizes for three 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 should be kept short. All
terminal block connections must be made with copper (type THW) wire.
6. Single conductors should be used for power connections as listed under “Power
Supply/Field Wire Size.”
7. “Recommended Fuse Sizes” are selected at approximately 150% to 175% of the largest
compressor RLA, plus 100% of all other loads in the circuit.
8. “Maximum Fuse Sizes” are selected at approximately 225% of the largest compressor
RLA, plus 100% of all other loads in the circuit.
9. The recommended power lead wire sizes are based on an ambient temperature of 86°F.
Ampacity correction factors must be applied for other ambient temperatures. Refer to
the National Electrical Code Handbook.
Voltage Limitations:
1. Within 10% of nameplate rating.
2. Maximum 2 % voltage unbalance between phases.
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. If unit is equipped with optional SpeedTrol
condenser fan motors, the first motor on each refrigerant circuit is a single phase, 1hp
motor, with a FLA of 2.8 amps at 460 volts, 5.6 amps at 208, 230, and 575 volts.
2. Compressor LRA for reduced inrush start are for the first winding only. If the unit is
equipped with optional SpeedTrol motors, the first motor is a single phase, 1 hp motor,
with a LRA of 7.3 amps at 460 volts, 14.5 amps at 208, 230, and 575 volts.
Notes for “Field Wiring Data” - Single Point Power:
1. Single point power supply requires a single disconnect to supply electrical power to the
unit. This power must be fused.
2. All field wiring to unit power block or non-fused disconnect switch must be copper.
3. All field wire size values given in table apply to 75°C rated wire per NEC.
IOMM ACZ1-2
ACZ 010A through 039A
21
Figure 7, ACZ 010A through 039A, Typical Field Wiring Diagram
UNIT MAIN
TERMINAL
BLOCK
DISCONNECT
(BY OTHERS)
GND LUG
3 PHASE
TO COMPRESSOR(S)
AND FAN MOTORS
POWER
SUPPLY
NOTE: ALL FIELD WIRING
TO BE INSTALLED AS NEC
CLASS 1 WIRING SYSTEM
WITH CONDUCTOR RATED
600 VOLTS
FUSED CONTROL
CIRCUIT
TRANSFORMER
120
VAC
DISCONNECT
(BY OTHERS)
TB1-20
N
TB1
10A
FUSE
120VAC
CONTROL POWER
CONTROL
CIRCUIT
FUSE
1
(BY OTHERS)
LIQUID LINE SOLENOID
120 VAC 1.0 AMP MAX
2
120 VAC
SV1
13
16
120 VAC
SV5
14
HOT GAS BYPASS SOLENOID
120 VAC 1.0 AMP MAX
120 VAC
12
N
17
DX EVAP. FAN PUMP RELAY
(BY OTHERS)
120 VAC 1.0 AMP MAX
ALARM BELL
OPTION
FACTORY SUPPLIED ALARM
FIELD WIRED
120 VAC
11
ALARM BELL RELAY
17
GND
TIME
CLOCK
AUTO
REMOTE STOP
SWITCH
(BY OTHERS)
OFF
TB2
ON
25
EVAP. FLOW SWITCH
---MANDATORY–(BY OTHERS)
843
IF REMOTE STOP CONTROL
IS USED, REMOVE LEAD 843
FROM TERM. 25 TO 35.
35
MANUAL
26
NOR. OPEN PUMP AUX.
CONTACTS (OPTIONAL)
ALARM BELL
RELAY
36
22
COM
NO
BELL
31
1
2
ALARM BELL OPTION
23
STAGE 1 NOR. OPEN CONTACTORS
33
J5-ID7
28
STAGE 2 NOR. OPEN CONTACTORS
34
FIELD WIRING
22
J5-ID8
FACTORY WIRING
ACZ 010A through 039A
LABEL DWG. 330539401 REV.0B
IOMM ACZ1-2
Dimensional Data
Figure 8, ACZ 010A through 020A
46.27
(1175.26)
POWER ENTRY
KNOCKOUT
(OTHER SIDE)
POWER
ENTRY
CONTROL PANEL
ACCESS DOORS
CONTROL
ELECTRICAL
KNOCKOUT
51.0
(1295.40)
SUCTION
INLET
ACCESS DOOR
HOT GAS BYPASS
Z
LIQUID
OUTLET
Y
X
21.32
(541.53)
46.23 (1174.24)
LIFTING SLOTS
Liquid Conn.
inches (mm)
010A, 013A
016A, 020A
7/8 (22.2)
7/8 (22.2)
7.55
(191.77)
3.94 (100.08)
M0UNTING HOLES
QTY. 4 01.00 (25.4)
49.06 (1246.12)
73.55 (1868.17)
ACZ Unit Size
31.11 (790.19)
MOUNTING
HOLES
Suction
Conn
inches (mm)
1 1/8 (28.6)
1 5/8 (41.3)
Optional
Hot Gas
Bypass
5/8 (15.8)
5/8 (15.8)
Center of Gravity inches (mm)
X
Y
Z
28 (711.2)
25 (635.0)
22 (558.8)
21 (553.4)
23 (584.2)
23 (584.2)
Figure 9, ACZ 025A through 039A
46.26
(1175.26)
POWER ENTRY
KNOCKOUT
(OTHER SIDE)
POWER
ENTRY
CONTROL PANEL
ACCESS DOORS
CONTROL
ELECTRICAL
KNOCKOUT
A
SUCTION
INLET
ACCESS DOOR
HOT GAS
BYPASS
Z
LIQUID
OUTLET
Y
X
21.32
(541.53)
49.06 (1246.12)
46.19 (1173.23)
49.06 (1246.12)
105.97 (2691.64)
ACZ Unit
Size
A
inches (mm)
025A, 028A
033A, 039A
51 (1295)
59 (1499)
IOMM ACZ1-2
Liquid
Conn.
inches (mm)
7/8 (22.2)
7/8 (22.2)
LIFTING SLOTS
31.11 (790.19)
7.55
MOUNTING
(191.77)
HOLES
3.94 (100.08)
MOUNTING HOLES
QTY. 6 0 1.00 (25.4)
Suction
Conn
inches (mm)
1 5/8 (41.3)
2 1/8 (53.9)
Optional Hot
Gas Bypass
5/8 (15.8)
5/8 (15.8)
ACZ 010A through 039A
Center of Gravity inches (mm)
X
Y
Z
35 (889.0)
35 (889.0)
21 (553.4)
25 (635.0)
23 (584.2)
24 (609.6)
23
System Maintenance
General
On initial start-up and periodically during operation, it will be necessary to perform certain
routine service checks. Among these are taking electric leg readings. Some readings are
readily available on the MicroTech II display.
Lubrication
No routine lubrication is required on the ACZ units. The fan motor bearings are of the
permanently lubricated type and require no lubrication.
Electrical Terminals
WARNING
Electric shock hazard. Disconnect and tag-out all sources of power to the unit
before continuing with following service to avoid risk of severe personal injury.
Normal heating and cooling of the wire will cause terminals to loosen. Retighten all power
electrical terminals every six months.
Condensers
Condensers are air-cooled and constructed with 3/8” (9.5mm) O.D. internally finned copper
tubes bonded in a staggered pattern into slit aluminum fins. No maintenance is ordinarily
required except the occasional removal of dirt and debris from the outside surface of the
fins. Use locally purchased foaming condenser coil cleaners for periodic cleaning of the
coil. Condenser cleaners may contain harmful chemicals. Wear protective gear and read
and follow manufacturer's safety instructions. Take care not to damage the fins during
cleaning. All chemical cleaners should be thoroughly rinsed from the coils.
