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Limit Control Checkout:
After the furnace has been in operation for at least 15
minutes, restrict the return air supply by blocking the
filters or closing the return registers and allow the furnace
to shut down on high limit. The main burners will shut
OFF and the main blower and combustion blower should
continue to run. Remove the restriction and the burners
should come back on in a few minutes.
Flame Rollout Switch:
This unit is equipped with two (2) manual reset flame-
rollout switches that protects against improper venting of
the flue gases from the heat exchanger due to blockage
causing heat (or flames) to "rollout" into the burner box
from the heat exchangers, either safety device will
activate and shut off power to the automatic gas valve
before there is damage to the furnace. The loss of power
to the gas valve will shut off the gas burners. Should this
occur, it will be necessary to determine the cause of the
rollout, correct the condition that caused it, and reset the
flame-rollout switch.
The furnace should be allowed to cool-off before
attempting to reset the switch. Failure to follow
these instructions could result in injury due to burns!
The switches are located behind the front access
door. Remove front access door from the furnace and
reset by pushing in the button in the middle of the switch
(between the two wire connections - See Figure 16).
Very little force is required to push the reset button, and
a "click" should be heard when the switch resets.
Figure 16
FLAME ROLLOUT SWITCH
Pressure Switch Check:
To check the operation of the pressure switch vent
safety control, remove the vent adaptor from the
combustion blower. Place the furnace into operation for
high fire. Gradually cover up the blower outlet; the
furnace should first drop to low fire and with further
restriction of the opening, the main burners should shut
OFF. Remove the restriction and the unit should relight.
Replace the vent adaptor and reseal the opened joints as
required.
The operational checkout is now complete. Be sure
to adjust the thermostat to the desired setting and inform
the homeowner how to operate the furnace system before
leaving the job site.
If the pressure switch activates to shut the furnace
down, the vent system must be checked and
cleared. Failure to do so may result in serious
bodily harm or nuisance furnace shutdown and/or
a hazardous condition that may lead to property
damage, personal injury or death.
20571201 Issue 0527 Page 22 of 28