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Filters
All air lters are installed external to the unit. Filters should 
be  inspected  monthly.  Clean  or  replace  the  lters  when 
necessary to ensure proper furnace operation. TABLE 30 
lists recommended lter sizes.
 IMPORTANT
If a high eciency lter is being installed as part of 
this system to ensure better indoor air quality, the 
lter must be properly sized. High eciency lters 
have a higher static pressure drop than standard 
eciency glass/foam lters. If the pressure drop is 
too great, system capacity and performance may 
be reduced. The pressure drop may also cause the 
limit to trip more frequently during the winter and 
the indoor coil to freeze in the summer, resulting in 
an increase in the number of service calls.
Before using any lter with this system,  check  the 
specications  provided  by  the  lter  manufacturer 
against the data given in the appropriate Lennox 
Product  Specications  bulletin.  Additional 
information is provided in Service and Application 
Note ACC002 (August 2000).
TABLE 30 
Furnace
Cabinet Width
Filter Size
16 x 25 x 1
17-1/2”
21”
Exhaust and air intake pipes
Check  the  exhaust  and  air intake  pipes  and  all  connec-
tions for tightness and to make sure there is no blockage.
NOTE - After any heavy snow, ice or frozen fog event the 
furnace vent pipes may become restricted. Always check 
the vent system and remove any snow or ice that may be 
obstructing the plastic intake or exhaust pipes.
Electrical
1 -   Check all wiring for loose connections.
2 -    Check for the correct voltage at the furnace (furnace 
operating).
3 -    Check amp-draw on the blower motor.
Motor Nameplate__________Actual__________
Winterizing and Condensate Trap Care
1 -   Turn o power to the furnace.
2 -    Have  a  shallow  pan  ready  to  empty  condensate 
water.
3 -    Remove the clean out cap from the condensate trap 
and empty water. Inspect the trap then reinstall the 
clean out cap.
Condensate Hose Screens (FIGURE 57)
Check  the  condensate  hose  screens  for  blockage  and 
clean if necessary.
1 -   Turn o power to the unit.
2 -   Remove  hoses  from  cold  end  header  box.  Twist 
and pull screens to remove.
3 -   Inspect screens and rinse with tap water if needed.
4 -   Reinstall  screens,  reconnect  hoses  and  turn  on 
power to unit.
Hose
FIGURE 57 
Cleaning Heat Exchanger
If cleaning the heat exchanger becomes necessary, follow 
the below procedures and refer to FIGURE 1 when disas-
sembling unit. Use papers or protective covering in front of 
furnace while removing heat exchanger assembly.
1 -   Turn o electrical and gas supplies to the furnace.
2 -   Remove the furnace access panels.
3 -   Disconnect the wires from the gas valve.
4 -   Remove  gas  supply  line  connected  to  gas  valve. 
Remove  the  burner  box  cover  (if  equipped)  and 
remove gas valve/manifold assembly.
5 -   Remove sensor wire from sensor. Disconnect 2-pin 
plug from the ignitor.
6 -   Disconnect wires from ame roll-out switches.
7 -   Loosen  clamps  at  vent  elbow.  Disconnect 
condensate  drain  tubing  from  ue  collar.  and 
remove the vent elbow.
8 -   Loosen clamps and remove combustion air intake 
exible connector if equipped.
9 -   Remove  four  burner  box  screws  at  the  vestibule 
panel  and  remove  burner  box.  Set  burner  box 
assembly aside.
NOTE - If  necessary,  clean  burners  at  this  time. 
Follow  procedures  outlined  in  Burner  Cleaning 
section.
10 -  Mark  and  disconnect  all  combustion  air  pressure 
tubing from cold end header collector box.
11 -  Mark  and  remove  wires  from  pressure  switch 
assembly.  Remove  pressure  switch  assembly. 
Keep tubing attached to pressure switch assembly.
12 -  Disconnect the plug from the combustion air inducer. 
Remove  two  screws  which  secure  combustion  air 
inducer  to  collector  box.  Remove  combustion  air 
inducer  assembly.  Remove  ground  wire from  vest 
panel.
13 -  Remove electrical junction box from the side of the 
furnace.
14 -  Disconnect  condensate  line from cold end  header 
box. Remove cold end header box.
15 -  Loosen clamps on exhaust and air intake pipe seal 
plate. Slide exhaust and intake pipes up and out to 
clear blower deck. Remove exhaust and air intake 
pipe seal plate.