Refrigerant Sight glass
Observe the refrigerant sight glass monthly. A clear glass of liquid indicates adequate subcooled refrigerant charge in the system to provide proper feed through the expansion valve.
Bubbling refrigerant in the sight glass indicates the system is short of refrigerant charge.
Sub-cooling should be verified to prevent overcharging. Refrigerant gas flashing in the
sight glass could also indicate an excessive pressure drop in the line, possibly due to a
clogged filter-drier or a restriction elsewhere in the system. The sight glass indicates what
moisture condition corresponds to a given element color. If the sight glass does not indicate
a dry condition after about 12 hours of operation, the refrigerant and oil should be tested for
moisture.
24
ACZ 010A through 039A
IOMM ACZ1-2
Standard MicroTech II Controller
Table of Contents
Overview ............................................................................ 26
General Description ............................................................ 26
Compressor Motor Description ...................................... 26
FanTrol Head Pressure Control ...................................... 26
Inputs/Outputs ............................................................... 27
Setpoints........................................................................ 27
Equipment Protection Alarms......................................... 28
Limit Alarms.................................................................. 30
Unit Enable.................................................................... 30
Control Functions and Definitions ....................................... 30
Compressor Control ............................................................ 35
Using the Controller ............................................................ 37
Display and Keyboard .................................................... 37
Getting Started .................................................................... 37
Menu Screens ................................................................ 38
Menu Matrix .................................................................. 40
View Screens Defined .................................................... 41
Alarm Screens Defined .................................................. 43
Set Screens Defined ....................................................... 43
Software Version: ACZSU0102B
BIOS Version: 3.56
BOOT File Version: 3.0
IOMM ACZ1-2
ACZ 010A through 039A
25
Overview
The MicroTech II controller's state-of-the-art design will not only permit the unit to run
more efficiently but also simplifies troubleshooting if a system failure occurs. Every
MicroTech II controller is programmed and tested prior to shipment to contribute to a
trouble-free start-up.
Software Version
This manual is based on software version ACZSU0102A
Operator-friendly
The MicroTech II controller menu structure is separated into three distinct categories,
which provide the operator or service technician with a full description of current unit
status, control parameters, and alarms. Security protection deters unauthorized changing of
the setpoints and control parameters.
MicroTech II control continuously performs self-diagnostic checks, monitoring system
temperatures, pressures and protection devices, and will automatically shut down a
compressor or the entire unit if a fault occurs. The cause of the shutdown will be retained
in memory and can be easily displayed in plain English for operator review. The
MicroTech II controller will also retain and display the time the fault occurred. In addition
to displaying alarm diagnostics, the MicroTech II controller also provides the operator with
a warning of limit (pre-alarm) conditions.
Staging
The two scroll compressors are staged on and off by contact closure of the field supplied
remote two-stage staging thermostat. Lead/lag is automatic and switched every ten starts.
General Description
NOTE: When the following descriptions refer to "evaporator pressure", the pressure is
actually the suction pressure within the condensing unit itself.
Compressor Motor Protection
ACZ 016 – 039: The solid-state compressor motor protector module incorporates a 2minute “time-off” relay utilizing the bleed-down capacitor principle. Any time the
protection system opens or power to the module is interrupted, the 2-minute “time-off”
delay is triggered and the module will not reset for two minutes. Once the 2-minute period
has passed the motor protector contacts M1 and M2 reset, provided the protection system is
satisfied and power is applied to the module.
Note: If the power circuit is broken once the 2-minute period is passed, the pilot
circuit will reset without delay when power is reapplied.
ACZ 010 - 013: The model ACZ 010 and ACZ 013 compressors have internal line
breakage with automatic reset.
FanTrol Head Pressure Control
FanTrol is the standard method of head pressure control that automatically cycles the
condenser fan motors in response to condenser pressure. This function is controlled by the
microprocessor, maintains head pressure and allows the unit to run at low ambient air
temperatures down to 35°F (1.7°C). Fans are staged as follows:
26
ACZ 010A through 039A
IOMM ACZ1-2
Table 8, Fan Staging Pressures
Fan
Two-Fan Unit
Three-Fan Unit
Stage #1
Stage #2
Stage #3
On 150 psig, Off with unit
On 290 psig, Off 170 psig
On 150 psig, Off with unit
On 290 psig, Off 170 psig
On 310 psig, Off 180 psig
Note: Fan #1 is on with first compressor above 75°F (24°C).
Inputs/Outputs
Table 9, Inputs and Outputs
Analog Inputs
#
1
2
3
4
5
Description
Open
Evaporator Refrigerant Pressure
Condenser Refrigerant Pressure
Open
Outside Ambient Temperature
Signal Source
Range
0.5 VDC to 4.5 VDC (NOTE 1)
0.5 VDC to 4.5 VDC (NOTE 1)
0 to 132 psi
3.6to 410 psi
Thermister (10k at 77°F, 25°C)
-58 to 212°F
NOTE: Value at the converter board input. Value at the converter board output is 0.1 VDC – 0.9 VDC.
Analog Outputs
#
1-4
Description
Output Signal
Range
None
Digital Inputs
#
1
2
3
4
5
6
7
8
Description
Unit OFF Switch
Remote Start/Stop
Evaporator Water Flow/Air Flow Switch
Motor Protection
Open
Phase Voltage Fault
Stage 1 Request
Stage 2 Request
Signal
0 VAC (Stop)
0 VAC (Stop)
0 VAC (No Flow)
0 VAC (Fault)
Signal
24 VAC (Auto)
24 VAC (Start)
24 VAC (Flow)
24 VAC (No Fault)
0 VAC (Fault)
0 VAC (Stop)
0 VAC (Stop)
24 VAC (No Fault)
24 VAC (Start)
24 VAC (Start)
Digital Outputs
#
1
3
4
5
6
7
8
Description
Alarm
Liquid Line
Motor Control Relay #1
Motor Control Relay #2
Condenser Fan #1
Condenser Fan #2
Condenser Fan #3
Load
Alarm Indicator
Solenoid
Starter
Starter
Fan Contactor
Fan Contactor
Fan Contactor
Output OFF
Alarm OFF
Cooling OFF
Compressor OFF
Compressor OFF
Fan OFF
Fan OFF
Fan OFF
Output ON
Alarm ON
Cooling ON
Compressor ON
Compressor ON
Fan ON
Fan ON
Fan ON
Setpoints
The setpoints shown in Table 10 are held in a non-volatile memory and remembered during
power off, are factory set to the Default value, and can be adjusted within the value shown
in the Range column.
