Other Unit Adjustments - Lennox Merit Series Installation Instructions Manual

Table 5
Pressure Switch and Gas Conversion kits at all Altitudes
Pressure Switch kit
Model
Input
Size
0-610m
(0-2000 ft) (2001-4000 ft)
070
090
No Change
110
135
NOTE: A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation
instruction for the conversion procedure.
PRIMARY AND SECONDARY LIMITS
The primary limit is located on the heating compartment
vestibule panel. The secondary limits (if equipped) are
located in the blower compartment, attached to the back
side of the blower. These auto reset limits are factory-set
and require no adjustment.
FLAME ROLL-OUT SWITCHES
This manually reset switches are located on the top of the
burner box.
PRESSURE SWITCH
The pressure switch is located in the heating compartment
adjacent to the combustion air inducer. The switch checks
for proper combustion air inducer operation before allowing
ignition trial. The switch is factory-set and requires no
adjustment.
TEMPERATURE RISE
After the furnace has been started, and supply and return
air temperatures have been allowed to stabilise, 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 decrease
the temperature. Decrease the blower speed to increase the
temperature rise. Failure to adjust the temperature rise may
cause erratic limit operation.
High Altitude
611-1219m 1220-1981m
(4001-6500 ft)
80W51 80W56
80W51 80W56
80W51 80W56
80W52 80W51

OTHER UNIT ADJUSTMENTS

High Altitude
Natural Gas to LP/
Natural Gas
Propane Gas Change
Burner Orifice
kit
0-1524m
1525-1981 m
(0-5000
(5001-6500 ft)
ft)
73W37 96W94
FAN CONTROL
The fan-on time of 30 seconds is not adjustable. The heat
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 delay setting of 60 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
between 32°C and 43°C at the moment that the blower is
de-energised. Longer off delay settings provide lower return
air temperatures; shorter settings provide higher return air
temperatures. See Figure 20.
Figure 20
HEAT-FAN OFF TIME IN SECONDS
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
NOTE: Do not secure the electrical conduit directly to the air
ducts or structure.
LP/Propane to
Natural Gas
over kit Change over kit
1525-
1981m 1-1524m
(5001- (1 5000 ft)
6500 ft)
97W04 96W95
120 Second
off Time
180 Second
off Time
27