McQuay SWT023C User Manual

Catalog 865-5

Modular Self-Contained Air Conditioning Systems

Type SWT 023C—040C
20 to 45 Tons

Engineered for flexibility and performance™

Continued Leadership in Floor-By-Floor,

Self-Contained System Designs . . . . . . . . . . . . . . 3

Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Agency Listed . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

System Performance Providing Tenant Comfort

and Operating Economy . . . . . . . . . . . . . . . . . . . . 4

McQuay Self-Contained VAV Systems . . . . . . . . . 4

Cabinet, Casing and Frame . . . . . . . . . . . . . . . . . 5

Modular Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Condensing Section . . . . . . . . . . . . . . . . . . . . . . . 5

Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Cooling Coil Section . . . . . . . . . . . . . . . . . . . . . . . 6

Heating Section . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Supply Fan Section . . . . . . . . . . . . . . . . . . . . . . . . 6

Economizer Options . . . . . . . . . . . . . . . . . . . . . . . 7

Filter Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Auxiliary Control Options . . . . . . . . . . . . . . . . . . . 8

Selection/Application Flexibility . . . . . . . . . . . . . . . 9

Modular Construction . . . . . . . . . . . . . . . . . . . . . . 9

System Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Ultraviolet Lights . . . . . . . . . . . . . . . . . . . . . . . . . 10

Refrigerant R-407C . . . . . . . . . . . . . . . . . . . . . . . 10

®

MicroTech

III Unit Controller . . . . . . . . . . . . . . . 11

Open Choices Benefits for Easy Integration . . . . 11

Alarm Management and Control . . . . . . . . . . . . . 17

Application Considerations . . . . . . . . . . . . . . . . . 18

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Unit Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Acoustical Considerations . . . . . . . . . . . . . . . . . . 19

Recommended Clearances . . . . . . . . . . . . . . . . 19

Equipment Room . . . . . . . . . . . . . . . . . . . . . . . . 19

Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Vibration Isolation . . . . . . . . . . . . . . . . . . . . . . . . 20

Condenser Water Piping . . . . . . . . . . . . . . . . . . . 20

Head Pressure Control . . . . . . . . . . . . . . . . . . . . 20

Variable Air Volume . . . . . . . . . . . . . . . . . . . . . . 20

Variable Frequency Drives . . . . . . . . . . . . . . . . . 20

Duct Static Pressure Sensor Placement . . . . . . . 20

Zone Sensor Placement . . . . . . . . . . . . . . . . . . . 20

Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

System Operating Limits . . . . . . . . . . . . . . . . . . . 21

Coil Freeze Protection . . . . . . . . . . . . . . . . . . . . 22

Air Density Correction . . . . . . . . . . . . . . . . . . . . . 22

Unit Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Application Considerations . . . . . . . . . . . . . . . . . 22

Selection Procedure . . . . . . . . . . . . . . . . . . . . . . . 23

Physical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Unit Efficiency Ratings . . . . . . . . . . . . . . . . . . . . 26

Correction Multipliers . . . . . . . . . . . . . . . . . . . . . 26

DX Cooling Capacity Data . . . . . . . . . . . . . . . . . 26

Performance Data . . . . . . . . . . . . . . . . . . . . . . . . . 26

Waterside Economizer Capacity . . . . . . . . . . . . . 29

Heating Capacity Data . . . . . . . . . . . . . . . . . . . . 31

Component Pressure Drops . . . . . . . . . . . . . . . . 31

Fan Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Dimensional Data . . . . . . . . . . . . . . . . . . . . . . . . . 37

Electrical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Supply Power Wiring . . . . . . . . . . . . . . . . . . . . . . 41

Unit Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Engineering Guide Specifications . . . . . . . . . . . . 43

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Safety Agency Listed . . . . . . . . . . . . . . . . . . . . . 43

Cabinet, Casing and Frame . . . . . . . . . . . . . . . . 43

Filter/Economizer Section . . . . . . . . . . . . . . . . . . 43

Fan Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Coils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

MicroTech III Unit Controller . . . . . . . . . . . . . . . . 46

Open Communications Protocol . . . . . . . . . . . . . 48

2 McQuay Catalog 865-5

SWT - 040 - C

Self-contained
Water-cooled
Top mounted fan

Design
vintage

Nominal
capacity

Introduction

Continued Leadership in Floor-By-Floor,
Self-Contained System Designs

McQuay SWT self-contained air conditioning systems trace their
history to the late 1970s and the pioneering concepts of Blazer
Industries. Working closely with the consulting engineer to solve
special system and space challenges, Blazer Industries developed
and provided the first self-contained, variable air volume systems
with water side economizer cycle for the prestigious 499 Park
Avenue office building. Following the success of this project was
more than a decade of innovation and product leadership, with
thousands of systems provided for prominent building projects.

In 1991, McQuay acquired Blazer Industries. The result has been
a continuation of this tradition of innovation and leadership. The
comprehensive, updated modular McQuay SWT system offering
is now supplying quiet, efficient and flexible systems to meet
today’s diverse and demanding performance needs for new and
retrofit, commercial, industrial and institutional buildings world­wide.

Nomenclature

Agency Listed

McQuay and MicroTech are registered trademarks of McQuay International.

DesignFlow, Hi-F, Protocol Selectability, RoofPak, SelectTools, SpeedTrol, SuperMod, UltraSeal, and VaneTrol

Microsoft is a registered trademark of Microsoft Corporation.

Copyright © 2011 McQuay International. All rights reserved throughout the world.

are trademarks of McQuay International.

Windows is a trademark of Microsoft Corporation.

