McQuay ARQ024 User Manual
Catalog UV1640
AAF®-HermanNelson® Self-Contained Water
Source Heat Pump Unit Ventilator
Standard Range Model ARQ
Extended Range Model ERQ
Geothermal Range Model GRQ
R-410A Refrigerant, MicroTech II™ (“F” Vintage)
C
Contents
Introduction
Nomenclature ...............................................................................3
AAF-HermanNelson Classroom Unit Ventilators ..........................4
Model AR, ER & GR Floor Unit ....................................................5
Features & Benets
GentleFlo Delivery ........................................................................6
The Right Amount of Fresh Air and Cooling .................................7
Precise Temperature and Dehumidication Control .....................7
Low Installation Costs ..................................................................8
Easy To Maintain ........................................................................10
Built To Last ................................................................................12
MicroTech II Controls
MicroTech II Controls For Superior Performance,
Easy Integration ................................................................... 13-18
MicroTech II Sensors & Control Component Locations ........ 19-21
Accessories
Time Clock ..................................................................................22
Wall Louvers & Grilles ..........................................................22-23
VentiMatic Shutter Room Exhaust Ventilation ...................... 24-25
Storage Cabinets, Sink & Bubbler ........................................ 26-27
End Panels .................................................................................27
Applications Considerations
Why Classrooms Overheat .................................................. 28-31
Meeting IBC Seismic Requirements ...........................................32
ASHRAE Cycle II ........................................................................33
Unit Installation Considerations ............................................ 34-36
Unit Arrangements & Louver Arrangements ......................... 37-44
Unit Selection
Quick Selection Procedure ................................................... 45-48
Selection Procedure ............................................................. 49-50
Engineering Data .................................................................. 51-52
Electrical Data - Size 024 and 040 .............................................51
Electrical Data - Size 048 ...........................................................52
Base Unit Data - AR, ER, GR .....................................................52
Details & Dimensions
Model AR, ER, GR Self Contained Unit Dimensions, 024 ..........53
Model AR, ER, GR Self Contained Unit Dimensions, 040 ..........54
Model AR, ER, GR Self Contained Unit Dimensions, 048 ..........55
End Panels .................................................................................56
Wall Intake Louvers & Grilles .....................................................57
VentiMatic Shutter Assembly ......................................................58
Sink & Bubbler Cabinet & Shelf Storage Cabinets .....................59
Utility Compartment & Filler Sections ........................................60
Wiring Diagrams
MicroTech II Wiring - DX Cooling with Electric Heat, Valve
Control 460Volt / 3-Phase ..........................................................61
Typical Wall Senors ....................................................................62
External Input Wiring ..................................................................62
External Output Wiring-Single Unit .............................................63
External Output Wiring-Multiple Units ........................................63
Guide Specications
AAF-HermanNelson Unit Ventilator Model ARQ, ERQ & GRQ
Guide Specications ............................................................. 64-68
C
McQuay is a registered trademark and MicroTech II, Digital Ready, GentleFlo, ServiceTools,
Microsoft is a registered trademark and Windows is a trademark of Microsoft Corporation.
and Protocol Selectability are trademarks of McQuay International.
Copyright © 2010 McQuay International. All rights reserved throughout the world.
Introduction
Nomenclature
U ARQ 6 024 H G 12 Z B1 AL 22 G B B 1
Unit Type
U = Unit Ventilator
Product Identier
ARQ = SC - WSHP 60°F EWT,
Standard Range, Ultra Quiet
ERQ = SC - WSHP 50°F EWT,
Extended Range, Ultra Quiet
GRQ = SC - WSHP 20°F EWT
Geothermal Range,
Ultra Quiet
Design Series
6 = F Design
Nominal Capacity, cubic
feet/minute (cfm)
024 = 24,000 Btuh
040 = 40,000 Btuh
048 = 48,000 Btuh
Voltage
C = 208-60-1
D = 208-60-3
G = 230-60-1
H = 230-60-3
K = 460-60-3
Cooling Options
G = Direct Expansion (DX)
H = Direct Expansion (DX) with refrigerant relief valve
Heating Options
00 = None
12 = Low Electric Heat, 3-element
13 = High Electric Heat, 6-element
Hand Orientation [Right (RH) Left (LH)]
Z = Not applicable
Controls (TC = Time Clock, CO2 = CO2 Sensor)
B1 = Basic Stand-Alone w/o TC
B2 = Basic Stand-Alone Master w/o TC
B3 = Basic Stand-Alone Slave w/o TC
B4 = Basic BACnet MS/TP w/o TC
B5 = Basic LonMark SCC w/o TC
B6 = Basic Metasys N2 Open w/o TC
B7 = Basic Stand-Alone w/ TC
B8 = Basic Stand-Alone Master w/ TC
B9 = Basic Stand-Alone w/o TC w/CO2
BA = Basic Stand-Alone Master w/o TC w/CO2
BB = Basic Stand-Alone Slave w/o TC w/CO2
BC = Basic BACnet MS/TP w/o TC w/CO2
BD = Basic LonMark SCC w/o TC w/CO2
BE = Basic Metasys N2 Open w/o TC w/CO2
BF = Basic Stand-Alone w/ TC w/CO2
BG = Basic Stand-Alone Master w/ TC w/CO2
E1 = Expanded Stand-Alone w/o TC
E2 = Expanded Stand-Alone Master w/o TC
E3 = Expanded Stand-Alone Slave w/o TC
E4 = Expanded BACnet MS/TP w/o TC
E5 = Expanded LonMark SCC w/o TC
Product Styles
1
Warranty
A = Standard
E = Extended
X = Special
SKU
B = Standard Delivery
Power Connection
G = Box w/Switch
Return Air
22 = RA Bottom Front / OA Rear Duct Collar
24 = Recirculation RA Bottom Front no RA/OA Dampers
Discharge
AK = 21-7/8" Unit, Top Bar Grille Discharge
AL = 16-5/8" Unit, Top Bar Grille Discharge
AM = 21-7/8" Unit, Top Bar Grille Discharge, 2" Step
AN = 21-7/8" Unit, Top Bar Grille Discharge
AP = 21-7/8" Unit, Top Bar Grille, Full Adapter Back
AB = 21-7/8" Unit, Top Bar Grille, Full Adapter Back,
Closed Pipe Tunnel w/Solid Back
E6 = Expanded Metasys N2 Open w/o TC
E7 = Expanded Stand-Alone w/ TC
E8 = Expanded Stand-Alone Master w/ TC
E9 = Expanded Stand-Alone w/o TC w/CO2
EA = Expanded Stand-Alone Master w/o TC w/CO2
EB = Expanded Stand-Alone Slave w/o TC w/CO2
EC = Expanded BACnet MS/TP w/o TC w/CO2
ED = Expanded LonMark SCC w/o TC w/CO2
EE = Expanded Metasys N2 Open w/o TC w/CO2
EF = Expanded Stand-Alone w/ TC w/CO2
EG = Expanded Stand-Alone Master w/ TC w/CO2
L1 = Leading Stand-Alone w/o TC
L2 = Leading Stand-Alone Master w/o TC
L3 = Leading Stand-Alone Slave w/o TC
L4 = Leading BACnet MS/TP w/o TC
L5 = Leading LonMark SCC w/o TC
L6 = Leading Metasys N2 Open w/o TC
L7 = Leading Stand-Alone w/ TC
L8 = Leading Stand-Alone Master w/ TC
L9 = Leading Stand-Alone w/o TC w/CO2
LA = Leading Stand-Alone Master w/o TC w/CO
LB = Leading Stand-Alone Slave w/o TC w/CO
LC = Leading BACnet MS/TP w/o TC w/CO
LD = Leading LonMark SCC w/o TC w/CO
LE = Leading Metasys N2 Open w/o TC w CO
LF = Leading Stand-Alone w/ TC w/CO
LG = Leading Stand-Alone Master w/ TC w/CO
44 = Electromech w/2-Pos Damper for Remote T'Stat
45 = Electromech w/2-Pos Damper w/Unit Mtd. ACO
46 = Electromech w/2-Pos Damper w/Unit Mtd. MCO
2
2
2
2
2
2
2
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 3
Introduction
AAF-HermanNelson Self-Contained Water Source Heat Pump Unit Ventilators
For more than 89 years, schools have relied on AAFHermanNelson unit ventilators to keep classrooms
comfortable. Students learn more readily in a quiet,
well-ventilated environment. That’s why Herman
Nelson invented the unit ventilator and why we remain
committed to meeting the changing requirements of
schools with the highest quality products available.
