Johnson Controls RL18 User Manual

Table 1: Unit clearances to combustibles
Top Front Rear Left side Right
side
Flue Floor or
bottom
Application
in. (cm) in. (cm) in. (cm) in. (cm) in. (cm) in. (cm) in. (cm)
Closet Alcove Attic Line
contact
Upflow 1 (2.5) 1 (2.5) 0 0 0 6 (15.2) Combustible Yes Yes Yes No
Upflow
B-Vent
1 (2.5) 1 (2.5) 0 0 0 1 (2.5) Combustible Yes Yes Yes No
Downflow 1 (2.5) 1 (2.5) 0 0 0 6 (15.2) 1 (25.4) Yes Yes Yes No
Downflow
B-Vent
1 (2.5) 1 (2.5) 0 0 0 1 (2.5) 1 (25.4) Yes Yes Yes No
Horizontal 1 (2.5) 1 (2.5) 0 0 0 6 (15.2) Combustible No Yes Yes Yes
Horizontal
B-Vent
1 (2.5) 1 (2.5) 0 0 0 1 (2.5) Combustible No Yes Yes Yes
Note:
• All surfaces are identified with the unit in an upflow configuration.
• For downflow applications: a combustion floor base accessory or an air conditioning coil is required for use
on a combustible floor.
• For horizontal applications: line contact is only permitted between lines formed by the intersection of the rear
panel and side panel (top in horizontal position) of the furnace jacket and building joists, studs, or framing.
Ductwork
Ductwork general information
The duct system's design and installation must adhere to
the following:
• The system must handle an air volume appropriate
for the served space and within the operating
parameters of the furnace specifications.
• Installation must be in accordance with the National
Fire Protection Association as outlined in NFPA
standard 90B (latest editions) or applicable national,
provincial, state, and local fire and safety codes.
• It must create a closed duct system. For residential
and non-HUD Modular Home installations, when
installing a furnace so that the supply ducts carry air
circulated by the furnace to areas outside the space
containing the furnace, handle the return air with
ducts sealed to the furnace casing and terminating
outside the space containing the furnace.
• Complete a path for heated or cooled air to circulate
through the air conditioning and heating equipment,
and to and from the conditioned space.
CAUTION
You must install the indoor coil in the supply air
duct, downstream of the furnace. Do not pass
cooled air over the heat exchanger.
When using the furnace with an indoor coil, install the
coil parallel with or on the supply air side of the furnace
to avoid condensation in the primary heat exchanger.
When using a parallel flow arrangement, dampers or
other means used to control airflow must be adequate to
prevent chilled air from entering the furnace. If manually
operated, equip the damper with means to prevent the
furnace or the air conditioner from operating unless the
damper is in full heat or cool position.
When replacing an existing furnace, if the existing plenum
is not the same size as the new furnace then remove
the existing plenum and install a new plenum that is the
correct size for the new furnace. If the plenum is shorter
than 12 in. (30.5 cm), the turbulent airflow may cause
the limit controls not to operate as designed or the limit
controls may not operate at all.
The duct system is a very important part of the
installation. If the duct system is incorrectly sized, the
furnace does not operate correctly. The ducts attached
to the furnace plenum must be of sufficient size so that
the furnace operates at the specified external static
pressure and within the air temperature rise specified on
the nameplate.
Important: The minimum plenum height is 12 in.
(30.5 cm). The furnace does not operate correctly on
a shorter plenum height. The minimum rectangular
duct height is 4 in. (10.2 cm) attached to the plenum.
Installation Manual: RL18 Single-Stage Standard ECM Residential Gas Furnaces (Non-condensing Multi-position Standard
Low NOx)
10
Johnson Controls Ducted Systems

Johnson Controls RL18 Specifications

General

Brand	Johnson Controls
Model	RL18
Category	Furnace
Language	English