Johnson Controls Unitary Products
13
923212-UTG-A-0113
DESCRIPTION OF EACH CONTROL
OPERATION
System Basic Functions
Cooling Mode
If the compressor is not running and one of the indoor units
makes a call for cooling, the electronic expansion valve, the
outdoor fan and the compressor start operating. When a call for
cooling is satisfied, the compressor stops immediately and the
outdoor fan stops running after 1 minute. In cases when some
indoor units have satisfied the cooling setpoint temperature and
some have not, the compressor does not stop running. It
adjusts to a lower frequency. For the indoor unit with no cooling
requirement, the corresponding electronic expansion valve
closes to OP.
1.
Cooling Mode Switching to Heating Mode:
When the unit
transfers to heating mode, the 4-way valve is energized after
the compressor stops for 2 minutes. The other components
react the same way described in Cooling Mode section.
When the switch occurs, the 4-way valve closes.
2.
Outdoor Fan in Cooling Mode:
Once the compressor starts
running, the outdoor fan follows after 5 seconds delay. The
outdoor fan runs at high speed for the first 3 minutes then it
will adjust to run at set speed. The fan will run at every speed
for at least 80 seconds. When the number of running indoor
units is changed, the outdoor unit will run according to sec-
tions 1.3.5.1 and 1.3.5.2. When the compressor stops, the
outdoor fan continues to run at current speed and stops after
1 minute delay.
Dry Mode
1. The dry conditions and process are the same as those in
cooling mode;
2. The status of 4-way valve: closed;
3. The temperature setting range: 61 °F ~ 86 °F;
Heating Mode
1. Heating Mode:
• When one of the indoor units calls for heating operation,
that indoor unit starts heating operation.
• When all the indoor units satisfy heating conditions, the
compressor stops and the outdoor fan stops 1 minute after.
• When some of the indoor units satisfy heating conditions
and other don't, the compressor reduces its frequency
immediately and operates according to the required fre-
quency load.
• When heating mode switches to cooling mode (or dry
mode) or fan mode, the compressor stops and the power of
4-way valve is shut off 2 minutes after, then the outdoor fan
stops 1 minute later. The 4-way valve stays energized.
2.
Outdoor fan in heating mode:
The outdoor fan starts 5 sec-
onds before the start of the compressor. It will run at its max-
imum speed for 40 seconds. The fan will run at every speed
for at least 80 seconds. When the compressor stops, the out-
door fan stops 1 minute later.
3.
Defrosting function:
When defrost conditions are met, the
compressor stops, the electronic expansion valves of all
indoor units are wide open, the outdoor fan stops 40 seconds
after the compressor is de-energized, the 4-way valve
reverses direction of the refrigerant flow, which is followed by
the start of the compressor. The defrost timer is initiated and
the frequency of the compressor increases to reach the
defrost frequency.
4.
Oil-returned in heating mode:
Oil-return happens when the
system has been operating at low frequency for a long time.
When this occurs, H1 will be displayed on the indoor unit.
The oil return timer in heating mode is 5 minutes.
Fan Mode
When the system is in fan mode operation, the compressor, the
outdoor fan and the 4-way valve are de-energized. Tempera-
ture setting range for fan mode is between 61 °F and 86 °F.
Protection Functions
Mode Conflict Protection of indoor unit
When different indoor units have different mode settings, the
system will run as follow:
• The mode of the first operating indoor unit is the basic
mode. This operating mode is compared to the mode of the
other indoor units to determine if there is a conflict (cooling
mode (dry mode) in conflict with heating mode).
• Fan mode in conflict with heating mode. In this case, the
heating mode is the basic mode no matter what mode was
initiated first.
1. Overload Protection
• Cooling Overload
When T
tube
≤
126
⁰
F, the system operates normally.
When T
tube
≥
131
⁰
F, compressor frequency is not
allowed to increase.
When T
tube
≥
136
⁰
F, compressor will run at reduced fre-
quency.
When T
tube
≥
144
⁰
F, compressor is de-energized and
the indoor fan will continue to run at preset speed.
Heating Overload
When T
tube
≤
126
⁰
F, the system operates normally.
When T
tube
≥
131
⁰
F, compressor frequency is not
allowed to increase.
When T
tube
≥
136
⁰
F, compressor will run at reduced fre-
quency.
When T
tube
≥
144
⁰
F, 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
⁰
F, com-
pressor frequency is not allowed to increase.
• When compressor discharge temperature is
≥
217
⁰
F, com-
pressor will run at reduced frequency.
• When compressor discharge temperature is
≥
230
⁰
F, the
compressor will stop.
• When compressor discharge temperature is
≤
194
⁰
F 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
⁰
F, the compressor
will stop and the outdoor fan will stop after 30 seconds.
• If the overload temperature drops below 203
⁰
F, 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
