Other Unit Adjustments - Lennox ML193UH030XE36B Installation Instructions Manual

Other Unit Adjustments

Primary Limit.
The primary limit is located on the heating compartment
vestibule panel. This limit is factory set and requires no
adjustment.
Flame Rollout Switches (Two)
These manually reset switches are located on the front of
the burner box.
Pressure Switch
The pressure switch is located in the heating compartment
on the cold end header box. This switch checks for proper
combustion air inducer operation before allowing ignition
trial. The switch is factory-set and must not be adjusted.
Temperature Rise
After the furnace has been started and supply and return
air temperatures have been allowed to stabilize, check the
temperature rise. If necessary, adjust the blower speed to
maintain the temperature rise within the range shown on
the unit nameplate. See 'Allowable Heating Speeds" table
on page 37. Increase the blower speed to decrease the
temperature. Decrease the blower speed to increase the
temperature rise. Failure to adjust the temperature rise
may cause erratic limit operation.
Fan Control
The fan on time of 30 seconds is not adjustable. The fan
off delay (amount of time that the blower operates after
the heat demand has been satisfied) may be adjusted by
changing the jumper position across the five pins on the
integrated control. The unit is shipped with a factory fan
off setting of 120 seconds. The fan off delay affects com-
fort and is adjustable to satisfy individual applications. Ad-
just the fan off delay to achieve a supply air temperature
between 90° and 110°F at the moment that the blower
is de-energized. Longer off delay settings provide lower
return air temperatures; shorter settings provide higher re-
turn air temperatures. See FIGURE 62.
Electrical
1 - 1 - Check all wiring for loose connections.
2 - Check for the correct voltage at the furnace operating).
Correct voltage is 120VAC + 10%
3 - Check amp-draw on the blower motor with blower
access panel in place.
Motor Nameplate__________Actual__________
Blower Speeds
Follow the steps below to change the blower speeds.
1 - Turn off electrical power to furnace.
2 - Remove blower access panel.
3 - Disconnect existing speed tap at integrated control
speed terminal.
HEAT FAN OFF TIME IN SECONDS
To adjust fan-off timing, reposition jumper across pins to
60 Second 90 Second
off Time
NOTE - Termination of any unused motor leads must be
insulated.
4 - Place unused blower speed tap on integrated control
"PARK" terminal or insulate.
5 - Refer to blower speed selection chart on unit wiring
diagram for desired heating or cooling speed.
See Product Specifications bulletin for blower
performance tables. See
speeds.
6 - Connect selected speed tap at integrated control
speed terminal.
7 - Resecure blower access panel.
8 - Turn on electrical power to furnace.
9 - Recheck temperature rise.
Electronic Ignition
The integrated control has an added feature of an internal
Watchguard control. The feature serves as an automat-
ic reset device for integrated control lockout caused by
ignition failure. This type of lockout is usually due to low
gas line pressure. After one hour of continuous thermostat
demand for heat, the Watchguard will break and remake
thermostat demand to the furnace and automatically reset
the integrated control to begin the ignition sequence.
Exhaust and Air Intake Pipe
1 - Check exhaust and air intake connections for
tightness and to make sure there is no blockage.
2 - Is pressure switch closed? Obstructed exhaust pipe
will cause unit to shut off at pressure switch. Check
termination for blockages.
3 - Obstructed pipe or termination may cause rollout
switches to open. Reset manual flame rollout
switches on burner box assembly if necessary.
Page 44
NO JUMPER
achieve desired setting.
120 Second
off Time off Time
FIGURE 62
for allowable heating
180 Second
off Time