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III-START‐UP
A-Preliminary and Seasonal Checks
1 - Inspect electrical wiring, both field and factory installed
for loose connections. Tighten as required.
2 - Check voltage at disconnect switch. Voltage must be with
in range listed on the nameplate. If not, consult the power
company and have voltage condition corrected be
fore starting unit.
3 - Inspect condition of condensate traps and drain as
sembly. Disassemble and clean seasonally.
B-Heating Start‐Up
BEFORE LIGHTING
the unit, smell all around the fur
nace area for gas. Be sure to smell next to the floor be
cause some gas is heavier than air and will settle on the
floor.
The gas valve on the ML193UHE is equipped with a gas
control switch. Use only your hand to move the switch.
Never use tools. If the the switch will not move by hand,
replace the valve. Do not try to repair it. Force or attempt
ed repair may result in a fire or explosion.
Placing the furnace into operation:
ML193UHE units are equipped with a SureLight ignition
system. Do not attempt to manually light burners on this
furnace. Each time the thermostat calls for heat, the
burners will automatically light The ignitor does not get
hot when there is no call for heat on units with SureLight
t
ignition system.
Priming Condensate Trap
The condensate trap should be primed with water prior to
start-up to ensure proper condensate drainage. Either
pour 10 fl. oz. (300 ml) of water into the trap, or follow
these steps to prime the trap:
1 - Follow the lighting instructions to place the unit into op
eration.
2 - Set the thermostat to initiate a heating demand.
3 - Allow the burners to fire for approximately 3 minutes.
4 - Adjust the thermostat to deactivate the heating de
mand.
5 - Wait for the combustion air inducer to stop. Set the
thermostat to initiate a heating demand and again al
low the burners to fire for approximately 3 minutes.
6 - Adjust the thermostat to deactivate the heating de
mand and again wait for the combustion air inducer to
stop. At this point, the trap should be primed with suffi
cient water to ensure proper condensate drain opera
tion.
WARNING
If you do not follow these instructions exactly, a fire
or explosion may result causing property damage,
personal injury or death.
Gas Valve Operation (Figure 53)
1 -
STOP
! Read the safety information at the beginning of
this section.
2 - Set the thermostat to the lowest setting.
3 - Turn off all electrical power to the unit.
4 - This furnace is equipped with an ignition device which
automatically lights the burners. Do
not
try to light the
burners by hand.
5 - Remove the upper access panel.
6 - Move gas valve switch to
OFF.
See figure 53.
7 - Wait five minutes to clear out any gas. If you then smell
gas, STOP! Immediately call your gas supplier from a
neighbor's phone. Follow the gas supplier's instruc
tions. If you do not smell gas go to next step.
8 - Move gas valve switch to
ON.
See figure 53.
GAS VALVE SHOWN IN ON POSITION
MA
PR
O
INLET
PRESSURE
PORT
MANIFOLD PRESSURE
ADJUSTMENT SCREW
(under barbed fitting)
FIGURE 53
9 - Replace the upper access panel.
10- Turn on all electrical power to to the unit.
11- Set the thermostat to desired setting.
NOTE
- When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
12- If the appliance will not operate, follow the instructions
“Turning Off Gas to Unit” and call your service techni
cian or gas supplier.
Turning Off Gas to Unit
1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to be
performed.
3 - Remove the upper access panel.
4 - Move gas valve switch to
OFF.
5 - Replace the upper access panel.
Failure To Operate
If the unit fails to operate, check the following:
1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse or tripped breaker?
5 - Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shut‐off valve open?
8 - Is the internal manual shut‐off valve open?
9 - Is the unit ignition system in lockout? If the unit locks out
again, inspect the unit for blockages.