McQuay Catalog 865-5 3

McQuay Self-Contained VAV Systems

System Performance Providing Tenant Comfort and Operating Economy

Since the introduction of self-contained systems in the late 1970s,
the industry has seen this concept grow into one of the most
widely specified systems for new office buildings, for retrofitting
existing structures, and for institutional, industrial, and other spe­cialized applications. The reason is simple: system performance.
Designed specifically to satisfy growing system retrofit needs,
McQuay SWT self-contained VAV systems provide the total per­formance advantage of:

• Modular construction

• Prime candidate for building renovation

• Special 34.5" maximum section width fits through a 3'
door frame

• Refrigerant lines always remain intact

• Requires minimum floor area when reassembled

• Retrofit alternative where existing chiller cannot be
accessed for replacement

• Tenant Comfort

• Tenants enjoy individual control over comfort conditions
and off-hour system operation

• Tenants benefit from their individual efforts to control
energy costs

• Routine service is located where it minimizes tenant
inconvenience

• Individual or dual systems per floor provide system
redundancy and standby

• First cost economics

• VAV system flexibility uses building diversity to reduce
system tonnage and first cost

• Factory packaged concept reduces field labor, installation
time and expense

• No expensive chilled water piping or chiller room

• Individually tested, factory designed systems reduce
start-up and installation expense

• Reduce penthouse and equipment room
requirements

• Centralize condenser water and condensate piping and
streamline system layout

• Energy-saving VAV system control

• Reduces fan kW and operating costs at part load condi­tions

• Savings maximized through use of variable speed fan
control

• Individual zone control without overcooling or use of
reheat

• Quiet system operation

• Provided by structural quality and specialized design

• Recognized for quiet operation by renowned U.S. acous­tical consultants

• Energy saving economizer operation

• Water or air economizer capability for optimized energy
savings

• Economizer reduces compressor operating hours and
energy costs

• Year-round “free cooling” capability

• Energy saving building part load operation

• System energy efficiency comparable to central chilled
water systems

• Multiple systems and compressors versus a single, large
central plant

• Efficient system for partial occupancy and after hours
operation

• Operate only the system(s) on the floor(s) requiring after
hours use

Figure 1. McQuay Self-Contained VAV Systems

• System savings of advanced MicroTech III™ DDC

control system

• Monitoring and diagnostics reduce the potential for
expensive field repairs

• Industry leading Protocol Selectability™ feature provides
effective BAS selection flexibility

• Reduced system maintenance and service costs

• No complicated central chiller plant to maintain

• Service and maintenance are performed out of the occu­pied space

• Control and product reliability functions designed by the
equipment manufacturer for single source responsibility
and improved reliability

4 McQuay Catalog 865-5

Fan Section

Filter / Waterside
Economizer Section

Main Heating /
Cooling Section

Design Features

Cabinet, Casing and Frame

For vibration control and rigging strength, the SWT unit base is
constructed of welded structural steel channel and 10- gauge gal­vanized steel panels. Heavy-duty lifting brackets are strategically
placed for balanced cable or chain hook lifting.

For long equipment life, unit exterior panels are constructed of
heavy gauge, pre-painted, galvanized steel. The complete cabinet,
frame and access panels are insulated with 1 inch thick, 1.5 lb.
dual density insulation. Double wall construction is available to
enhance performance and satisfy IAQ requirements.

For maintenance and service ease, system components are strate­gically located for ease of inspection and maintenance. Refrigera­tion components are positioned out of the airstream so
adjustments and readings can be made without disrupting system
operation. Service friendly access is made through heavy-duty,
conveniently removable panels. Access panels are set on neoprene
gaskets to prevent air leakage.

Modular Design

The SWT unit is easily disassembled into three compact sections;
main cooling/heating, filter/waterside economizer and fan. See
“Modular Construction” under “System Flexibility” on page 9.

Figure 2. SWT Cabinet

Condensing Section

Multiple compressors are featured in all SWT systems for effi­cient system part load control, quiet operation and system redun­dancy. Compressors are quiet, reliable hermetic scroll type
complete with sightglass, anti-slug protection, and motor overload
protection. Suction and discharge service valves, with gauge
ports, are available on each compressor. Individual branch circuit
fusing protects each compressor. The unit’s MicroTech III™ con­trol system incorporates timing functions to prevent compressor
short cycling. All compressors are resiliently mounted to mini­mize any noise transmission. The condensing section is insulated
and segregated from the air handling section of the unit to avoid
transmission of noise to the circulated air stream.

Figure 3. Copeland SpecterTM scroll compressor

Each compressor is on an independent refrigerant circuit complete
with filter-drier, liquid moisture indicator/sightglass, thermal
expansion valve capable of modulation from 100-25% of its rated
capacity, liquid line shutoff valve with charging port, high pres­sure relief device and high and low pressure cutouts. If any com­pressor is made inoperable, the remaining compressors are still
allowed to operate.

The unit’s MicroTech III controller senses entering condenser
water temperature and prevents mechanical cooling when the tem­perature falls below an adjustable setpoint value, minimum 55°F.
For systems which will see entering condenser water temperatures
below 55°F, a waterside economizer or head pressure activated
control valve is available.

SWT water cooled condensers feature a mechanically cleanable,
all copper design using the same high performance enhanced tub­ing found in modern centrifugal chillers. Liquid refrigerant sub­cooling is provided as standard. Each condenser is part of an
independent refrigerant circuit and comes complete with a spring
loaded high pressure relief valve. All condensers are indepen­dently leak tested. All completed units are leak tested, evacuated
and shipped with a full operating charge of R-22 and oil. R-407C
is also available as an alternate selection.

The condenser assembly and all factory water piping is rated for a
waterside working pressure of 400 psig and is factory leak tested
before shipment. Condenser water channels are mechanically
cleanable by removing brass service plugs that are sealed with

McQuay Catalog 865-5 5

Refrig. Flow Ckt 1
Refrig. Flow Ckt 2

Ckt 2

Ckt 1

Ckt 1

Ckt 1

Ckt 1

Ckt 1

Ckt 1

Ckt 1

Ckt 1

Ckt 2

Ckt 2

Ckt 2

Ckt 2

Ckt 2

Ckt 2

Ckt 2

Airflow

a02

Design Features

reusable o-ring gaskets. Main interconnecting condenser water
headers include vent and drain plugs and a large cleanout plug for
removing debris dislodged during cleaning. Condensers are fac­tory piped for a single condenser water supply and a single con­denser water return connection.