The PW (password) column indicates the password level that must be entered in order to
change the setpoint. Passwords are as follows:
O = Operator [0100]
M = Manager, [2001}
IOMM ACZ1-2
ACZ 010A through 039A
27
Table 10, Setpoints
Description
Unit
Unit Enable
Available mode
Control Source
Air Flow Timer
Low Ambient Lockout
Refrigerant Type
BAS Protocol
Ident number
Baud rate
Evaporator Refrig Press Sensor Offset
Condenser Refrig Press Sensor Offset
Outside Ambient Temperature Sensor
Password
Compressor
Clear Cycle Timers
Start-Start
Stop-Start
Stage Up Delay
Stage Down Delay
Comp 1 Enable
Comp 2 Enable
Alarms
Low Evap Pressure-Hold
Low Evap Pressure-Unload
Evap Flow Proof
High Condenser Pressure
High Condenser Stage Down
Phase Voltage Protection
Low OAT Start Timer
Condenser Fans
Fan Stages
Speedtrol Option
Stage #1 On (OAT < 75°F)
Stage #2 On
Stage #3 On
Stage #1 Off
Stage #2 Off
Stage #3 Off
Default
Range
PW
Off
Cool
Switches
30
35.0 °F
None
Modbus
001
9600
0 psi
0 psi
0 °F
0000
Off, On
Cool, Test
Keypad, Network, Switches
10 to 60 seconds
–2(35) to 70 °F
R22, R407c
BACnet, LonWorks, Modbus
001-999
1200,2400,4800,9600,19200
-20.0 to 20.0 psi
-20.0 to 20.0 psi
-5.0 to 5.0 °F
0000 to 9999
O
M
O
M
M
M
M
M
M
M
M
M
N/a
No
15 min
5 min
240
30
Enable
Enable
No, Yes
10 to 60 min
3 to 20 min
20 to 480 sec
10 to 60 sec
Enable, Disable
Enable, Disable
M
M
M
M
M
M
M
[59,60] psi
[58,59] psi
5 sec
380 psi
370 psi
N
165 sec
[20, 24] to 65 psi
[20, 24] to 65 psi
3 to 120 sec
380 to 390 psi
365 to 375 psi
N,Y
150 to 240 sec
M
M
M
M
M
M
M
2
N
200 psi
290 psi
300 psi
140 psi
180 psi
190 psi
2,3
N,Y
140 to 200 psi
230 to 330 psi
230 to 330 psi
130 to 170 psi
150 to 200 psi
150 to 200 psi
M
M
M
M
M
M
M
M
Automatic Adjusted Limits
The following are setpoints that will be limited based on the option selected.
Low Ambient Lockout Temperature
Speedtrol
Speedtrol = N
Speedtrol = Y
Range
35 – 60°F
-2 – 60°F
Low Evaporator Pressure Hold and Unload
Refrigerant
R22
R407C
28
ACZ 010A through 039A
Range
24 to 65 Psig
20 to 65 Psig
IOMM ACZ1-2
Dynamic Default Values
Some setpoints will have different default values loaded depending on the value of other
setpoints.
Low Evaporator Pressure Inhibit
Refrigerant
R22
R407C
Default Value
59 psi
60 psi
Low Evaporator Pressure Unload
Refrigerant
R22
R407C
Default Value
58 psi
59 psi
Equipment Protection (Stop) Alarms
Equipment protection (stop) alarms execute rapid compressor shutdown without going
through the normal shutdown cycle.
The following table identifies each of these alarms, gives the condition that causes the
alarm to occur, and states the action taken because of the alarm. If the alarm is autoclearing, the reset condition is shown below. Otherwise, the alarm is manually reset,
requiring the operator to clear the alarm.
Table 11, Stop Alarms
Description
No Evaporator (Water/Air)
Flow
Low Evaporator Pressure
High Condenser Pressure
Motor Protection
Occurs When:
Any compressor is running AND
Evap Flow Digital Input = No Flow for time >
Evap Flow Proof SP
Evaporator Press < Low Evap Pressure SP
for time> Low Evap Pressure Time Delay
Condenser Press > High Condenser
Pressure SP
Digital Input = High Motor Temperature
AND Delay 150 Sec. after power up has
passed
Action Taken
Rapid Stop
Reset
Evap flow switch
closes OR Unit
State=Off
Rapid Stop
Manual
Rapid Stop
Manual
Rapid Stop
Manual
Phase Voltage Protection
(opt)
If Phase Voltage Protection = Y, Then Digital
Input = Phase/Voltage Problem
Rapid Stop
Phase/Voltage
input returns to
normal
Low Ambient Restart Fault
Failed three consecutive low ambient start
attempts
Rapid Stop
Manual
Sensor shorted or open
Rapid Stop
Manual
Sensor shorted or open
Rapid Stop
Manual
Sensor open or shorted
Normal Stop
Manual
Evaporator Pressure
Sensor Fault
Condenser Pressure
Sensor Fault
Outside Ambient
Temperature Sensor Fault
Evaporator Freezestat
Freezestat logic allows the circuit to run for varying times at low pressures. The lower the
pressure, the shorter the time the compressor can run. This time is calculated as follows:
Freeze error = Low Evaporator Pressure Unload – Evaporator Pressure
Freeze time = 60 – 1.6 x freeze error, limited to a range of 20-70 seconds
When the evaporator pressure goes below the Low Evaporator Pressure Unload setpoint, a
timer starts. If this timer exceeds the freeze time, then a freezestat trip occurs. If the
evaporator pressure rises to the unload setpoint or higher, and the freeze time has not been
exceeded, the timer will reset.
IOMM ACZ1-2
ACZ 010A through 039A
29
Events (Limit Alarms)
The following events limit the operation of the unit in some way as described in the Action
Taken column. These alarms are auto-clearing based on reaching the conditions in the reset
column.
Table 12, Event (Limit) Alarms
Description
Condenser Pressure
High Unload
Evaporator Pressure
Low – Hold
Evaporator Pressure
Low – Unload
Occurs When:
Pressure > High Condenser Stage
Down setpoint
Pressure < Low Evap Pressure–Hold
setpoint AND one compessor is running
Pressure < Low Evap Pressure–Unload
setpoint
Failed Pumpdown
Unit is pumping down for 60 seconds
Action Taken
Shutoff
Stage #2
Hold @
Stage 1
Shutoff
Stage 2
Shutoff
Compressors
Reset
Condenser Press drops
below (SP – 100psi)
Evap Press rises above
(SP + 8psi)
Evap Press rises above
(SP + 10 psi)
N/A
Active Alarm List
When an alarm occurs, it appears in the active alarm list. The active alarm list holds a
record of all active alarms, which includes the date and time each occurred. The active
alarms can be cleared by pressing the Edit key when the end of the list has been reached by
scrolling.
Active alarms may be cleared without a password being active. The condition that caused
the alarm must be corrected prior to clearing the alarm to avoid filling the buffer with
duplicate entries and also to avoid repeated trips from the same cause.
Alarm Logging
A separate alarm log stores the last 25 alarms to occur. When an alarm occurs, it is put into
the first slot in the alarm log and all others are moved down one, dropping the last alarm.
In the alarm log, the date and time the alarm occurred are stored, as well as a list of other
parameters. These parameters include compressor states, evaporator pressure, condenser
pressure, number of fans on, and OAT.
Event Logging
An event log similar to the alarm log holds the last 25 events to occur. When an event
occurs, it is put into the first slot in the event log and all other entries are moved down one,
dropping the last event. Each entry in the event log includes an event description as well as
the time and date of the occurrence. No additional parameters are logged for events. A
password must be active to view the event log.
Control Functions and Definitions
Refrigerant Saturated Temperature
Methods for calculating saturated refrigerant temperature differ with each refrigerant as
explained below.
R22 Saturated Temperature
Evaporator saturated temperature and condenser saturated temperature are calculated from
the pressures for each circuit. The pressure is fit to a curve made up of 13 straight line
segments. The points used to define these segments are as follows:
30
ACZ 010A through 039A
IOMM ACZ1-2
Table 13, R-22 Saturated Temperatures
o
Pressure (psi)
24.0
34.7
47.6
62.8
80.8
101.6
126.2
153.8
185.2
220.6
260.5
305.2
355.1
430.4
Temperature ( F)
0
12.0
24.0
36.0
48.0
60.0
72.0
84.0
96.0
108.0
120.0
132.0
144.0
160.0
R407C Saturated Temperature
Evaporator dew point and condenser mid point are calculated using 32 bit math. The
equation is as follows:
If Pressure < 120 psi Then
Saturation = [Pressure x 145/105] – [(Pressure2)/2000] – 250
If Pressure >= 120 psi Then
Saturation = [Pressure x 46/94] – [Pressure2/25000] + 145
Pumpdown Pressure
The pressure to which a circuit will pumpdown is based on the Low Evaporator Pressure
Unload setpoint. The equation is as follows:
Pumpdown pressure = Low Evaporator Pressure Unload Setpoint – 15 psi (with the
calculated value limited to a minimum of 10 psi).
