ACS Marvair MAA1020H User manual

Single Stage Models:
MAA1020H • MAA1024H • MAA1030H
MAA1036H • MAA1042H • MAA1048H
MAA1060H • MGA1072H
2-Stage Models:
MAA2024H • MAA2030H • MAA2036H
MAA2042 •MAA2048H • MAA2060H
Installation & Operation Manual
Vertical Wall-Mount Heat Pumps
IMPORTANT
This manual may include information for options and features which may not be
included on the unit being installed. Refer to the unit data label or Model Identication
to determine which features and options this unit is equipped with.
INSTALLER: Afx the instructions on the inside of the building adjacent to the thermostat.
END USER: Retain this manual for future reference.
Heat Pump Product Manual
Vertical Wall-Mount Heat Pumps
Marvair Wall Mount Heat Pump I&O Manual
06/2023 Rev.7
Manufactured By:
Marvair, An AirX Climate Solutions Brand
P.O. Box 400 • Cordele, Georgia 31010 • 156 Seedling Drive • Cordele, Georgia 31015
[phone] • Fax [phone]
E-mail: [e-mail] • Internet: www.Marvair.com
The most current version of this manual can be found at www.Marvair.com.

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How To Use This Manual
This manual is intended to be a comprehensive guide to the installation of the Marvair®MAA family of vertical packaged
heat pumps. It contains installation, troubleshooting, maintenance, warranty, and application information. The information
contained in this manual is to be used by the installer as a guide only. This manual does not supersede or circumvent
any applicable national or local codes. For information on the efciency, cooling and heating performance, please refer
to the Product Data Sheets. The most current version of all literature can be found on our website at www.Marvair.com.
If you are installing the heat pump unit, rst read Chapter 1 and scan the entire manual before beginning the installation
as described in Chapter 2. Chapter 1 contains general, descriptive information and provides an overview which can
speed up the installation process and simplify troubleshooting.
If a malfunction occurs, follow this troubleshooting sequence:
1. Make sure you understand how the heat pump unit works (Chapters 1 & 3).
2. Identify and correct installation errors (Chapter 2).
3. Refer to the troubleshooting information in Chapter 4.
4. Identify defective part(s). (Chapter 5).
If you are still unable to correct the problem, contact the Factory at 1-800-841-7854 for additional assistance.
Please read the following “Important Safety Precautions” before beginning any work. Failure to follow these rules
may result in death, serious bodily harm, property damage and damage to the equipment.
Important Safety Precautions
1. USE CARE when LIFTING or TRANSPORTING equipment.
2. TRANSPORT the UNIT UPRIGHT. Laying it down on its side may cause oil to leave the compressor and breakage
or damage to other components.
3. TURN ELECTRICAL POWER OFF AT THE breaker or fuse box BEFORE installing or working on the equipment.
LINE VOLTAGES ARE HAZARDOUS or LETHAL.
4. OBSERVE and COMPLY with ALL applicable PLUMBING, ELECTRICAL, and BUILDING CODES and ordinances.
5. SERVICE may be performed ONLY by QUALIFIED and EXPERIENCED PERSONS.
* Wear safety goggles when servicing the refrigeration circuit
* Beware of hot surfaces on refrigerant circuit components
* Beware of sharp edges on sheet metal components
* Use care when recovering or adding refrigerant
6. Use COMMON SENSE - BE SAFETY-CONSCIOUS
This is the safety alert symbol . When you see this symbol on the unit and in the instruction manuals be alert to
the potential for personal injury. Understand the signal word DANGER, WARNING, CAUTION and IMPORTANT.
These words are used to identify levels of the seriousness of the hazard.
DANGER Failure to comply will result in death or severe personal injury and/or property damage.
WARNING Failure to comply could result in death or severe personal injury and/or property dam-
age.
CAUTION Failure to comply could result in minor personal injury and/or property damage.
IMPORTANT Used to point out helpful suggestions that will result in improved installation, reliability
or operation.
© 06/2023 Marvair, An AirX Climate Solutions Brand
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE.

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Table of ConTenTs
Chapter 1 - Description & Specications
1.1 General Description................................................................................................................................. 5
1.2 Serial Number Date Code ....................................................................................................................... 5
1.3 Model Identication ................................................................................................................................ 6
1.4 Air Flow, Weights, Filter Sizes, Refrigerant Charges and Ambient Operating Ranges ......................... 6
1.5 General Operation ................................................................................................................................... 7
1.6 Options .................................................................................................................................................. 10
Chapter 2 - Electronic Control Board
2.1 Introduction........................................................................................................................................... 11
2.2 Installation and Replacement ................................................................................................................ 12
2.3 PCB Details and Information................................................................................................................ 12
2.4 Operation............................................................................................................................................... 16
2.5 Sequence of Operation .......................................................................................................................... 16
Chapter 3 - Installation
3.1 Equipment Inspection............................................................................................................................ 28
3.2 Installation Requirements...................................................................................................................... 28
3.3 Installation Materials ........................................................................................................................... 29
3.4 Porting and Duct Work ......................................................................................................................... 31
3.5 Fresh Air Hood Adjustment .................................................................................................................. 32
3.6 Bracket Installation .............................................................................................................................. 32
3.7 Mounting the Unit ................................................................................................................................ 33
3.8 Electrical Connections........................................................................................................................... 34
Chapter 4 - Start-Up
4.1 Check-Out of Cooling Cycle ................................................................................................................ 37
4.2 Check-Out of Heating Cycle................................................................................................................. 38
4.3 Discharge Air Adjustment for Modulating Hot Gas Reheat (HGR) Valve ........................................... 38
4.4 Ventilation System Set Up .................................................................................................................... 39
WARNING
• If the information in these instructions are not followed exactly, a re may result
causing property damage, personal injury or loss of life.
• Read all instructions carefully prior to beginning the installation. Do not begin
installation if you do not understand any of the instructions.
• Improper installation, adjustment, alteration, service or maintenance can cause
property damage, personal injury or loss of life.
• Installation and service must be performed by a qualied installer or service
agency in accordance with these instructions and in compliance with all codes and
requirements of authorities having jurisdiction.
INSTALLER: Afx the instructions on the inside of the building adjacent to the thermostat.
END USER: Retain these instructions for future reference.

