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Ductwork Requirements; Electrical Requirements - Whirlpool WFM18 Installation Instructions Manual

80% single-stage multispeed gas furnace


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Furnace Suspension
If you are suspending the furnace from the rafters or joists, use a
³⁄₈" (1 cm) threaded rod and 2" x 2" x ³⁄₈" (5.1 cm x 5.1 cm x 1 cm)
angle iron as shown below. The length of the rod will depend on
the application and the clearances necessary.
Suspended Furnace
A. ³⁄₈ " (1 cm) diameter threaded
rod (6)
B. 8" (20.3 cm) minimum
clearance between center rod
and furnace cabinet to allow for
circulator blower removal.
C. Level furnace end to end, slight
forward tilt with front 0" to ³⁄₄ "
(1.9 cm) below back.
Existing Furnace Removal
NOTE: When an existing furnace is removed from a venting
system serving other appliances, the venting system may be too
large to properly vent the remaining attached appliances.
The following vent testing procedure is reproduced from the
American National Standard/National Standard of Canada for
Gas-Fired Central Furnaces ANSI Z21.47-Latest Edition, CSA-
2.3-Latest Edition Section 1.23.1. The following steps shall be
followed with each appliance connected to the venting system
placed in operation, while any other appliances connected to the
venting system are not in operation.
1. Seal any unused openings in the venting system.
2. Inspect the venting system for proper size and horizontal
pitch, as required by the National Fuel Gas Code, ANSI
Z223.1 or the CAN/CSA B149 Installation Codes and these
instructions. Determine that there is no blockage or
restriction, leakage, corrosion and other deficiencies which
could cause an unsafe condition.
3. In so far as practical, close all building doors and windows
and all doors between the space in which the appliance(s)
connected to the venting system are located and other
spaces of the building. Turn on clothes dryers and any
appliance not connected to the venting system. Turn on any
exhaust fans, such as range hoods and bathroom exhausts,
so they shall operate at maximum speed. Do not operate a
summer exhaust fan. Close fireplace dampers.
4. Follow the lighting instructions. Place the appliance being
inspected in operation. Adjust thermostat so appliance shall
operate continuously.
5. Test for draft hood equipped appliance spillage at the draft
hood relief opening after 5 minutes of main burner operation.
Use the flame of a match or candle.
D. Tilt outward to allow for door and
circulator blower removal.
E. Position as close as possible to
blower deck to allow for circulator
blower removal.
F. 2" x 2" x ³⁄₈ " (5.1 cm x 5.1 cm x
1 cm) angle iron (3)
G. Support nuts
H. Hold down nuts
6. After it has been determined that each appliance connected
to the venting system properly vents when tested as outlined
above, return doors, windows, exhaust fans, fireplace
dampers and any other gas burning appliance to their
previous conditions of use.
7. If improper venting is observed during any of the above tests,
the common venting system must be corrected.
Corrections must be in accordance with the latest edition of the
National Fuel Gas Code NFPA 54/ANSI Z223.1 and/or CAN/CSA
B149 Installation Codes.
If resizing is required on any portion of the venting system, use
the appropriate table in Appendix G in the latest edition of the
National Fuel Gas Code ANSI Z223.1 and/or CAN/CSA B149
Installation Codes.

Ductwork Requirements

Install all conditioned air plenums, ducts and air filters (if not
provided on the furnace) in accordance with NFPA 90B
Standard for the Installation of Warm Air Heating and Air-
Conditioning Systems (latest edition).
The furnace is provided with flanges for the connection of the
plenum and ducts.
All air filters must be listed as Class 2 furnace air filters.
All ductwork must be made of materials and insulated to
meet local, state and national codes. Ductwork installed
outdoors must be sealed, weatherproof and kept from
physical damage. Caulking, flashing or other means of
adequately providing a permanent weather seal should be
used where duct penetrates a building or structure opening.
A closed return duct system must be used with the return
duct connected to the furnace.
Do not attach ductwork to the back of the furnace.
Flexible joints may be used for supply and return connections
to reduce noise transmission.
A connecting duct must be installed between the furnace and
the utility room wall to keep the blower from interfering with
combustion air or draft when a central return is used.
Do not use a room, closet or alcove as a return air chamber.
For models with airflow over 1,800 CFM, install a bottom
return, 2 side returns or 1 side and 1 bottom return.

Electrical Requirements

To avoid the risk of injury, electrical shock or death, the
furnace must be electrically grounded in accordance with
local codes or, in their absence, with the latest edition of the
National Electric Code (NEC).
The furnace must be grounded and wired in accordance with
local codes or, in the absence of local codes, with the
National Electrical Code ANSI/NFPA No. 70 (latest edition).
In all instances, other than wiring for the thermostat, the
wiring to be done and any replacement of wire shall conform
with the temperature limitation for Type T wire (63°F [17ºC]


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