Unit Enable
The Unit Enable status determines whether the unit is enabled to run or not. This can be
altered by the Unit Switch input, Remote input, Keypad entry, and BAS request. The
Control Source Setpoint determines which sources can change the Unit Enable status with
options of SWITCHES, KEYPAD or NETWORK.
Changing the Unit Enable status can be accomplished according to the following table.
NOTE: An “x” indicates that the value is ignored.
Unit
Switch
OFF
x
ON
ON
ON
ON
ON
ON
IOMM ACZ1-2
Control Source
Setpoint
x
SWITCHES
SWITCHES
KEYPAD
KEYPAD
NETWORK
NETWORK
NETWORK
Remote
Input
x
OFF
ON
x
x
x
OFF
ON
Keypad
Entry
x
x
x
OFF
ON
x
x
x
ACZ 010A through 039A
BAS
Request
x
x
x
x
x
OFF
x
ON
Unit
Enable
OFF
OFF
ON
OFF
ON
OFF
OFF
ON
31
Unit Mode
The overall operating mode of the chiller is set by the Available Mode Setpoint with
options of COOL and TEST.
Unit Test Mode
The unit test mode allows manual testing of controller outputs. Entering this mode requires
the following conditions.
•
•
•
Unit Switch = OFF
Manager password active.
Available Unit Mode setpoint = TEST
A test menu can then be selected to allow activation of the outputs. It is possible to switch
each digital output ON or OFF and set the analog outputs to any value. In test mode, the
compressors can be started, but will automatically turn off after 10 seconds. Also, if any
outputs are left on in test mode, they will be automatically turned off and/or normal control
logic resumed when the unit is taken out of test mode.
Power Up Start Delay
After powering up the unit, the motor protectors may not seem to work properly for up to
150 seconds. After the control is powered up, no compressor can start for 150 seconds. In
addition, the motor protect inputs are ignored during this time so as to avoid tripping a false
alarm.
Unit State
The Unit is always in one of three states. These states are Off, Auto, and Pumpdown.
Transitions between these states are shown in the following diagram.
Figure 10, Unit State Diagram
Unit State Diagram
Off
Power On
T3
Pumpdown
T4
T2
T1
Auto
T1: Transition from Off to Auto
Requires all of the following:
• Unit Enable = True
• No Alarm
• At least one compressor enabled via manual setpoint
32
ACZ 010A through 039A
IOMM ACZ1-2
T2: Transition from Auto to Pumpdown
Requires any of the following:
• Keypad Enable = Off OR
• BAS Enable = Off OR
• Remote Switch = Off OR
• Pumpdown Alarm Active
T3: Transition from Pumpdown to Off
Requires any of the following:
• Unit Alarm OR
• Unit Switch Off OR
• All compressors off
T4: Transition from Auto to Off
Requires any of the following:
• Unit Alarm OR
• Unit Switch Off
• Both compressors disabled via manual setpoint
Evaporator Fan State Control
Operation of the evaporator fan output is controlled by the state-transition diagram shown
below.
Figure 11, Fan Output State
Evaporator Fan Output State
Diagram
Off
Unit State=Auto
Unit State = Off
Unit State = Off
Run
[Evap State = Start AND
Flow Switch Closed] for
time > Evap Recirc Tmr
Start
Condenser Fans
Condenser fans are staged up and down based on the fan stage setpoint. These setpoints
define pressures at which fans should start or stop. Comments for “fan 3” apply to 3-fan
units only.
fan 1 will start with the first compressor when the ambient temperature is greater than 75°F.
Below 75°F, this fan starts when the condenser pressure gets up to the Stage #1 On setpoint.
fan 2 will start when the condenser pressure gets up to the Stage #2 On setpoint, and fan 3
will start when the condenser pressure gets up to the Stage #3 On setpoint.
IOMM ACZ1-2
ACZ 010A through 039A
33
Fan 3 will stop when the condenser pressure drops to the Stage #3 Off setpoint, and fan 2
will stop when the condenser pressure drops to the Stage #2 Off setpoint. Fan 1 will stop
when the pressure drops down to the Stage #1 Off setpoint.
Low OAT Start
In order to avoid low-pressure alarms at startup, low OAT start logic allows for running at
low pressures for a longer time than normal as well as multiple start attempts.
A low OAT start is initiated if the condenser saturated temperature is less than 85°F when
the compressor starts. Once this happens, the circuit is in this low OAT start state for a
time equal to the low OAT start timer setpoint. During this time, the freezestat logic and
the low pressure events are disabled. The absolute limit of 5 psi is still enforced.
At the end of the low OAT start, the evaporator pressure is checked. If the pressure is
greater than or equal to the low evaporator pressure unload setpoint, the start is considered
successful. If the pressure is less than the unload setpoint, the start is not successful and
the compressor will stop. Three start attempts are allowed before tripping on the restart
alarm; so if on the third attempt the start is not successful the restart alarm is triggered.
The restart counter will be reset when either a start is successful or the circuit is off on an
alarm.
Capacity Overrides
The following conditions override the automatic capacity control when the chiller is in
Cool mode only. These overrides keep the unit from entering a condition in which it is not
designed to run.
Low Evaporator Pressure
If the evaporator pressure drops below the Low Evaporator Pressure Hold setpoint, the Low
Evaporator Pressure Inhibit event is triggered. This can occur with either one or two
compressors running. When triggered, the second compressor will not be allowed to start if
only one is currently running. If both compressors are already running, no action is taken.
If the evaporator pressure drops below the Low Evaporator Pressure Unload setpoint, the
Low Evaporator Pressure Unload event is triggered. This can only occur when both
compressors are running. When triggered, one compressor is shut off.
These events are logged to an event log when they occur. Both remain active until the
evaporator pressure rises 5 psi above the hold setpoint or both compressors are off.
High Condenser Pressure
If the discharge pressure rises above the High Condenser Pressure Unload setpoint and both
compressors are running, the High Condenser Pressure Unload event is triggered. One
compressor will be shut off when this occurs.
This event will also be logged to an event log when it occurs. It will remain active until the
condenser pressure drops 100 psi below the unload setpoint. While active, the second
compressor cannot turn back on.
34
ACZ 010A through 039A
IOMM ACZ1-2
Low Ambient Lockout
If the OAT drops below the low ambient lockout setpoint, the unit will do a normal stop.
Once the lockout has been triggered, no compressors will start until the OAT rises to the
lockout setpoint plus 5°F.
Compressor Control
Compressor Available
A compressor is available to start when the following are true:
• Unit state = auto
• Evap state = run
• Low OAT lockout is not active
• Power start delay is expired
• No limit events active
• No cycle timers active for the compressor
• Compressor enable setpoint = On
Compressor Start/Stop Timing
This section determines when to start or stop a compressor. There are two separate
functions used, one for staging up and one for staging down.
Stage Up Now
The Stage Up Now flag is set based on the following tests:
IF Stage Request > Stages On AND
Stage up timer expired THEN
Stage Up Now = True
Stage Down Now
The Stage Down Now flag is set based on the following tests:
IF Stage Request < Stages On AND
Stage down timer expired THEN
Stage Down Now = True
Compressor Sequencing
Compressor staging is primarily based on compressor run-hours and starts. Compressors
that have fewer starts will normally start before those with more starts. Compressors that
have more run hours will normally shut off before those with fewer run hours. In the event
of a tie on number of starts, the lower numbered compressor will start first. In the event of
a tie on run-hours, the lower numbered compressor will shut off first. Run-hours will be
compared in terms of tens of hours.
