- 18 -
STEP
ACTION
YES
NO
GO TO
34.
You have excessive restriction in combustion-air or vent pipe. Also check for proper vent
sizing for installation.
16
35.
Continue to observe furnace operation for 20 minutes or until status code starts flashing.
36
36.
Does status code 3 flash?
38
37
37.
Does a different status code flash?
7
50
38.
Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.
39
39.
Connect 1 side of slope manometer with a tee to collector box pressure tap. Refer to pressure
check diagram in Appendix C.
40
40.
Turn power on and jumper R and W/W1 thermostat terminals.
41
41.
Monitor slope manometer. Does the pressure reading appear to be stable when fault occurs?
43
42
42.
Check for a sag in vent pipe or partially clogged drain trap or line. Also check for improperly
plumbed drain tubing within furnace.
8
43.
Does the pressure reading slowly drop off before flashing status code 3?
45
44
44.
Problem could be caused by excessive wind conditions. If so the furnace will run the next
cycle in maximum heat. Check wiring for an intermittent connection in low pressure switch
LPS circuit. If problem still persists and wind conditions are not excessive turn setup switch
SW1-3 ON to boost inducer speed. On the Communicating Wall Control select MIN/INT
RISE ADJ.
8
45.
Check for partially clogged drain trap or line. If furnace is installed in the horizontal position
make sure the furnace is pitched forward ¼ inch minimum to ½ inch maximum. If furnace is
installed in the upflow or downflow position make sure the furnace is level or pitched
forward within ½ inch.
8
46.
Check the collector box pressure tap for blockages. Use the back end of a small drill bit to
clear debris out of the collector box pressure tap opening. It may be necessary to remove the
collector box and clear away the debris if it keeps clogging.
47
47.
Check the tubing between the collector box and the pressure switch assembly for leaks or
blockages.
48
48.
Check the tube between the pressure switches for leaks or blockages.
49
49.
Check the unused trap openings and make sure they are plugged.
20
50.
Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.
51
51.
Install the control door.
52
52.
Turn power on and jumper R and W/W1 thermostat terminals. Wait 1 minute.
53
53.
Does status code 3 flash?
55
54
54.
Does a different status code flash?
7
8
55.
Is there any frost build-up on the combustion-air inlet?
33
34
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