Both right-hand and left-hand piping locations are available.

Cooling Coil Section

SWT evaporator coils incorporate a high efficiency ripple corru­gated fin design. SWT system design maximizes coil face area
without developing uneven, performance robbing di sr upt ions in
airflow patterns. The result is high coil performance and reduced
static pressure losses. Coils are 4 or 6 row configurations.

The evaporator coil is mounted in a stainless steel double sloped
drain pan. The condensate drain line is trapped internal to the unit,
eliminating the expense and inconsistency of field installed traps.

Figure 4. Evaporator Coil Circuiting

Hot Water Heat

Hot water coils have 1 or 2 rows with high efficiency ripple corru­gated fin design and 1/2 inch O.D. seamless copper tubes. Coils
are available complete with a factory mounted, piped and wired 2­way or modulating valve controlled by the unit’s MicroTech III
controller. A factory mounted freezestat is provided to help pro­tect against coil freeze-up.

Supply Fan Section

Figure 5. Supply Fan

The supply fan section uses one or two double width, double inlet
medium pressure forward curved fans and housings. Each fan is
statically and dynamically balanced. The fan assembly is con­structed of high strength structural steel and welded for maximum
strength. The entire fan assembly is mounted on spring isolators
for excellent isolation effectiveness. Seismic control restrained
spring isolators are available. A vibration dampening flex connec­tion is installed at the fan discharge. The entire fan, motor and
drive assembly is dynamically balanced at the factory for quiet
operation.

All evaporator coils are interlaced circuiting, keeping the full face
of the coil active to eliminate air temperature stratification. For
optimum part load performance, all three and four circuit evapora­tor coils are circuited for both interlaced and row control. Com­pressor staging is sequenced to take maximum advantage of
available coil surface.

Each evaporator coil circuit is furnished with a wide range ther­mostatic expansion valve with an adjustable superheat setting and
external equalizer.

Supply fans are configured with a gradual expansion, aerody­namic duct within the cabinet. This unique gradual expansion fea­ture contributes to the high performance of the SWT by lowering
brake horsepower and sound power levels.

All fans are mounted on solid steel shafts rotating in 200,000 hour
pillow block ball bearings with grease fittings. Multiple belt,
fixed pitch sheaves are matched to the specific cfm, static pres­sure and horsepower requirements of the system. Drives rated for
a minimum of 150% of fan design are available. Drive compo­nents and fan bearings are easily accessed for periodic mainte-

Heating Section

SWT units are available as cooling only systems or with factory
installed electric or hot water heat for morning warm-up, constant
volume and specialty heating requirements.

Electric Heat

nance.
Fan motors are three phase, NEMA design B, rated at 40°C.

Motor availability includes high efficiency open drip-proof and
totally enclosed, EPACT compliant, NEMA T-frame selections
and premium efficiency selections. Motors are 1800 RPM with
grease lubricated ball bearings.

The factory assembled electric heating coils are constructed of
low watt density nickel-chromium elements for long lasting dura­bility. Electric heaters are protected by automatic reset high limit
controls and line break protection. Heater branch circuits are indi­vidually protected by branch circuit fusing. The MicroTech III
control system sequences the electric heating elements for operat­ing economy.

6 McQuay Catalog 865-5

Design Features

Energy saving advanced technology variable frequency drive
(VFD) fan speed control is available with the convenience and
cost savings of factory mounting and testing. All VFD selections
are plenum rated. A manually activated bypass contactor is avail­able to allow system operation even in the event of drive service.

MicroTech III controls provide advanced duct static pressure con­trol. Static pressure can be controlled by either a single or two
duct static pressure sensors. All VAV systems include an adjust­able duct high-limit switch to protect duct work from excessive
pressure.

Economizer Options

Waterside Economizer

An energy saving, waterside economizer package is available on
all units. The complete economizer system is factory mounted
including a 4-row mechanically cleanable coil, control valves and
factory piping complete with cleanouts. The complete economizer
package is rated for up to 400 psig waterside working pressure
and the entire coil and piping assembly is factory leak tested.

Economizer operation is controlled by the SWT’s MicroTech III
controller to maximize free cooling potential. Economizer opera­tion is enabled whenever the available cooling tower water tem­perature is less than the unit entering air temperature by a field
adjustable value, generally 5-7°F. The economizer control valve
modulates in response to the cooling load. Control valve operation
can be selected to (1) maintain full flow through the unit at all
times or (2) isolate the unit from the condenser water loop when
there is no call for cooling to save energy with a variable pumping
system. (Economizer control valves do not eliminate the need to
provide unit isolation valves.) To extend free cooling savings,
mechanical cooling is enabled during economizer operation. Only
when the economizer valve is driven 90% open and the cooling
load is not satisfied, will compressors be staged to maintain cool­ing setpoint. Economizer control will maintain full free cooling
capability until disabled by the economizer changeover setpoint.
A factory mounted freezestat is provided to help protect against
coil freeze-up.

Condenser Head Pressure Control

For applications where a waterside economizer package is not
being used and entering condenser water temperatures can be less
than 55°F, condenser head pressure control is required. To satisfy
these applications, a factory installed 2-way, head pressure acti­vated control valve is available to maintain unit operation with
entering condenser water temperatures as low as 40°F.

