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269441-UIM-A-0407
Downflow/Horizontal furnaces for installation on combustible floor-
ing 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.
Installation in a residential garage:
1.
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 18 inches (46 cm) above the floor, and the furnace must
be located or protected to avoid physical damage by vehicles.
TABLE 1: Unit Clearances to Combustibles
Application
Top
In. (cm)
Front
In. (cm)
Rear
In. (cm)
Left Side
In. (cm)
Right Side
In. (cm)
Flue
In. (cm)
Floor / Bottom
In. (cm)
Closet
Alcove
Attic
Line Contact
1. Combustible floor base or air conditioning coil required for use on combusti-
ble floor.
2. Line contact only permitted between lines formed by the intersection of the
rear panel (top in horizontal position) of the furnace jacket and building
joists, studs or framing.
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 Non-HUD Modu-
lar Home installations, when a furnace is installed so that the sup-
ply ducts carry air circulated by the furnace to areas outside the
space containing 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.
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.
4
Downflow
Horizontal
1 (2.5)
0 (0)
3 (7.6)
3 (7.6)
0 (0)
0 (0)
0 (0)
1 (2.5)
0 (0)
1 (2.5)
0 (0)
0 (0)
1
0 (0)
1 (2.5)
Yes
Yes
Yes
Yes
Yes
Yes
2
NA
Yes
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.
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.
FLOOR BASE AND DUCTWORK INSTALLATION
Downflow Combustible Floor Base
Installations on combustible materials require the use a com-
bustible floor base shown in Figure 1.
The floor base must be secured to the floor. A supply air duct
plenum with 1" (2.54 cm) flange is installed through the
opening provided. The supply air duct is then secured to the
duct system with screws and sealed to prevent leaks. Do not
shoot screws through the flanges of the supply air duct into the top of
the combustible floor base. Install the furnace on the combustible floor
base so that the corners of the furnace are parallel with the corner
brackets of the floor base. Follow the instructions supplied with the
combustible floor base accessory.
This combustible floor base can be replaced with a matching cooling
coil, properly sealed to prevent leaks. Follow the instructions supplied
with the cooling coil cabinet for installing the cabinet to the duct connec-
tor. Refer to the installation instructions for additional information.
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.
Ductwork Installation
NOTE: When attaching duct flange, do not shoot the screw down into
the casing. Use the formed flange intended for duct flange attachment.
A proper Heat Loss/Gain Calculation should be done on all installations
for proper application of equipment. From this the ductwork sizing can
be calculated, ACCA Manual J and D and industry standards are help-
ful.
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 plenum should be if sufficient size so that the fur-
nace operates at the specified external static pressure and within the air
temperature rise specified on the nameplate.
Table 2 is a guide for determining whether the rectangular duct system
that the furnace is being connected to be of sufficient size for proper fur-
nace operation.
Unitary Products Group
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