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.