Johnson Controls Unitary Products
17
923178-UTG-B-0114
DESCRIPTION OF EACH CONTROL
OPERATION
Temperature & Current Parameters
• Indoor preset temperature (T
preset
)
• Indoor ambient temperature (T
amb
.)
• Evaporator coil temperature (T
evap
)
• Condenser coil temperature (T
outdoor pipe
)
• Defrost compensation temperature (T
compensation
)
• Outdoor ambient temperature (T
outdoor amb
)
• Measured temperature of outdoor condensing coil under
cooling mode and measured temperature of indoor evapo-
rator coil under heating mode (T
tube
).
• Indoor ambient temperature (T
indoor amb)
Basic Functions
Once energized, the compressor should never be restarted
within less than 3 minutes. In a situation where memory func-
tion is available when energized for the first time, if the com-
pressor is at stop before de-energized, it will re-start without a
3-minute lag. If it has been in operation before de- energized,
the compressor will start with a 3-minute lag. Once started, the
compressor will not be stopped within 6 minutes regardless of
changes in room temperature.
Cooling Mode
1. Cooling Mode Operation
• When T
amb
T
preset
, cooling mode is activated. The indoor
fan, outdoor fan and the compressor will operate simulta-
neously. The indoor fan will run at preset speed.
• When T
amb
T
preset
- 3.6,°F the compressor will stop, the
outdoor fan will stop with a time lag of 60 seconds, and the
indoor fan will run at preset speed.
• When T
preset
- 3.6°F < T
amb
. < T
preset
+ 1.8°F, the unit will
remain at its previous state.
In cooling mode, the four-way valve will be de-energized and
temperature can be set within a range from 61 to 86°F. If the
compressor stops running, the indoor fan and the swing device
will operate at original state.
2. Protection – Cooling Mode
• Antifreeze protection - In cooling and dehumidification
mode, antifreeze protection is activated 6 minutes after the
compressor has started if one of followings occur:
T
evap
35.6 °F, the compressor will operate at reduced
frequency.
T
evap
30.2 °F is detected for a duration of 3 minutes,
the compressor will stop and after 60 seconds, the out-
door fan will stop. In cooling mode, the indoor fan and the
swing motor will remain at the original state.
T
evap
.
42.8 °F and the compressor has remained in
OFF mode for at least 3 minutes, the compressor will
resume its original operation state.
• Total current up and frequency down protection if the fol-
lowings occur:
I
total
16A, the compressor frequency will start to
increase
I
total
17A, the compressor frequency will not increase
I
total
18A, the compressor will run at reduced frequency
I
total
20A, the compressor will immediately stop and the
outdoor fan will stop after 60 seconds
18K & 24K Indoor Heat Pumps
18K
24K
Start cooling
Stop cooling
sor
s
e
r
p
m
o
C
Original working state
Run
Stop
Outdoor fan
Indoor fan
T
preset
T
preset
+3.6
T
amb.
Preset fan speed
6 minutes
6 minutes
3 minutes
ºF
