Service - Lennox MERIT Series Installation Instructions Manual

HEAT FAN OFF TIME IN SECONDS
NO JUMPER
To adjust fan-off timing, reposition jumper across pins to
achieve desired setting.
60 Second 90 Second
off Time off Time
Figure 33
Ignition Control 107163-01
The heat fan-on time of 30 seconds is not adjustable The
heat fan-off delay (amount of time that the blower oper-
ates after the heat demand has been satisfied) may be
adjusted by changing the two position dip switch on the
integerated control, to one of four slections. Blower off de-
lay is factory set at 90 seconds. For other blower off delay
settings, please refer to the following chart:
Blower Delay Select
60
90
120
180
Factory Setting is 90
Constant Torque Motor
ML180UHE units are equipped with a constant torque
ECM motor. It has a DC motor coupled to an electronic
control module both contained in the same motor hous-
ing. The motor is programmed to provide constant torque
at each of the five selectable speeds. The motor has five
speed taps. Each tap requires 24 volts to energize.
Input Voltage Requirements
The circuit is designed to be operated with AC voltage. A
voltage of 12 to 33VAC is required to energize the motor.
Expected current draw will be less than 20mA.
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.
NOTE - Termination of any unused motor leads
must be insulated.
4 - Place unused blower speed tap on integrated control
"PARK" terminal or insulate.
120 Second 180 Second
off Time off Time
SW2-1 SW2-2
OFF ON
OFF OFF
ON OFF
ON ON
5 - Refer to blower speed selection chart on unit
wiringdiagram for desired heating or cooling speed.
See Product Specifications manual for blower
performance data. See TABLE 7 for allowable heating
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 re-set and remake
thermostat demand to the furnace and automatically reset
the integrated control to begin the ignition sequence.

Service

Failure to follow safety warnings exactly
could result in dangerous operation, serious
injury, death or property damage.
Improper servicing could result in dangerous
operation, serious injury, death, or property
damage. Before servicing, disconnect all
electrical power to furnace.
When servicing controls, label all wires prior
to disconnecting.
Take care to reconnect wires correctly.
Verify proper operation after servicing.
Annual Furnace Maintenance
At the beginning of each heating season, and to comply
with the Lennox Limited Warranty, your system should
be checked by a licensed professional technician (or
equivalent) as follows:
1 - Check wiring for loose connections, voltage at
indoor unit and amperage of indoor motor.
2- Check the condition of the belt and shaft bearings if
applicable.
3- Inspect all gas pipe and connections for leaks.
4- Check the cleanliness of filters and change if
necessary (monthly).
5- Check the condition and cleanliness of burners and
heat exchanger and clean if necessary.
Page 31
WARNING
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.