14
AIR CIRCULATION BLOWER TIMING
All items in this section refer to the air circulation blower, not
to the induced draft blower. The timing sequence for the
induced draft blower is not adjustable.
When a call for cooling occurs, the air circulation blower will
come on. It will remain on for 45 seconds after the call for
cooling ends. This fan timing is not adjustable.
During normal heating operation, the air circulation blower
will come on 37 seconds after the gas valve opens. This
timing is not adjustable.
As shipped, the air circulation blower will remain on for 90
seconds after the gas valve closes. If desired, this timing
may be adjusted. The adjustment switches are near the low
voltage terminal strip. See Figure 20.
12
12
12
12
ON
OF
F
ON
OF
F
ON
OF
F
ON
OF
F
60
Second
Delay
90
Second
Delay
180
Second
Delay
120
Second
Delay
Figure 20
Switches
(Viewed in an Upflow Installation)
LINE VOLTAGE CONNECTION FOR OPTIONAL
HUMIDIFIER AND ELECTRONIC AIR CLEANER
The control module is equipped with line voltage accessory
terminals used for controlling the power to an optional field-
supplied humidifier and/or electronic air cleaner.
Accessory Load Specification
Air Cleaner: 1.0 Amp max. at 120 VAC
Humidifier: 1.0 Amp max. at 120 VAC
Accessory Installation:
Follow the electronic air cleaner and humidifier manufactur-
ers’ instructions for mounting and electrically grounding
these accessories. Check that the power supply to the
furnace has been disconnected. Wire the accessories to
the control module as shown below. All connections to the
control module are to be made through 1/4” female termi-
nals.
If it is necessary to supply additional line voltage wiring to
the interior of the furnace, the wiring must comply with all
local codes. This wiring must have a minimum temperature
rating of 105°C and must be routed away from the burner
compartment. All line voltage wire splices must be made
inside the furnace junction box.
Co
ol
Pa
rk
He
at
L
o
He
at
H
i
Li
ne
T
ran
sf
or
m
e
r
EAC
Hu
m
Li
ne
T
ran
sf
or
m
e
r
C
irc
u
lat
or
EAC
Hu
m
Air Cleaner
Humidifier
Control Module
Hot 120 VAC
Neutral 120 VAC
Optional
Accessories
{
Figure 21
Accessory Operation
Accessory Operation:
The furnace control module ener-
gizes the humidifier whenever the induced draft blower is
energized (when an air cleaner is installed on the system,
the humidifier is not energized until the air cleaner is
energized). The control module energizes the air cleaner
whenever the air circulation blower is energized.
VlI. Circulating Air and Filters
DUCTWORK - AIR FLOW
Duct systems and register sizes must be properly designed
for the CFM and external static pressure rating of the
furnace. Ductwork should be designed in accordance with
the recommended methods of “Air Conditioning Contrac-
tors of America” Manual D.
A duct system must be installed in accordance with Stan-
dards of the National Board of Fire Underwriters for the
Installation of Air Conditioning, Warm Air Heating and
Ventilating Systems. Pamphlets No. 90A and 90B. Ductwork
must never be attached to the back of the furnace.
A closed return duct system must be used, with the return
duct connected to the furnace. Supply and return con-
nections to the furnace may be made with flexible joints to
reduce noise transmission. To prevent the blower from
interfering with combustion air or draft when a central return
is used, a connecting duct must be installed between the
unit and the utility room wall. A room, closet, or alcove must
not be used as a return air chamber.
When the furnace is used in connection with a cooling unit,
the furnace should be installed in parallel with or on the
upstream side of the cooling unit to avoid condensation in
the heating element. With a parallel flow arrangement, the
dampers or other means used to control the flow of air must
be adequate to prevent chilled air from entering the furnace
and, if manually operated, must be equipped with means to
prevent operation of either unit unless the damper is in the
full heat or cool position.
When the furnace is installed without a cooling coil, it is
recommended that a removable access panel be provided
in the outlet air duct. This opening shall be accessible when
the furnace is installed and shall be of such a size that the
heat exchanger can be viewed for visual light inspection or
such that a sampling probe can be inserted into the air-
stream. The access panel must be made to prevent air
leaks when the furnace is in operation.
