ACS Marviar MGA3090A User manual

Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
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.
Manufactured By:
Marvair, An ACS Brand
P.O. Box 400 • Cordele, Georgia 31010 • 156 Seedling Drive • Cordele, Georgia 31015
[phone] • Fax [phone]
www.Marvair.com
The most current version of this manual can be found at www.Marvair.com.
MODELS:
MGA3090A • MGA3120A
MGA3150A • MGA3180
(Dual Compressor)
Installation & Operation Manual
10 EER Vertical Wall-Mount Air Conditioners
Installation & Operation Manual
7.5, 10, 12.5 & 15 Ton 10EER Vertical
Wall Mount Air Conditioners

2
Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
How To Use This Manual
This manual is intended to be a guide to Marvair's line of vertical air conditioners. It contains installation, troubleshoot-
ing, 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.
If you are installing the air conditioner 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 air conditioner works (Chapters 1 & 3).
2. Identify and correct installation errors (Chapter 2).
3. Refer to the troubleshooting information in Chapter 4.
If you are still unable to correct the problem, contact the Factory at 1-229-273-9558 for additional assistance.
Please read the following “Important Safety Precautions” before beginning any work.
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 ordi-
nances.
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 air conditioning unit and in the instruction
manuals be alert to the potential for personal injury. Understand the signal word DANGER, WARNING and
CAUTION. 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 damage.
CAUTION Failure to comply could result in minor personal injury and/or property damage.
IMPORTANT Used to point out helpful info that will result in improved installation, reliability or operation.
© 04/2023 Marvair, An ACS Brand
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE.

3Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
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.
Table of Contents
Chapter 1 Air Conditioner Description & Specications
1.1 General Description .................................................................................................................................5
1.2 Model Identication .................................................................................................................................6
1.3 Serial Number Date Code ........................................................................................................................6
1.4 Capacities, Weights and Filter Sizes ........................................................................................................6
1.5 General Operation ..................................................................................................................................10
1.6 Programmable Logic Controller (PLC) .................................................................................................10
1.7 Unit Operation........................................................................................................................................12
1.8 Optional Controls and Packages ............................................................................................................13
1.9 Electrical Operation ...............................................................................................................................14
Chapter 2 Electronic Control Board
2.1 Introduction ............................................................................................................................................16
2.2 Installation and Replacement .................................................................................................................17
2.3 PCB Details and Information .................................................................................................................17
2.4 Operation................................................................................................................................................17
2.5 Sequence of Operation ...........................................................................................................................21
Chapter 3 Installation
3.1 Equipment Inspection.............................................................................................................................33
3.2 Installation Requirements.......................................................................................................................33
3.3 Installation Materials .............................................................................................................................34
3.4 Porting and Duct Work ..........................................................................................................................36
3.5 Top Flange Installation ..........................................................................................................................36
3.6 Installing the Lifting Brackets................................................................................................................37
3.7 Mounting the Unit .................................................................................................................................37
3.8 Electrical Connections ...........................................................................................................................38
Chapter 4 Start-Up
4.1 Check-Out of Cooling Cycle .................................................................................................................42
4.2 Check-Out of Heating Cycle..................................................................................................................42

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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
Chapter 5 Troubleshooting
5.1 Overview ................................................................................................................................................43
5.2 Failure Symptoms Guide........................................................................................................................44
5.3 Compressor Troubleshooting .................................................................................................................44
Chapter 6 Maintenance
6.1 Scheduled Maintenance .........................................................................................................................46
Chapter 7 Warranty
7.1 Limited Product Warranty ......................................................................................................................47
Chapter 8 Start-Up Check List
8.1 Start-Up Check List................................................................................................................................48
Illustrations
Figure 1. PLC ............................................................................................................................................10
Figure 2. Typical Electrical Schematic......................................................................................................15
Figure 3. Enthalpy Sensor & Temperature Control Points ........................................................................26
Figure 4. Dry Bulb Sensor.........................................................................................................................27
Figure 5. Top Flange and Lifting Bracket Installation ..............................................................................37
Figure 6. Wall Mounting Detail.................................................................................................................38
Figure 7a. Humidistat Wiring to a Marvair Air Conditioner with Reheat...................................................40
Figure 7b. Thermostat Connection Diagram ...............................................................................................41
Figure 7c. CommStat™ 4 Wiring Detail.....................................................................................................41
Tables
Table 1 Efciency and Capacity Ratings at ANSI/AHRI Standard 390..................................................... 7
Table 2 SCFM @ Various External Static Pressures .................................................................................. 7
Table 3 Single Compressor Cooling Performance (BTUH) at Various Outdoor Temperatures ................. 7
Table 4 Dual Compressor Cooling Performance (BTUH) at Various Outdoor Temperatures.................... 8
Table 5 Economizer Cooling Performance................................................................................................. 8
Table 6 Ambient Temperature Operating Ranges....................................................................................... 8
Table 7 Shipping Weights & Dimensions ................................................................................................... 9
Table 8 Return Air Filter Sizes ................................................................................................................... 9
Table 9 Refrigerant Charge......................................................................................................................... 9
Table 10 Minimum Clearances................................................................................................................... 34
Table 11 Voltage Limitations...................................................................................................................... 34
Appendix A
Fresh Air Damper Installation..........................................................................................................................52

5Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
Chapter 1 Description & Specications
1.1 General Description
The Marvair MGA3090A, MGA3120A, MGA3150A & MGA3180A are a series of vertical wall-
mounted air conditioning systems that provide heating, cooling, and ventilation for telecommunication
shelters, and other applications with high internal heat gains. The series is available in nominal cooling
capacities of 90,000-180,000 BTUH. A factory installed economizer, resistance heating elements and
reverse ow congurations are available.
All Marvair MGA wall mount air conditioners feature an exclusive electronic control board or PLC-
based controls.
The control board and PLC consolidate several of the electrical components, improves the air
conditioner’s reliability and has LED’s to indicate operating status and fault conditions to assist the
service technician. A complete description of functions is in Section 1.6
Other standard components include:
• Hot gas by-pass valve to allow operation in cold temperatures
• Thermal expansion valve to improve both efciency and capacity over a wide range of ambient
temperatures
• Phase monitor to prevent operation if the unit is not properly phased
Marvair air conditioners are designed for easy installation and service. Major components are accessible
for service beneath external panels.
All units have internal disconnects. Depending upon state and local code requirements, this feature
may eliminate the need for an external breaker or disconnect.

6
Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
1.2 Model Identication
The model identication number is found on the data sticker. Rating plate located on side panel.
Example M G A 3 0 9 0 A D 1 5 0 C + + + + 1 C A + A 2 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
2Energy Efciency Ratio (EER) G = 10
3Refrigerant Type A = R-410a
4Compressor Type/
Quantity
1 = Single
3 = Dual Compressors
5Unit Capacity/Nominal
Cooling (BTUH)
090 = 90,000 150 = 150,000
120 = 120,000 180 = 180,000
6
7
8System Type A = Air Conditioner
9Power Supply
(Volts-Phase-Hz)
A= 208/230-60-1
C= 208/230-60-3
D= 460-60-3
E= 380-50-3 - 4 Wire
F= 220-50-1
Z= 575-60-3
10 Heat Designation
@ Rated Voltage
KW = Kilowatt
000 = No Heat
050 = 5KW
090 = 9KW
150 = 15KW
180 = 18KW
11
12
13 Ventilation
Conguration
A = Solid Front Door
C = Economizer
D = Motorized Damper w/Pressure Relief
E = Motorized Damper w/Pressure
Relief & Independent Motorized
Damper Control
F = No Free Cooling, 100% Emergency
Ventilation Only w/Independent Control
14 Dehumidication
R = Electric Reheat
T = Electric Reheat w/Humidity Control
+ = None
15 Controls
A = Power Fail Alarm w/Additional Lockouts
C = 24V EMS Relay Kit
D = 24V EMS Relay Kit
w/Factory Installed T-Stat
E = Factory Installed T-Stat
F = ModBus Interface
G = ModBus Interface
w/Factory Installed T-Stat
H = Bac-Net
J = Bac-Net Controls
w/Factory Installed T-Stat
+ = None
16 Operating Condition
A = Evaporator Freeze Sensor (EFS)
C = EFS w/Hot Gas Bypass
N = Hard Start
P = Hard Start w/Low Ambient & CCH
Q = Hard Start w/Low Ambient &
Fan Cycle Control (FCC)
R = Crank Case Heater (CCH)
T = Hard Start w/EFS
U = Hard Start w/Hot Gas Bypass
V = Hard Start w/Low Ambient &
CCH & EFS
W = Low Ambient w/CCH
X = Hot Gas Bypass
Y = Low Ambient w/CCH & FCC
Z = Low Ambient w/CCH & EFS
1 = Low Ambient w/FCC
2 = Low Ambient w/FCC & EFS
3 = CCH w/Hot Gas Bypass
+ = None
17 Indoor Air Quality
Features
D = Dry Bulb Sensor
E = Dry Bulb Sensor w/Dirty Filter
G = Dirty Filter Sensor
+ = None
18 Air Flow 1 = Top Supply/Bottom Return
2 = Center Supply (Reverse)
19 Compressor
Location
C = Center
D = Left Hand
E = Right Hand
20 Filter Option
A = 2” Pleated (MERV 8, AC/HP-C)
C = 2” Charcoal
D = MERV 11 High Filtration Package
E = MERV 13 High Filtration Package
F = Filter Access Through Return Air Grille
W = Aluminum Washable
+ = None
21 Corrosion
Protection
A = Condenser Coil Only
C = Evaporator Coil Only
D = Both Coils Condenser & Evaporator
E = All Coils Cond/Evap/Reheat
F = Coat All
K = Coastal Package
+ = None
$ = Special
22 Engineering
Revision Level
A2
B2 B3
23
24 Cabinet Color
1 = Marvair Beige
2 = Gray
3 = Carlsbad Canyon
4 = White
5 = Stainless Steel Exterior
6 = Dark Bronze
7 = .050 Aluminum Stucco
8 = Mesa Tan
9 = Pebble Gray
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
27 Fastener/Drain Pan
Option
A = Stainless Steel Fasteners
C = Stainless Steel Drain Pan
D = Stainless Steel Fasteners & Drain Pan
E = IP55 Ingress
+ = None
28 Unused + = None
$ = Special
29 Unused + = None
$ = Special
30 Special Variation
+ = None
$ = Special Conguration Not Covered by
Model Nomenclature
1.3 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
1.4 Capacities, Weights and Filter Sizes
See the Product Data Sheet for complete electrical and performance specications and dimensional
drawings.

7Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
Note: Follow local codes and standards when designing duct runs to deliver the required airow.
Minimize noise and excessive pressure drops caused by duct aspect ratio changes, bends, dampers and
outlet grilles in duct runs.
Model Number Cooling BTUH1EER2Rated Air Flow (CFM)3
MGA3090A 89,000 10 3,500
MGA3120A 118,000 10 4,000
MGA3150A 146,000 10 4,500
MGA3180A 182,000 10 6,000
1Cooling rated at 95°F (35°C) outdoor and 80°F DB/67° WB (26.5°C DB/19.5°C WB) return air. 2EER=Energy Efciency Ratio
3CFM=Cubic Feet per Minute
Ratings are with no outside air. Performance will be affected by altitude.
Ratings are at 230 volts for 208/230 volt units (“A” & “C” models) and 460 volts for “D” models. Operation of units at a different voltage
from that of the rating point will affect performance and air ow.
Table 1. Efficiency and Capacity Ratings at ANSI/AHRI Standard 390
Model Number IWG Static Pressure
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
MGA3090A 3,846 3,570 3,286 3,003 2,722¹ 2,515¹ 2,164¹ 1,888¹ 1,612¹ 1,338¹ 1,065¹ 794¹
MGA3120A 4,301 4,064 3,808 3,533 3,238 2,924¹ 2,590¹ 2,237¹ 1,865¹ 1,472¹ 1,061¹ 630¹
MGA3150A 4,801 4,564 4,308 4,033 3,738 3,424 3,090 2,737 2,365 1,972 1,561 1,130
MGA3180A 6,876 6,622 6,378 6,143 5,916 5,686 5,487 5,285 5,090 4,902 4,721 4,547
¹Operation in the shaded area is not recommended
Table 2. SCFM @ Various External Static Pressures
Model
Number
Return
Air
DB/WB
°F (°C)
Outdoor Temperature
Cooling
Capacity
BTUH
75°F
(24°C)
80°F
(27°C)
85°F
(30°C)
90°F
(32°C)
95°F
(35°C)
100°F
(38°C)
105°F
(41°C)
110°F
(43°C)
115°F
(46°C)
120°F
(49°C)
125°F
(52°C)
130°F
(54°C)
MGA3090A
72/61
(22/16)
Total 42,039 40,581 39,164 37,706 36,248 34,790 33,332 31,914 31,185 30,456 29,727 28,998
Sensible 37,564 37,021 36,494 35,953 35,414 34,790 33,332 31,914 31,185 30,456 29,727 28,998
76/63
(24/17)
Total 43,700 42,201 40,662 39,164 37,665 36,167 34,668 33,129 32,400 31,671 30,942 30,213
Sensible 41,395 40,856 40,305 39,164 37,665 36,167 34,668 33,129 32,400 31,671 30,942 30,213
80/67
(27/19)
Total 46,980 45,360 43,740 42,120 40,500 38,192 37,260 35,640 34,830 34,101 33,372 32,643
Sensible 40,841 40,300 39,761 39,224 38,688 37,926 37,260 35,640 34,830 34,101 33,372 32,643
84/71
(29/22)
Total 50,261 48,519 46,818 45,077 43,335 41,594 39,852 38,151 37,260 36,531 35,802 35,073
Sensible 40,097 39,560 39,037 38,503 37,970 37,438 36,908 36,392 36,122 35,901 35,681 35,073
MGA3120A
72/61
(22/16)
Total 61,242 59,118 57,053 54,929 52,805 50,681 48,557 46,492 45,430 44,368 43,306 42,244
Sensible 61,242 59,118 57,053 54,929 52,805 50,681 48,557 46,492 45,430 44,368 43,306 42,244
76/63
(24/17)
Total 63,661 61,478 59,236 57,053 54,870 52,687 50,504 48,262 47,200 46,138 45,076 44,014
Sensible 63,661 61,478 59,236 57,053 54,870 52,687 50,504 48,262 47,200 46,138 45,076 44,014
80/67
(27/19)
Total 68,440 66,080 63,720 61,360 59,000 56,640 54,280 51,920 50,740 49,678 48,616 47,554
Sensible 68,440 66,080 63,720 61,360 59,000 56,640 54,280 51,920 50,740 49,678 48,616 47,554
84/71
(29/22)
Total 73,219 70,682 68,204 65,667 63,130 60,593 58,056 55,578 54,280 53,218 52,156 51,094
Sensible 72,324 70,682 68,204 65,667 63,130 60,593 58,056 55,578 54,280 53,218 52,156 51,094
MGA3150A
72/61
(22/16)
Total 75,809 73,180 70,623 67,994 65,365 62,736 60,107 57,550 56,236 54,921 53,607 52,292
Sensible 75,809 73,180 70,623 67,994 65,365 62,736 60,107 57,550 56,236 54,921 53,607 52,292
76/63
(24/17)
Total 78,803 76,101 73,326 70,623 67,921 65,219 62,517 59,741 58,427 57,112 55,798 54,483
Sensible 78,803 76,101 73,326 70,623 67,921 65,219 62,517 59,741 58,427 57,112 55,798 54,483
80/67
(27/19)
Total 84,719 81,798 78,876 75,955 73,034 70,112 67,191 64,269 62,809 61,494 60,180 58,865
Sensible 84,374 81,798 78,876 75,955 73,034 70,112 67,191 64,269 62,809 61,494 60,180 58,865
84/71
(29/22)
Total 90,635 87,494 84,427 81,286 78,146 75,005 71,865 68,798 67,191 65,876 64,562 63,247
Sensible 83,360 82,358 81,383 80,389 78,146 75,005 71,865 68,798 67,191 65,876 64,562 63,247
MGA3180A
72/61
(22/16)
Total 94,458 91,182 87,997 84,721 81,445 78,169 74,893 71,708 70,070 68,432 66,794 65,156
Sensible 94,458 91,182 87,997 84,721 81,445 78,169 74,893 71,708 70,070 68,432 66,794 65,156
76/63
(24/17)
Total 98,189 94,822 91,364 87,997 84,630 81,263 77,896 74,438 72,800 71,162 69,524 67,886
Sensible 98,189 94,822 91,364 87,997 84,630 81,263 77,896 74,438 72,800 71,162 69,524 67,886
80/67
(27/19)
Total 105,560 101,920 98,280 94,640 91,000 87,360 83,720 80,080 78,260 76,622 74,984 73,346
Sensible 105,560 101,920 98,280 94,640 91,000 87,360 83,720 80,080 78,260 76,622 74,984 73,346
84/71
(29/22)
Total 112,931 109,018 105,196 101,283 97,370 93,457 89,544 85,722 83,720 82,082 80,444 78,806
Sensible 108,205 106,965 105,196 101,283 97,370 93,457 89,544 85,722 83,720 82,082 80,444 78,806
Table 3. Single Compressor Cooling Performance (BTUH) at Various Outdoor Temperatures

