Other Unit Adjustments - Lennox MERIT ML195UH 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. Increase the blower speed to de-
crease the temperature. Decrease the blower speed to
increase the temperature rise. Failure to adjust the tem-
perature 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 comfort
and is adjustable to satisfy individual applications. Adjust
the fan off delay to achieve a supply air temperature be-
tween 90° and 110°F at the moment that the blower is
de-energized. Longer off delay settings provide lower re-
turn air temperatures; shorter setting
Electrical
1 - Check all wiring for loose connections.
2 - Check for the correct voltage at the furnace (furnace
operating). Correct voltage is 120VAC + 10%
3 - Check amp-draw on the blower motor with blower
access panel in place.
Motor Nameplate__________Actual__________
HEAT FAN OFF TIME IN SECONDS
To adjust fan-off timing, reposition jumper across pins to
60 Second
off Time
Blower Speeds
Follow the steps below to change the blower speeds.
1 - Turn off electrical power to furnace.
2 - 2 - Remove blower access panel.
3 - Disconnect existing speed tap at integrated
controlspeed terminal.
See unit Product Specifications Manual for indoor blower
data.
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.
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.
Page 45
NO JUMPER
achieve desired setting.
90 Second 120 Second
off Time off Time
FIGURE 61
180 Second
off Time