Lennox MS8 SERIES Installation And Service Procedures page 62

Table 19. 18-24 kBtu System Status and 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
NONE
C5
o o o
EE
® ®
o
E1
n n
o
E2
n n
o
E4
n ®
o
E5
o o o
E6
n n
o
E8
MS8C / MS8H (208-230V)
Error Description
BLINKS
D30
n
System is operating within normal parameters
Indoor control jumper is
missing (labeled JUMP)
n
EEPROM failure
®
System high pressure
Indoor coil freeze
o
protection
Discharge line temperature
®
protection
Compressor over-current
o
protection
Communication failure between
®
indoor unit and outdoor unit
Compressor high temperature
n
protection
System Status
All system functions are
terminated.
The indoor coil sensor (RT2) moni­
tors the coil temperature continu­
ously. When the coil
temperature drops below 30.2ºF
(-1ºC), the compressor and out­
door fan (30 seconds later) are
switched off until the coil tempera­
ture rises above 42.8ºF (6ºC) and
the compressor has
been off for a minimum of three
minutes. All system functions are
terminated except indoor fan.
The compressor discharge line
sensor (RT5) monitors the temper­
ature continuously and communi­
cates with the outdoor unit micro­
processor. Depending on the tem­
perature measured, the compres­
sor speed will be increased to
meet the load or will continue to
run at the existing speed. If the
discharge line temperature be­
comes excessively high, the com­
pressor will be de-energized.
When the compressor discharge
temperature drops below 194ºF
(90ºC), the unit will resume normal
operation. See figure 72.
All system functions are termi­
nated except indoor fan.
All system functions except indoor
fan are terminated after a 3-minute
delay.
All system functions are termi­
nated except indoor fan.
Page 62
Troubleshooting for Possible
Causes
Indoor control jumper is missing or
is not installed correctly. (Indoor
control jumper location is labeled
JUMP.)
Replace outdoor control.
Check for low refrigerant charge,
blocked coil or excessively high
outdoor ambient temperature.
Check for reduced indoor airflow
(restricted filter), restricted refriger­
ant flow, low ambient temperature
(outdoor) and low indoor system
load. Correct, if necessary.
Check for low system refrigerant
charge. Check capillary tubes for
blockage. Correct, if necessary.
Over-current protection error can
result due to any of the following:
S Ambient temperature is too high.
Check for locked rotor on the
compressor.
S Check for blocked refrigeration
circuit (capillary tubes for exam­
ple). Correct, if necessary.
S Check for blocked or restricted
outdoor air. Correct, if necessary.
If error is displayed on outdoor
unit, check communications cable /
wire at indoor and outdoor controls
to verify proper connection. See
unit information manual for further
information.
See unit information manual for
further information.