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Chapter 5 - Troubleshooting
5.1 Overview ............................................................................................................................................... 4 0
5.2 Failure Symptoms Guide....................................................................................................................... 41
5.3 Compressor Troubleshooting ................................................................................................................ 42
5.4 Electric Heat Control............................................................................................................................. 43
Chapter 6 - Electrical Schematics
6.1 Electrical Schematics ............................................................................................................................ 44
Chapter 7 - Periodic Maintenance Requirements
7.1 Scheduled Maintenance......................................................................................................................... 48
Chapter 8 - Warranty Information
8.1 Standard Product Warranty...................................................................................................................... 49
Appendix A - Installation Instructions of Field Installed Electric Heat ......................................................... 50
Appendix B - Heat Pump Start-Up - Commissioning Checklist ................................................................... 53
figures
Figure 1 PC Control Board.................................................................................................................... 11
Figure 2 Enthalpy Sensor Temperature Control Points ......................................................................... 21
Figure 3 Dry Bulb Sensor...................................................................................................................... 22
Figure 4 Fresh Air Hood Damper .......................................................................................................... 32
Figure 5 Heat Pump Wall Mounting Detail........................................................................................... 33
Figure 6a Humidity Control Wiring Detail ............................................................................................. 35
Figure 6b Thermostat Connection Diagram ............................................................................................ 36
Figure 7 Temperature Sensor Wires - Modulating HGR Valve ............................................................ 39
Figure 8 Desired Temperature Set Point - Modulating HGR Valve ..................................................... 39
Figure 9 Typical Configuration for Single Element Heater .................................................................. 43
Figure 10a Typical 1ø Electrical Schematic Diagram Heat Pump with Manual Outside Air Damper..... 45
Figure 10b Typical 208/230v. 3ø Heat Pump Electrical Schematic Diagram........................................... 46
Figure 10c Typical 460v. 3ø Heat Pump Electrical Schematic Diagram, with PC Control Board........... 47
Tables
Table 1 CFM @ External Static Pressure............................................................................................... 6
Table 2 Ship Weight ............................................................................................................................... 7
Table 3 Filter Sizes ................................................................................................................................. 7
Table 4 Refrigerant Charge..................................................................................................................... 7
Table 5 Ambient Temperature Operating Ranges .................................................................................. 7
Table 6 Minimum Clearances .............................................................................................................. 29
Table 7 Voltage Limitations.................................................................................................................. 29

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Chapter 1 Description and Specications
1.1 General Description
Marvair® Wall Mount Heat Pumps are high efficiency, vertical wall mounted heat pumps that provide
heating, cooling and ventilation for a wide range of applications. Single stage nominal cooling capacities
range from 20,000 to 60,000 & 72,000 BTUH. 2-Stage units have nominal cooling capacities from 24,000
to 60,000 BTUH.
All models have EER's of 11.00 and feature quiet operation. Resistance heating is available in all models.
Please see appendix A for the installation instructions on field installing electric heaters.
Marvair heat pumps are designed for easy installation and service. All units have built-in side mounting
flanges and are shipped with a bottom support bracket. The unit has been factory charged. Service ports
have been provided for field service, if required. All internal wiring is complete.
Marvair MAA heat pump models are available in a wide variety of styles and configurations to meet the
various ventilation and cooling requirements. For school classrooms, models are available to comply
with the ASHRAE 62-1999 standard, “Ventilation for Acceptable Indoor Air Quality.” Where cooling
is required during cool or cold weather, e.g., telecommunication shelters, a factory-installed economizer
can be used. To insure proper operation and optimum performance, all outside air ventilation packages
and the economizer are non-removable, factory installed and tested. Instructions for the MAA models
with the GreenWheel® ERV are included in this manual.
All Marvair heat pumps are tested and certified for efficiency and capacity in accordance with the ANSI/
AHRI (Air-Conditioning, Heating and Refrigeration Institute) Standard 390-2017 (Single Package
Vertical Units). All MAA models meet or exceed the efficiency requirements of ANSI/ASHRAE/IESNA
90.1.2019. All heat pump models are listed by ETL and tested to UL standard 1995, 4th Edition. Marvair
heat pumps are commercial units and are not intended for use in residential applications.
1.2 Serial Number Date Code
20 = 2020 01 = January 05 = May 09 = September
21 = 2021 02 = February 06 = June 10= October
22 = 2022 03= March 07 = July 11 = November
23 = 2023 04 = April 08 = August 12 = December

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1.3 Model Identification
Example M A A 1 0 3 6 H A 0 5 0 C + + R + 1 E A + A 1 1 + + + + + +
Position 1234567891011 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
1Unit Designation/Family M = Marvair Wall Mount
S = Stock Unit
2Energy Efciency Ratio
(EER)
A = 11
G = 10
3Refrigerant Type A = R-410a
4Compressor Type/Quantity 1 = Single Fixed Speed
2 = 2-Stage Compressor
5
Unit Capacity/Nominal
Cooling (BTUH)
020 = 20,000 042 = 42,000
024 = 24,000 048 = 48,000
030 = 30,000 060 = 60,000
036 = 36,000 072 = 72,000
6
7
8System Type H = Heat Pump
9Power Supply
(Volts-Phase-Hz)
A= 208/230-1-60 D= 460-3-60
C= 208/230-3-60
10
Heat Designation
@ Rated Voltage
000 = No Heat 090 = 9KW
040 = 4KW 100 = 10KW
050 = 5KW 120 = 12KW
060 = 6KW 150 = 15KW
080 = 8KW
11
12
13 Ventilation
Conguration
C = Economizer
D = Motorized Damper w/Pressure Relief
E = Motorized Damper w/Pressure Relief &
Independent
K = Economizer w/Factory Inst. CO2 Control
N = Barometric Damper w/15% OSA
+ = None
$ = Special
14 Dehumidication
R = Electric Reheat
T = Electric Reheat w/Humidity Control
+ = None
$ = Special
15 Controls
A = Power Fail Alarm w/Additional Lockouts
C = 24V EMS Relay Kit
D = 24V EMS Relay Kit w/Factory
Installed T-Stat
+ = None
$ = Special
16 Operating Condition
N = Hard Start
1 = Low Ambient w/FCC
R = Crank Case Heater (CCH)
+ = None
$ = Special
17 Indoor Air Quality Features
A = UV Light
K = Bi-Polar Ionization
M = Dry Bulb Sensor & CO2 Sensor
(Only w/Economizer)
+ = None
$ = Special
18 Air Flow 1 = Top Supply/Bottom Return
$ = Special
19 Compressor Location D= Left Hand - All 31/2 to 5 ton units
E= Right Hand - All 11/2 to 3 ton units
20 Filter Option
A = 2” Pleated (MERV 8, AC/HP-C)
D = MERV 11 High Filtration Package
E = MERV 13 High Filtration Package
+ = None
$ = Special
21 Corrosion Protection
A = Condenser Coil Only
C = Evaporator Coil Only
D = Both Coils Condenser & Evaporator
F = Coat All
G = Coastal Package & Evaporator Coil
K = Coastal Package
+ = None
$ = Special
22 Engineering Revision
Level
A3
B3
23
24 Cabinet Color
1 = Marvair Beige
2 = Gray
4 = White
5 = Stainless Steel Exterior
6 = Dark Bronze
7 = .050 Aluminum Stucco
A = Stainless Steel - Unit
$ = Custom Color (Powder Coat)
25 Sound Attenuation 2 = Compressor Blanket
+ = None
26 Security Option
A = Lockable Access Plate/Tamper Proof
+ = None
$ = Special
27 Fastener/Drain Pan Option
A = Stainless Steel Fasteners
C = Stainless Steel Drain Pan
D = Stainless Steel Fasteners & Drain Pan
+ = None
$ = Special
28 Unused
C = Copeland Compressor
+ = None
$ = Special
29 Unused + = None
$ = Special
30 Special Variation
+ = None
$ = Special Conguration Not Covered by
Model Nomenclature
Note: Not all options are available with all congurations.
Contact your Marvair sales representative for conguration
details and feature compatibility.
1.4 Air Flow, Weights, Filter Sizes, Refrigerant Charges and Ambient Operating Ranges
Model Number External Static Pressure (WET COIL)
0.10 0.20 0.25 0.30 0.40 0.50
MAA1020H/1024H/2024H 889 831 820 801
MAA1030H/2030H 1152 1122 1100 1075 1028
MAA1036H/2036H 1265 1222 1200 1175 1133
MAA1042H/2042H 1650 1585 1520 1450 1360
MAA1048H/2048H 1693 1650 1619 1591 1529
MAA1060H/2060H 1693 1650 1619 1591 1529
MGA1072H 1987 1950 1865 1783 1661
Air flow ratings of 208-230v. Units are at 230v. Air flow ratings of 480 v. units are at 460 volts. Operation of units at a different voltage from the rating
point will affect air flow.
Table 1. Air Flow (Cubic Feet per Minute)