Next On = 1 if compressor 1 starts <= compressor 2 starts, or compressor 2 not available
Next On = 2 if compressor 1 starts > compressor 2 starts, or compressor 1 not available
Next Off = 1 if compressor 1 run-hours > compressor 2 run-hours
Next Off = 2 if compressor 1 run-hours <= compressor 2 run-hours
IOMM ACZ1-2
ACZ 010A through 039A
35
Compressor State
A compressor will start when all of the following are true:
• The compressor is “next on”
• Stage Up Now is set
• The compressor is available to start
A compressor will stop when any of the following conditions are true:
• Unit state = Off
• Evap flow alarm active
• Low Ambient start attempt failed
• Stage Down Now is set, both compressors are running, and the compressor is “next
off”
• Pumpdown is complete
Normal Shutdown
If a condition arises that requires the unit to shut down, a pumpdown will be performed if it
is not an emergency situation. A normal shutdown will be initiated when any of the
following occur:
• Unit State = Pumpdown
• Low Ambient Lockout
• A normal stagedown occurs, and only one compressor is running
Pumpdown Procedure
•
•
•
•
If both compressors are running, shut off the appropriate compressor based on
sequencing logic
With one compressor left running, turn off hot gas output and liquid line output
Keep running until evaporator pressure reaches the pumpdown pressure, then stop
compressor
If evaporator pressure does not reach pumpdown pressure within two minutes, stop
compressor and log pumpdown failure alarm
Rapid Shutdown
A situation may arise that requires the unit to shut down immediately, without doing a
pumpdown. This rapid shutdown will be triggered by any of the following:
• Unit State = Off
• Stop Alarm
• Low ambient start attempt failed
All compressor and liquid line outputs will be turned off immediately for a rapid shutdown.
Liquid Line Solenoid
The liquid line output will be on any time a compressor is running and the unit is not
performing a pumpdown. This output will be off at all other times.
36
ACZ 010A through 039A
IOMM ACZ1-2
Using the Controller
4x20 Display & Keypad
Layout
The 4-line by 20-character/line liquid crystal display and 6-key keypad are shown below.
Figure 12, Display (in MENU mode) and Keypad Layout
Key to Screen Pathway
Red Alarm Light
MENU Key
Air Conditioning
< ALARM
VIEW
<
SET
<
ARROW Keys
ENTER Key
Note that each ARROW key has a pathway to a line in the display. Pressing an ARROW
key will activate the associated line when in the MENU mode.
Getting Started
There are two basic procedures to learn in order to utilize the MicroTech II controller:
1. Navigating through the menu matrix to reach a desired menu screen and knowing where
a particular screen is located.
2. Knowing what is contained in a menu screen and how to read that information or how
to change a setpoint contained in the menu screen.
Navigating Through the Menus
The menus are arranged in a matrix of screens across a top horizontal row. Some of these
top-level screens have sub-screens located under them. The general content of each screen
and its location in the matrix are shown in Figure 14. A detailed description of each menu
begins on page 40.
There are two ways to navigate through the menu matrix to reach a desired menu screen.
One is to scroll through the matrix from one screen to another using the four ARROW keys.
The other way is to use shortcuts to work through the matrix hierarchy. From any menu
screen, pressing the MENU key will take you to the top level of the hierarchy. The display
will show ALARM, VIEW, and SET as shown in Figure 12. This corresponds to the second
row of screens on Figure 14. One of these groups of screens can then be selected by
pressing the key connected to it via the pathway shown in Figure 12.
For example, selecting ALARM will go the next row of menus under ALARM (ALARM
LOG or ACTIVE ALARM). Selecting VIEW will go the next level of screens under VIEW
(VIEW UNIT STATUS or VIEW UNIT TEMP). Selecting SET will go to a series of
screens for looking at and changing setpoints.
IOMM ACZ1-2
ACZ 010A through 039A
37
MENU Key
The MENU key is used to switch between the shortcut method (known as the MENU mode
and as shown in Figure 12) and scrolling method (known as the SCROLL mode). The
MENU mode is the shortcut to specific groups of menus used for checking ALARMS, for
VIEWING information, or to SET setpoint values. The SCROLL mode allows the user to
move about the matrix (from one menu to another, one at a time) by using the four
ARROW keys. A typical menu screen is shown in Figure 13.
Pressing the MENU key from any menu screen will automatically return you to the MENU
mode as shown in Figure 12.
Figure 13, Display in the Shortcut (SCROLL) Mode and Keypad Layout
MENU Key
Air Conditioning
VIEW UNIT STATUS
Unit = COOL
Compr. #1/#2=OFF/OFF
Evap Pump = RUN
ARROW Keys
ENTER Key
Menu Screens
Various menus are shown in the controller display. Each menu screen shows specific
information; in some cases menus are used only to view the status of the unit, in some cases
they are used for checking and clearing alarms, and in some case they are used to set
setpoint values.
The menus are arranged in a matrix of screens across a top horizontal row. Some of these
top-level screens have sub-screens located under them. The general content of each screen
and its location in the matrix are shown in Figure 14. A detailed description of each menu
begins on page 40.
The ARROW keys on the controller are used to navigate through the menus. The keys are
also used to change numerical setpoint values contained in certain menus.
Changing Setpoints
Pressing the ENTER key changes the function of the ARROW keys to the editing function
as shown below:
LEFT key
RIGHT key
setting.
UP key
DOWN key
Default, changes a value to the factory-set default value.
Cancel, cancels any change made to a value and returns to the original
Increment, increases the value of the setting.
Decrement decreases the value of a setting.
These four edit functions are indicated by one-character abbreviation on the right side of
the display (this mode is entered by pressing the ENTER key).
38
ACZ 010A through 039A
IOMM ACZ1-2
Most menus containing setpoint values have several different setpoints shown on one menu.
When in a setpoint menu, the ENTER key is used to proceed from the top line to the second
line and on downward. The cursor will blink at the entry point for making a change. The
ARROW keys (now in the edit mode) are used to change the setpoint as described above.
When the change has been made, press the ENTER key to enter it. No setting is changed
until the ENTER key is pressed.
For example, to change the number of unit fans setpoint:
1. Press MENU key to go to the MENU mode (see Figure 12).
2. Press SET (the UP Key) to go to the setpoint menus.
3. Press SET FAN SP (the Right key) to go to setpoints associated with unit operation.
4. Since the first (or top) menu will be used, there is no need to press the DOWN key to
scroll down through other setpoint menus.
5. Press the ENTER key to move the cursor down from the top line to the second line in
order to make the change.
6. Use the ARROW keys (now in the edit mode as shown above) to change the setting.
7. When the desired value is achieved, press ENTER to enter it. The cursor will
automatically move down.
At this point, the following actions can be taken:
1. Change another setpoint in this menu by scrolling to it with the ENTER key.
2. Using the ENTER key, scroll to the first line in the menu. From there the ARROW keys
can be used to scroll to different menus.