We realize that keeping expenditures down is a high
priority for school administrators and school boards.
AAF-HermanNelson unit ventilators are inexpensive to
install and operate, and they are designed and built to
provide decades of trouble-free service.
The ARQ, ERQ and GRQ models are designed and
built for new construction and for retrot commercial and
industrial applications such as schools, hospitals, ofce
buildings and other buildings with large conference
rooms and common areas. These units contain a built-in
refrigeration section that eliminates the need for chillers
and outdoor condensing units, making them the right
choice for low- rst cost new or retrot construction.
Quiet Operation
AAF-HermanNelson unit ventilators are engineered
and manufactured to deliver quiet, continuous comfort.
We developed our GentleFlo™ air moving system to
minimize operating sound levels—even as demands for
more fresh air require units to operate longer and work
harder.
Low Operating Costs
When running, AAF-HermanNelson unit ventilators can
use as little electricity as two 100-watt light bulbs. They
take maximum advantage of “free” cooling opportunities
to reduce operating costs. During unoccupied periods
and at night, units operate sparingly to conserve energy.
MicroTech II Control For Superior Performance, Easy Integration
AAF-HermanNelson unit ventilators can be equipped
with MicroTech II™ unit controllers for superior
performance. Factory integrated and tested controller,
sensor, actuator and unit options promote quick, reliable
start-up and minimize costly eld commissioning. Our
Protocol Selectability feature provides easy, low-cost
integration into most building automation systems.
Select BACnet®, LonTalk® or Metasys® N2 Open
communications to communicate control and monitoring
information to your BAS, without the need for costly
gateways. Unit controllers are LONMARK® certied
with the optional LonWorks® communication module.
The Geothermal System (Model GRQ)
Model GRQ Ground Source heat pump utilize the
natural properties of the earth to provide heating and
cooling to a building. Heat addition and rejection take
place below the ground, inside hundreds of feet of
high density polyethylene pipe, known as a ground
loop. Fluid is circulated through the ground loop and
into the geothermal units. The Geothermal heat pump
unit simply amplies and directs conditioned air to the
desired location.
In the Heating Mode the earth acts as a heat source,
allowing the circulating uid to extract natural heat from
the earth and transfer it to the space where it can be
used for heating.
In the Cooling Mode, the earth acts as a heat sink
enabling the circulating uid to transfer the excess heat,
absorbed by the unit, from the building zones to the
earth where it is absorbed and stored for future heating
requirements.
Built To Last
Our proven institutional design can withstand the rigors
of the classroom environment. It features an extra
sturdy chassis and double-wall damper on the inside;
scuff resistant nishes and tamper prevention features
on the outside. In fact, many units installed over 30
years ago continue to provide quiet, reliable classroom
comfort.
R-410A
Refrigerant
4 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
Cooling
Cold
Rejection of heat
into the ground
Heating
Warm
Addition of warmth
from the ground
Introduction
Models ARQ, ERQ & GRQ Water Source Heat Pump Unit Ventilators
1 Welded One-Piece Chassis offers
superior strength, durability, and
vibration reduction.
2
Unique Draw-Thru Design provides
uniform air distribution across the coil
for even discharge air temperatures.
3
Quiet, Aerodynamic Fans utilize
GentleFlo technology for exceptionally quiet unit operation.
4 Modular Fan Section improves
balance, alignment and simplies
maintenance.
5 Fan Motor Located Out of Air
Stream and away from heating coil
reduces heat exposure to prolong
life.
6 Outside Air/Return Air Damper &
Linkage Provides superior mixture of
outdoor air and room air for precise
temperature control.
Model ARQ – Self-Contained - Standard Range WSHP 60°F EWT, Ultra Quiet
Model ERQ – Self-Contained - Extended Range WSHP 50°F EWT, Ultra Quiet
Model GRQ – Self-Contained - Geothermal Range WSHP 20°F EWT, Ultra Quiet
Available in three sizes, 024 (24,000 Btuh), 040 (40,000 Btuh) and 048 (48,000 Btuh)
7 MicroTech II Controls provide
superior comfort control and easy
integration into the building automation system of your choice.
8 Advanced Heat Transfer Coil de-
sign provides extra capacity.
9 Sturdy Cabinet Construction
includes hidden reinforcement, a
non-glare textured surface, and a
tough, scuff- and mar-resistant nish
to stand up to the abuses of a classroom environment.
10 Sectionalized Front Access Pan-
els provide easy access to unit inte-
rior. Panels are easily removed by a
single person. Front side panels can
be removed while unit is running.
11 Two Hinged Top Access Doors
provide easy access to the motor,
electrical, and refrigeration
components.
12 Sampling Chamber for unit-
mounted sensor provides accurate
sensing of room temperature.