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Model Weight Base w/Economizer w/3 Phase w/Economizer & 3 Phase
MAA1020H/MAA1024H/MAA2024H Lbs (Kg) 337 (153) 357 (162) 356 (161) 376 (171)
MAA1030H/MAA1036H/MAA2030H/MAA2036H Lbs (Kg) 397 (180) 419 (190) 416 (189) 438 (199)
MAA1042H/MAA1048H/MAA2042H/MAA2048H Lbs (Kg) 453 (205) 476 (216) 491 (223) 514 (233)
MAA1060H/MAA2060H Lbs (Kg) 469 (213) 492 (223) 522 (237) 545 (247)
MGA1072H Lbs (Kg) 576 (261) 599 (272) 629 (285) 652 (296
Table 2. Installed Weight (lbs (Kg)
Model FILTER TYPE INCHES MILLIMETERS PART
NUMBER
FILTERS
PER UNIT
MERV
RATING
MAA1020H/MAA1024H/MAA2024H Return Air Filter 30 x 16 x 2 762 x 406 x 51 80138 1 8
MAA1030H/MAA1036H/MAA2030H/MAA2036H Return Air Filter 36½ x 22 x 2 927 x 559 x 51 80162 1 8
MAA1042H/MAA1048H/MAA2042H/MAA2048H Return Air Filter 36½ x 22 x 2 927 x 559 x 51 80162 1 8
MAA1060H/MAA2060H Return Air Filter 18 x 24 x 1 457 x 610 x 25 81199 2 8
MGA1072H Return Air Filter 18 x 24 x 2 457 x 610 x 51 81257 2 8
Table 3. Filter Size (inches)
Model MAA1020H MAA1024H MAA1030H MAA1036H MAA1042H MAA1048H MAA1060H MGA1072H
A A C D A C D A C D A C D A C D A C D C D
Charge Amount 100 11 0 114 130 185 185 185 210
Model MAA2024H MAA2030H MAA2036H MAA2042H MAA2048H MAA2060H
A C D A C D A C D A C D A C D A C D
Charge Amount 120 120 150 185 185 220
Table 4. Refrigerant Charge (R410A, Ounces)
Basic Model Special Option TEMPERATURE RANGES
Non-Economizer
Base Unit *20ºF - 131ºF (-7ºC - 55ºC)
Desert Duty *20ºF - 131ºF (-7ºC - 55ºC)
Extreme Duty *0ºF - 131ºF (-18ºC - 55ºC)
Economizer-Equipped
Base Unit -40ºF - 131ºF (-29ºC - 55ºC)
Desert Duty -40ºF - 131ºF (-29ºC - 55ºC)
Extreme Duty -40ºF - 131ºF (-29ºC - 55ºC)
**An Optional FCC switch is required for the cooling Mode. Heating mode ratings are @47°F Outdoor Temperature. Performance loss
realized below this rating point.
Table 5. Ambient Temperature Operating Ranges
1.5 General Operation
Refrigerant Cycle
Marvair heat pumps use R-410A refrigerant in a conventional vapor-compression refrigeration cycle to
transfer heat. In the cooling mode, a double blower assembly blows indoor air across the evaporator (indoor
coil). Liquid refrigerant passing through the evaporator is boiled into gas by heat removed from the air.
The warmed refrigerant gas enters the compressor where its temperature and pressure are increased. The
hot refrigerant gas condenses to liquid as heat is transferred to outdoor air blown across the condenser
(outdoor coil) by the condenser fan. Liquid refrigerant is metered into the evaporator through a metering
device to repeat the cycle. In the heating mode, the process is reversed.
Heating Mode
During heating mode a special reversing valve reverses the flow of refrigerant through the system
exchanging the roles of the condenser and evaporator. Now the outdoor coil becomes the evaporator and
the indoor coil becomes the condenser. The refrigerant then flows through the outdoor coil, picks up heat
and becomes vaporized. The vapor then enters the compressor where it is compressed to a higher pressure
and temperature. Next it is pumped to the indoor coil where the heat will be released into the room. The
compressed refrigerant vapor will condense to its liquid state as it gives up heat. Finally, liquid flows
through a metering device into the evaporator where the cycle will be repeated.
Optional electric strip heat is available for all models. Please see Appendix A for instructions on field
installation of electric heat.

