45
Installation Manual
Due to our policy of continuous product innovation, some specifications may change without notification.  
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Duct Work For Vertical / Horizontal Air Handler Units
•  Use at least ten (10) M4-25L screws when attaching the supply duct 
to the vertical-horizontal air handler unit. 
•  To prevent vibration transmission, install exible connectors be-
tween the supply duct and the vertical-horizontal air handler unit. If an 
electrical heater is included, the exible connector must be construct-
ed from a heat-resistant material.
•  When routed through unconditioned spaces, ducts must be insu-
lated and covered with vapor barriers.
•  Internal acoustical insulation lining may be necessary for a metal 
duct system if it does not have a 90° elbow and ten (10) feet of main 
duct to the rst branch takeoff.
•  Fibrous ducts could be used as a substitute if built and installed in 
accordance with the most recent edition of the Sheet Metal and Air 
Conditioning Contractors’ National Association (SMACNA) Construc-
tion Standard.
•  Fibrous ducts and acoustical linings must follow National Fire 
Protection Association (NFPA) Standards 90A or 90B as tested by UL 
Standard 181 for Class 1 ducts. 
•  Seal around the ducts to prevent air leaks.
At least ten (10) screws
(M4-25L)
At least six (6) screws (M-4-25L)
More than 
1 inch 
Figure 28: Attaching Ducts to the Vertical / Horizontal Air Handler Unit.
Top 
Front 
Bottom 
Right Side
Refrigerant Pipe 
Connections 
Drain Connections 
for Horizontal-Left 
Installation
Drain 
Connection
for Upflow 
Installation 
Air Filter Cover
Model No.
Dimensions (inches)
A B C
D E F G H
Height Width Depth
NJ Chassis
ARNU123NJA4
48-5/8 18 21-1/4 1-9/16 17-1/2 20 17 12-1/8
ARNU183NJA4
ARNU243NJA4
48-5/8 18 21-1/4 1-9/16 17-1/2 20 17 12-1/8
ARNU303NJA4
ARNU363NJA4
NK Chassis
ARNU423NKA4
48-5/8 25 21-1/4 1-9/16 24-1/2 20 24 12-1/8ARNU483NKA4
ARNU543NKA4
Figure 29: Vertical / Horizontal Air Handler Unit Duct Connection 
Dimensions Diagram.
Table 21: VAHU Unit Duct Connection Dimensions Table.
General Mounting  - Vertical / Horizontal Air Handler Units
GENERAL INSTALLATION GUIDELINES
More than 
23-5/8 inches
0 inches*
Minimum 14 inches
0 inches*
*When using top panel access holes 
for power wiring / communications cable
Rear
0 inches
Front
Minimum 14 inches
Figure 30: Clearances Requirements for Vertical / Horizontal Air Handler 
Units.