13 Optional Adjustable Caster (Left
and Right Ends).
14 Insulated Double-Wall Outdoor
Air Damper seals tightly without
twisting.
15 Full-length Air Filter is efcient
and easy to replace. All air deliv-
ered to classroom is ltered.
16 Corrosion Proof Sloped Drain
Pan (Not Shown).
17 Tamper Resistant Fasteners on
Access Panels
Overall Unit Dimensions:
Size 024 – 86" × 30 × 16-5/8" or (21-7/8 with Adapter Back)
Size 040 – 98" × 30" × 16-5/8" or (21-7/8" with Adapter Back)
Size 048 – 110" × 30" × 16-5/8" or (21-7/8" with Adapter Back)
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 5
Note: Unit size 024 shown (3-fans)
Features and Benets
GentleFlo Delivery
AAF-HermanNelson unit ventilators are engineered
and manufactured to deliver quiet, continuous comfort.
We developed our GentleFlo™ air moving system to
minimize operating sound levels – even as demands for
more fresh air require units to operate longer and work
harder. GentleFlo features include:
• Fan wheels are large, wide and rotate at a low
speed to reduce fan sound levels. They are impactresistant and carefully balanced to provide consistent performance.
• Offset, aerodynamic fan wheel blades move air
efciently (Figure 1).
• Precision tolerances help reduce ow and pressure
turbulence, resulting in lower sound levels.
Figure 1: GentleFlo Fan Technology
Expanded Discharge
Air Opening
• Fan housings incorporate the latest logarithmic-
expansion technology for smoother, quieter air ow
(Figure 2).
• A large, expanded discharge opening minimizes air
resistance, further lowering sound levels.
• Modular fan construction contributes to equal outlet
velocities and promotes quiet operation.
• Fan shafts are of ground and polished steel to mini-
mize deections and provide consistent, long-term
operation.
• Fan assemblies are balanced before unit assembly,
then tested after assembly (and rebalanced if necessary) to provide stable, quiet operation.
Offset Aerodynamic Blades
Logrithmic Expansion Housing
Precision T olerances
Figure 2: GentleFlo Reduces Turbulence
High
Minimal
Turbulence
Offset Aerodynamic
Blades
GentleFlo Fan Blade Design Typical Fan Blade Design
Turbulence
6 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
Features and Benets
The Right Amount of Fresh Air and
Cooling
AAF-HermanNelson unit ventilators deliver required
amounts of fresh air to meet ventilation requirements
and added cooling capacity to maintain consistent
comfort for students and teachers. Our Economizer
Operation, Demand Control Ventilation (DCV) and Part
Load, Variable Air options allow you to match classroom
comfort requirements even more closely, and reduce
operating costs.
This means that you can be condent that your school
is meeting ventilation standards for Indoor Air Quality
and that your students are receiving adequate air to be
attentive to instruction. At the same time, you are saving
money in early morning hours, between classes or after
hours when classrooms are heated and cooled but not
always fully occupied.
Economizer Operation
It is well recognized that cooling, not heating, is the
main thermal challenge in school classrooms. The
typical classroom is cooled by outdoor air over half
the time, even in cold climates. It is therefore essential
that unit ventilators efciently deliver outdoor air when
classroom conditions call for “free” or economizer
cooling.
With AAF-HermanNelson unit ventilators, you can
have outdoor air whenever it is needed. Economizer
operation is facilitated by the outdoor air damper, which
automatically adjusts the above-minimum outside
air position to provide free cooling when the outdoor
air temperature is appropriate (Figure 3). On units
equipped with MicroTech II controls, three levels of
economizer control are available (see See “Economizer
Modes” on page 14).
Figure 3: Full Economizer Mode
100% Outdoor Air Into Classroom
Part-Load Variable Air Control
Part Load Variable Air control can be used to
automatically adjust the unit ventilator fan speed
based upon the room load and the room temperature.
This MicroTech II control option provides higher latent
cooling capabilities and quieter operation during nonpeak load periods by basing indoor fan speed upon
room load. Lower fan speeds in conjunction with our
GentleFlo fan technology contributes to a very quiet
classroom environment.
Room-temperature PI control loops determine the
speed of the fan, which varies according to the
room load. It also provides a built-in delay to prevent
overshooting for better comfort control. The outdoor air
damper’s minimum-air position is adjusted with the fan
speed to bring in a constant amount of fresh air.
Precise Temperature and Dehumidication Control
AAF-HermanNelson unit ventilators provide precise
temperature and dehumidication control to keep
students and teachers comfortable while making
maximum use of “free” outdoor-air cooling to reduce
operating costs. They utilize a draw-thru fan design
that contributes to even heat transfer and provides
uniform discharge air temperatures into the classroom.
MicroTech II control strategies and 2-stage compressor
operation, provide precise control of temperature and
humidity levels under both part-load and full-load
conditions.
Draw-Thru Design For Even Discharge
Temperatures
The AAF-HermanNelson Draw-Thru design sets our unit
ventilators apart from most competitive models. With
this system, fans draw air through the entire heat transfer element (Figure 4) rather than blowing it through
highly concentrated areas of the coil element. The result
is more uniform discharge air temperatures into the
classroom and more efcient unit ventilator operation.
Figure 4: Draw-Thru Design Provides Even Discharge Air
Uniform Discharge Air (Shaded)
Motor
Filter
Room Air Damper
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 7
Outdoor Air Damper
Outdoor Air
Fans
Condenser
Features and Benets
Figure 5: Draw-Thru Vs. Blow-Thru Design
Coil
Coil
Room Air
Damper
Room Air
AAF-HermanNelson
Draw-Thru Design
Outdoor Air
Damper
Outside Air
Filter
RA/OA
Divider
Room Air
Outside Air
Blow-Thru Design
Low Installation Costs
Perfect For Both New & Retrot
Applications
New construction installations are easily accomplished
with AAF-HermanNelson unit ventilators because they
avoid the added cost and space required for expensive
duct work. Further savings can be realized because
piping installations use less space than duct systems.
This is important in existing buildings and also in new
construction where oor-to-oor heights can be reduced,
saving on overall building costs.
Retrot installations are economical because new units
typically t the same space occupied by existing ones.
Figure 7: Optional Unit Casters
Left Caster
Counter-clockwise to lower
Clockwise to raise
Casters can be adjusted
Right Caster
Controls Flexibility
Multiple control options—including MicroTech II controls
with our Protocol Selectability feature—provide easy,
low cost integration of AAF-HermanNelson unit ventilators into the building automation system of your choice
(See “MicroTech II Controls” on page 13). You can also
operate these units individually or in a master-servant
control conguration.