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Ventilation Options
ASHRAE standard 62 requires 15 cfm of outside air per occupant of a classroom. To meet this requirement,
Marvair offers seven ventilation packages for every budget and requirement.
Configuration “C”: Up to 100% Modulating Economizer
The economizer reduces the cost of air conditioning by using outside air when acceptable to cool the
room (Free Cooling). The factory installed Marvair® economizer has integral pressure relief.
Control Board Logic: Upon a “Call for Cooling”, the economizer control board calculates whether the
HVAC operates in economizer mode or mechanical cooling mode based on outdoor temperature (dry bulb)
or temperature/humidity (enthalpy). When outdoor conditions are favorable for economizer cooling, the
damper drives open and modulates to maintain a 55ºF mixed air temperature through the supply grille.
When outdoor conditions are not favorable for economizer cooling, the economizer damper remains
closed, and the HVAC unit will operate in mechanical cooling mode.
Features Designed for Telecommunication applications:
Hydrogen Fault Input: When 24VAC is applied to the Emergency Ventilation (EV) input, the economizer
board forces the damper to open 100% for emergency ventilation. The compressor does not operate during
Hydrogen Fault/Emergency Ventilation.
Forced Mechanical Cooling: When 24VAC is applied to the FC input of the economizer board, the
economizer damper is forced closed, and the HVAC will operate in mechanical cooling mode. This is
considered as economizer override in the event economizer cooling is not sufficient for the heat load.
Thermostat must provide the fan “G” signal to HVAC to activate the indoor blower.
Economizer Status: The economizer board has contacts that when used with the Marvair CommStat 4
Telecom HVAC Controller, change state to provide feedback to the CommStat 4 to indicate when the
HVAC is in economizer mode verses mechanical cooling mode. This feedback allows the CommStat 4
to initiate the forced cooling feature to override economizer cooling and force mechanical cooling.
When used with minimum position potentiometer (optional), the Marvair® economizer can meet
requirements of ASHRAE Std. 62.
Configuration “D”: Two-Position Motorized Fresh Air Damper w/Pressure Relief Ventilation
Control Board Logic: The 92589 control board allows the position of the “D” damper to be set for desired
outside air intake from fully closed to fully open. Setting 15 of the control board configuration menu
allows the user to set the position from 20 (2VDC / Closed) to 100 (10VDC 100% open). The damper
position can be adjusted in 1VDC increments to any position from closed to 100% open as required.
Operation: Anytime the indoor blower operates, the damper drives open to the position selected in the
control board configuration menu setting 15. When the indoor blower stops operation the motorized
damper spring returns to the fully closed position.
Note: This circuit does not interrupt the compressor or heater operation.

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Configuration “E”: Two-Position Motorized Fresh Air Damper w/Pressure Relief Ventilation &
Independent Control
Control Board/Factory Installed Relay Logic: The 92589 control board allows the position of the “E”
damper to be set for desired outside air intake from fully closed to fully open. Setting 15 of the control
board configuration menu allows the user to set the position from 20 (2VDC / Closed) to 100 (10VDC
100% open). The damper position can be adjusted in 1VDC increments to any position from closed to
100% open as required.
Operation: Upon a “Call for Motorized damper” via a 24V signal from an external user-installed device,
the motorized damper opens to the position selected in the control board configuration menu setting 15
and the indoor blower operates. A 24VAC signal {sourced from LVTB 24VAC “R” and supplied through
a user-provided Normally Open (NO) contact} activates (opens) the Motorized Damper and connected
Relief Damper. When the 24VAC signal is removed, the motorized damper spring returns to the fully
closed position and the indoor blower stops operation. The motorized damper Does NOT open when
there is a call for the indoor fan (G).
Note: This circuit does not interrupt the compressor or heater operation.
Configuration “N”: Barometric Fresh Air Damper (Standard)
Barometric damper capable of up to 15% of rated airflow of outside air; field adjustable, no pressure relief.
Hot Gas Reheat (HGR) Dehumidification Mode (Special Option “G”)
When the HGR is in the dehumidification mode, the hot gas reheat (HGR) coil is energized. The cooled,
dehumidified air exits the evaporator coil and is blown through the HGR coil. This coil is sized to the
sensible capacity of the unit. The heat in the HGR coil is transferred to the air stream. The use of the HGR
coil allows the indoor humidity of the classroom to be maintained at or below a certain set humidity set
point without over cooling the classroom. These units can not add humidity to the classroom.
The operation of the HGR coil is controlled by a humidity controller. If the humidity rises above the set
point on the controller and the temperature in the classroom is satisfied, both mechanical cooling and
the HGR coil operate to temper the air and lower the humidity. If the temperature in the classroom rises
above or falls below the set point of thermostat and the unit is operating in the dehumidification mode,
the need for cooling or heating will override the call for dehumidification and the HGR coil is disengaged
until the thermostat is satisfied. This assures the classroom temperature is maintained as first priority
and humidity control is second.
The humidity controller or BAS control is required for proper operation of the HGR coil.

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1.6 Options
Low Ambient Control
The low ambient control permits mechanical cooling when outdoor ambient temperatures are low. The
control uses a reverse-acting high pressure switch to cycle the condenser fan motor according to liquid
refrigerant pressure conditions. Switch closure and fan operation occurs when the pressure reaches 400
PSIG. The switch opens again when the refrigerant pressure falls to 245 PSIG. Therefore, the outdoor
fan always starts after the compressor, and it will cycle frequently during normal operation at low
outdoor conditions.
Hard Start Kit
Used on single phase equipment to give the compressor higher starting torque under low voltage conditions.
Field installed only. (Not generally recommended for use on scroll compressor.)
Adjustable Outdoor Thermostat
Will not allow electric resistance heat to be energized unless the outdoor temperature is below the desired
set point. Field or factory installed. Available on all Marvair units. P/N 93934
Single Point Feed
When multiple internal disconnects are used, single point feed permits only one field power supply to
heat pump. Field installed only. Available on all Marvair H/P units.
Energy Management System (EMS)
Relay to control the heat pump. Available in 24, 120 or 240 VAC. Field or factory installed.
Electric Reheat for Dehumidification
Control provides simultaneous operation of compressor when in cooling mode and the electric elements
to provide dehumidification without over cooling the room. The electric element (kW) must be properly
sized for each model for proper operation. Factory installed. Available on all MAA units. Consult factory
for details.
Hot Gas Reheat (HGR)
Marvair® heat pumps equipped with the Hot Gas Reheat (HGR) allow the indoor humidity of the controlled
environment to be maintained at or below a certain humidity set point. These units do not have the ability
to add humidity to the classroom.
Dehumidification is achieved by operating mechanical cooling in conjunction with a hot gas reheat coil.
The coil is sized approximately to the sensible capacity of the total tonnage of the machine.
Speed Control for GreenWheel®ERV Exhaust Blower
For separate control of the exhaust blower. When used, the standard speed controller operates the intake
blower and the optional second controller the exhaust blower. Individual blower control allows positive
pressurization of the classroom. Can be factory or field installed.

