MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 18
circulating blower motor will be de-energized and the control
board will enter the fan failure lockout mode until the thermostat
is reset or power to the furnace is cycling o and back on.
Pressure Switch Opens
If the pressure switch opens after ame has been established, the
control board de-energized the gas valve and initiates a normal
post-purge and blower heating o-delay. When the blower
heating o-delay is complete, the circulating blower motor is
de-energized. If the pressure switch closes, the control board
begins an ignition sequence if the thermostat is still calling for
heat.
The control board will ignore a pressure switch opening of
less than 2 seconds, but the gas valve will be de-energized
momentarily while the pressure switch is open which may cause
a loss of ame. If there is a loss of ame, the control board will
initiate the Ignition Recycle procedure.
If the pressure switch opens for more than 2 seconds during a
pre-purge or inter-purge period, the control board will wait for
the pressure switch to re-close. The purge time re-starts when
the pressure switch closes. If the pressure switch remains open
for 60 seconds, the control board will enter the lockout mode,
de-energize the induced draft blower, and begin to ash a “2” fault
code on the Status LED.
Undesired Flame
If ame is sensed while the gas valve is de-energized, the control
board will energize the induced draft blower and circulating
blower motor on heating speed. All other outputs will remain o
and the Status LED will ash a “5” fault code. When ame is no
longer sensed, the induced draft blower will enter a post-purge
period and the circulating blower motor will continue to operate
until selected heating blower o-delay is completed. The control
will not be locked out and continue with normal operation
following the blower o-delay.
Lockout
Soft Lockout: The gas valve will be de-energized and the control
board will not initiate an ignition attempt. The control board
will still respond to an open limit switch and undesired ame by
energizing the induced draft blower and circulating blower motor.
The control board will automatically exit the lockout mode after
1 hour. The control can be manually forced to exit the lockout
mode by cycling the electrical power to the furnace o and then
back on or removing the thermostat call for heat for more than 2
seconds.
Hard Lockout: If a gas valve hardware fault, a ame sense
hardware fault has occurred or if the limit switch is open for
more than 5 minutes, the control board will enter a hard lockout
condition. To exit a hard lockout, electrical power to the furnace
must be cycled o and then back on or the thermostat call for
heat must be removed.
For personnel safety, turn the electrical power “OFF” at
the main electrical panel (circuit breaker box) and at the
furnace before attempting any service or maintenance
operations. Homeowners must never attempt to perform
any maintenance on the furnace or remove any furnace
access panels except for removing the louvered return air
lter door when replacing the lters with the electrical
power to the furnace disconnected.
SECTION 5: TROUBLESHOOTING
The following checks should be made before troubleshooting
the furnace controls for a no-heat issue. If the integrated furnace
control board Status LED is not on, perform the following checks.
1. Check the circuit breakers or fuses that supply line voltage
electrical power to the furnace to make sure they are in the
“ON” position and have not tripped.
2. Check any “ON/OFF” switches that are external to the furnace
to make sure they are turned on.
3. Check to make sure the connections to the line voltage
electrical supply pigtails are secure.
4. Check for a loose or missing ground wire to the furnace.
5. Check for loose wiring connections on the 115 VAC power
supply control board terminals.
6. Check for loose connections on the integrated furnace control
board terminals.
7. Check the control board is connected securely to the chassis
ground connection.
8. Check for 24 VAC between the “R” and “COM” terminals on
the control board. If 24 VAC is not present, check for a failed
transformer.
9. If 24 VAC is present between the “R” and “COM” terminals on
the control board, check for 24 VAC between the “W” and
“COM” terminals. If 24 VAC is not present between the “W”
and “COM” terminals, replace the control board.
10. Check for loose wiring connections on the furnace components.
11. Check all gas line shuto valves to make sure the valves are in
the “ON” position.
12. If the furnace is operating, but not operating correctly,
review Section 4: Sequence of Operation to determine
which component is malfunctioning.
Integrated Furnace Control Board Diagnostics
The control continuously monitors its own operation and the
operation of the system. A green LED labeled “STATUS” is provided
on control board to indicate system status and faults. Below is a
guide to the Status LED codes. If a failure occurs, the STATUS LED
will indicate the failure code by the number of ashes. If the LED
is on and not ashing, the control is operating normally. If the LED
is o, the power to the control is o, the 3 amp fuse on the control
board has blown, or the control board is defective. Check the
power to the control board and check to see if the fuse is blown.
If there is 115 VAC between the control board “L1” and “NEUTRAL”
terminals and 24 VAC between the control board “R” and “C”
terminals and the STATUS LED is not on, the board is defective and
must be replaced.
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