With MicroTech II controls, you can select BACnet, LonTalk or Metasys N2 communications to communicate
control and monitoring information to your BAS, without
the need for costly gateways. Unit controllers are LONMARK certied with the optional LonWorks communica-
tion module.
Built In Flexibility
AAF-HermanNelson unit ventilators include features that
make them easy to set up and recongure as needed to
meet special requirements. These features include:
• Built-In Wire Race A built-in metal wire race runs
from one end of the unit to the other to provide extra
protection for wires and protect them from unit air.
8 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
Features and Benets
Low Operating Costs
Schools consume more than 10% of the total energy
expended in the United States for comfort heating and
cooling of buildings. As energy costs increase, educators are placed in a difcult position: caught between rising costs, lower budgets and the requirements to raise
educational standards.
Fortunately, the technology and the system exists for
schools to take control of their energy expenditures
while providing a comfortable environment for learning.
And that system is the AAF-HermanNelson unit
ventilator.
Consider these realities of school environments:
• Most heating energy in schools is expended to heat
unoccupied spaces. Because lights, computers
and students give off considerable heat, occupied
spaces require little supplemental heat.
• The removal of heat is usually required in occupied
classrooms, even when outside temperatures are
moderately cold (i.e., 35 to 40°F).
• Then consider how AAF-HermanNelson unit ventilators, located in each classroom, take advantage of
these realities to lower operating costs:
• They provide individual classroom control and
comfort.
• They can be cycled on when the room is occupied
and cycled off when it is not.
• They bring in fresh air from directly outside the
classroom for high indoor air quality.
• During most of the school year, they use outdoor air
to keep classrooms comfortable without the expense of mechanical cooling.
Figure 8: Energy Savings with Demand Control Ventilation
100%
Energy Savings
with DCV
20%
Unoccupied
DCV's fresh air for indoor air quality
6:00 8:00 10:00 12:00 2:00 4:00 6:00 8:00
School Hours
Cleaning
Unoccupied
After Hours
• Occupancy Mode Operation Units can be pro-
grammed to operate only sparingly during unoccupied periods and at night to conserve energy.
Two-Stage Compressor
Air conditioning units are usually sized for worse case
conditions. During high load requirement the unit
will operate in high fan speed and high compressor
capacity. Most of the time there is not a full load on
the compressor. Operation in lower load will be at
medium or low fan speeds which will be at the lower
displacement compressor stage. The two stage
compressor will remain at low speed until more cooling/
heating is required. With the two-stage compressor,
these units will run on lower fan speeds most of the time
improving comfort through better humidity control and
quieter operation, while minimizing issues with oversizing.
Other units utilizing single stage compressors operate at
full compressor capacity all of the time regardless of fan
speed.
MicroTech II Control Options Further
Reduce Operating Costs
• Many of the MicroTech II control options available
with AAF-HermanNelson unit ventilators can further
reduce operating costs. For example:
• Economizer Operation Economizer operation automatically adjusts the above-minimum outside air
position to provide free cooling when the outdoor air
temperature is appropriate.
• Demand Control Ventilation By using CO2 levels
to monitor the actual occupancy pattern in a room,
the system can allow code-specic levels of outdoor air to be delivered when needed without costly
over-ventilation during periods of low or intermittent
occupancy (Figure 8).
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 9
Features and Benets
Easy To Maintain
Fan Deck
The fan deck’s rotating element has one large, selfaligning, oilable end bearing for smoother operation.
Figure 9: Long-Life Bearings
Long Life Bearing
Even “permanently” lubricated motors are supplied with
recommended lubrication charts calling for lubrication
every seven years. Maintenance instructions of the
motor manufacturer should be followed closely.
Figure 11: Fan Deck
Heavy-Duty Discharge Grille
The discharge grille on the top of the unit is made
from extra-strength steel bar stock, promoting long life
(Figure 10). It can be removed to facilitate cleaning of
fans and fan housings.
Figure 10: Heavy-Duty Steel Discharge Grille
Internal Fan Deck Components
Unlike with many competitive models, the motor in
AAF-HermanNelson unit ventilators is separate from
the fan assembly and is located out of the airstream at
the end of the fan shaft—away from the hot coil—for
easier maintenance and removal. Locating the motor
away from the coil (Figure 11) has the added benet of
extending motor life. Our direct-coupled motor and selfaligning motor mount facilitate motor change-out. The
motor comes with a molex plug that ts all sizes and
further simplies removal.
Aerodynamic Fans
Modular Fan Deck
1/4" Mesh Screens Protects Against Objects Dropping into Fan Housings
Heavy-Duty Discharge Grille
Motor Located Out of Airstream
Unit Power On/Off Switch and Wire Trough
10 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
Features and Benets
Tamper-Resistant Fasteners
Front panels and top access doors are held in place by
tamper-resistant, positive-positioning fasteners. They
are quickly removed or opened with the proper tool, but
deter unauthorized access to the unit’s interior (Figure
12).
Sectionalized Access Panels and Doors
All units have three separate front panels and hinged
top access doors, sized for convenient handling by a
single person (Figure 12). The result is easy, targeted
access to the component that needs servicing:
• Two end panels provide easy access to piping,
temperature control components and the fan switch.
Unlike units with full-length front panels, these can
be removed without disturbing the normal operation
of the unit.
• Hinged top access doors provide easy access
into the end compartments to facilitate convenient
servicing of the motor, electrical, and refrigeration
components.
• Center front panel provides easy access to the lter
and the fan shaft bearing on unit size 048.
Filter
Three lter types are offered:
• Units come standard with a single-use lter which is
designed to be used once and discarded.
• Optional, permanent metal lters are available and
can be removed for cleaning and reused numerous
times.
• Renewable media lters, which consist of a heavy-
duty, painted-metal structural frame and renewable
media.
Figure 13: Easy Access to Filter
Figure 12: Easy Access with Tamper-Resistant Fasteners
Tamper Resistant Fasteners
Tamper Resistant Fasteners
Removable Filter
Discharge Grille
Tamper Resistant Fasteners
Tamper Resistant Fasteners
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 11
Features and Benets
Built To Last
Durable, Energy Efcient Fan Motors
AAF-HermanNelson unit ventilators are equipped with
115/60/1 NEMA motors that feature low operating
current and wattage (Figure 14).
Figure 14: Energy-Efcient Fan Motor
Energy Efcient NEMA Motor
Decoupled Isolation System
Additional features of these motors include:
• Split-capacitor (PSC) design with automatic reset
and thermal-overload protection.
• No brushes, contacts or centrifugal starting switch-
es – the most common causes of motor failure.
• A built-in, decoupled isolation system to reduce
transmission of vibrations for quieter operation.