Figure 6. Mechanically Cleanable Waterside
Economizer Coil

Figure 7. Economizer Piping

Airside Economizer

An airside economizer control package is available for controlling
field installed mixing dampers capable of 100% outside airflow.
Economizer operation will be controlled by the SWT's MicroTech
III controller to maximize free cooling potential. Economizer
operation is enabled whenever an outside air (or comparative)
enthalpy sensor or outside air temperature sensor indicates that
outside air is suitable for free cooling. The economizer damper
control actuator shall modulate in response to the cooling load.
The outside air damper will be positioned to maintain minimum
ventilation requirements when economizer is disabled.

To extend free cooling savings, mechanical cooling is enabled
during economizer operation. Only when the economizer damper
is driven 90% open and the cooling load is not satisfied, will com­pressors be staged to maintain cooling setpoint. Economizer con­trol will maintain full free cooling capability until disabled by the
economizer changeover setpoint. Factory supplied mixing boxes
are available for airside economizer use using the McQuay
Vision™ air handling unit platform.

McQuay Catalog 865-5 7

Filter Section

All SWT units are provided, as standard, with 4" deep extended
media 30% efficient filters. For higher filtration requirements,
65% and 85% AmericanAirFilter
with an optional pre-filter rack. Filters are removable from the
rear of the unit or through hinged and latched side access doors on
the filter box.

TM

Varicel® filters are available

Design Features

Electrical

Each unit is completely wired and tested at the factory prior to
shipment. Wiring complies with NEC requirements and conforms
to all applicable UL standards for reliability and safety. All elec­trical components are labeled according to the electrical diagram
and are UL recognized whenever applicable. Line voltage compo­nents and wiring are physically separated from the low voltage
control system.

The supply fan motor, compressor motors and electric heat all
have individual branch circuit fuse protection. Control circuit
power is supplied through a factory installed, low voltage trans­former. The supply fan motor circuit includes a three phase con­tactor and ambient compensated overload protection with manual
reset. Each refrigerant circuit includes both a high and low pres­sure cutout switch and a coil frost protection thermostat.

A terminal block is provided for the single, main power connec­tion and a terminal board is provided for low voltage control wir­ing. A factory mounted, non-fused main circuit interrupter is
available for disconnecting the main electrical power to the unit.
The switch is visible, located at the front of the unit, and is acces­sible without unit penetration. Dual power blocks or disconnect
switches are available to accommodate requirements for standby,
emergency power supplies.

Controls

Phase Failure/Undervoltage Protection – Factory installed
phase failure/under voltage protection is available to protect three
phase motors from damage due to single phasing, phase reversal
and low voltage conditions.

Individual Unit Factory T est – All SWT units are provided com­pletely factory assembled, piped, wired, tested, and shipped in one
piece. Each unit undergoes a factory test that includes:

• Dynamic trim balance of the completed fan assembly

• Run check of all electrical components, alarms and shutdowns,

including proper control sequencing

• Pressure test, at rated pressure, of refrigerant coils, water coils

and condensers prior to assembly

• Final leak check of the completed refrigerant circuits

• Final leak check of the completed water circuit

• Compressor run check

Verification of factory run test is available at time of unit ship­ment.

Figure 8. Test Stand

MicroTech III Unit Controls

All SWT units feature advanced MicroTech III DDC controls to
provide all temperature and static pressure control, product reli­ability control functions, system time clock and all monitoring
and diagnostics. Each MicroTech III control system features a
human interface with a 4-line, 20 character English language dis­play for fast system diagnostics and adjustments. The complete
control system is factory installed and commissioned prior to
shipment.

Protocol Selectability™ Feature

All MicroTech III control systems have McQuay's exclusive Pro­tocol Selectability feature. MicroTech III control systems can be
factory configured for standalone operation or for incorporation
into an independent building automation system using either the



BACnet

MS/TP, BACnet/IP or LonTalk protocols.

Auxiliary Control Options

Condenser Water Flow Switch –A factory installed, flow switch
is available to verify water flow status at each unit. Compressor
operation is disabled and an alarm signal provided if condenser
water flow is lost. Unit operation is restored when water flow has
again been sensed. Water flow status is displayed at the Micro­Tech III control’s plain language screen.

Freezestat – A nonaveraging type freezestat is available factory
installed on the entering face of the economizer coil. Upon sens­ing a potential freeze condition, the unit supply air fan is shut
down, the economizer (and heating) valve drives to the full open
position and an alarm signal is provided. Unit operation is
restored following the manual reset of the freezestat.

8 McQuay Catalog 865-5

Fan Section

Main Heating /
Cooling Section

Optional Hot
Water Coil
Connections

Condensate
Drain

Filter /
Waterside

Economizer
Section

Water In

Water Out

System Flexibility

Along with providing high quality and state-of-the-art innovation,
SWT self-contained systems emphasize system flexibility, flexi­bility not even considered by the competition. McQuay SWT sys­tems offer customized flexibility to satisfy a wide range of diverse
applications.

Selection/Application Flexibility

Nominal cooling capacities range from 15 to 45 tons and all units
feature a 6 row evaporator coil. In addition, all units offer multiple
compressor selections to meet exacting system requirements.
Many standard compressor/coil capacity selections are available.
The flexibility to optimize the self-contained system to fit the
application is a McQuay SWT advantage. Available system appli­cations include:

• VAV discharge air temperature control with static

pressure control

• Discharge air temperature control with constant air

volume

• Constant volume, zone temperature control

• 100% outside air control

• Dehumidification control, with or without reheat control

In addition to compressor/coil flexibility, SWT systems offer dou­ble width, double inlet, forward curved fans with factory mounted
variable frequency drives for maximizing VAV system fan perfor­mance. High efficiency fan capability coupled with extensive
compressor flexibility can provide the right system selection for
the application.

pressure, a 20% reduction in supply air CFM can reduce the
fan BHP requirements by 25% or more.

• Reduced supply air CFM provides reduced fan sound power

generation and a quieter room environment.

• Reduced supply air CFM can often reduce the equipment room

size due to the use of a physically smaller unit size.

