Function - IVT 12KHR-N Service Manual

[3] FUNCTION

1. Function
1.1. Restart control
Once the compressor stops operating, it will not restart for 180 sec-
onds to protect the compressor.
Therefore, if the operating compressor is shut down from the remote
control and then turned back on immediately after, the compressor will
restart after a preset delay time.
(The indoor unit will restart operation immediately after the ON switch
is operated on the remote control.)
Compressor operation
Compressor ON
Compressor remains OFF
for 180 seconds
OFF operation on
ON operation on
remote control
remote control
1.2. Cold air prevention control
When the air to air heat pump starts up in heating mode, the indoor
unit fan will not operate until the temperature of the indoor unit heat
exchanger reaches about 23 C in order to prevent cold air from blow-
ing into the room.
Also, the indoor unit fan operates at low speed until the temperature of
the indoor unit heat exchanger reaches about 38 C so that people in
the room will not feel chilly air flow.
Indoor unit heat exchanger temperature
Set fan speed
38
Indoor unit fan at low speed
23
Indoor unit fan in non-operation
1.3. Indoor unit heat exchanger freeze prevention control
If the temperature of the indoor unit heat exchanger remains below
0 C for 4 consecutive minutes during cooling or dehumidifying opera-
tion, the compressor operation stops temporarily in order to prevent
freezing.
When the temperature of the indoor unit heat exchanger rises to 2 C
or higher after about 180 seconds, the compressor restarts and
resumes normal operation.
1.4. Outdoor unit 2-way valve freeze prevention control
If the temperature of the outdoor unit 2-way valve remains below 0 C
for 10 consecutive minutes during cooling or dehumidifying operation,
the compressor operation stops temporarily in order to prevent freez-
ing.
When the temperature of the 2-way valve rises to 10 C or higher after
about 180 seconds, the compressor restarts and resumes normal
operation.
Compressor can
turn ON
Compressor ON
35
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1.5. Indoor unit overheat prevention control
During heating operation, if the temperature of the indoor unit heat
exchanger exceeds the indoor unit heat exchanger overheat preven-
tion temperature (about 45 to 54 C) which is determined by the operat-
ing frequency and operating status, the operating frequency is
decreased by about 4 to 15 Hz. Then, this operation is repeated every
60 seconds until the temperature of the indoor unit heat exchanger
drops below the overheat protection temperature.
Once the temperature of the indoor unit heat exchanger drops below
the overheat protection temperature, the operating frequency is
increased by about 4 to 10 Hz every 60 seconds until the normal oper-
ation condition resumes.
If the temperature of the indoor unit heat exchanger exceeds the over-
heat protection temperature for 60 seconds at minimum operating fre-
quency, the compressor stops operating and then restarts after about
180 seconds, and the abovementioned control is repeated.
1.6. Outdoor unit overheat prevention control
During cooling operation, if the temperature of the outdoor unit heat
exchanger exceeds the outdoor unit heat exchanger overheat preven-
tion temperature (about 55 C), the operating frequency is decreased
by about 4 to 15 Hz. Then, this operation is repeated every 60 sec-
onds until the temperature of the outdoor unit heat exchanger drops to
about 54 C or lower.
Once the temperature of the outdoor unit heat exchanger drops to
about 54 C or lower, the operating frequency is increased by about 4
to 10 Hz every 60 seconds until the normal operation condition
resumes.
If the temperature of the outdoor unit heat exchanger exceeds the out-
door unit heat exchanger overheat protection temperature for (120 sec
: outdoor temperature 40 C
at minimum operating frequency, the compressor stops operating and
then restarts after about 180 seconds, and the abovementioned con-
trol is repeated.
1.7. Compressor overheat prevention control
If the temperature of the compressor exceeds the compressor over-
heat prevention temperature (110 C), the operation frequency is
decreased by about 4 to 10 Hz. Then, this operation is repeated every
60 seconds until the temperature of the compressor drops below the
overheat protection temperature (100 C).
Once the temperature of the compressor drops below the overheat
protection temperature, the operating frequency is increased by about
4 to 10 Hz every 60 seconds until the normal operation condition
resumes.
If the temperature of the compressor exceeds the overheat protection
temperature (for 120 seconds in cooling operation or 60 seconds in
heating operation) at minimum operating frequency, the compressor
stops operating and then restarts after about 180 seconds, and the
abovementioned control is repeated.
1.8. Startup control
When the air to air heat pump starts in the cooling or heating mode, if
the room temperature is 2 C higher than the set temperature (in cool-
ing operation) or 3.5 C lower (in heating operation), the air to air heat
pump operates with the operating frequency at maximum. Then, when
the set temperature is reached, the air to air heat pump operates at the
operating frequency determined by fuzzy logic calculation, then enters
the normal control mode after a while.
12KHR-N
60 sec : outdoor temperature < 40 C)