• A multi-tap, auto-transformer (Figure 15) provides
multiple fan motor speed control through the speed
switch. The motor is independent of supply voltage,
which allows stocking of one motor (school districtwide) for various voltage applications.
Figure 15: Multi-Tap Auto-Transformer
Additional features include:
• Outdoor air dampers are made of galvanized steel
to inhibit corrosion, with double-wall welded construction for rigidity and encapsulated insulation
(Figure 16). Additional insulation is provided on the
exterior of the outdoor air damper blade and on the
outdoor air entry portion of the unit.
Figure 16: Outdoor Damper Seals Out Cold Weather
Turned Metal Damper Stop
Wool Mohair
End Seal
Additional
Insulation
Wool Mohair
End Seal
Turned Metal Damper Blade
Full-Length Wool
Mohair Damper
• Room air dampers are free-oating and designed
to prevent intermittent gusts of cold air from blowing directly into the classroom on windy days
(Figure 17). They are constructed of aluminum with
built-in rigidity. The metal forming technique that is
employed resists twisting and incorporates a fulllength counter weight for easy rotation. The simple
principle of an area exposed to a force is used to
automatically close the damper, rather than open it,
when gusts of cold air occur.
Figure 17: Room Air Damper Auto-Closed By Wind Gusts
Wind
Gust
Durable Damper Design
All dampers in AAF-HermanNelson Unit Ventilators use
the turned-metal principle on their long closing edges
(Figure 16). Positive sealing is provided by embedding
the edge into wool mohair (no metal to metal contact).
There are no plastic gaskets to become brittle with
time, sag with heat or age, or require a difcult slot t to
seal. Nylon damper bearings foster quiet, maintenancefree operation.
12 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
MicroTech II Controls
MicroTech II Controls For Superior Performance, Easy Integration
AAF-HermanNelson unit ventilators equipped with MicroTech II
unit controllers can provide superior performance and easy integration into your building automation system of choice. MicroTech II
benets include:
• Factory integrated and tested controller, sensor,
actuator and unit options promote quick, reliable
start-up and minimize costly eld commissioning.
• High-performance features and advanced control
options can quickly pay for themselves in saved
energy costs and more comfortable classrooms.
• Select from three control levels: stand-alone,
master-servant or network control.
• For network control applications, our Protocol
Selectability feature provides easy, low-cost integration of AAF-HermanNelson unit ventilators into most
building automation systems.
• Flexible BAS network communication options guard
against controls obsolescence, keeping MicroTech
II controls viable for the life of your AAF-HermanNelson equipment.
Three Control Levels
MicroTech II unit controllers provide the exibility to
operate AAF-HermanNelson unit ventilators on any of
three levels:
• As stand-alone units, with control either at the unit
or from a wall sensor.
• In a master-servant relationship, where servant
units follow the master unit for some or all functions.
• Controlled as part of a network using a centralized
building automation system.
Stand-Alone Control
• When operating in stand-alone mode, the MicroTech II controller performs complete room temperature and ventilation control. Units can be operated in
occupied, unoccupied, stand-by, or bypass (tenant
override) modes. Occupied/unoccupied changeover
can be accomplished:
• Automatically by a unit-mounted occupied/unoccupied time clock.
• Automatically by a remote-mounted time clock
Master-Servant Control
Designate the master and servant units and we will
factory congure and install the controllers so they are
set up for a local peer-to-peer network between units
(leaving only the network wiring between these units to
be eld installed).
Servant units can be eld-congured to be dependent or
independent as follows:
• Dependent servant units follow the master unit
completely. They are ideal for large spaces that
have even loads across the space (such as some
libraries).
• Independent servant units (default) use master setpoints and servant sensors. The servant follows the
master unit modes, such as heat or cool, but has
the exibility to provide the conditioning required for
its area within the space. Independent servant units
perform better in spaces where loads vary from one
area of the space to the other (such as stairwells or
cafeterias).
Network Control
MicroTech II unit controllers provide easy integration
into your building automation system of choice. All
factory-installed options are handled by the unit control-
ler. This simplies the transmission of monitoring and
setpoint data to the building automation system.
You select BACnet, LonTalk or Metasys N2 Open
communications to communicate control and monitoring
information to your BAS, without the need for costly
gateways (see “Optional Communication Modules” on
page 18). Unit controllers are LONMARK certied with
the optional LonWorks communication module.
Flexible network communication options via our Proto-
col Selectability feature help you avoid control obsolescence over the life of your AAF-HermanNelson equipment.
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 13
MicroTech II Controls
Control Modes and Functions
AAF-HermanNelson unit ventilators equipped with
MicroTech II unit controllers can be programmed to
operate in a variety of modes based on the current
situation in the room and the status of the unit ventilator.
Changes in mode can be triggered manually, via
network signals, by sensor readings, or by date and
time. External inputs and outputs can be used to
change modes, communicate data to network controls
or change the functional operation of the unit.
Occupancy Modes
MicroTech II unit controllers can be set up to change
modes based on room occupancy. Four different
occupancy modes are provided, as described below.
Occupied Mode
This is the normal daytime operation mode. The
controller maintains a room set point using the outside
air capability and other functions.
Note: For non-school applications, the unit can also
be congured to cycle the fan in response to the
room load. In this case, the fan would normally
be in the Off Mode until heating or cooling is
required. The outside air damper is always closed
when the fan is off. When the fan starts, the
outside air damper opens to the required position,
usually minimum position.
Unoccupied Mode
This is the night setback operating mode, in which the
unit responds to a new room set point and cycles to
maintain the condition. The fan comes on when heating
or cooling is needed and runs until the load is satised.
The outdoor air damper is closed during this mode.
When a cooling load is satised by a refrigerant system,
the compressor is de-energized and the unit ventilator
indoor fan continues to run for a xed period of time to
remove coldness from the evaporator coil.
Stand By Mode
In this mode, the unit maintains the occupied mode set
point temperature with the outdoor air damper closed.
The fan runs continuously unless it is congured to
cycle in response to the load.
Economizer Modes
Economizer operation is facilitated by the outdoor
air damper, which automatically adjusts the aboveminimum outside air position to provide free cooling
when the outdoor air temperature is appropriate. Three
levels of economizer control are available:
Basic Economizer Operation:
The MicroTech II controller compares the inside and
outside temperatures. If the temperature comparison is
satisfactory, then free-air economizer operation is used
to cool the space. Reheat units also come congured
with an indoor humidity sensor.
Expanded Economizer Operation:
In addition to comparing inside and outside
temperatures, outdoor relative humidity is measured
to calculate outside air enthalpy. Free economizer
operation is used to cool the space. This helps to
minimize the entrance of humid outside air.