Figure 9. Modular Construction

Modular Construction

The SWT unit has been designed with the flexibility to be easily
disassembled into three compact sections. The three sections are
the main cooling/heating, filter/waterside economizer and fan sec­tions. Whereas most competitive products require removal of the
door frame, each SWT section has a maximum width of 34.5",
including fastener heads, and can fit through standard 3' steel door
frames.

The system installer is able to break the unit down into its three
main sections without breaking any refrigerant lines. All SWT
refrigerant lines remain intact, contained in the main cooling/heat­ing section. This SWT feature can add up to substantial savings
by avoiding the field expense to braze, evacuate and charge each
refrigerant circuit.

Optimal Discharge Air Temperature:

More and more system engineers are designing optimal discharge
air temperature systems to improve system performance and sys­tem first cost, and the McQuay SWT provides the flexibility to do
it successfully. Optimal discharge air temperature systems are
designed to provide unit leaving air temperature selections of 52­53°F versus more conventional systems that supply air at temper­atures closer to 58°F. This five to six °F reduction in air tempera­ture to the room diffusers can subsequently reduce the required
supply air volume to the room by 20-25%.

The benefits of optimal discharge air temperature systems become
quite apparent with a look at the advantages offered with reduced air­flow:

• Reduced supply air CFM reduces first cost and installation

cost by allowing smaller duct sizes and a smaller air distribu­tion system.

• Reduced supply air CFM reduces fan BHP requirements.

Depending on changes in duct size and the resulting total static

Arrangement Flexibility

All SWT systems offer the flexibility of right-hand and left-hand
piping arrangements and front and rear fan discharge orientations.
Piping and fan arrangement flexibility can simplify mechanical
equipment room arrangement, improve installed cost and improve
total system performance.

Filtration Flexibility

SWT systems are offered with 4 inch, 30% efficient pleated filters
as standard. 4 inch, 65% efficient pleated filters and 4 inch, 85%
efficient filters with pre-filters are also available.

Energy Saving Economizer Flexibility

To improve system operating performance, all SWT s ystems of fer
complete factory mounted and controlled waterside economizer
capability. Each waterside economizer system includes a 4 row,
mechanically cleanable coil with dual, two-way control valves to
allow use in either a constant or variable volume pumping system.
In addition, units can be applied with air economizer cycles with
integrated factory control.

Heating Flexibility

A variety of heating media is offered with each SWT system. Hot
water coils with modulating valve and actuator are available along
with staged electric heat to provide heating control in a variety of
applications.

McQuay Catalog 865-5 9

System Flexibility

Controllers

MicroTech III DDC control systems provide constant volume,
variable air volume, 100% outside air, and/or dehumidification
control flexibility. Each MicroTech III control system comes with
a control screen conveniently mounted on the front of the unit to
allow easy adjustment and monitoring of control functions. And
with its easy to follow and read English language menus and data
displays, it simply encourages and invites the operator to take
advantage of its many capabilities.

Figure 10. MicroTech III Controller

Protocol Selectability Feature

All MicroTech III control systems have McQuay's exclusive Protocol
Selectability feature. MicroTech III control systems can be factory
configured for standalone operation or for incorporation into an inde­pendent building automation system using either the BACnet
MS/TP, BACnet/IP or LonTalk protocols.

Summary of Available Options:

• Multiple compressor/coil capacity selections

• Multiple control op ti on s: VAV, C V, 100% OA,

dehumidification

• Non-fused main power disconnect switch

• Dual non-fused main disconnect switches

• Non-averaging freezestat for hot water, or waterside econo-

mizer coil protection

• Unit phase failure/under voltage protection

• Premium efficiency fan motors

• TEFC fan motors

• Condenser water flow switch

• 4-row waterside economizer system

• Air cycle economizer system

• Modulating hot water heat

• Staged electric heat

• Factory mounted and controlled variable

frequency drives

• High efficiency filtration options

• Right- and left-hand piping selections

• Front and back fan discharge arrangements

• Head pressure control valve

• Special coil coatings

• Double wall cabinet construction

• Seismic fan isolation

• R407C refrigerant

• UV lights



Ultraviolet Lights

Factory-installed ultraviolet lights are available on the down­stream side of all cooling coils and above the unit drain pan.

All ultraviolet lights are pre-engineered and factory installed for
ease of use and proper placement for maximum effectiveness. The
ultraviolet lamps irradiate the coil and drain pan surfaces with
light in the 245 nanometer wavelength of the light spectrum (UV­C). UV-C light has proven effective in killing most bacteria,
molds, and viruses in both laboratory and practical application.
This complete package of equipment and ultraviolet lights
includes Intertek Services Inc. (ETL) safety agency certification.

Figure 11: Ultraviolet light

Features

• High-output, hot cathode lamps produce ultraviolet germicidal

irradiation (UVGI) for 254 nm that constantly irradiates the
coil and drain pan surfaces.

• Fixture design and stainless steel construction make the ultra-

violet light device suitable for saturated air conditions.

• Automatic disconnects are standard on all doors (or panels)

with line-of-sight access to the lamps to help prevent eye con­tact with the UV-C ultraviolet light.

• Special ultraviolet filtering glass windows block ultraviolet

light, allowing the coil, drain pan, and lights to be inspected
while in use from outside the unit.

Benefits

• For pennies a day, UVGI can improve IAQ by destroying

mold, fungi, and bacteria on coil and drain pan surfaces.

• Clean coil surfaces maintain peak heat tra nsfer for “ near new”

performance and lower energy costs.

• Reduced coil and drain pan maintenance requirements and

costs.

• Satisfies GSA federal facilities standard requirements for

UVGI lights to be incorporated downstream of all cooling
coils and above all drain pans to control airborne and surface
microbial growth and transfer.

