Johnson Controls Unitary Products 19
923178-UTG-B-0114
• When T
preset
+3.6°F< T
amb.
< T
preset
+41°F, the system con-
tinues to run normally
• When 71.6°F<T
amb.
<78.8°F, the system continues to run
normally.
2. Protection – Auto Mode
• When the system is running in cooling mode, the protec-
tions described in “Protection - Cooling Mode” apply.
• When the system is running in heating mode, the protec-
tions described in “Protection – Heating Mode” apply.
• When the ambient temperature changes, operation mode
will switch back and forth. Once the compressor is ener-
gized, it will keep running for a minimum of 6 minutes.
COMMON PROTECTION FUNCTIONS AND
FAULT DISPLAY UNDER COOL, HEAT, DRY
AND AUTO MODES
1. Overload Protection
• Cooling Overload
When T
tube
≤ 126⁰F, the system operates normally.
When T
tube
≥ 131⁰F, compressor frequency is not
allowed to increase.
When T
tube
≥ 136⁰F, compressor will run at reduced fre-
quency.
When T
tube
≥ 144⁰F, compressor is de-energized and
the indoor fan will continue to run at preset speed.
Heating Overload
When T
tube
≤ 126⁰F, the system operates normally.
When T
tube
≥ 131⁰F, compressor frequency is not
allowed to increase.
When T
tube
≥ 136⁰F, compressor will run at reduced fre-
quency.
When T
tube
≥ 144⁰F, compressor is de-energized and
the indoor fan will continue to run for about 30 seconds
and stops.
2. High Discharge Temperature Compressor Protection
• When compressor discharge temperature is ≥ 208 ⁰F, com-
pressor frequency is not allowed to increase.
• When compressor discharge temperature is ≥ 217 ⁰F, com-
pressor will run at reduced frequency.
• When compressor discharge temperature is ≥ 230 ⁰F, the
compressor will stop.
• When compressor discharge temperature is ≤ 194 ⁰F and
the compressor has been idle for at least 3 minutes, it will
resume its operation.
3. Communication Fault
If the system fails to receive communication signals for more
than 3 minutes, its operation will stop.
4. Module Protection
• Under module protection mode, the compressor will stop.
• If the compressor remains idle for at least 3 minutes, it will
resume its operation.
• If module protection occurs six consecutive times, the com-
pressor will not be allowed to start again.
5. Overload Protection
• If the overload temperature is over 239 ⁰F, the compressor
will stop and the outdoor fan will stop after 30 seconds.
• If the overload temperature drops below 203 ⁰F, the com-
pressor overload protection is reset.
• If voltage on the DC bus is below 150V or over 420V, the
compressor will stop and the outdoor fan will stop after 30
seconds.
• When voltage on the DC bus returns to its normal value
and the compressor has been idle for at least 3 minutes,
the compressor will resume its operation.
6. Temperature Sensors Faults.
Designation of Sensors Faults
Indoor ambient temperature The sensor is detected to be open-circuited or short-circuited for a continuous 30 seconds.
Indoor tube temperature The sensor is detected to be open-circuited or short-circuited for a continuous 30 seconds.
Outdoor ambient temperature The sensor is detected to be open-circuited or short-circuited for a continuous 30 seconds.
Outdoor tube temperature
The sensor is detected to be open-circuited or short-circuited for a continuous 30 seconds and no detection is
performed within 10 minutes after defrost begins.
Exhaust
After the compressor has operated for 3minutes, the sensor is detected to be open-circuited or short-circuited for a
continuous 30 seconds.
Overload
After the compressor has operated for 3minutes, the sensor is detected to be open-circuited or short-circuited for a
continuous 30 seconds.
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