IOMM ACZ1-2
ACZ 010A through 039A
39
Figure 14, Menu Matrix
"MENU"
"VIEW" MENUS
REFRIGERANT
FANS
VIEW UNIT
UNIT
VIEW UNIT
VIEW COMP #1
COMP
VIEW COMP #2
VIEW EVAP/COND PRESS
VIEW
STATUS 1-3
TEMP
STATUS 1-2
STATUS 1-2
1-2
FANS
⇐ Continued ⇐
(Right side of matrix continued from above)
"ALARM" MENUS
ALARM LOG
"SET" MENUS
EVENT LOG ACTIVE ALARM SET UNIT SPs,
(1) MODE
(LAST)
(LAST)
(1)
TYPE, TIME
TYPE, TIME
TYPE, TIME
ALARM LOG
EVENT LOG ACTIVE ALARM SET UNIT SPs,
(NEXT TO LAST)
SET FANS (1)
SET COMP
SET LIMIT
SPs (1)
ALARMS (1)
STAGES
STOP/START
EVAP PRESS
FANTROL
SET COMP
SET LIMIT
SET FANS (2)
(NEXT TO
(n)
(2) MODE =
SPs (2)
ALARMS (2)
STAGE ON
LAST)
TYPE, TIME
COOL
INTER-
FREEZE/ FLOW
STAGE
ADDITIONAL
ALARM LOG
EVENT LOG ACTIVE ALARM SET UNIT SPs,
(SECOND TO
(SECOND TO
(3)
LAST)
LAST)
CLEAR/VIEW
(3) CLOCK
SET LIMIT
SET FANS (3)
ALARMS (3)
STAGE OFF
COND PRESS
ALARM LOG
EVENT LOG
SET UNIT SPs,
SET LIMIT
LAST 25 SHOWN
LAST 25
(4) ENGLISH
ALARMS (4)
SHOWN PHASE/VOLT
LOW AMB
LOCKOUT
SET UNIT SPs,
SET LIMIT
(5) PROTOCOL
ALARMS (5)
LOW EVAP PR
SET UNIT SPs,
(6) EVAP
OFFSET
SET UNIT SPs,
(7) COND
OFFSET
SET UNIT SPs,
(8) AMBIENT
OFFSET
SET UNIT SPs,
(9) ENTER
PASSWORD
Menu Structure (Hierarchical)
As discussed previously, a hierarchical menu structure can be used to access the various
screens. One to twelve levels are used with two or three being typical. Optionally, the last
menu selection can access one of a set of screens that can be navigated with the UP/DOWN
ARROW keys (see the scrolled menu structure below).
Menu selection is initiated by pressing the MENU key that changes the display from a
regular data screen to a menu screen. Menu selections are then made using the arrow keys
according to labels on the right side of the display (the arrows are ignored). When the last
40
ACZ 010A through 039A
IOMM ACZ1-2
menu item is selected, the display changes to the selected data screen. An example follows
showing the selection of the “VIEW REFRIGERANT” screen.
Suppose the initial screen is as below or any other menu screen:
ALARM LOG
(data)
(data)
(data)
After pressing the MENU key, the top level menu screen will show:
< ALARM
< VIEW
<
SET
After pressing the “VIEW” menu key, a menu screen will show:
VIEW
<
UNIT
< COMPRESSOR
< REFRIGRANT
<
FANS
Selection of any of these will advance to the appropriate data menu. For example, after pressing the
“REFRIGERANT” menu button, the selected data screen will show:
VIEW REFRIG
PSI
SAT EVAP XXX.X
SAT COND XXX.X
°F
XX.X
XX.X
The ARROW keys will automatically return to the “scroll” mode at this time.
Screen Definitions VIEW
This section contains information on each screen. The menu screens are in order of the
matrix in Figure 14, going from left to right and then down when there are sub-menus.
Many menus are self-explanatory.
VIEW UNIT
VIEW UNIT STATUS (1)
Unit = AUTO
Stage=X
Request=X
Unit status can be OFF, AUTO, and ALARM as determined from the Unit State variable,
the Unit Mode setpoint, the Unit Enable and the presence of an alarm.
VIEW UNIT STATUS (2)
Stg Up Delay=XXXsec
Stg Dn Delay=XXXsec
IOMM ACZ1-2
ACZ 010A through 039A
41
VIEW UNIT STATUS (3)
D.O
D.I.
12345678 12345678
00000000 00000000
View Unit Temperatures
VIEW UNIT TEMP °F
Outside Amb = XX.X°F
VIEW COMPRESSORS
VIEW COMP#1
(1)
State
= OFF LEAD
Cycle Timer: XXmin
Manual Disable
Cycle timer only visible when active. Manual Disable visible only when compressor is
disabled via manual enable setpoint.
VIEW COMP#1
Hours = XXXXX
Starts = XXXXX
(2)
Above two screens duplicated for Compressor #2.
VIEW REFRIGERANT
VIEW REFRIG
(1)
EVAP Press = XX.Xpsi
COND Press - XX.Xpsi
With R22 Refrigerant
VIEW REFRIG
(2)
SAT EVAP = XXX.X°F
SAT COND = XXX.X°F
EvapApproach = XX.X°F
With R407C Refrigerant
VIEW REFRIG
(2)
Evap Dew = XXX.X°F
Cond Mid = XXX.X°F
EvapApproach = XX.X°F
See page 30 for an explanation of saturated temperatures for R22 and R407C.
Approach is the difference between the leaving fluid temperature and the saturated
evaporator temperature. It is an indication of the evaporator efficiency; an increasing
approach temperature indicates decreasing heat transfer efficiency.
42
ACZ 010A through 039A
IOMM ACZ1-2
VIEW FANS
VIEW FANS
Stages ON = 2 of 3
Screen Definitions – ALARM
ALARM ACTIVE (X)
ALARM ACTIVE (X)
Alarm Description
No more alarms
hh:mm:ss dd/mmm/yyyy Press ENTER to clear
all active alarms
If the unit is off on a shutdown alarm or running but in a limit alarm condition, the cause
and date will appear in the upper screen. If there is a simultaneous occurrence of more than
one alarm, the others will appear in additional screens below this one, accessed by the
DOWN ARROW. Either type alarm will light a red light in back of the LEFT-KEY. The
light will go out when the fault is cleared.
To clear the fault, scroll down to the last screen and press ENTER. If other faults have
appeared, they will all be cleared at the same time.
ALARM LOG (1)
High Condenser Press
hh:mm:ss d/mmm/yyyy
The last 25 alarms, either shutdown or limit, are shown in this menu with subsequent menus
stored under it. ARROW DOWN from this menu will go to the next-to-last alarm, ARROW
DOWN again will go to the second from last, and so on through the last 25 occurrences.
The screens are numbered (1), (2),, etc.
Screen Definitions – SET
Changing setpoints; in general, setpoints are changed as follows:
1. Select the desired menu by scrolling through SET menus with the UP and DOWN
ARROWS.
2. When the desired menu is selected, select the desired entry by moving between lines
using the ENTER key.
3. If a numerical value is being changed, use the INCREMENT key (UP ARROW) to
increase or the DECREMENT key (DOWN ARROW) to decrease the value of the
setpoint.
If a word type setpoint (for example, YES or NO) is to be selected, the choices are
loaded into the menu and selected by scrolling through the available setpoint options
using the UP ARROW key.
4. Enter the desired value or word into the controller by pressing the SET key.
IOMM ACZ1-2
ACZ 010A through 039A
43
SET UNIT SPs
SET UNIT SPs (1)
Unit Enable=OFF
Source=KEYPAD
Unit Enable is an external signal or a keypad setting that keeps the unit off when the setting
is OFF and allows it to run if there is a call for cooling. The source for the signal is
selected in the 3td line and can be:
1. KEYPAD, in which case the selection is made in line 2 and would be normally selected
as ON. This is the normal setting when no external signals are controlling the unit.
2. SWITCHES, in which an external switch is wired across terminals #25 and #35.
3. NETWORK, used with BAS signal, which is wired to the three communication ports.
SET UNIT SPs (2)
Available Modes
=COOL
Set w/ FP Switch Off
Available Modes setting is the standard COOL or TEST as selected from the available
modes imbedded in the menu. The 4th line is a reminder that the ON/OFF switch on the
front panel (FP) must be in the OFF position before the MODE can be changed. This
prevents a mode change while the unit is operating.