Refrigerant R-407C

McQuay SWP units with independent refrigerant circuits are
available with non-ozone depleting R-407C refrigerant.

Features

• HFC-407C refrigerant is environmentally friendly with zero

ozone depleting allowance (ODP).

• ASHRAE Standard 34, Designation and Safety Classification

of Refrigerants, classifies HFC-407C as an A1 (lower toxic­ity—no flame propagation) refrigerant.

• Units are factory engineered for proper cooling performance

using R-407C.

• Units are factory charged with R-407C and synthetic oil (such

as POE), and they include components and controls specifi­cally tailored to R-407C.

• Units are factory tested prior to shipment.

Benefits

• HFC-407C allows you to provide your tenants with a comfort-

able building environment in an environmentally friendly way.

• With no phase out date for production of HFC-407C, a reliable

supply should be available for the life of your equipment.

10 McQuay Catalog 865-5

MicroTech® III Unit Controller

McQuay SWP systems continue to provide industry leading
performance, equipped with a complete MicroTech III
control system. In addition to providing stable, efficient
temperature, and static pressure control, the controller is
capable of providing comprehensive diagnostics, alarm
monitoring, and alarm specific component shutdown if
critical equipment conditions occur. The unit controllers are
factory mounted and configured for stand-alone operation or
integration with a building automation system (BAS)
through an optional communication module with our Open
Choices feature.

Open Choices Benefits for Easy Integra­tion

Easy, low cost integration into most building automation
systems without costly gateway panels.

• Flexibility to select either BACnet® or L

communication. Units are LonMark® 3.4 certified with
the appropriate communications module for L
networks.

• Comprehensive unit control and status information is

available at the BAS regardless of communication
protocol.

• Long-term choices for equipment adds or replacements,

and for service support.

• Flexible alarm notification and prioritization with Intrinsic

Alarm Management (BACnet).

• Simplified BAS integration with the ability to set network

parameters at the unit controller, reducing installation time
and costs.

• Easy monitoring and troubleshooting of communication

status from the unit controller to the BAS.

Components

Each SWP self-contained system is equipped with a
complete MicroTech III unit control system that is pre­engineered, preprogrammed, and factory tested prior to
shipment. Each of the MicroTech III unit control systems is
composed of several components that are individually
replaceable for ease of service.

ONWORKS®

ONWORKS

These components include:

• Unit controller with user interface display and naviga­tion wheel

• Optional expansion modules

• Communication module (optional)

• Pressure transducers

• Unit-mounted temperature sensors

• Zone temperature sensor packages

• Humidity sensor

Main Control Board (MCB)

The main control board (MCB) contains a microprocessor
that is preprogrammed with the software necessary to
control the unit. This provides that schedules, set points and
parameters are not lost, even during a long-term power
outage. The microprocessor board processes system input
data and then determines and controls output responses. An
RS-232 communication port is provided as standard to allow
for direct or modem access with a PC-based service tool.

Expansion Modules

These boards are used to expand the input and output
capability of the unit controller. Each board communicates
via serial data communications. These microprocessor based
boards provide independent operation and alarm response
even if communication is lost with the unit controller.

Communication Module

An optional communication module provides the means to
factory or field configure MicroTech III unit controls for
interoperability with an independent BAS. Communication
modules are available to support industry recognized
communication protocols including BACnet MS/TP,
BACnet/ IP and L

Keypad/Display

All MicroTech III unit controllers include a push/pull
navigation wheel and display. The display is a supertwist
nematic type with highly visible black characters on a
yellow background. The 5-line by 22-character format
allows for easy to understand plain English display
messages. All operating conditions, system alarms, control
parameters and schedules can be monitored from the
keypad/display. If the correct password has been entered,
any adjustable parameter or schedule can be modified from
the keypad.

ONWORKS.

Figure 12. MicroTech III Keypad/DisplayMicroTech III Unit Controls

McQuay Catalog 865-5 11

MicroTech® III Unit Controller

Temperature and Humidity Sensors

With the exception of the zone, outside air and return air
sensors, all temperature sensors are factory installed and
tested. Zone sensor packages are available to suit any
application. A humidity sensor is available for field
installation.

Static Pressure Transducers

All pressure transducers are factory installed and tested.
Connection and routing of field-supplied sampling tubes is
done at time of unit installation.

Zone Temperature Sensors

Two optional zone temperature sensors are available:

• Zone sensor with tenant override switch

• Zone sensor with tenant override switch and remote set
point adjustment

Timed tenant override is a standard MicroTech III
control feature.

Zone sensors are required for the controller’s purge cycle,
space reset of supply air set point, and night setback or setup
features. All zone sensors are field installed with field
wiring terminated at a separate, clearly marked terminal
strip.

Stand-alone Controller Features

MicroT ech III applied rooftop unit controls include all of the
essential features required to make them capable of
completely independent, stand-alone operation.

Internal Time Clock

An internal, battery-backed time clock is included in the
MicroTech III unit controller. Current date and time can be
quickly and easily set at the user interface keypad.

Internal Schedule

Seven daily schedules and one holiday schedule can be
entered at the keypad of all unit controllers. For each of
these eight schedules, one start and one stop time can be
entered. Up to 10 holiday periods, of any duration, can be
designated. The unit will automatically run according to the
holiday schedule on the holiday dates. To handle special
occasions, an additional ‘one event’ schedule can also be
used.

In lieu of its internal schedule, the unit can be operated
according to a network schedule from a BAS.

External Time Clock or Tenant Override Input

An input is supplied that can be used to accept a field wired
start/stop signal from a remote source. An external time
clock, a tenant override switch, or both may be connected.
Whenever the external circuit is closed, the controller
overrides the internal schedule (if activated) and places the
unit into the occupied mode.

If the internal schedule or a BAS network schedule is used,
field wiring is not required.