Leading-Edge Economizer Operation:
The MicroTech II controller compares both indoor and
outdoor temperatures and indoor and outdoor relative
humidities to determine if free economizer operation can
cool the space with non-humid outside air. This is a true
enthalpy economizer.
Night Purge Mode
Under this mode, the unit is congured to purge the
room space for one hour for various reasons (odor
or fume removal, drying, etc.).During Night Purge the
outside air damper is open full and the fan is run on
high speed. No “normal” heating or cooling takes place
(the emergency heat set point is maintained) and the
exhaust fan, if the room is so equipped, is signaled to
turn on.
Emergency Heat Mode
If the unit is left in a mode that does not normally allow
heating (such as Off, Fan Only, Cool, or Night Purge)
and the room temperature falls below 55°F, the unit
will heat the space to above 55°F and then return to
the previously set mode of operation. This mode of
operation can be eld congured and/or be disabled.
Bypass Mode
This is a tenant override operating mode in which
the unit is placed back into the Occupied Mode for
a predetermined time. The default is 120 minutes.
Settings can be made in 1-minute increments from
1 minute to 240 minutes through the Unit Ventilator
Service Tool or a network.
14 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
MicroTech II Controls
External Input Functions
The unit ventilator controller is provided with three (3)
binary inputs that allow a single set of dry contacts to be
used as a signal to it. Input signal choices are described
below. Multiple units can be connected to a single set of
dry contacts.
Note: Not all of the functions listed can be used at the
same time. The unit ventilator controller is pro-
vided with conguration parameters that can be
adjusted to select which function will be used for
these inputs where multiple functions are indicated below. For wiring examples see installation manual IM 747: MicroTech II Unit Ventilator
Controller.
Unoccupied Input Signal
This input signals the unit ventilator controller to go
into unoccupied or occupied mode. When the contacts
close, the unit ventilator controller goes into unoccupied
mode; when the contacts open, it goes into occupied
mode. Additional variables can affect occupancy mode
and override this binary input. See “Occupancy Modes”
on page 14.
Remote Shutdown Input Signal
This input signals the unit ventilator controller to go into
shutdown mode. When the contacts close, the controller
goes into shutdown mode; when the contacts open, it
returns to normal operation.
External Output Functions
The unit ventilator controller is provided with three (3)
binary outputs to perform the functions described below.
These are relay type outputs that are intended to be
used with signal level voltages only (24 VAC max).
Note: Not all of the functions listed can be used at the
same time. The unit ventilator controller is pro-
vided with conguration parameters that can be
adjusted to select which function will be used for
these outputs when multiple functions are indicated below. For wiring examples, see installation manual IM 747: MicroTech II Unit Ventilator
Controller.
Lights On/Off Signal
This relay output provides one set of NO dry contacts
that can be used to signal the operation of the room
lights. When the unit ventilator controller is in occupied,
standby or bypass occupancy modes, the relay output
will signal the lights on (contacts closed); when the
controller is in unoccupied occupancy mode the relay
output will signal the lights off (contacts open).
Fault Signal
This relay output provides NO, NC, and Common
connections that can be used to signal a fault condition.
When a fault exists, the unit ventilator controller
energizes this relay output. When the fault or faults are
cleared, it de-energizes this relay output.
Ventilation Lockout Input Signal
This input signals the unit ventilator controller to close
the outdoor air damper. When the contacts close
(ventilation lockout signal) the controller closes the
outdoor damper; when the contacts open, it returns to
normal outdoor damper operation.
Exhaust Interlock Input Signal
This input signals the unit ventilator controller that an
exhaust fan within the space has been energized. The
controller then repositions the outdoor air damper to a
user-adjustable minimum position. When the contacts
close (exhaust fan on signal) the controller uses the
value dened by the Exhaust Interlock OA Damper
Min Position Setpoint as the new minimum outdoor air
damper position regardless of the indoor air fan speed.
When the contacts open, it returns to normal outdoor
damper operation.
Exhaust Fan On/Off Signal
This relay output provides one set of NO dry contacts
that can be used to signal the operation of an exhaust
fan. When the outdoor air damper opens more than the
Energize Exhaust Fan OA Damper Setpoint, the relay
output will signal the exhaust fan on (contacts closed).
When the outdoor damper closes below this setpoint,
the relay output will signal the exhaust fan off (contacts
open).
Auxiliary Heat Signal
This relay output provides one set of NO dry contacts
that can be used to operate an auxiliary heat device.
The unit ventilator controller by default is congured to
operate a NO auxiliary heat device (de-energize when
heat is required) such as a wet heat valve actuator with
a spring setup to open upon power failure. However,
the Auxiliary Heat Conguration variable can be used
to set the controller to use an NC auxiliary heat device
(energize when heat is required) such as electric heat.
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 15
MicroTech II Controls
Advanced Control Options
MicroTech II controls make possible a number of
advanced control options that can quickly pay for
themselves in saved energy costs and more comfortable
classrooms, as described below.
Part Load Variable Air Control
Part Load Variable Air control can be used to
automatically adjust the unit ventilator fan speed based
upon the room load and the room-temperature PI control
loop. This MicroTech II control option provides higher
latent cooling capabilities and quieter operation during
non-peak load periods by basing indoor fan speed upon
room load.
During low-load or normal operation (about 60% of
the time) the fan will operate on low speed. When the
load increases to an intermediate demand, the fan
will automatically shift to the medium-speed setting.
Under near-design or design-load conditions, the fan
will operate on high speed. A built-in, 10-minute delay
helps minimize awareness of fan speed changes. Lowspeed fan operation under normal operating conditions,
in conjunction with our GentleFlo fan technology
contributes to a very quiet classroom environment.
Demand-Controlled Ventilation (Optional)
AAF-HermanNelson unit ventilators can be equipped to
use input from a CO2 controller to ventilate the space
based on actual occupancy instead of a xed design
occupancy. This Demand Controlled Ventilation (DCV)
system monitors the amount of CO2 produced by
students and teachers so that enough fresh outdoor air
is introduced to maintain good air quality. The system
is designed to achieve a target ventilation rate (e.g., 15
cfm/person) based on actual occupancy.
By using DCV to monitor the actual occupancy pattern
in a room, the system can allow code-specic levels of
outdoor air to be delivered when needed. Unnecessary
over-ventilation is avoided during periods of low or
intermittent occupancy.
With DCV you can be condent that your school is
meeting ventilation standards for Indoor Air Quality
and that your students are receiving adequate air to be
attentive to instruction. At the same time, you are saving
money in early morning hours, in between classes, or
after hours when classrooms are heated and cooled but
not always fully occupied.