SET UNIT SPs (3)
Air Flow Timer=XXsec
LowAmblock= XX.X°F
SET UNIT SPs (4)
CLOCK
dd/mmm/yyyy
hh:mm:ss
SET UNIT SPs (5)
Units = °F/psi
Lang = ENGLISH
Refrig=R22
Unit settings are only °F/psi at the present time. °C/kPa will be available later.
Lang (Language) settings can be only ENGLISH at present.
Refrig (Refrigerant) is set for the correct refrigerant in the factory prior to shipment.
SET UNIT SPs (6)
Protocol = NONE
Ident Number=001
Baud Rate=9600
Protocol selection for BAS will be available in June 2002.
44
ACZ 010A through 039A
IOMM ACZ1-2
SET UNIT SPs (7)
Evaporator Refrig
Press Sensor
Offset= 00.0 psi
The pressure offsets on menus 7 and 8 and the temperature offset on menu 9 correct the
controller's display of the parameters. The sensors used in these units have a high degree of
repeatability but may need correction (offset). An accurate pressure gauge or thermometer
is used to determine the correct temperature or pressure. A positive or negative offset value
is then entered to make the controller reading agree with the measured value.
SET UNIT SPs (8)
Condenser Refrig
Press Sensor
Offset= 00.0 psi
SET UNIT SPs (9)
Outside Ambient
Temperature Sensor
Offset= 00.0oF
SET UNIT SPs (10)
ENTER PASSWORD XXXX
Active Password
Level:None
Two four-digit passwords provide OPERATOR and MANAGER levels of access to
changeable parameters. The passwords are preprogrammed into the controller. The
Operator Password is 0100. Either password must be entered using the ENTER
PASSWORD (12) screen before a protected setting can be changed.
This screen can be accessed either through the SET OTHER menu or by simply pressing
the ENTER key while on one of the SET screens. The controller will automatically go
from the screen with the setting change to this screen. After the correct password has been
entered, the controller will automatically return to the original set screen.
Once a password has been entered, it remains valid for 15 minutes after the last key-press.
SET COMP SPs
SET COMP SPs (1)
Clear Cycle Tmr=No
Stop-Start =XXmin
Start-Start =XXmin
This menu sets the anti-recycle timers. Stop-Start is the time required before starting a
compressor after it has stopped. Start-Start is the time required before starting a
compressor after the last time it has started. It is recommended that these default values
not be changed.
SET COMP SPs (2)
InterStageUp=XXXsec
InterStageDn=XXXsec
IOMM ACZ1-2
ACZ 010A through 039A
45
InterStageUp is the time delay since the last stage change before a compressor can stage on.
InterStageDn is the time delay since the last stage change before a compressor can stage off
normally (not by an alarm).
SET COMP SPs (3)
Manual Comp Enable
Comp 1= Enable
Comp 2= Enable
SET ALARM SETPOINTS
SET ALARM LMTS (1)
Low Evap Pressure
Hold = 59.0 psi
Unload = 58.0 psi
If two compressors are running, the LowEvPr Unld is in effect and the lag compressor will
be shut off to unload the unit. If one compressor is running, the LowEvPr Hold is in effect
and the lag compressor is prevented from starting, thereby holding the unit capacity.
SET ALARM LMTS (2)
EvapFlowProof=XXXsec
EvapFlowProof is the flow switch interlock. Closing the flow switch and therefore proving
the existence of chilled water or air flow resets this trip.
SET ALARM LMTS (3)
HighCondPr = XXXpsi
HiCondStgDn = XXXpsi
HighCondPr (the unit high-discharge-pressure shutdown) is a stop alarm that shuts off the
unit when the discharge pressure reaches the setting. The default setting is 380 psi. The
HiCondStDn is a limit alarm that unloads the unit in an attempt to prevent total shutdown
from the HighCondPr. The stage down is set at 370 psi.
SET ALARM LMTS (4)
PhaseVoltage=YES/NO
LowOATStrtTmr=XXXsec
LowAmbientLock prevents unit operation below the setting. If the unit is equipped with
the standard FanTrol pressure-activated control, the available range is 35°F to 60°F with a
default of 35°F. With the optional SpeedTrol variable speed control, the range becomes –
2°F to 60°F with default of 0°F. Input to line 3 of the next screen, SET FANS SP (1),
informs the controller which type of control is installed and which range of setting to allow.
46
ACZ 010A through 039A
IOMM ACZ1-2
SET FANS SETPOINTS
SET FANS SPs (1)
Fans Stages = X
Speedtrol = NO
The Fan Stages line tells the controller the number of fans on the unit. The UP ARROW
toggles between 1, 2, and 3. 1 is not used; 2 should be used for Models ACZ 010, 013, and
017; and 3 should be used for ACZ 020, 025, 029, and 039.
SpeedTrol tells the controller whether the optional SpeedTrol is installed in the unit. The
UP ARROW toggles between YES and NO. The setting changes the range available: YES
= 35°F to 60°F, with 35°F being the recommended setting; NO = -2°F to 60°F, with 0°F
being the recommended setting.
SET FANS SPs (2)
Stage ON psi
#1
#2
#3
XXX
XXX
XXX
SET FANS SPs (3)
Stage Off psi
#1
#2
#3
XXX
XXX
XXX
These two menus set the on and off staging pressures for the fans. The third fan is for only
for three-fan units. These settings are used with both FanTrol and SpeedTrol. SpeedTrol
takes effect when the last fan is running after FanTrol cycles off the others. Fan #1 is
staged by condensing pressure and does not or stop start automatically when the unit does.
Screen Definitions – TEST
The test screens are only available when the unit is in TEST mode. Using these screens,
any digital output can be controlled manually.
TEST UNIT
(1)
Alarm Signal= OFF
Evap Fan=OFF
TEST UNIT
(2)
Liquid Line Sol=OFF
Compressor #1 = OFF
Compressor #2 = OFF
TEST UNIT
(3)
Fan Motor #1 = OFF
Fan Motor #2 = OFF
Fan Motor #3 = OFF
IOMM ACZ1-2
ACZ 010A through 039A
47
Service
DANGER
Disconnect and tag-out all sources of power to the unit before doing any
service inside the unit. Failure to do so can cause serious personal injury or
death.
CAUTION
Service on this equipment must be performed only by trained, experienced,
qualified service personnel with special regard to regulations concerning
release of refrigerant to the atmosphere.
Note: Repeated tripping of equipment protection controls must be investigated and
corrected.
Thermostatic Expansion Valve
The field-installed expansion valve is responsible for allowing the proper amount of
refrigerant to enter the evaporator regardless of cooling load. It does this by maintaining a
constant superheat. (Superheat is the difference between refrigerant temperature as it
leaves the evaporator and the saturation temperature corresponding to the evaporator
pressure.) Typically, superheat should run in the range of 8°F to 12°F (4.4°C to 6.6°C).
Maintaining correct superheat to the compressor is an important element in extending
compressor life.
Filter-Driers
In general, the pressure drop across the field-installed filter-drier should be in the 6 to 10
psi range. It should be monitored and changed when the pressure drop reaches 10 psi.
After changing the filter-drier, check for leaks before recharging and returning unit to
operation.
Liquid Line Solenoid
The field installed liquid line solenoid valve does not normally require any maintenance.
Reliable operation of the solinoid valve is necessary for the pump-down function of the
unit's control system.