Timed Tenant Override

Off-hour operation flexibility is a must in today’s office
environments and even stand-alone MicroTech III controls
handle it with ease. When unit operation is desired during
unoccupied hours, initiate timed tenant override by pressing
the tenant override button on either of the optional zone
sensor packages. The unit then starts and runs in the
occupied mode for a keypad-adjustable length of time (up to
five hours). If the button is pressed again while the unit is
operating, the timer resets to the full time allowance without
interrupting unit operation. Tenant override operation also
can be initiated by a BAS.

Three Remote Set Point Adjustment Options

1 Remote user interface option (RUI).

2 Building automation system (BAS). See “Open Choices

Benefits for Easy Integration” on page 11.

3 All constant air volume-zone temperature control

(CAV-ZTC) unit controllers include an input that can
be used to remotely adjust the zone cooling and
heating set points. To use this feature, wire the optional
zone sensor package with set point adjustment to the
controller. The remote set point adjustment feature can
be enabled or disabled from the keypad at any time.
When enabled, remote set point adjustment is
available even if the return temperature is selected to
be the Control Temperature.

Auto/Manual Operation Selection

Automatic or manual operation can be controlled either
remotely or at the keypad.

All controllers include three inputs that can be used to
enable or disable cooling, heating, and fan operation from
remote switches. With the “heat enable” and “cool enable”
terminals, the operator can enable cooling, heating, or both
as desired. Using the system “off” terminals, the operator
can disable the fans, and thus the entire unit.

12 McQuay Catalog 865-5

MicroTech® III Unit Controller

From the keypad, there are a variety of occupancy and auto!
manual control mode selections available to the operator:

• Occupancy modes
– Auto
– Occupied
– Unoccupied
– Bypass (tenant override)

• Control modes
– Off manual
– Auto
– Heat/cool
– Cool only
– Heat only
– Fan only

Compressor Lead-lag Selection

All unit controllers are capable of automatic compressor,
lead-lag control.

Waterside Economizer Changeover

On units equipped with a waterside economizer package, the
MicroTech III unit controller includes an internal
changeover strategy that compares entering cooling tower
water temperature to the unit’s mixed air temperature. If the
entering water temperature is less than the mixed air
temperature by a field-adjustable differential (typically 5°F
to 7ºF), the economizer control valve modulates in response
to the cooling load.

warm-up or cool-down periods or when the outdoor air
temperature is mild.

Night Setback and Setup Control

When one of the zone temperature sensors is connected to
the unit controller, night setback heating and night setup
cooling control are available. Separate, keypad
programmable night heating and cooling set points are used
to start the unit when necessary. After the unit starts, night
setback and setup control is similar to normal occupied
control except that the minimum outside air damper position
is set to zero. If the outside air is suitable for free cooling, it
is used during night setup operation.

Airside Economizer Changeover Selection

On units equipped with an economizer, there are three
methods of determining whether the outdoor air is suitable
for free cooling: two methods sense enthalpy (dry bulb
temperature and humidity) and one senses outdoor air dry
bulb temperature.

The two enthalpy changeover methods use external, factory
installed controls. One compares the outdoor ambient
enthalpy to a set point; the other is a solid state device that
compares the outdoor ambient enthalpy to the return air
enthalpy. This comparative enthalpy control can improve
total economizer performance.

All unit controls include an internal dry bulb changeover
strategy that can be selected at the keypad. When this
method is selected, the controller compares the outdoor air
dry-bulb temperature to a keypad programmable set point.
The external enthalpy control input is then ignored.

Cooling and Heating Lockout Control

All unit controls include separate keypad programmable set
points for locking out mechanical cooling and heating.
Mechanical cooling is locked out when the outdoor
temperature is below the cooling lockout set point; heating is
locked out when the outdoor temperature is above the
heating lockout set point. This feature can save energy cost
by eliminating unnecessary heating and cooling during

McQuay Catalog 865-5 13

MicroTech® III Unit Controller

Except for 100% outside air applications, night setback
control is available even if the unit is not equipped with any
heating equipment. When the space temperature falls to the
night setback set point, the fans simply start and run until the
temperature rises above the differential. This feature might
be useful for applications that use, for example, duct­mounted reheat coils.

Morning Warm-up Control

If the Control Temperature (space or return) is below set
point when the unit enters the occupied mode, the morning
warm-up control function will keep the outside air dampers
closed while heat is supplied to satisfy set point. The outside
air damper will remain closed until either the space
temperature rises to the

heating set point or the keypad adjustable morning warm-up
timer expires (default is 90 minutes). The morning warm-up
timer supplies the minimum required amount of outdoor air
after a certain time regardless of the space temperature.

Morning warm-up control is automatically included on all
except 100% outside air units. It is available even if the unit
is not equipped with any heating equipment, for applications
that utilize, for example, duct-mounted reheat coils.

Condenser Head Pressure Control (units without
waterside economizer only)

Mechanical cooling is allowed whenever the entering
cooling tower water temperature is 55ºF or warmer, without
the use of head pressure control. When the entering water
temperature is below 55ºF, a factory-installed and factory­controlled two-way modulating head pressure control valve
can be utilized. The regulating valve is controlled by the
MicroTech III controller to maintain refrigerant head
pressure.

During the purge time window, the unit starts and runs
whenever these three requirements are met:

• The space temperature must be warm enough to enable
occupied cooling.

• The outside air enthalpy must be low enough to enable
the economizer.

• The outside air temperature must be at least 3°F less
than the space temperature.

When any one of these conditions is no longer true, the unit
shuts down. As conditions allow, purge cycles the unit in
this manner until it enters the occupied mode.

Proportional Integral (PI) Control

The Proportional Integral (PI) control algorithm controls
modulating actuators to maintain a measured variable
(temperature or pressure) at or near its set point. For
example, it controls economizer dampers to maintain the
discharge cooling set point and it controls the supply fan
variable frequency drives to maintain the duct static pressure
set point. The integral control feature effectively eliminates
“proportional droop” (load dependent offset) resulting in the
tightest possible control.