8
Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
Model
Number
Return Air
DB/WB
°F (°C)
Outdoor Temperature
Cooling
Capacity
BTUH
75°F
(24°C)
80°F
(27°C)
85°F
(30°C)
90°F
(32°C)
95°F
(35°C)
100°F
(38°C)
105°F
(41°C)
110°F
(43°C)
115°F
(46°C)
120°F
(49°C)
125°F
(52°C)
130°F
(54°C)
MGA3090A
72/61
(22/16)
Total 92,382 89,178 86,063 82,859 79,655 76,451 73,247 70,132 68,530 66,928 65,326 63,724
Sensible 68,795 67,490 66,228 64,938 63,655 62,379 61,110 59,883 59,255 58,629 58,004 57,381
76/63
(24/17)
Total 96,031 92,738 89,356 86,063 82,770 79,477 76,184 72,802 71,200 69,598 67,996 66,394
Sensible 74,809 73,513 72,189 70,907 69,633 68,366 67,107 65,821 65,214 64,609 64,006 63,404
80/67
(27/19)
Total 103,240 99,680 96,120 92,560 89,000 83,927 81,880 78,320 76,540 74,938 73,336 71,734
Sensible 74,266 72,960 71,663 70,374 69,092 67,278 66,551 65,292 64,665 64,103 63,542 62,982
84/71
(29/22)
Total 110,449 106,622 102,884 99,057 95,230 91,403 87,576 83,838 81,880 80,278 78,676 77,074
Sensible 73,358 72,057 70,794 69,509 68,233 66,964 65,702 64,478 63,840 63,319 62,799 62,281
MGA3120A
72/61
(22/16)
Total 122,484 118,236 114,106 109,858 105,610 101,362 97,114 92,984 90,860 88,736 86,612 84,488
Sensible 90,613 88,836 87,121 85,368 83,627 81,897 80,179 78,519 77,669 76,823 75,979 75,138
76/63
(24/17)
Total 127,322 122,956 118,472 114,106 109,740 105,374 101,008 96,524 94,400 92,276 90,152 88,028
Sensible 98,429 96,663 94,862 93,121 91,391 89,673 87,966 86,225 85,404 84,586 83,771 82,959
80/67
(27/19)
Total 136,880 132,160 127,440 122,720 118,000 113,280 108,560 103,840 101,480 99,356 97,232 95,108
Sensible 97,820 96,040 94,274 92,519 90,778 89,048 87,330 85,625 84,776 84,015 83,257 82,500
84/71
(29/22)
Total 146,438 141,364 136,408 131,334 126,260 121,186 116,112 111,156 108,560 106,436 104,312 102,188
Sensible 96,728 94,953 93,233 91,483 89,747 88,023 86,312 84,652 83,787 83,082 82,379 81,678
MGA3150A
72/61
(22/16)
Total 151,618 146,359 141,247 135,988 130,730 125,472 120,213 115,101 112,472 109,842 107,213 104,584
Sensible 107,262 105,020 102,857 100,648 98,455 96,279 94,118 92,033 90,966 89,904 88,845 87,790
76/63
(24/17)
Total 157,606 152,202 146,651 141,247 135,842 130,438 125,033 119,483 116,854 114,224 111,595 108,966
Sensible 115,990 113,761 111,489 109,294 107,115 104,952 102,806 100,617 99,587 98,560 97,536 96,517
80/67
(27/19)
Total 169,438 163,595 157,752 151,910 146,067 140,224 134,382 128,539 125,618 122,988 120,359 117,730
Sensible 115,320 113,072 110,842 108,629 106,434 104,255 102,093 99,949 98,882 97,926 96,973 96,024
84/71
(29/22)
Total 181,269 174,988 168,853 162,573 156,292 150,011 143,730 137,595 134,382 131,752 129,123 126,494
Sensible 114,052 111,808 109,634 107,426 105,237 103,064 100,909 98,821 97,734 96,848 95,964 95,084
MGA3180A
72/61
(22/16)
Total 188,916 182,364 175,994 169,442 162,890 156,338 149,786 143,416 140,140 136,864 133,588 130,312
Sensible 137,105 134,350 131,690 128,973 126,274 123,594 120,932 118,362 117,046 115,735 114,429 113,127
76/63
(24/17)
Total 196,378 189,644 182,728 175,994 169,260 162,526 155,792 148,876 145,600 142,324 139,048 135,772
Sensible 148,659 145,921 143,128 140,428 137,747 135,085 132,440 129,744 128,473 127,206 125,944 124,686
80/67
(27/19)
Total 211,120 203,840 196,560 189,280 182,000 174,720 167,440 160,160 156,520 153,244 149,968 146,692
Sensible 147,750 144,990 142,250 139,530 136,830 134,149 131,488 128,845 127,531 126,352 125,178 124,006
84/71
(29/22)
Total 225,862 218,036 210,392 202,566 194,740 186,914 179,088 171,444 167,440 164,164 160,888 157,612
Sensible 146,097 143,344 140,675 137,962 135,270 132,597 129,945 127,374 126,034 124,942 123,853 122,767
Table 4. Dual Compressor Cooling Performance (BTUH) at Various Outdoor Temperatures
Basic Model Fan Watts Fan CFM EER @ 55 F OAT Outside Air Temperature ºF (ºC)
50 (10) 55 (13) 60 (16) 65 (18) 70 (21)
MGA3090A 730 3,500 125 110,128 91,140 72,153 53,165 34,178
MGA3120A 970 4,000 107 125,860 104,160 82,460 60,760 39,060
MGA3150A 1,300 4,500 90 141,593 117,180 92,768 68,355 43,943
MGA3180A 1,850 6,000 84 188,790 156,240 123,690 91,140 58,590
Based upon indoor setpoint temperature of 79 (26).
Table 5. Economizer Cooling Performance
Basic Model Special Option TEMPERATURE RANGES
Non-Economizer Base Unit 0ºF - 131ºF (-18ºC - 55ºC)
Economizer-Equipped Base Unit -40ºF - 131ºF (-40ºC - 55ºC)
Table 6. Ambient Temperature Operating Ranges

9Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
Model Unit Weight Shipping Weight Shipping Dimensions Height Width Depth
LBS KG LBS KG Inches MM Inches MM Inches MM
MGA3090A 1,085 492 1,160 527 98 2,489 56 1,422 48 1,219
MGA3090A Reverse Flow 1,085 492 1,160 527 98 2,489 56 1,422 48 1,219
MGA3090A Reverse Flow w/Economizer 1,131 513 1,210 550 98 2,489 56 1,422 48 1,219
MGA3120A 1,195 542 1,277 579 98 2,489 56 1,422 48 1,219
MGA3120A Reverse Flow 1,195 542 1,277 579 98 2,489 56 1,422 48 1,219
MGA3120A w/Economizer 1,245 565 1,331 604 98 2,489 56 1,422 48 1,219
MGA3120A Reverse Flow w/Economizer 1,245 565 1,331 604 98 2,489 56 1,422 48 1,219
MGA3150A 1,212 550 1,294 587 98 2,489 56 1,422 48 1,219
MGA3150A Reverse Flow 1,212 550 1,294 587 98 2,489 56 1,422 48 1,219
MGA3150A w/Economizer 1,262 572 1,348 611 98 2,489 56 1,422 48 1,219
MGA3150A Reverse Flow w/Economizer 1,262 572 1,348 611 98 2,489 56 1,422 48 1,219
MGA3180A 2,463 1,117 2,523 1,148 98 2,489 56 1,422 48 1,219
MGA3180A Reverse Flow 2,247 1,019 2,307 1,049 98 2,489 56 1,422 48 1,219
MGA3180A w/Economizer 2,603 1,181 2,663 1,208 98 2,489 56 1,422 48 1,219
MGA3180A Reverse Flow w/Economizer 2,285 1,036 2,345 1,063 98 2,489 56 1,422 48 1,219
Table 7. Shipping Weights & Dimensions
Model Description INCHES MILLIMETERS PART NO. FILTERS PER UNIT MERV RATING
MGA3090A Exterior Access Return Air Filter 25" x 16" x 2" 635 x 406 x 51 80137 3 8
Interior Access Return Air Filter 15" x 20" x 2" 381 x 508 x 51 92365 3 8
MGA3090A
Reverse Flow
Exterior Access Return Air Filter 25” x 16” x 2” 635 x 406 x 51 80137 3 8
Interior Access Return Air Filter 15” x 20” x 2” 381 x 508 x 51 92365 3 8
MGA3090A
Reverse Flow
w/Economizer
Exterior Access Return Air Filter 25” x 16” x 2” 635 x 406 x 51 80137 3 8
Interior Access Return Air Filter 15” x 20” x 2” 381 x 508 x 51 92365 3 8
Economizer Pre-lter 9.25” x 37” x .375” 235 x 940 x 10 92127 1 N/A
MGA3120A &
MGA3150A
Exterior Access Return Air Filter 25” x 16” x 2” 635 x 406 x 51 80137 3 8
Interior Access Return Air Filter 15” x 20” x 2” 381 x 508 x 51 92365 3 8
For Optional Fresh Air Hood, #K/04657 11” x 22” x 1” 279 x 559 x 25 80119 2 N/A
MGA3120A &
MGA3150A
Reverse Flow
Exterior Access Return Air Filter 25” x 16” x 2” 635 x 406 x 51 80137 3 8
Interior Access Return Air Filter 15” x 20” x 2” 381 x 508 x 51 92365 3 8
MGA3120A &
MGA3150A
w/Economizer
Exterior Access Return Air Filter 25” x 16” x 2” 635 x 406 x 51 80137 3 8
Interior Access Return Air Filter 15” x 20” x 2” 381 x 508 x 51 92365 3 8
Fresh Air Hood Pre-lters 26” x 12” x 1” 660 x 305 x 25 92526 2 N/A
MGA3120A &
MGA3150A
Reverse Flow
w/Economizer
Exterior Access Return Air Filter 25” x 16” x 2” 635 x 406 x 51 80137 3 8
Interior Access Return Air Filter 15” x 20” x 2” 381 x 508 x 51 92365 3 8
Economizer Pre-lter 9.25” x 37” x .375” 235 x 940 x 10 92127 1 N/A
MGA3180A
1Exterior Access Return Air Filter 25 x 16 x 2 635 x 406 x 51 80137 4 8
Interior Access Return Air Filter 24 x 18 x 2 610 x 457 x 51 81257 3 8
MGA318A
Reverse Flow
Interior Access Return Air Filter 24 x 18 x 2 610 x 457 x 51 81257 4 8
Mist Eliminator Filter 15 5/8 x 25 5/8 x 1 397 x 625 x 25 92971 1 N/A
MGA3180A
w/Economizer
1Exterior Access Return Air Filter 25 x 16 x 2 635 x 406 x 51 80137 4 8
Interior Access Return Air Filter 24 x 18 x 2 610 x 457 x 51 81257 3 8
Fresh Air Hood Pre-Filter 26 x 12 x 1 660 x 305 x 25 92526 2 N/A
MGA3180A
Reverse Flow
w/Economizer
Interior Access Return Air Filter 20 x 30 x 2 508 x 762 x 51 92545 3 N/A
Mist Eliminator Filter 15 5/8 x 24 5/8 x 1 397 x 625 x 25 92971 4 N/A
Fresh Air Hood Pre-filters 14 x 32 x 1 356 x 813 x 25 93187 2 N/A
1Standard Conguration 2Optional (can not be combined)
Table 8. Return Air Filter Sizes
MGA3090A MGA3120A “A” MGA3120A “B” MGA3150A MGA3180A
A C D Z C D Z A C D Z C D Z C D Z
146 168 128 144 240
Table 9. Refrigerant Charge Per Circuit (R410A, Ounces)

