Lennox LHT Series Service Manual page 18

15-Second-Stage Power
(Staged-Blower units equipped with power exhaust)
The second power exhaust fan is controlled by K231.
A133 will enable K231 only when the blower reaches 70%
of full speed (adjustable ECTO). This prevents a nega-
tive building pressure when the blower is operating in low
speed. Refer to the Unit Controller manual and ECTO la-
bels on the unit.
TRIP
INDICATION
WINDOW
AMP SETTING
POINTER
AMP SETTING
CONTROL
(BLUE DIAL)
RED TEST
BUTTON
(Push To Test)
Lift clear cover to adjust relay amp setting according to value given on the blower motor nameplate. Proper relay
The red STOP button opens the normally closed contacts which power the blower motor. This button stops blower
Exhaust Relay
LINE VOLTAGE IN
(Shown in AUTO position as
LOAD VOLTAGE
OUT
amp setting equals motor nameplate FLA X service factor of 1.15 X .95.
Cover must also be lifted to adjust control mode from automatic reset to manual reset (see detail above) and to
ton. A yellow marker should appear in the trip indication window to the right of the amp setting control. Press the
motor operation as long as it is pressed in.
K231 15-Fuse F61 (Higher SCCR units only)
Fuse F61 is used on units with higher SCCR rating. F61
provides overcurrent protection to compressor and other
cooling components. F61 and S48 are located inside a
sheet metal enclosure in the unit left front corner mullion.
16-Blower Motor Overload Relay S42
The relay (S42) is connected in line with the blower motor
to monitor the current flow to the motor. When the relay
senses an overload condition, a set of normally closed
contacts open to de-energize pin #1 in plug P299 of the
A55 Unit Controller. A55 de-energizes all outputs. Units
will be equipped with a relay manufactured by Teleme-
canique figure 5 or Siemens figure 6.
.
TELEMECANIQUE OVERLOAD RELAY
CLEAR
COVER
(SHOWN
CLOSED)
Lift clear cover and turn adjustment screw
STOP
counterclockwise. Reset screw will pop out
BUTTON
when pointer is in M (manual position). Close
(RED)
BLUE RESET SCREW
shipped from the factory)
test the control.
blue reset screw to reset the relay.
FIGURE 5
Page 18
DETAIL SHOWING RESET BUTTON
ADJUSTED TO MANUAL POSITION
cover to lock reset screw into position.