For each PI loop, four keypad adjustable parameters allow
the control loop to be properly tuned for any application:

•Period

• Dead band

• Proportional band

• Integral time

Appropriate default values for these parameters are loaded
into each controller. These default values will provide proper
control for most applications; therefore, field tuning is
usually not required and thus start-up time is reduced.

Outdoor Air Purge Control (units with airside
economizer only)

Purge control is designed to take advantage of cool early
morning outside air conditions. It starts the fans and
modulates the economizer dampers to maintain occupied
cooling requirements during unoccupied periods, if
conditions are appropriate. This provides the opportunity to
flush the space with fresh outdoor air prior to occupancy.
Purge operation is possible only during a keypad-adjustable
time window prior to occupancy (0 to 240 minutes). When
the purge-cycle is active, mechanical cooling is disabled. To
use the purge feature, connect one of the zone temperature
sensors to the unit controller. Below is a description of purge
control operation.

14 McQuay Catalog 865-5

Change Algorithm

The PI function is also used to adjust set points instead of
controlling variable speed drives or actuators directly. For
example, in zone control applications, the PI loop
automatically “changes” the discharge temperature set point
(cooling or heating) as the Control Temperature deviates
from the zone set point. Another PI loop then controls the
economizer actuator or heating valve actuator using the
current discharge temperature set point. Unlike a typical
“mastersubmaster” reset strategy, this “cascade control”
continuously adjusts the discharge set point, even if the
Control Temperature’s deviation from set point remains
constant. This means that the unit’s cooling or heating
output is set according to the actual load, not just the current
zone temperature. The tightest possible zone temperature
control results because “proportional droop” (load
dependent offset) is eliminated.

Calibrat

When initiated at the keypad by an operator, the Calibrate
function automatically calibrates all actuator position
feedback inputs and all pressure transducer inputs. It does

e

MicroTech® III Unit Controller

this by shutting the unit down and then driving all actuators
to the full closed and full open positions. The controller
records the input voltage values that correspond to these
positions. The pressure transducer input voltages, which are
assumed for 0.00-in. W.C., are also recorded. When
Calibrate is finished, enter an operator command at the
keypad to start the unit.

Field Output Signals

All MicroTech III controls include two solid-state relay
outputs that are available for field connection to any

suitable device: the remote alarm output and the occupied
output. These two outputs are used to signal field equipment
of unit status.

Remote Alarm Output: The remote alarm output can
be used to operate a 24 volt relay to provide a remote
alarm signal to a light, audible alarm, or other device
when an alarm condition exists at the unit.
Fan Operation Output: The fan operation output is
used to operate a 24 volt relay to control field equip­ment that depends on fan operation; for instance, to
open field installed isolation dampers or VAV boxes. T o
allow actuators enough time to stroke, the fan operation
output is energized three minutes before the fans start. It
then remains energized until thirty seconds after the uni t
airflow switch senses no airflow. The fan operation out­put is on whenever the unit airflow switch senses air­flow.
Outside Air Damper output: Use to signal an outside
air damper actuator to open whenever the unit is in an
occupied cooling or heating condition.

Standard Control Options

SWP Self-Contained systems are available for most any
constant or variable air volume application. MicroTech III
controls offer three basic control configurations that use
sophisticated state change control logic to provide stable,
reliable and efficient control:

• Variable air volume with discharge temperature control
(DAC)

• Constant air volume with zone temperature control (S
CC)

• Constant air volume with discharge temperature con­trol (DAC)

When combined with MicroTech III’s many available
control capabilities, both factory-installed and keypad­programmable, these three basic configurations can be
customized to meet the requirements of the most demanding
applications.

Constant Air Volume with Zone Temperature
Control (SCC)

SCC units are available in either cooling only or cooling
with modulating heat configurations. Either of these
configurations is available for 100% recirculated, mixed, or
100% outdoor air applications.

Constant Air Volume with Discharge Temperature
Control (DTC)

DTC units are available in cooling only, cooling with single­stage “morning warm-up” heat, or cooling with modulating
heat configurations. This unit configuration can be used for
applications that have zone controlled terminal heating coils
or for constant volume, 100% outdoor air applications. The
discharge temperature control strategies used with the hybrid
DTC unit are identical to those used with the DTC unit.

Discharge Temperature Control

MicroTech III VAV-DTC and CAV-DTC controls provide
sophisticated and flexible discharge air temperature control
that is only possible with DDC systems. Separate discharge
air temperature set points are used for cooling and
modulating heating control. At the keypad, the operator can
either enter the desired set points or select separate reset
methods and parameters for each set point.

Control Temperature

The Control Temperature make s the heat/cool changeover
decision. It determines whether cooling or heating is
enabled; the discharge temperature then determines whether
cooling or heating is actually supplied. At the keypad, the
operator can choose the source of the Control Temperature
from among the following selections.

• Space temperature sensor

• Return temperature sensor

• Outside air temperature sensor (modulating heat only)

• Network communication

The operator enters separate cool and heat enable set points
and deadbands that the Control Temperature is compared
with (see <CrossReference>Figure 13). When the Control
Temperature is greater than or equal to the cooling set point
plus DB/2, cooling is enabled. When the Control
Temperature is less than or equal to the heat set point minus
DB/2, heating is enabled. If desired, these set points and
differentials can be set so that there is a dead band in which
both cooling and heating are disabled. The controller’s
software prevents simultaneous cooling and heating.

Variable Air Volume with Discharge Temperature
Control (DTC)

All VAV units provide true discharge temperature control in
addition to duct static pressure control. Cooling only,
cooling with single-stage “morning warm-up” heat, and
cooling with modulating heat configurations are available.

McQuay Catalog 865-5 15