Troubleshooting; Diagnostics Codes - Lennox Harmony III Installation Instructions Manual

2. Establish a compressor heating demand and allow
system to begin operating (see heat pump heating
checkout section for details).
3. Allow system to operate several minutes so refrigerant
pressures can balance.
4. Momentarily block the return air opening and observe
the high pressure gauge. When hot gas line pressure
reaches approximately 375 psig for R−22 and 550 for
R−410A, an error code will be set in the zone control
system, DIAGS 1 and 4 will turn on, and outdoor unit
will stage down and turn off if the switch does not close
within 90 seconds. Afterwards, backup heat will be
used to satisfy the demand.
5. Remove the restriction. When hot gas pressure drops
below 275 psig (for R−22) or 425 psig (for R−410A), all
DIAGs should turn off.
Blower Speed Checkout
The indoor blower speed should vary as zone demand
changes. The fan speed LED varies in brightness as the
blower varies in speed. The brighter the LED, the more
CFM being delivered. Blower speed can also be viewed by
attaching an electronic voltmeter between DS and any C
terminal on the zone control board. While not a precise
measurement, the voltmeter fluctuation indicates that the
blower speed is changing.
1. Connect electronic voltmeter between DS and any C
terminal on the zone control board. Leave all field wir-
ing in place.
2. Select DC volts scale.
3. Start zone heating or cooling checkout procedure.
4. Observe voltages:
22 volts DC = high speed (varies depending on in-
D
put voltage at primary transformer).
11 volts DC (approx.) = medium speed 50% into
D
adjustment band of blower.
(0−off;1−on)
Diag LED
Code Fault
1234
# Indicated
0 0000 Normal
operation
1 1000 Insufficient
cooling
2 0100 Defrost time
> 20 minutes
3 1100 Unsteady
thermostat
input
Table 10

Diagnostics Codes

Remedy
No remedial action required.
Occurs when unable to maintain desired temperature in cooling. Dis-
plays code and no further action is taken.
The defrost board should never allow a defrost for greater than 20 min-
utes. If this error occurs, check the outdoor unit to see if it is stuck in
defrost mode. The zone control system will use the backup heat during
this error and not the heat pump.
This error occurs when a thermostat changes state repeatedly and rap-
idly, indicating that the thermostat is making intermittent contact and
needs attention. The offending thermostat will be ignored for 4 minutes
after the zone control system detects the problem. After 4 minutes if the
signal from the thermostat is steady again, it will be recognized by the
zone control system. Disconnect thermostats until error goes away. This
will identify the source of bad input. If error remains after all inputs have
been disconnected, replace zone control board.
Page 25
0 volts DC = low speed or off.
D
All speeds in between are a percentage of 22VDC.

Troubleshooting

Zone Control Board Diagnostics (Diagnostic
LEDs)
When the zone control system finds a problem (error con-
dition), it will turn on one or more of the diagnostic LEDs on
the board.
Decoding the Light Patterns
The LEDs can be lit in several different patterns, each pat-
tern corresponding to a different error condition. Table 10
shows each possible display pattern, a description of the
error, and ways to correct the error.
Some of the errors found in table will cause a fail−safe or
shutdown condition. The system will shutdown after the er-
ror is present for about five seconds. During a shutdown
condition, all dampers will open, there is no demand to the
condensing unit or furnace. Normal operation will resume
five seconds after the error has been corrected.
The blower may run during a fail−safe condition after a
heating demand. This is due to the operation of the blower
control board inside the furnace.
If a shutdown condition occurs while there is a call for cool-
ing, a five−minute timer is initiated before cooling can be
called for again. The timer begins at the time of the shut-
down condition and does not affect the response to, nor is
affected by a heating demand.
Troubleshooting diagrams (figures 23, 24, 25) identify
common areas to check when troubleshooting. The dia-
grams provide checkpoints related to connectivity and op-
eration of system equipment. Use these diagrams, along
with installation information contained throughout this
manual, to identify and correct problems.
Fail-safe
(System
Shut Down)
No
No
No
table continued on next page
HARMONY IIIT SERIES