Acceptance by Codes and Standards
ASHRAE Standard 62-2004 Ventilation for Indoor Air
Quality recognizes CO2 based DCV as a means of controlling ventilation based on occupancy. The ASHRAE
standard has been referenced or adopted by most
regional and local building codes. This standard references ventilation on a per-person basis.
Using CO2 control will sometimes lower the absolute
amount of outside air delivered into a room but will
maintain the per-person rate. For example, if a classroom is designed for 30 students, the ventilation rate is
450 cfm (30 students × 15 cfm/student). However, when
there are only ten students in the classroom, the CO2
control will adjust ventilation to 150 cfm (10 students
× 15 cfm/student). A minimum base ventilation rate
(typically 20% of design levels) is provided when in the
occupied mode. This provides outdoor air to offset any
interior source contamination while allowing for proper
space pressurization.
DX System Control
The unit ventilator controller is congured to operate the
compressor as secondary (mechanical) cooling when
economizer cooling is available, and as primary cooling
when economizer cooling is not available. Additional DX
control features include:
Compressor Envelope:
This helps protect the compressor from adverse
operating conditions that can cause damage and
or shortened compressor life. It ends compressor
operation if coil temperatures exceed the dened
operating envelope.
Compressor Cooling Lockout:
The unit ventilator controller is congured to lock out
compressor cooling when the outdoor air temperature
falls below the compressor cooling lock out setpoint.
Below this temperature setpoint only economizer
cooling will be available.
Minimum On and Off Time:
The unit ventilator controller is provided with minimumon and minimum-off timers to prevent adverse
compressor cycling (3-minutes default).
16 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
MicroTech II Controls
System Components
The main components of the MicroTech II system are:
• The Unit Ventilator Controller (UVC)
• The Local User Interface (LUI)
• Optional plug-in network communication modules
In addition, unit ventilators equipped with MicroTech
II controllers feature factory-mounted sensors and
actuators for system control and feedback.
Unit Ventilator Controller
The MicroTech II UVC is a DDC, microprocessor-based
controller designed to provide sophisticated comfort
control of an economizer-equipped AAF-HermanNelson
unit ventilator. In addition to normal operating control,
it provides alarm monitoring and alarm-specic
component shutdown if critical system conditions occur.
Each UVC is factory wired, factory programmed and
factory run-tested for the specic unit ventilator model
and conguration ordered by the customer.
Figure 18: MicroTech II Control Board
Terminal Connections Plug-In Control Module
Figure 19: User Interface Touch Pad
The User Interface has individual touch-sensitive printed
circuit board mounted buttons, and comes with a built-in
menu structure (Hidden Key and Password Protected)
to change many of the common operating variables.
Four Operating Mode States
Four different user operating mode states can be
chosen on the LUI:
Heat: Heating and economizer operation only.
Cool: Cooling and economizer operation only.
Fan Only: Fan only operation.
Auto: The unit automatically switches between heating,
cooling and economizer operation to satisfy the room
load conditions. The current unit state is also displayed.
Local User Interface
A built-in LUI touch pad with digital LED Display is
located in the right hand compartment below the top
right access door. In addition to the Operating Mode
States and Fan Functions, the Touch Pad will digitally
display:
• The room set point temperature.
• The current room temperature.
• Any fault code for quick diagnostics at the unit.
Four Fan States
Four fan states are provided on all units: high, medium
low and Auto speed modulation. The Auto speed
function (part load, variable air) varies the fan speed
automatically to meet the room load whether the unit is
in heating, cooling or economizer mode.
All this is accomplished with a standard, single-speed
NEMA frame motor. A built-in 10-minute delay helps
minimize awareness of speed changes. During low-load
or normal operation (about 60% of the time) the fan will
operate at low speed. The low speed operation, along
with GentleFlo fan technology, contributes to a very
quiet classroom environment.
When the load increases to an intermediate demand,
the fan automatically shifts to the medium speed setting.
At near-design or design-load conditions the fan will
operate on high speed.
With four fan states and GentleFlo fan technology,
there is no need to oversize units or worry about
uncomfortable conditions.
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 17
MicroTech II Controls
Optional Communication Modules
Optional communication modules provide control and
monitoring information to your building automation
system without the need for costly gateways. Available
communication protocols include BACnet, LonTalk and
Metasys N2 Open. The communication modules for
each are described below.
Figure 20: Typical 2" x 4" Communication Module
BACnet MS/TP Communication Module
This module allows the UVC to inter-operate with
systems that use the BACnet (MS/TP) protocol with a
conformance level of 3. It meets the requirements of the
ANSI/ASHRAE 135-1995 standard for BACnet systems.
LonWorks SCC Communication Module
This module supports the LONWORKS SCC (Space
Comfort Communication) prole number 8500-10. Unit
controllers are LonMark certied with this optional LON-
WORKS communication module.
Figure 21: Wall-Mounted Temperature Sensors
Standard Expanded
Standard Sensor:
This sensor has no remote setpoint adjustment
capability.
Expanded Sensor:
This sensor has a remote room setpoint adjustment
of ±3°F (±1.5°C) from the room setpoint established
on the unit ventilator’s local user interface touch pad.
Five temperature settings are provided on each side of
center.
Humidity Sensors
On units equipped with humidity sensors, the UVC is
congured to use a 0-100% RH, 0 VDC, capacitive
humidity sensor. Humidity sensors are available as unitmounted only. The humidity sensors are used with units
using an outdoor enthalpy economizer or an indoor/
outdoor enthalpy economizer.
Metasys™ N2 Communication Module
This module provides N2 Open network communication
capability to the UVC for communication with Johnson
Metasys systems.
Sensors
The UVC is congured to use passive Positive
Temperature Coefcient (PTC) unit-mounted and
wall-mounted sensors. These sensors vary their input
resistance to the UVC as the sensed temperature
changes.
CO2 Sensor for Demand Controlled Ventilation
On units equipped for Demand Controlled Ventilation
(DCV) the UVC is congured to use a 0-2000 PPM,
0-10 VDC, single beam absorption infrared gas sensor.
CO2 sensors are available as unit mounted only. An air
collection probe (pitot tube and lter) is installed in the
return air of the unit.
Figure 22: CO2 Sensor For Demand Control Ventilation
Remote Wall-Mounted Temperature Sensors
MicroTech II unit ventilators offer two choices for remote
wall-mounted room sensors (Figure 21). Each has a tenant override capability and comes with an international,
quick-fastening connection capability.
18 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
MicroTech II Controls
MicroTech II Sensors and Component Locations
Figure 23: MicroTech II Sensor and Component Locations
1. MicroTech II Unit Ventilator Controller (UVC):
(Located Beneath the Local User Interface Panel).