11 Marvair Wall Mount Heat Pump I&O Manual
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Chapter 2 Electronic Control Board
2.1 Introduction
WARNING
Failure to observe the instructions contained in this document may result in personal
injury and/or property damage and may void the warranty. Read this manual before
installing, replacing or using this product.
Marvair’s proprietary Printed Circuit Board (PCB) sets the standard for the industry in flexibility,
reliability and performance. This UL certified component is engineered to optimize Heating, Cooling and
Dehumidification operation while communicating valuable information to the end user. Special features
include 2-Stage operation with varying speed control to optimize latent and sensible capacity, built in
remote communication (Modbus) for monitoring and/or control, optimized head pressure control and
configurable menu options for various operations and control. The Marvair PCB comes equipped with
seven segment display to annunciate faults, which drastically reduces troubleshooting time and system
downtime. Lockout contacts are also provided along with the alarms being transferred via Modbus.
This chapter provides the necessary information for installing and operating the Marvair PCB. The diagram
below identifies the inputs, outputs and connections for the Marvair PCB. See I/O table.
1
16
17
18
19
20
21
22
23
2 3 4 5 6 7
121315 14
9 10
11
8
Figure 1. PC Control Board

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Item Description
1Economizer Actuator Output 2-10 VDC
2Outdoor Motor Control Output 0-10 VDC or PWM
3Indoor Motor Control Output 0-10 VDC or PWM
4Enthalpy Sensor Signal Input 4-20mA
5Outdoor Sensor Signal 10K NTC (Heat Pumps) / Dry Bulb Sensor Signal Input 10K NTC
(Systems Equipped with Dry Bulb Economizer)
6Supply Air Sensor Signal Input 10K NTC (Systems Equipped with Economizer)
7Defrost Sensor Signal Input 10k NTC (Heat Pumps Only)
8Head Pressure Control Sensor Signal 10k NTC (ECM Motors)
9Control Board Menu/Fault Display
10 Menu/Up/Down Selection Buttons
11 Modbus RJ11 Communications Ports
12 Low Pressure / Freeze Sensor Signal Input 10k NTC
13 High Pressure Switch Input (Normally Closed)
14 Thermostat Inputs/Alarm And Status Terminals
15 24 VAC To Power Board (18 VAC To 30 VAC)
16 Indoor Blower Output 24 VAC (PSC Motors)
17 Reheat Output 24 VAC (Hot Gas Or Electric Reheat Dehumidication)
18 Reversing Valve Output 24 VAC (Heat Pumps Only)
19 Electric Heat Output 24 VAC
20 Outdoor Fan Output 24 VAC (PSC Motors)
21 Compressor 1/1st Stage Output 24 VAC (Single Stage Compressor)
22 Compressor 2/2nd Stage Output 24 VAC (Dual Compressor System 2nd Compressor)
(Single Compressor 2nd Stage)
23 Control Board Power Indicator LED
2.2 Installation and Replacement
The PCB is factory installed. To install a replacement PCB, use the six mounting holes along with the
appropriate screw size to rmly secure the board to the control box. After this is achieved, follow the
wiring diagram and menu conguration for the respective system for appropriate operation. Ensure
that the terminals used do not make any unwanted electrical connection (via strands etc.) with any
other terminals. Please allow a 1” creepage distance between the board and all other adjacent electrical
components.
2.3 PCB Details and Information
The PCB is equipped with an on board seven-segment display (Item #9) for
conguring various settings and displaying faults. During normal operation the
display remains off unless the conguration menu is accessed or a fault has occurred.
Faults will be annunciated on the display as shown below:
Display Displayed Faults
AS-F Supply Air Sensor Fault (Sensor Disconnected Or Faulty) If Equipped
DB-F Dry Bulb / Outdoor Sensor Fault (Sensor Disconnected Or Faulty) If Equipped
DS-F Defrost Sensor Fault (Sensor Disconnected Or Faulty) Heat Pumps Only
ES-F Enthalpy Sensor Fault (Sensor Disconnected Or Faulty) If Equipped
LP-1 Low Pressure Lockout Compressor Circuit 1
LP-2 Low Pressure Lockout Compressor Circuit 2
HP-1 High Pressure Lockout Compressor Circuit 1
HP-2 High Pressure Lockout Compressor Circuit 2
03 Low Voltage "Brownout" 16VAC or Less for 10 Minutes

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2.3.1 – Programming Menu Conguration
1. To Enter Programming Mode:
• Press and hold the Menu button for 5 seconds until P-01 is displayed.
2. While in Programming Mode main menu:
• Press the Menu button to enter the displayed parameter menu.
• Press the Up/Down buttons to adjust the current parameter number.
• The current parameter number will be displayed seven segments alternating showing "P-"
and the number every 0.5s.
3. While in parameter menu:
• The current parameter selection will be displayed seven segments.
• Press the Menu button to save the current parameter selection return to the programming
main menu.
• Press the Up/Down buttons to adjust the current parameter selection.
4. To exit programming mode, press and hold the Mode and Up buttons while in the programming
main menu.
• Press and hold the Menu button for 5 seconds.
• Note: The control will automatically exit the programming mode after 2 minutes with no
activity.
Note: 100 will be displayed by alternating between "1" and "00" every 0.5s.
Conguration Menu
Menu
Setting Name Default Selections General Description
1AC/HP Select AC AC, HP HP = Heat Pump Unit, AC = AC Unit
2IBM Select P P, dC P = PWM, dC = 0-10V
3FAN PURGE 90 N, 10-90 Indoor Blower off delay in seconds
4IBM Y1 Set 80 40-100 “G” Fan only and “Y1” 1st Stage Cooling Indoor Blower
Speed Setting
5IBM Y2 Set 100 40-100 “Y2” 2nd Stage Cooling Indoor Blower Speed Setting
6OFM Select P P, dC P = PWM, dC = 0-10V
7OFM Set 80 65-100 Outdoor Fan Motor Max Speed setting
8Defrost Timer 30 30, 60, 90 Defrost cycle timer in minutes
9EHDD select Y Y, n CAN ONLY BE "Y" IF SCKT IS "N"
10 SCKT select n Y, n SCKT= Y OVERRIDES EHDD
11 ODS set 50 0-70 Outdoor Sensor for HP or Econo. Dry Bulb Setpoint
12 ECONO select n Y, n n = Disabled (No Econo.), Y = Enabled (W/Econo.)
13 Sensor Type EN EN or DB Economizer sensor type selection EN= Enthalpy, DB = Dry Bulb
14 ECONO set d A-E Selections A=73F, B=70F, C= 67F, D =63F E= 55F all @
50%RH (Only available if EN sensor type is se-lected)
15 MIN POS 20 20-100 Sets the damper position for Minimum Open
16 W2 speed 100 70-100 Sets the Indoor Blower Speed for Electric Heat
17 Dehum speed 80 60-100 Sets the Indoor Blower Speed for Dehumidication
18 DS calibration 0-18 Defrost Sensor Calibration
19 SAS calibration 0-18 Supply Air Sensor Calibration
20 T'STAT Select H H, C H = hardwired 24V Tstat, C = communicating Tstat
21 Modbus ID 1 36161 Sets the Modbus ID for the unit
22 Modbus BAUD rate 19 9.6, 19 Available Baud Rates 9.6 = 9600, 19 = 19200
23 Modbus timeout 25 21916 Communications Timeout in minutes
24 Test n Y, n When set to “Y” all timers are reduced for testing
25 SW version number N/A N/A Displays the current version software

