Page 87
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 34 
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 34 
Furnace
Cabinet Width
Filter Size
Side Return Bottom Return
17-1/2” 16 X 25 X 1 (1) 16 X 25 X 1 (1)
21” 16 X 25 X 1 (1) 20 X 25 X 1 (1)
24-1/2” 16 X 25 X 1 (2) 24 X 25 X 1 (1)
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 58)
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
Hose
FIGURE 58 
Cleaning Heat Exchanger
If cleaning the heat exchanger becomes necessary, follow 
the  below  procedures  and  refer  to  gure  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 2 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 -  Disconnect  combustion  air  intake  pipe.  It  may  be 
necessary to cut the existing pipe to remove burner 
box assembly.
8 -  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.
9 -  Loosen the clamps to the exible exhaust coupling.
10 -  Disconnect condensate drain line from the cold end 
header box.
11 -  Disconnect condensate drain tubing from ue collar. 
Remove  screws  that  secures  the  ue  collar  into 
place. Remove ue collar. It may be necessary to 
cut the exiting exhaust pipe for removal of the tting.
12 -  Mark  and  disconnect  all  combustion  air  pressure 
tubing from cold end header collector box.
13 -  Mark  and  remove  wires  from  pressure  switch 
assembly.  Remove  the  assembly.  Keep  tubing 
attached to pressure switches.
14 -  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.
15 - Disconnect the condensate drain line.
16 - Remove cold end header box.