268894-UIM-A-0407
4
Unitary Products Group
Installation in a residential garage:
A gas-fired furnace for installation in a residential garage must be
installed so the burner(s) and the ignition source are located not less
than eighteen (18) inches (46 cm) above the floor, and the furnace must
be located or protected to avoid physical damage by vehicles.
SECTION II: DUCTWORK
DUCTWORK GENERAL INFORMATION
The duct system’s design and installation must:
1.
Handle an air volume appropriate for the served space and within
the operating parameters of the furnace specifications.
2.
Be installed in accordance with standards of NFPA (National Fire
Protection Association) as outlined in NFPA pamphlets 90A and
90B (latest editions) or applicable national, provincial, or state, and
local fire and safety codes.
3.
Create a closed duct system. For residential and Modular Home
installations, when a furnace is installed so that the supply ducts
carry air circulated by the furnace to areas outside the space con-
taining the furnace, the return air shall also be handled by a
duct(s) sealed to the furnace casing and terminating outside the
space containing the furnace.
4.
Complete a path for heated or cooled air to circulate through the
air conditioning and heating equipment and to and from the condi-
tioned space.
When the furnace is used in conjunction with a cooling coil, the coil
must be installed parallel with, or in the supply air side of the furnace to
avoid condensation in the primary heat exchanger. When a parallel flow
arrangement is used, dampers or other means used to control airflow
must be adequate to prevent chilled air from entering the furnace. If
manually operated, the damper must be equipped with means to pre-
vent the furnace or the air conditioner from operating unless the damper
is in full heat or cool position.
FLOOR BASE AND DUCTWORK INSTALLATION
Downflow Combustible Floor Base
Installations on combustible material or floors must use a
combustible floor base shown in Figure 1. Follow the
instructions supplied with the combustible floor base acces-
sory. This combustible floor base can be replaced with a
matching cooling coil, properly sealed to prevent leaks. Fol-
low the instructions supplied with the cooling coil cabinet for
installing the cabinet to the duct connector. Refer to the
installation instructions for additional information.
Downflow Duct Connectors
All downflow installations must use a suitable duct connector approved
by the furnace manufacturer for use with this furnace. The duct connec-
tors are designed to be connected to the rectangular duct under the
floor and sealed. Refer to the instructions supplied with the duct con-
nector for proper installation. Refer to the separate accessory parts list
at the end of these instructions for the approved accessory duct con-
nectors.
When replacing an existing furnace, if the existing plenum is not the
same size as the new furnace then the existing plenum must be
removed and a new plenum installed that is the proper size for the new
furnace.
The duct system is a very important part of the installation.
If the duct
system is improperly sized the furnace will not operate properly.
The ducts attached to the furnace plenum, should 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.
Downflow furnaces for installation on combustible flooring only
when installed on the accessory combustible floor base on wood
flooring only and shall not be installed directly on carpeting, tile or
other combustible material.
Check the rating plate and power supply to be sure that the electri-
cal characteristics match. All models use nominal 115 VAC, 1
Phase 60Hz power supply.
Furnace shall be installed so the electrical components are pro-
tected from water.
TABLE 1:
Unit Clearances to Combustibles
Application
Top
Front
Rear
Left Side Right Side
Flue
Floor/
Bottom
Closet
Alcove
Attic
Line
Contact
In. (cm)
In. (cm)
In. (cm)
In. (cm)
In. (cm)
In. (cm)
Downflow
1 (2.5)
6 (15.2)
0 (0.0)
0 (0.0)
3 (7.6)
6 (15.2)
1 (25.4)
1
1.
Special floor base or air conditioning coil required for use on combustible floor.
Yes
Yes
Yes
No
Downflow B-Vent
1 (2.5)
3 (7.6)
0 (0.0)
0 (0.0)
0 (0.0)
1 (2.5)
1 (25.4)
1
Yes
Yes
Yes
No
Horizontal
1 (2.5)
6 (15.2)
0 (0.0)
0 (0.0)
3 (7.6)
6 (15.2)
Combustible
No
Yes
Yes
Yes
2
2.
Line contact 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.
Horizontal B-Vent
1 (2.5)
3 (7.6)
0 (0.0)
0 (0.0)
0 (0.0)
1 (2.5)
Combustible
No
Yes
Yes
Yes
2
The cooling coil must be installed in the supply air duct, down-
stream of the furnace. Cooled air may not be passed over the heat
exchanger.
The duct system must be properly sized to obtain the correct airflow
for the furnace size that is being installed.
Refer to Table 7 and the furnace rating plate for the correct rise
range and static pressures
If the ducts are undersized, the result will be high duct static pres-
sures and/or high temperature rises which can result in a heat
exchanger OVERHEATING CONDITION. This condition can result
in premature heat exchanger failure, which can result in personal
injury, property damage, or death.
