035-20401-001 Rev. A (0904)
Unitary Products Group
11
LOCKOUT MODES
Soft Lockout
The control will cause a soft lockout during the following conditions.
Detailed descriptions of the conditions required for the control to enter
the soft lockout mode are contained in other sections of this document.
1.
High-pressure switch
a.
Two openings within six hours
2.
Low-pressure switch
a.
One opening of the switch for more than five seconds except
under certain conditions.
3.
High discharge temperature (with optional discharge sensor)
a.
Temperature reading exceeds 263F
4.
Low discharge temperature (with optional discharge sensor)
a.
Temperature reading does not reach 90F following timer expi-
ration under certain conditions.
During the soft lockout mode, the control will do the following.
1.
De-energize the compressor
2.
If in heating mode, the control will energize auxiliary heat as if the
outdoor ambient temperature was below the LTCO setting.
3.
Energize the LED and X/L outputs with the appropriate flash codes
4.
Store the appropriate fault code in memory.
The control will reset the soft lockout condition when any of the follow-
ing occur following removal of the fault condition.
1.
Power is cycled to the R or Y1 inputs of the control. This will cause
the soft lockout condition to be reset when the thermostat is satis-
fied or when the thermostat is set to SYSTEM OFF and back to
HEAT or COOL mode.
2.
The TEST terminals are shorted for more than two seconds.
When the soft lockout condition is reset, the control will stop displaying
the fault code and will respond to thermostat inputs normally.
Hard Lockout
If four soft lockouts occur within a twelve-hour period, the control shall
cause a hard lockout condition. These soft lockouts can be caused by
the same or different conditions. The control will function in the same
way during soft and hard lockout conditions. The difference is in the
requirements for resetting the lockout condition. The control will reset
the hard lockout condition when any of the following occur following
removal of the fault condition.
1.
Power is removed from the R input of the control.
2.
The TEST terminals are shorted for more than two seconds.
A hard lockout condition will not be reset when the thermostat is satis-
fied or when the thermostat is set to SYSTEM OFF and back to HEAT
or COOL mode. Power (24 VAC) to the control must be removed and
reapplied.
When the hard lockout condition is reset, the control will de-energize
the LED and X/L outputs and respond to thermostat inputs normally.
Wiring or Setting Related Lockouts
The control will not operate the compressor when the following faults
occur. These faults can be reset using the same methods used to reset
a soft lockout. However, two occurrences of these faults will not cause a
hard lockout condition.
1.
Presence of Y2 thermostat signal without Y1.
2.
Shorted discharge sensor input
3.
Shorted bonnet sensor
4.
Shorted or open liquid line or outdoor ambient sensor
5.
Defrost curve jumper error
If a compressor wiring error is detected, the control will not operate the
compressor. Once the compressor wiring error has been detected,
power (24 VAC) must be cycled to the control for the control to sense
the wiring change and clear the lockout condition.
DEFROST OPERATION
General
The control maintains proper airflow through the outdoor coil during
heating operation by melting frost and ice that may form on the coil.
Frost may accumulate unevenly in different sections of the coil because
of the arrangement of the refrigeration circuit within the coil. The control
may initiate a defrost cycle even when the coil is not completely cov-
ered with frost. This is normal operation.
The control regulates the defrost operation of the heat pump based on
accumulated compressor run time, outdoor coil temperature, and out-
door ambient temperature. The control will cause the unit to operate in
the normal heating mode until it determines that a defrost cycle is
needed.
All defrost timings are based on accumulated compressor run time.
Operation
The defrost mode is equivalent to the cooling mode except that the out-
door fan motor is de-energized. The control shall do the following to ini-
tiate a defrost cycle.
•
De-energize the outdoor fan
•
Energize the crankcase heater
•
Energize the reversing valve
•
Energize the auxiliary heat outputs based on the system configu-
ration
•
Energize Y2 OUT terminal if not already energized
•
Begin the maximum defrost cycle length timer
If the call for heating (Y1) is removed from the control during the defrost
cycle, it will terminate the defrost cycle and de-energize the compres-
sor. The control will also stop the defrost cycle length timer but not reset
it. When the control receives another call for heating, it will restart the
defrost cycle and the timer at the point at which the call for heating was
removed. This will happen only if the liquid line temperature conditions
allow defrost to occur.
