Control Specification (15/18/24 Class) SiUS04-702
50 Function and Control
4.3 Controls at Mode Changing / Start-up
4.3.1 Preheating Operation
Outline Operate the inverter in the open phase operation with the conditions including the preheating
command from the indoor, the outdoor air temperature and discharge pipe temperature.
Detail Preheating ON Condition
When outdoor air temperature and discharge pipe temperature are below 51ºF, inverter in open
phase operation starts.
OFF Condition
When outdoor air temperature or discharge pipe temperature is higher than 54ºF, inverter in
open phase operation stops.
4.3.2 Four Way Valve Switching
Outline Heat Pump Only
During the heating operation current must be conducted and during cooling and defrosting current
must not be conducted. In order to eliminate the switching sound (as the four way valve coil
switches from ON to OFF) when the heating is stopped, the delay switch of the four way valve must
be carried out after the operation stopped.
Detail The OFF delay of four way valve
Energize the coil for 150 sec after unit operation is stopped.
4.3.3 Four Way Valve Operation Compensation
Outline Heat Pump Only
At the beginning of the operation as the four way valve is switched, acquire the differential pressure
required for activating the four way valve by having output the operating frequency, which is more
than a certain fixed frequency, for a certain fixed time.
Detail Starting Conditions
1. When starting compressor for heating.
2. When the operating mode changes from the previous time.
3. When starting compressor for starting defrosting or resetting.
4. When starting compressor for the first time after the reset with the power is ON.
Set the lower limit frequency to 55 (model by model) Hz for 70 seconds with any conditions 1
through 4 above.
4.3.4 3 Minutes Stand-by
Prohibit to turn ON the compressor for 3 minutes after turning it off.
(except when defrosting)
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