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Page 29
Unit Start−Up
FOR YOUR SAFETY READ BEFORE LIGHTING
WARNING
Do not use this furnace if any part has been under-
water. A flood−damaged furnace is extremely dan-
gerous. Attempts to use the furnace can result in
fire or explosion. Immediately call a qualified ser-
vice technician to inspect the furnace and to replace
all gas controls, control system parts, and electrical
parts that have been wet or to replace the furnace,
if deemed necessary.
WARNING
If overheating occurs or if gas supply fails to shut off,
shut off the manual gas valve to the appliance before
shutting off electrical supply.
CAUTION
Before attempting to perform any service or mainte-
nance, turn the electrical power to unit OFF at dis-
connect switch.
BEFORE LIGHTING smell all around the appliance area for
gas. Be sure to smell next to the floor because some gas is
heavier than air and will settle on the floor.
The gas valve on the ML180UHE unit is equipped with a
gas control switch. Use only your hand to move the switch.
Never use tools. If the switch will not turn or if the control
switch will not move by hand, do not try to repair it.
Placing the furnace into operation:
ML180UHE units are equipped with an automatic ignition
system. Do not attempt to manually light burners on these
furnaces. 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 an automatic
ignition system.
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 35)
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 switch on gas valve to OFF. Do not force. See
figure 35.
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.
FIGURE 35
GAS VALVE SHOWN IN ON POSITION
MANIFOLD
PRESSURE
OUTLET
PORT
INLET
PRESSURE
PORT
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
8 − Move switch on gas valve to ON. Do not force. See fig-
ure 35.
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 switch on gas valve to OFF. Do not force.
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 circuit 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 lock out? If the unit locks out
again, call the service technician to inspect the unit for
blockages.
10 − Is pressure switch closed? Obstructed flue will cause
unit to shut off at pressure switch. Check flue and outlet
for blockages.