MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 5
EXAMINING THE FURNACE
It is the homeowner’s or user’s responsibility to ensure that an
annual inspection of this furnace is made by a qualied service
agency. The qualied service agency must examine the furnace as
outlined in steps below before each heating season.
1. Examine the heat exchanger, vent pipe, combustion air
passages, vent connectors and chimney to be sure they are
clear and free of obstructions.
2. Examine the vent pipe making sure it is rmly in place, that it
is attached to the top of the furnace and it is physically sound
without holes and all of the connections are secure.
3. Examine the return air louvered door to make sure it is
physically sound, fastened securely to the furnace casing.
4. Examine the furnace casing making sure the physical support is
sound without sagging, cracks, or gaps.
5. Examine the furnace base making sure it is physically sound
without cracks, gaps, or sagging and that it has a good seal to
the casing.
6. Examine the furnace casing for obvious signs of deterioration.
7. Examine the burner ame to make sure the burner is adjusted
properly. The ame should appear long and cylindrical with a
blue color. Some yellow streaks may appear, especially near the
tip of the ame. The ame on a furnace operating on propane
(LP) will appear less blue and has considerably more yellow
streaking.
Figure 3: Burner Flame
SECTION 2: HOMEOWNER/USER INFORMATION
How the Furnace Works
Heating Cycle
1. The thermostat calls for heat which energizes furnace control
board “W” terminal.
2. The combustion air blower is energized for a pre-purge period
to remove any remaining gases from the heat exchanger and
will send those gases out the exhaust vent.
3. After the pre-purge period, the combustion air proving
pressure switch electrical contacts close if there is no exhaust
vent restriction.
4. After the pressure switch contacts closes, the hot surface igniter
is energized and will glow.
5. After the igniter has time to become suciently hot, the gas
valve will open and allow gas to ow to the burner. The gas will
ignite as it passes by the igniter and a ame will be established.
The ame sensor will sense the presence of ame and send
a signal back to the control board that a ame is present. The
control board will keep the gas valve open as long as the ame
sensor detects the presents of a ame and there is a call for heat
by the thermostat unless one of the 2 limit switches senses an
over-temperature condition.
6. After ignition has been established long enough for the heat
exchanger to heat up, the circulating blower motor will be
energized which distributes warm air throughout the home.
7. When the temperature of the home has reached the
temperature setting on the thermostat, the 24 VAC signal will be
removed from the “W” terminal on the control board which
causes the gas valve to de-energize and the burner ame to
extinguish. The circulating blower motor will shut down after
the heat exchanger has suciently cooled down.
8. The furnace will then be in “stand-by” mode until there is
another call for heat.
The furnace is equipped with the components and controls
necessary for proper and safe operation and identied in Figure 1.
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