48
ACZ 010A through 039A
IOMM ACZ1-2
Optional Controls
SpeedTrol Head Pressure Control
The SpeedTrol method of head pressure control operates in conjunction with FanTrol by
modulating the motor speed on system #1 fan in response to condenser pressure. By
reducing the speed of the last fan as the condensing pressure falls, the unit can operate to
0°F (-18°C) ambient air temperature.
The SpeedTrol fan motor is a single-phase, 230/460 volt, thermally protected motor
specially designed for variable speed operation. The solid-state speed control is mounted in
the unit control panel and is connected to a Schrader fitting on the liquid line. The control
is factory-set to start modulating fan speed at 230 psig, and it will maintain a minimum
condensing pressure of 170 to 180 psig. Minimum starting voltage for SpeedTrol motors is
120 volts.
A low ambient timer function is included in the microprocessor. When the solenoid valve
and lead compressor are energized by the controller, the low pressure cutout control is
bypassed and the compressor is allowed to start with the low pressure control open.
After about 2-3/4 minutes, the time delay will open and the low pressure cutout function is
again operable. If the system has not built up enough evaporator pressure to close the low
pressure setting, the compressor will stop.
Due to the vertical condenser design, it is recommended that the unit be oriented so that
prevailing winds blow parallel to the unit length, thus minimizing effects on minimum
ambient operation. If it is not practical to orient the unit in this manner, a wind deflector
should be constructed.
Hot Gas Bypass
Hot gas bypass is a system for maintaining evaporator pressure at or above a minimum
value. The purpose for doing this is to keep the velocity of the refrigerant as it passes
through the evaporator high enough for proper oil return to the compressor when cooling
load conditions are light. It also maintains continuous operation of the chiller at light load
conditions.
The field installed hot gas solenoid valve should be as shown on Figure 7, ACZ 010A
through 039A, Typical Field Wiring Diagram. This can be accomplished by wiring the hot
gas solenoid (SV5) to terminals 14 and 16. The pressure-regulating valve is factory-set to
begin opening at 58 PSIG (32°F for R-22) when the air-charged bulb is in an 80°F ambient
temperature. The bulb can be mounted anywhere as long as it senses a fairly constant
temperature at various load conditions. The compressor suction line is one such mounting
location. It is generally in the 50°F to 60°F range.
The chart below (Figure 16) indicates that when the bulb is sensing 50°F to 60°F
temperatures, the valve will begin opening at 54 PSIG. This setting can be changed as
indicated above, by changing the pressure setting, remove the cap on the bulb and turn the
adjustment screw clockwise. To lower the setting, turn the screw counterclockwise. Do not
force the adjustment beyond the range it is designed for, as this will damage the adjustment
assembly.
The regulating valve opening point can be determined by slowly reducing the system load
(or increasing the required evaporator temperature setting indicated on the unit thermostat),
while observing the suction pressure. When the bypass valve starts to open, the refrigerant
line on the evaporator side of the valve will begin to feel warm to the touch.
IOMM ACZ1-2
ACZ 010A through 039A
49
WARNING
The hot gas line can become hot enough to cause injury in a very short time.
Do not allow prolonged contact during valve checkout.
On installations where the condensing unit is remote from the evaporator, it is
recommended that the hot gas bypass valve be mounted near the condensing unit to
minimize the amount of refrigerant that will condense in the hot gas line during periods
when hot gas bypass is not required.
Figure 15, Hot Gas Bypass Piping
Suction Line
Hot Gas Bypass
Solenoid Valve
Adjustable
Remote Bulb
External Equalizer
Connection to Suction
Side of Evaporator
Discharge
Line
To Evaporator Inlet
After Expansion Valve
Hot Gas
Bypass Valve
Figure 16, Hot Gas Bypass Adjustment
REMOTE BULB ADJUSTMENT RANGE
70
MAXIMU
ADJUSTMENT
RANGE
VALVE OPENING PRESSURE (PSIG)
80
M
60
ING
Y SETT
FACTOR
50
M
MINIMU
40
30
30
40
50
60
70
80
90
100
110
TEMP (°F) AT BULB LOCATION
50
ACZ 010A through 039A
IOMM ACZ1-2
Troubleshooting Chart
WARNING
Troubleshooting must be done only by trained, experienced technicians.
Troubleshooting presents risks of severe personal injury and death from
cuts, burns, electrocution and suffocation.
Table 14, Troubleshooting Chart
PROBLEM
COMPRESSOR WILL
NOT RUN
COMPRESSOR NOISY
OR VIBRATING
HIGH DISCHARGE
PRESSURE
LOW DISCHARGE
PRESSURE
HIGH SUCTION
PRESSURE
LOW SUCTION
PRESSURE
UNIT WILL NOT LOAD
OR UNLOAD
LOAD/UNLOAD
INTERVAL TOO
SHORT
COMPRESSOR
LOSES OIL
MOTOR OVERLOAD
RELAYS OPEN OR
BLOWN FUSES
COMPRESSOR
THERMAL SWITCH
OPEN
IOMM ACZ1-2
POSSIBLE CAUSES
1. Main switch open
2. Fuse blown, breakers open
3. Thermal overloads tripped
4. Defective contactor or coil
5. System off by protection device
6. No cooling required
7. Liquid line solenoid will not open
8. Motor electrical problem
9. Loose wiring
1. Refrigerant flooding compressor
2. Improper line support
3. Worn compressor
1. Noncondensables in system
2. Refrigerant overcharge
3. Fan not running
4. Dirty condenser coils
5. FanTrol out of adjustment
1. Faulty condenser control
2. Low refrigerant charge
3. Low suction pressure
1. Excessive load
2. Expansion valve overfeeding
1. Lack of refrigerant
2. Evaporator dirty
3. Clogged filter-drier
4. Expansion valve malfunctioning
5. Low condensing temperature
1 Faulty controller sensor/broken wire
2. Stages not set for application
1. Erratic thermostat
2. Insufficient water flow
POSSIBLE CORRECTIVE STEPS
1. Close switch
2. Check electrical circuits and motor windings for
shorts. Check for overloads and loose connections.
Replace fuse or reset breaker.
3. Check unit when back on line, auto reset
4. Repair or replace
5. Determine cause and correct
6. None, should start on call for cooling
7. Repair or replace coil
8. Check motor for open or short circuit, or burnout
9. Check all wire junctions. Tighten all terminals.
1. Check expansion valve setting
2. Relocate or add supports
3. Replace
1. Remove with authorized procedures
2. Remove excess
3. Check electrical circuit
4. Clean coil
5. Adjust FanTrol setting
1. Check condenser control operation
2. Check for leaks. Add refrigerant
3. See low suction pressure steps below
1. Reduce load or add capacity
2. Check remote bulb. Regulate superheat
1. Check for leaks. Repair and replace refrigerant.
2. Clean chemically
3. Replace
4. Check and adjust for proper superheat
5. Check discharge pressure control settings
1. Replace
2. Adjust thermostat setting
1. Replace
2. Adjust flow
1. Lack of refrigerant
2. Suction superheat too high
3. Crankcase heater burned out
1. Low voltage during high loads
2. Defective or grounded motor wiring
3. Loose power wiring
4. High condensing temperature
5. Unbalanced voltage
1. Operating beyond design conditions
1. Check for leaks and repair
2. Adjust superheat
3. Replace crankcase heater
1. Check supply voltage
2. Replace compressor
3. Check all connections and tighten
4. See steps for high discharge pressure
5. Check voltage. Contact power company.
1. Add facilities so conditions are within allowable limits
ACZ 010A through 039A
51
Post Office Box 2510, Staunton, Virginia 24402 USA • (540) 248-0711 • www.mcquay.com
IOMM ACZ1-2 (6/05)
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