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Conguration Menu Details
1. AC/HP Select: This setting allows the PCB to be congured for AC (air-conditioner) or HP (heat-
pump). The system type is congured at the factory during production testing for the appropriate
system type. The default system type is AC.
2. IBM Select: This setting allows the IBM (Indoor Blower) control signal to be congured for
PWM or 0-10vdc control. The default control output signal is PWM.
3. Fan Purge: This setting allows the delay off time of the indoor blower once the call for the indoor
blower has been removed. The selections are N (no delay) or 10-90 seconds. After the default time
of 90 seconds the indoor blower will shut off. Selecting the N (no delay) will allow the Indoor
blower to shut off immediately after any request has been removed.
4. IBM Y1 Set: This is an independent setting for the speed at which the Indoor blower will operate
upon a request for Y1 (1st stage cooling) via Digital Input or Modbus. The default setting for
the IBM Y1 Set is 80% of maximum speed. The speed may be adjusted from 40-100% in 1%
increments to meet desired airow requirements. Note: Adjusting the speed too low will result
in coil freezing.
5. IBM Y2 Set: This is an independent setting for the speed at which the Indoor blower will operate
upon a request for Y2 (2nd stage cooling) via Digital Input or Modbus. The default setting for
the IBM Y1 Set is 100% of maximum speed. The speed may be adjusted from 40-100% in 1%
increments to meet desired airow requirements.
Note: Adjusting the speed too low will result in coil freezing, low-pressure or high-pressure lockout.
6. OFM Select: This setting allows the IBM (Indoor Blower) control signal to be congured for
PWM or 0-10vdc control. The default control output signal is PWM.
7. OFM Set: This is an independent setting for the max speed at which the Outdoor fan will operate.
The default setting for the OFM Set is 80% of maximum speed. The speed may be adjusted from
65-100% in 1% increments to meet desired airow requirements.
Note: Adjusting the speed too low will result in coil freezing, low-pressure or high-pressure lockout.
8. Defrost Timer: The defrost timer only applies to Heat-pump systems (when setting 1 is set to
HP). This is the accumulation timer used to monitor for heat-pump defrost control. The selections
for defrost timing is 30, 60 and 90 minutes. The defrost timer accumulates the compressor runtime
in the heat-pump mode and monitors the defrost sensor for freezing conditions to initiate a defrost
cycle at the selected defrost timing interval. The default defrost time is 30 minutes.
9. EHDD Set: The Electric heat during defrost setting allows the electric heat to operate when a
defrost cycle is being performed in heat-pump mode. The selections for the EHDD Set are Y (yes)
or N (no). When set to N (no) the electric heat will not operate automatically during a defrost
cycle in heat-pump mode. When the EHDD Set is set to Y (yes, Default) the electric heat will
operate upon each defrost cycle in the heat-pump mode.
Note: EHDD and SCKT cannot both be set to the Y (yes) selection at the same time. SCKT takes
priority over EHDD.
10. SCKT Set: The SCKT setting is used to prevent simultaneous operation of the electric heat and
compressor. The selections for the SCKT Set are Y (yes) or N (no). When set to N (no, Default)
the electric heat will be allowed to operate with the compressor in heat-pump mode upon a call

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for W2 (auxiliary / emergency heat). When the SCKT Set is set to Y (yes) the electric heat will
not be allowed to operate with the compressor in the heat-pump mode. When set to Y (yes) and
upon a request for W2 (auxiliary / emergency heat) the compressor will shut off and the electric
heat will operate.
Note: SCKT and EHDD cannot both be set to the Y (yes) selection at the same time. SCKT takes
priority over EHDD.
11. ODS Set: The ODS Set is used to set the Outdoor Sensor temperature for Heat-pump systems.
When the system type is congured for Heat-pump (when setting 1 is set to HP), the ODS Set
allows the outdoor sensor to be used to govern when electric heat is allowed to operate. When
the outdoor temperature is below the ODS setpoint, the electric heat will be allowed to operate.
The adjustable range is 0F-70F in 1F increments with a default setpoint of 50F.
12. ECONO Select: The ECONO Select is used to select whether the system has an economizer
system installed or not. When set to the Y (yes) selection the system will include the economizer
cooling algorithm within its sequence of operation and utilize the economizer package when
conditions are favorable for economizer cooling. When set to the N (no) selection the system will
only utilize the compressor for cooling operation. This setting is congured at the factory during
production testing for the appropriate system type.
Note: When ECONO Set is set to Y (yes) the system must have an Enthalpy or Dry Bulb and
Supply Air sensor connected and properly selected in setting 13 in order to operate in economizer
cooling. The system will default to compressor cooling if any sensor becomes disconnected or
faulty. Changing the ECONO Select to N (no) will disable economizer operation and the economizer
function will be ignored.
13. SensorType: This setting is used for selecting the type of economizer sensor used EN (Enthalpy) or
DB (Dry Bulb). The appropriate sensor must be connected and selected for economizer operation.
This setting is congured at the factory during production testing for the appropriate sensor type.
14. ECONO Set: This setting is used to set the economizer setpoint at which the economizer is
allowed to operate for cooling. When setting 13 is set for EN (Enthalpy), the selections are A=
73F, B=70F, C=67F, D=63F and E=55F all at 50% relative humidity. The A – E selections will only
be available when setting 13 is set to EN (Enthalpy). When setting 13 is set for DB (Dry Bulb),
the selection is from 20F to 105F in 1F increments. The 20F-105F range will only be available
when setting 13 is set to DB (Dry Bulb).
15. MIN POS: The MIN POS setting is for setting the minimum position of the economizer or
motorized damper. When set above 20 (2vdc) the damper will remain open to the selected position
at all times, hence minimum position. The adjustable range is from 20 (2vdc) to 100 (10vdc) in
1vdc increments.
16. W2 Speed: This is an independent setting for the speed at which the Indoor blower will operate
upon a request for W2 (Electric heat) via Digital Input or Modbus. The default setting for the W2
speed is 100% of maximum speed. The speed may be adjusted from 70-100% in 1% increments
to meet desired airow requirements.
Note: Adjusting the speed too low will result in increased supply air temperatures in electric heat
mode.
17. Dehum Speed: This is an independent setting for the speed at which the Indoor blower will operate
upon a request for HUM (Dehumidication) via Digital Input or Modbus. The default setting for