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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
1.5 General Operation
Optional Hot Gas By-Pass
Normally used in specialty applications (i.e Magnetic Resonance Imaging (MRI) buildings) to prevent
magnetic voltage disturbance caused by cycling. This technology is applied in this product to extend
the operation envelope for the compressor to 20º F (-6.6ºC). Combined with a condenser low ambient
Fan Cycle feature, compressor operation can be extended to 0º F (-17.8ºC). During Hot Gas operation
mode, system performance will be reduced. If product operation is in mild outdoor ambient conditions,
the installed shut-off ball valve may be closed, thus disabling the Hot Gas By-Pass feature.
Refrigerant Cycle (Cooling Mode)
The air conditioners use R-410A refrigerant in a conventional vapor-compression refrigeration cycle to
transfer heat from air in an enclosed space to the outside. A motorized impeller assembly blows indoor
air across the evaporator. Cold 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 drawn across the condenser by the condenser fan. Liquid refrigerant is metered with a thermal
expansion valve (TXV) into the evaporator to repeat the cycle.
MGA3090A/3120A/3150A (Dual Compressor) Units: These units are factory wired for maximum
cooling utilizing both compressors. If 2 stage compressor operation is desired, the factory installed
jumper between terminals 1 and 2 of the low voltage terminal strip must be removed. The 1st stage
cooling input is terminal 1 of the low voltage terminal strip and the 2nd stage cooling input is terminal
2 of the low voltage terminal strip. The thermostat must be programmed for 2 stage cooling operation
when 2 stage compressor operation is desired.
Heating Mode
A wall-mounted thermostat controls the heating cycle of models which incorporate resistance heating
elements. On a call for heat, the thermostat closes the heat relay to energize the indoor fan and the
resistance elements.
1.6 Programmable Logic Controller (MGA3120)
MGA3120A-3180A models include a factory installed PLC
to control the operation of the HVAC system (MGA3090
models are standard with the Marvair printed circuit board,
see Chapter 2). LEDs on the PLC show operational status and
provide assistance with diagnosis if troubleshooting is ever
required. Various control functions are eld selectable and
programmable. The PLC is also capable of communicating
to other PLCs to allow run time leveling and does not require
additional equipment to be installed. The PLC provides
improved reliability because of the reduction of components.
The components utilized are more durable and the control box
wiring has been simplied. Pertinent statistical data about the
life of the refrigeration system can be accessed through the PLC. Figure 1.
Programmable Logic Controller
The PLC is factory installed and tested, requires no adjustments or changes when the air conditioning
system is installed.
Location
The PLC is located in the unit control panel. Remove the HVAC unit front access panel and open the
panel door to the control cabinet.

