Sears 9MPD - Manual (Page 39)

To check temperature rise,use the following procedure:
1. Place thermometers in supply and return air registers as
close to furnace as possible, avoiding direct radiant heat
from heat exchangers.
2. Operate furnace continuously for 15 minutes with all regis­
ters and duct dampers open.
3. Take reading and compare with range specified on rating
plate.
4. Ifthe correct amount oftemperature rise is NOT obtained, it
may be necessary to change blower speed. A higher blow­
er speed will lower the temperature rise. A lower blower
speed will increase the temperature rise.
Changing Blower Speed
ELECTRICAL SHOCK HAZARD
Failure to do so can result in death and/or personal
injury.
Turn OFF powerto furnace before changing speed taps.
NOTE: The speed taps that the manufacturer sets from the facto­
ry for this product are based on a nominal 400 CFM per ton cool­
ing and the basic mid range on the temperature rise for heating.
Since the manufacturer cannot establish the static pressure that
will be applied to the unit, it is the responsibility of the installer
dealer/contractor to select the proper speed taps for the applica­
tion when the unit is installed.
If it is necessary to change speeds, refer to steps below.
1. Refer to Furnace Wiring Diagramfor location of the heating
and cooling speed taps located on the electronic fan control
as well as location of unused blower motor speed leads.
Use the chart (Table 9) to determine the blower motor
speed settings.
Table; 9 Blower Speed Chart
Wire Co or Motor Speed
Black High
Orange* Med-High
Blue Medium
Red Low
* Med-High speed may not be provided on all models.
2. Change the heat or cool blower motor speed by removing
the motor lead from the "Heat" or "Cool" terminal and re­
place It with the desired motor speed lead from the "Un­
used Motor Lead" location. Connect the wire previously
removed from the "Heat" or "Cool" terminal to the vacated
"Unused Motor Lead" terminal.
3. Ifthe same speed must be used for both heating and cool­
ing, remove the undesired motor speed lead from the
"Heat" or "Cool" terminal and connect that lead to the open
terminal at "Unused Motor Lead" location. Attach ajump-
er between the "Heat" and "Cool" terminals and the re­
maining motor speed lead.
Note: For motors with (4) speed leads, it will be necessary
to tape off the terminal of the motor speed lead removed
from the
"Heat" or "Cool" terminal with electrical tape since
an open terminal will not be available at the "Unused Mo­
tor Lead" location.
Continuous Fan Operation
A terminal is provided on the electronic fan control located in the
circulating blower compartment for operation of the continuous
fan option. This connection is intended for the low speed motor
tap, and has a lower contact rating
( 8
amps) than the heat and
cool taps. When the low speed blower lead is connected to this
terminal, this will provide low speed blower operation whenever
the other two speeds
(Heat or Cool) are not energized.
Thoroughly check the system after modification to ensure the
proper operation of the circulating air blower in all modes of opera­
tion.
Separate speed selections for Heat, Cool, and
Continuous Fan
Connect low speed lead from circulating motor to the "Cont." ter­
minal at the electronic fan control. The appropriate motor leads
should already be connected to the
"Heat" and "Cool" terminals.
Heating and Continuous Blower Speed the
Same
If it is necessary to operate the heating speed and continuous
blower speed using the same blower speed, connect a jumper be­
tween the "Heat" and "Cont." terminals on the electronic fan con­
trol.
Note: There should be only ONE motor lead going to the "Heat"
and "Cont." terminals.
9. Furnace Maintenance
CAUTION
It is recommended that the furnace be inspected and
serviced on an annual basis (before the heating season) by a
qualified service technician.
See "User's Information Manual" and the "Service Manual".
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