Factory mounted and run tested, microprocessorbased DDC control device capable of complete
Standalone unit control, Master/Servant control or
incorporated into a building-wide network using an
optional plug-in communication module. The UVC
contains a microprocessor that is preprogrammed
with the application code required to operate the
unit. The UVC supports up to 6 analog inputs,
12 binary inputs, and 9 binary outputs. The UVC
EXP I/O board supports up to 4 additional analog
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 19
inputs and 8 additional binary outputs. Master/Ser-
vant units have the controller factory congured and
installed for a local peer-to-peer network between
these units (network wiring between these units
needs to be eld installed). Optional network communication is provided via plug-in communication
modules that connect directly to the UVC.
2. Communication Module (optional): Plug-in network communication module that is attached to the
UVC via a 12-pin header and 4 locking standoffs.
Available communication modules:
MicroTech II Controls
• Building Automation and Control Network (BACnet®) Master Servant/Token Passing (MS/TP) Allows the UVC to inter-operate with systems that
use the BACnet (MS/TP) protocol with a conformance level of 3. Meets the requirements of ANSI/
ASHRAE 135-1995 standard for BACnet systems.
• LonWorks® compliant Space Comfort Controller
(SCC) – Supports the LonWorks SCC prole number 8500_10.
• Metasys N2® Open – Provides N2 Open network
communication capability to the UVC.
3. Local User Interface (LUI): The LUI provides a unit
mounted interface which indicates the current unit
operating state and can be used to adjust the unit
ventilator operating parameters (operating mode,
temperature set points, fan speed and occupancy
mode). The LUI features a 2-digit display, 7 keys (1
key is hidden), and 9 individual LED indicators. See
“Local User Interface” for further details.
4. Tenant Override Switch: Provides a momentary
contact closure that causes the unit to enter the
“tenant override” operating mode for a set time
period (default = 120 minutes).
5. Time Clock (TC) (optional on standalone units
only): Factory mounted 7 day/24 hour, digital time
clock with up to twenty (20) programs to sequence
the unit ventilator through occupied and unoccupied
modes in accordance with a user programmed time
schedule.
6. External Signal Connection Plugs: Three (3)
multi-pin plugs are factory provided and pre-wired
with short wire whips that are capped (they must
remain capped if not used).
Provided for eld wiring of :
• Remote Wall Mounted Temperature Sensor (op-
tional accessory).
• External Input Signals (by others): unoccupied,
remote shutdown, ventilation lockout, dew point/
humidity (night time operation), or exhaust interlock
signals
• External Output Options (by others): lights on/off,
fault indication signal, exhaust fan on/off or auxiliary
heat signal.
7. Motor Speed Transformer: (Located beneath the
Local User Interface Panel). Multi-tap auto-transformer provides multiple fan motor speed control
through the LUI.
8. Unit Main Power “On-Off” Switch (SW1): Disconnects the main power to the unit for servicing or
when the unit is to be shut down for an extended
period of time.
Figure 24: Unit Main Power “On-Off” Switch (SW1)
9. Fuse(s): Fan motor and controls have the hot
line(s) protected by factory installed cartridge type
fuse(s).
10. Control Transformer: 75 VA 24-volt NEC Class
2 transformer for 24 volt power supply. (Located
behind the motor transformer).
11. Outdoor Air/Return Air Damper Actuator (A1):
Direct coupled, oating point (tristate) actuator that
spring returns the outdoor air damper to the closed
position upon a loss of power.
12. Low Refrigerant Temperature Sensor (S4): The
S4 sensor is provided on all units with a direct
expansion (DX) cooling coil. It is located on the right
hand side of the air coil “u-bend”.
13. Room Temperature Sensor (S1): The unit mounted sensor is located in the sampling chamber (front,
center section) where room air is continuously
drawn through for prompt response to temperature
changes in the room. A Remote Wall Mounted
Temperature Sensor is also available for remote
room temperature sensing. (optional accessory).
14. Discharge Air Temperature Sensor (S2): The
sensor is located on the second fan from the right to
sense discharge air temperatures.
20 AAF-HermanNelson Model AR, ER & GR Unit Ventilator
MicroTech II Controls
15. Outdoor Air Temperature Sensor (S3): The sen-
sor is located in the outdoor air section of the unit
before the outdoor air damper. With network applications, the unit mounted sensor can be overridden
by a remote sensor through the network.
16. Outdoor Air Humidity Sensor (S8) (optional):
Unit mounted humidity sensor for units using
Expanded outdoor enthalpy economizer or Leading Edge indoor/outdoor, true enthalpy comparison
economizer. The sensor is located in the outdoor air
section of the unit before the outdoor air damper.
With network applications, the unit mounted sensor
can be overridden by a remote sensor through the
network.
17. Room Humidity Sensor (S6) (optional): Unit
mounted humidity sensor for units capable of active
dehumidication or with units using Leading Edge
indoor/outdoor, true enthalpy comparison economizer. The sensor is located in the sampling chamber (front, center panel) where room air is continuously drawn through for fast response to humidity
changes in the room. With network applications, the
unit mounted sensor can be overridden by a remote
sensor through the network.
18. CO2 Sensor (S7) (optional): Unit mounted, single
beam absorption infrared gas sensor with a sensing
range of 0 – 2000 ppm and voltage output of 0 to 10
VDC (100 ohm output impedance). The Pitot Tube
sensing device is located in the unit ventilator’s
return air stream. The optional CO2 sensor is used
with the UVC’s Demand Control Ventilation feature
to vary the amount of outside air based on actual
room occupancy. With network applications, the
unit mounted sensor can be overridden by a remote
sensor through the network.
19. Water Out Temperature Sensor (S9): The water
out temperature sensor is factory wired. The sensor
must be eld-installed and insulated (by others) and
located on the return connection of the plate heat
exchanger.
20. Water Coil DX Temperature Sensor (S5): The S5
sensor is factory wired, installed and insulated. It is
located on the lower left refrigerant line of the plate
heat exchanger leading to the expansion valve.
Figure 25: Water Out & Water Coil DX Temperature
Sensors
Actuators
Outdoor Air/Return Air Damper (OAD) Actuator
The UVC is congured to operate a oating-point (tri-
state) direct-coupled actuator for the outdoor air damper. This actuator provides spring-return operation upon
loss of power for positive close-off of the outdoor air
damper. To determine damper position, the UVC uses
a separate, factory-preset, congurable setting for each
actuator's stroke time.
Figure 26: Outdoor Air Damper Actuator
AAF-HermanNelson Model AR, ER & GR Unit Ventilator 21
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