11 Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
PLC Inputs & Outputs
e PLC has inputs located along the top right of the controller and outputs along the bottom right of
the controller. An input is a signal to the PLC from either the thermostat, sensors in the air conditioner,
or a customer supplied input, e.g., EMS (Energy Management System). An output is a signal from the
PLC to the air conditioner, to the thermostat or to the customer.
PLC Inputs
e PLC inputs are powered by 24 VDC. e inputs are:
• Y – Compressor
• Y2 – Dual Compressor
• HUM – Humidier (uses optional electric heat)
• HPS – High Refrigerant Pressure Switch. The HPS is ON during normal operation. No light indicates
an open switch. See lockout indicator “A” under Outputs. HPS B available for dual compressor
systems.
• LPS – Low Refrigerant Pressure Switch. The LPS is ON during normal operation. No light indicates
an open switch. See lockout indicator “A” under Outputs. LPS B available for dual compressor
systems.
• EMS – Energy Management System. A shutdown input from an external source. When EMS input
is de-energized, the unit compressor and fans will also de-energize.
• PMF - Phase monitor fault to monitor phase operation for 3 phase systems, light is on when 3 phase
power is powered and connected correctly
PLC Outputs
The PLC outputs are connected to 24VDC and supply 24VDC loads within the control panel. These
outputs are:
• OFM – Outdoor Fan Motor Starter
• IBM – Indoor Blower Motor Starter
• CC – Compressor Starter
• CC2 – Compressor Starter B (Dual Systems)
• LOI – Lock Out Indicator. A blinking LED indicates that a pressure switch has opened or a motor
fault has occured. Refer to section 1.8 for additional information concerning this indicator.
• FR – Fault Relay. An isolated form C relay contact is provided for the customer’s use to monitor
for fault conditions with the HPS or LPS switches.
On the left side of the PLC unit, there are three LED’s that indicate the operational status of the PLC.
1. STOP/RUN
a. Solid yellow indicates STOP mode
b. Solid green indicates RUN mode
c. Flashing (alternating green and yellow) indicates that the CPU is in STARTUP mode
2. ERROR
a. Flashing red indicates an error, such as an internal error in the CPU, an error with the memory
card, or a conguration error (mismatched modules)
b. Solid red indicates defective hardware
c. All LEDs ash if the defect is detected in the rmware