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the Dehum speed is 80% of maximum speed. The speed may be adjusted from 60-100% in 1%
increments to meet desired airow requirements.
18. DS Calibration: This setting is used to calibrate the defrost sensor from 0 to -18F.
19. SAS Calibration: This setting is used to calibrate the supply air sensor from 0 to -18F.
20. T’STAT Select: The thermostat type can be selected with this setting for an option of H=
Hardwired 24vac Thermostat or C = Communicating Thermostat via Modbus. The default setting
is H= Hardwired 24vac Thermostat.
21. Modbus ID: This setting allows the Modbus ID to be entered for Modbus communications for
the unit. The range for the Modbus ID is 1 – 36161 the default Modbus ID is 1.
22. Modbus Baud Rate: This setting allows the Modbus Baud Rate to be entered for Modbus
communications. The available Baud Rates are 9.6= 9600 and 19= 19200. The default Modbus
Baud Rate is 19 = 19200.
23. Modbus Timeout: This is the setting for the Modbus communications timeout in minutes. The
range of communications timeout is from 25 minutes to 21916 minutes. The default communications
timeout is 25 minutes.
24. Test: The Test feature has two options Y= Yes or N= No. When this setting is set to Y=Yes, all
circuit timers are reduced to expedite testing for various system operations. When set to N=No,
all circuit timers are used in their default conguration and normal operation.
25. Software Version Number: The software version of the 92589-control board will be displayed
on the seven-segment display. This is for informational purposes only.
2.4 Operation
Power
The Marvair PCB requires 24 VAC to operate. When the board is sufciently powered, the “PWR”
status light on the PCB illuminates “Green.” When the power supply voltage is 16vac or less for 10
seconds the control board will de-energize all outputs. This is considered a voltage brownout (low
voltage) condition and the display of the control board will show “03” as an indicator of brownout (low
voltage). When the voltage rises back to 17 VAC, the control board will allow the system to operate.
Note: The nominal power supply for the control board is 24 VAC and this voltage should be conrmed
during startup to assure normal operation.
Communication
The Marvair PCB comes equipped the Modbus communications standard. There are 2 adjacent RJ11
Modbus communication ports connected in parallel. That is, both ports transmit the same information.
The board allows you to set the Baud Rate at 9600 bits per second or 19200 bits per second. The board
also allows the Modbus ID to be selected in the conguration menu with the available range from 1 to
36161. The default Modbus ID is 1. See section 2.1 for reference.
2.5 Sequence of Operation
IMPORTANT
All equipment should go through the recommended commissioning/start up sequence
to ensure safety and system reliability. This document is only valid if the system is
used as intended.
This section denes the manner and method of control of the HVAC system. It will cover the
following operations and protections.

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1.0 Indoor Blower Operation
1.1 G - Indoor Blower Only
1.2 Y1 - Indoor Blower Operation
1.3 Y2 - Indoor Blower Operation
1.4 W2 – Indoor Blower Operation
1.5 HUM – Indoor Blower Operation
2.0 Cooling Operation AC / HP
2.1 Mechanical Cooling (AC systems)
2.1.1 Partial Capacity
2.1.2 Full Capacity
2.2 Mechanical Cooling (HP systems)
2.2.1 Partial Capacity
2.2.2 Full Capacity
3.0 Economizer Operation
3.1 Enthalpy Sensor and Operation
3.2 Dry Bulb Sensor and Operation
3.3 Supply Air Sensor
3.4 Minimum Position
4.0 Heating Operation AC / HP
4.1 Electric Heat (AC systems)
4.2 Heat Pump Heating Operation
4.3 Defrost Operation (Heat Pumps)
4.4 Electric Heat / Outdoor Sensor / SCKT / EHDD (Heat Pumps)
5.0 Dehumidication Operation AC / HP
5.1 Hot Gas Reheat
5.2 Electric Reheat
6.0 Refrigeration Protection
6.1 High Pressure lockout
6.2 Low Pressure Lockout / Freeze Protection
6.3 Anti Short Cycle
7.0 Additional Features
7.1 Modulating Head pressure Control (ECM Outdoor Motors)
7.2 Emergency Ventilation
7.3 Forced Cooling
7.4 Modbus Communications
7.5 Low Voltage (Brownout)
8.0 Smoke / Fire Shutdown
8.1 System Shutdown Contact Wiring
Note: Equipment, devices and necessary system components are specied in the respective section.
Note:
1. All inputs on the control board go through a 5 seconds Time-On Delay to prevent nuisance request.
Compressor Outputs go through 5 seconds staggered Time On delay to prevent nuisance tripping of
breaker due to the inrush associated with these large inductive loads.
2. Normal Operating Mode describes a mode in which there are no active faults which would interrupt
the operation of the system.

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1.0 Indoor Blower Operation
The speed at which the indoor blower will operate is based on the discrete operational inputs that have
24vac applied. These inputs are listed below.
1.1 G Input – A request for Fan Only (independent G-signal via Digital input or Modbus), results in
the indoor motor turning “ON” and operating at the “Y2” (BY DEFAULT) motor speed (Only
Applicable for EC motors).
1.2 Y1 Input – A request for Y1 (independent Y1-signal via Digital input or Modbus), results in
the indoor motor turning “ON” and operating at the “Y1” motor speed (Only Applicable for
EC motors).
1.3 Y2 Input – A request for Y2 (independent Y2-signal via Digital input or Modbus), results in
the indoor motor turning “ON” and operating at the “Y2” motor speed (Only Applicable for
EC motors).
1.4 W2 Input – A request for W2 (independent W2-signal via Digital input or Modbus), results in
the indoor motor turning “ON” and operating at the “W2” motor speed (Only Applicable for
EC motors).
1.5 HUM Input – A request for HUM (independent HUM-signal via Digital input or Modbus), results
in the indoor motor turning “ON” and operating at the “HUM” motor speed (Only Applicable
for EC motors).
When there is a request for Indoor Fan (G-input High) along with a request for cooling, heating or
dehumidication, the G-Input becomes lowest priority. This means that in any combination involving
the G-input, the speed associated to Fan Only will never take precedence.
The priority list from Highest to Lowest goes as follows:
1. Y2 - Request
2. Y1 - Request
3. W2 - Request
4. HUM - Request
5. G - Request
Note: The priority list above also describes the operation that takes precedence in the event that there
is a request for all operations or a combination of operations. The controller will NOT energize the
compressor outputs and the heater output simultaneously if congured for AC. The controller WILL
energize the compressor outputs and the heater output simultaneously if congured for HP.
The speed at which the Indoor Fan Operates during Stage 1 (Y1) and Stage 2 (Y2) Cooling Request can
be set directly at the board using the conguration menu settings 4 and 5. All requests are interlocked
with the Indoor Fan and will run the Fan at the respective speed associated with the operation. This
means that a lone call for Stage 1 (Y1) Cooling will automatically run the Indoor Fan at Stage 1 (Y1)
Cooling Speed even without a request for Indoor Fan. This holds true for all request.
2.0 Cooling Operation
AC Systems Request Active Input Active Output
Stage 1 Cooling (Fixed Compressor) Y1 CC1 (Partial Capacity)
Stage 1 Cooling (2 Fixed Compres-sors) Y1 or Y2 CC1 or CC2 Respectively (Partial Capacity)
Stage 1 Cooling (1 Staged Compressor) Y1 CC1 (Partial Capacity)
Stage 2 Cooling (2 Fixed Compres-sors) Y1 + Y2 CC1 + CC2 (Full Capacity)
Stage 2 Cooling (2 Staged Compres-sors) Y1 + Y2 CC1 + CC2 (Full Capacity)

