Lennox MS8 SERIES Installation And Service Procedures page 63

Continued — 18 - 24 kBtu System Status or Error Codes — Indoor Character Display and Outdoor LEDs
Outdoor Unit LED Status
This unit has three display
Indoor
status indicators
Unit
n ®
o OFF
Display ON
D5 D6 D16
n n n
EU
n n n
FH
F1
F2
®
o o
F3
®
o o
F4
®
o o
F5
n ®
o
F6
n n
o
F8
n n
o
F9
n ®
o
HC
n ®
o
H0
H1
H2
Error Description
BLINKS
D30
Intelligent Power Module
®
protection limit
Anti-freezing upper and lower
o
limit range
Indoor ambient sensor (RT1)
open or short-circuited
Indoor coil sensor (RT2) open
or short-circuited
Outdoor ambient sensor (RT4)
n
open or short-circuited
Outdoor coil sensor (RT3) open
o
or short-circuited
Discharge line sensor (RT5)
®
error
Compressor overload limit
®
issue
n
High current limit issue
o
Discharge temperature too high
Power factor correction protec­
®
tion
Heating mode anti-high
®
temperature protection
Defrosting (heat pump only)
Electrostatic protection
System Status
System will continue to run; how­
ever at reduced compressor speed
until issue is corrected.
System will continue to run; how­
ever at reduced compressor speed
until issue is corrected.
Cooling and dehumidify will contin­
ued to operate as well as indoor
fan. Heating will not operate.
All system functions are termi­
nated except indoor fan.
All system functions except indoor
fan will be terminated after 3-min­
ute delay.
Normal operational state with com­
pressor speed automatically adjust
for operational conditions. System
will continue to operate at reduced
compressor speed until issue is
corrected.
System will continue but will re­
duce compressor speed to correct
issue
System will continue operation at a
reduced compressor speed until
issue is resolved.
Normal operation
System protection feature. All sys­
tem functions are terminated ex­
cept indoor fan.
Page 63
Troubleshooting for Possible
Causes
Intelligent Power Module
protection limit error can result
from any of the following:
S Loss of cooling to the heat sink
S Low voltage
S High ambient temperature
S Loose screws fastening the out­
door control to the heat sink
Check all and correct, if necessary.
See figure 92 for troubleshooting.
The indoor coil sensor (RT2) moni­
tors the coil temperature continu­
ously. Any time the coil tempera­
ture falls between 42.8ºF (6ºC)
and 30.2ºF (-1ºC), the micropro­
cessor will initiate anti-freeze
protection operation.
Sensor input is out of acceptable
input range. Check sensor for
proper resistance. Replace sensor
if shorted, open or out-of-calibra­
tion.
Sensor input is out of acceptable
input range. Check sensor for
proper resistance. Replace sensor
if shorted, open or out-of-calibra­
tion.
Sensor input is out of acceptable
input range. Check sensor for
proper resistance. Replace sensor
if shorted, open or out-of-calibra­
tion.
S Check outdoor ambient air tem­
perature. Could be too high.
S Check for locked compressor ro­
tor
S Check for locked refrigeration cir­
cuit (capillary tubes for example)
S Check for blocked or restricted
outdoor air flow. Clear, if neces­
sary.
S Check for low refrigerant charge.
See unit information manual for
further information.
Check input voltage. It may be ei­
ther too low or too high.
Discharge line temperature is high.
See figure 72.
See unit information manual for
further information.
See unit information manual for
further information.
Normal operation to defrost out­
door coil.
Excessive electrostatic charge
present. Correct, if possible.
Corp. 1244-L9