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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
3. MAINT – (Maintenance) ashes whenever you insert a memory card. The CPU then changes to
STOP mode. After the CPU has changed to STOP mode, perform one of the following functions to
initiate the evaluation of the memory card:
a. Change the CPU to RUN mode
b. Perform a memory reset (MRES)
c. Power-cycle the CPU
The PLC has indicator LED’s that show the status of all thermostat inputs and outputs. For example, if
the “G” LED is on, this means that voltage is present from the “G” terminal on the thermostat.
1.7 Unit Operation
Modes of Operation
• Normal Start-Up – On a call for cooling, and with the high pressure switch closed, the cooling
system (compressor, indoor blower motor and outdoor fan motor) will be energized. (Note: See
the Delay on Make feature). e cooling system will remain energized during the three minute low
pressure switch bypass cycle. If the low pressure is closed, the cooling system will continue to operate
aer the three-minute bypass. If the low pressure switch is open aer the three-minute bypass, the
cooling system will be de-energized.
• Lockout Mode – If either the high or low pressure switch opens on the same call for cooling, the
PLC system enters into and indicates the lockout mode. In the lockout mode, the compressor is
turned o, the alarm output is energized and the status LED’s will blink to indicate which fault has
occurred. If there is a call for air ow, the indoor blower will remain energized. When the lockout
condition has cleared, the unit will reset if the demand of the thermostat is removed or when power
is reset. e lockout circuit has a 3-second delay to prevent premature activation and is factory wired
for normally open contacts. e user can select either normally closed or normally open remote
alarm dry contacts.
PLC External LED Indicator Lights
Type LED Indicator Color Description
Power
RUN/STOP Green PLC is in run mode
Yellow PLC is in stop mode
ERROR Red PLC has encountered an error
MAINT Yellow Maintanence is required
Inputs
DI a .0 Green High Pressure Switch A
DI a .1 Green Low Pressure Switch A
DI a .2 Green High Pressure Switch B
DI a .3 Green Low Pressure Switch B
DI a .4 Green Emergency Management System
DI b .1 Green Phase Monitor
DI b .2 Green Call for rst stage cooling from thermostat
DI b .3 Green Call for second stage cooling from thermostat
DI b .4 Green Call for heating from thermostat
DI b .5 Green Call for indoor blower from thermostat
Outputs
DQ a .0 Green Output to call for compressor A
DQ a .1 Green Output to call for for the indoor blower
DQ a .2 Green Output to call for the outdoor fan
DQ a .4 Green Output to call for compressor B
DQ a .5 Green Output to call for the heater
DQ a .6 Green Flashing lockout indicator (See below for ash code)
DQ a .7 Green Fault relay

13 Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
PLC Flash Code for Lockout Indicator
Number of Flashes Description of Fault
1High pressure switch A fault
2Low pressure switch A fault
3High pressure switch B fault
4Low pressure switch B fault
5Phase fault
10 Heater current overload fault
11 Emergencey Management System fault
• Delay on Make – On initial power up or on resumption of power, the air conditioner will wait 3
minutes from a call for cooling before allowing the contactor to energize.
1.8 Optional Controls & Packages
Protective Coating Packages
Two corrosion protection packages are offered- one for the condenser section (the Coastal Environmental
package) and the other for the entire unit (the Coat-All Package).
The condenser protection package includes:
• Corrosion resistant fasteners
• Sealed or partially sealed condenser fan motor
• Two layer epoxy/urethane applied to all exposed internal copper and metal in the condenser section
• A protective coating on the condenser coil
The Coat-all package includes all of the above but also includes a protective coating on the evaporator
coil and the two layer epoxy/urethane on all exterior and interior components and sheet metal. (Note:
the internal sheet metal which is insulated and the internal control box are not coated).
Dirty Filter Indicator
A diaphragm type of indicator measures the air pressure on either side of the lter and when the pressure
drops below the set point, a red LED is illuminated. The set point is adjustable.
Protective Coil Coatings
Either the condenser or evaporator coil can be coated. For harsh conditions, e.g., power plants, paper
mills or sites were the unit will be exposed to salt water, the condenser coil should be coated. Note:
Cooling capacity may be reduced by up to 5% on units with coated coils.
Cabinet Color and Material
The air conditioners are available in two standard cabinet colors -the standard grey with beige as an
option. The standard cabinet’s sides, top and front panels are constructed of 16 gauge painted steel.
Contact your Marvair representative for color chips, custom colors and 316 stainless steel cabinets.
Dual Compressors With Lead/Lag Operation
Freeze Sensor On Indoor Coil
Prevents frost on the indoor coil caused by a loss of air ow or restrictive duct work.
Filter Access From Return Air Grille
Factory or eld installed lter bracket allows changing and access to the lters from the return air grille.
See model ID, special option code “I”.
Reverse Air Flow Conguration
Location of Supply and Return Air Openings are reversed.

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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
1.9 Electrical Operation
The compressor and condenser fan are energized with a contactor controlled by a 24 VAC pilot signal.
Some compressors incorporate an internal PTC crankcase heater that functions as long as primary power
is available. The heater drives liquid refrigerant from the crankcase and prevents loss of lubrication
caused by oil dilution. Power must be applied to the unit for 24 hours before starting the compressor.
The condenser (outside fan) motor is energized by the same contactor.
The indoor evaporator fan motor is controlled by the fan purge on the electronic control board.

15 Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
RELAY OUTPUTS
X12
DQ.a
1L .0 .1 .2 .3 .4 2L .5 .6 .7 .0 .1
DQ b
CPU 1215C
DC/DC/RLY
L+ M
X12
24VDC 24VDC
L+ M1M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1 .2 .3 .4 .5 2M 01
Dl a Dl b
24VDC INPUTS
3M 01
X11
AQ
ANALOG
OUTPUTS INPUTS
ANALOG
Al
PLC
Figure 2. Typical Electrical Schematic

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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
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

17 Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
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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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
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 PP, 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 PP, 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 YY, 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

19 Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
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

20
Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
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