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2.1 Mechanical Cooling (AC systems) – This section will describe the sequence of operation which
takes place during Direct Expansion (DX) cooling from a control standpoint.
Note: The system type must be congured for “AC” operation in setting 1 of the conguration
menu of the control board for proper AC system operation. This system type is selected at the
factory and there’s no need to change this setting.
2.1.1 Y1 Cooling (Partial Capacity 1st Stage) – In normal operating mode, a request for
“Stage1 Cooling” Y1-signal via Digital input or Modbus), energizes Compressor 1 Relay
Output (CC1) on the PCB. The controller provides a continuous control signal associated
to the Indoor Fan Motor, that is proportional to the “Y1” speed setting on the board or
via Modbus. It also outputs a request dependent (based on FCC IN) control signal for
the Outdoor Fan Motor (Only applicable to ECM motors). In Stage 1 Cooling operation,
the compressor operates at partial capacity and the indoor fan remains on continuously
but the outdoor fan modulates based on liquid line temperature. The Fan Cycle Control
Sensor (Low Ambient Control Sensor) monitors the liquid line to maintain a 90F liquid
line temperature. When the liquid line temperature is below 80F the outdoor fan will
shut off. A liquid line temperature above 115F will force the outdoor fan to operate at
the maximum speed set on the control board for setting 7 in the conguration menu. The
outdoor fan will speed up and slow down between liquid line temperature of 80F and
115F. Systems with (PSC Outdoor Motors) utilizes a Fan Cycle Switch which closes at
400 PSIG to energize the OFR (outdoor fan relay) to start the outdoor fan which runs
until the switch reopens (at 290 PSIG). These outputs function as described until the
Cooling setpoint is satised. This is considered as ON/OFF fan cycle control and the
PSC motor will not modulate.
Note: Single Stage compressors operate at full capacity upon a request for Y1.
2.1.2 Y1 and Y2 Cooling (Full Capacity 2nd Stage) – If the space temperature continues to
increase pass the dened differential, Stage 2 Cooling (Y2-input) is energized. Under
normal operation, this energizes the Compressor 2 Output (CC2). The Indoor Fan motor,
will operate at “Y2” speed instead of “Y1” speed since Y2 has higher priority. These
outputs remain energized until the cooling setpoint is satised. Once the setpoint is
satised, the Compressor and the Outdoor fan outputs are de-energized. The Indoor motor
continues to run based on the fan purge timer setpoint (default 90 seconds) selected in
setting 3 of the conguration menu of the control board.
Note: 2 Stage compressors require a request for Y2 to operate at full capacity in Cooling
operation. All Air-conditioners and Heat Pump systems with 2 stage compressors are
allowed 2 stage cooling operation.
2.2 Mechanical Cooling (HP systems) – This section will describe the sequence of operation which
takes place during Direct Expansion (DX) cooling from a control standpoint. The reversing
valve (O Input) must be energized for Cooling operation on Heat Pump systems.
Note: The system type must be congured for “HP” operation in setting 1 of the conguration
menu of the control board for proper HP system operation. This system type is selected at the
factory and there’s no need to change this setting.
2.2.1 Y1+ O Cooling (Partial Capacity 1st Stage) – In normal operating mode, a request for
“Stage1 Cooling” Y1 + O signal via Digital input or Modbus), energizes the Reversing
Valve Output (RV) and Compressor 1 Relay Output (CC1) on the PCB. The controller
provides a continuous control signal associated to the Indoor Fan Motor, that is proportional

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to the “Y1” speed setting on the board or via Modbus. It also outputs a request dependent
(based on FCC IN) control signal for the Outdoor Fan Motor (Only applicable to ECM
motors). In Stage 1 Cooling operation, the compressor operates at partial capacity and the
indoor fan remains on continuously but the outdoor fan modulates based on liquid line
temperature. The Fan Cycle Control Sensor (Low Ambient Control Sensor) monitors the
liquid line to maintain a 90F liquid line temperature. When the liquid line temperature is
below 80F the outdoor fan will shut off. A liquid line temperature above 115F will force
the outdoor fan to operate at the maximum speed set on the control board for setting
7 in the conguration menu. The outdoor fan will speed up and slow down between
liquid line temperature of 80F and 115F. Systems with (PSC Outdoor Motors) utilizes a
Fan Cycle Switch which closes at 400 PSIG to energize the OFR (outdoor fan relay) to
start the outdoor fan which runs until the switch reopens (at 290 PSIG). These outputs
function as described until the Cooling setpoint is satised. This is considered as ON/
OFF fan cycle control and the PSC motor will not modulate.
Note: Single Stage compressors operate at full capacity upon a request for Y1.
2.2.2 Y1 + Y2 + O Cooling (Full Capacity 2nd Stage) – If the space temperature continues
to increase pass the dened differential, Stage 2 Cooling (Y1+Y2+O input) is energized.
Under normal operation, this energizes the Compressor 2 Output (CC2). The Indoor Fan
motor, will operate at “Y2” speed instead of “Y1” speed since Y2 has higher priority.
These outputs remain energized until the cooling setpoint is satised. Once the setpoint
is satised, the Compressor and the Outdoor fan outputs are de-energized. The Indoor
motor continues to run based on the fan purge timer setpoint (default 90 seconds) selected
in setting 3 of the conguration menu of the control board.
Note: 2 Stage compressors require a request for Y2 to operate at full capacity in Cooling
operation. All Air-conditioners and Heat Pump systems with 2 stage compressors are
allowed 2 stage cooling operation.
Note: With staged compressors, a CC2 output without a CC1 output will neither result
in partial capacity nor full capacity. Only CC1 output can achieve partial capacity. Both
CC1 and CC2 outputs are required to achieve full capacity.
3.0 Economizer Operation (If Equipped)
Damper Actuator
The damper actuator is a 24V motor that modulates the position of the damper blade. It is capable
of driving a full 90 degrees within 90 seconds. The assembly has a spring return to close the
damper during power outage.
3.1 Enthalpy Sensor and Operation – The enthalpy sensor responds to the total heat content of
the outdoor air to provide the changeover to outside air for free cooling. The control board must
be congured for proper operation of the economizer by selecting Y= Yes in the conguration
menu setting 12. The sensor type must be selected in setting 13 for EN=Enthalpy. The desired
changeover setpoint must be selected in setting 14 (default D=63F@50% rh). Example of
Enthalpy Sensor and Enthalpy curve is shown below.
Note: Selecting N=No in conguration setting 12 will disable economizer operation.
DANGER
Sever hazard. The economizer contains moving parts capable of causing serious
injury or death. Disconnect power before removing the covering panel.