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After the hot surface igniter is heated for 17 seconds, the
gas valve permits gas to flow to the main burners. After
ignition and a time delay of about 60 sec, the furnace
blower will start. Variable-capacity furnaces start at low
speed until the control makes the necessary adjustments
to operate the blower at either the low- or high-heat speed.
NOTE:
If the burners fail to ignite after 4 attempts, the fur-
nace control system will lock out. If lockout occurs, main
burners fail to light, or blower does not come on, shut down
the furnace and call your dealer for service.
12. Set your thermostat to the temperature that satisfies
your comfort requirements.
SUGGESTION: Setting the thermostat back a few
degrees—and compensating for the difference with
warmer clothing—can make a big difference in your fuel
consumption. The few degrees at the top of your thermo-
stat “comfort level’’ are the most costly degrees to obtain.
When the room temperature drops below the temperature
selected on the thermostat, the furnace will switch on auto-
matically. When the room temperature reaches the tempera-
ture selected on the thermostat, the furnace will be switched
off automatically.
Some thermostats have a FAN mode with 2 selections: AUTO
and ON. When set on AUTO, the furnace blower cycles on
and off. In the ON mode, the furnace blower runs continu-
ously. Continuous fan keeps the temperature level in your
home more evenly balanced. It also permits the indoor air to
be continuously filtered. ComfortFan™ –On all but the
58MCB, the blower speed can be increased or decreased if
desired due to change of seasons, large gatherings in your
home, etc. Simply change your FAN from ON to OFF for 1
to 3 seconds (or AUTO depending on your thermostat), and
then return to ON. The blower will switch to the next higher
speed. There are at least 3 speeds to choose from. If the
blower is running on its highest speed, a request to change
will direct the blower to return to its lowest speed.
SHUTTING DOWN YOUR FURNACE
Should you ever need to shut down your furnace for service
or maintenance, you will need to turn the furnace off. The
following procedures must be followed:
1. Set your room thermostat to the lowest temperature
setting. (See Fig. 21.)
21
2. Close the external manual gas valve (See Fig. 11.)
3. Turn off electrical supply to the furnace. (See Fig. 22.)
4. Remove main furnace door. (See Fig. 13.)
5. Turn the switch on the gas control to the OFF position.
(See Fig. 23 or 24.)
22
For 58MTB and 58MVB
23
For 58MCB and 58MXB
24
6. Replace the main furnace door. (See Fig. 18.)
7. If the furnace is being shut down because of a malfunc-
tion, call your dealer as soon as possible.
PERFORMING ROUTINE
MAINTENANCE
NOTE:
The qualified installer or agency must use only
factory-authorized replacement parts, kits, and accessories
when modifying this product.
Installing and servicing heating equipment can be hazard-
ous due to gas and electrical components.
®
CAUTION
UNIT AND PROPERTY DAMAGE
Failure to follow this caution may result in damage
to the furnace and other property damage.
Furnace is not to be installed, operated, and then turned
off and left turned off in an unoccupied structure during
winter. (See “Heading South for the Winter” procedures
in maintenance section on page 10).
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