System control Si18-201
152 Main Functions
3.28 BP Unit Motorized Valve Control
Purpose of the
Function
This function provides instructions regarding the absolute flow rate, relative flow rate and fully
closing from the outdoor unit to the BP unit in order to ensure outdoor unit compressor safety
and optimum refrigerating cycle of the system.
When the specification of the BP unit or outdoor unit is changed, the air flow rate is used as the
transmission data to maintain compatibility.
With the transmission a permit/prohibit flag for each distribution control in the BP unit, the
distribution control startup timing is controlled by the outdoor unit.
3.28.1 BP Unit Motorized Valve Control at Startup and During The Number
of Operating Room Units Change
Outline Heating operation startup under low outside air temperature
To ensure sufficient oil level.
To prevent refrigerant flowing noise in indoor units.
To improve heating operation startup performance.
The motorized valve is moved slightly in the closing direction.
In cooling operation
The valve opens slightly more than at the stable position to prevent rotor dew condensation.
3.28.2 BP Unit Motorized Valve Control During Frequency Change
This function improves the convergibility and stability of refrigerating cycle when the frequency
varies significantly.
Outline When the target frequency (FMK) fluctuates as much as the specified frequency range for a
certain time duration (10 sec) during discharge pipe temperature control, the discharge pipe
temperature control is stopped and the target motorized valve opening is adjusted according to
the amount of frequency change.
3.28.3 Motorized Valve Flow Rate Restriction
This function prevents the deviation from the motorized valve specification range by restricting
the motorized valve flow rates of the operating and non-operating room units during compressor
operation. It also prevents the generation of abnormal noise such as refrigerant flowing sound
by restricting the circulation of refrigerant according to the operating conditions (unit ON/OFF) of
room units.
Outline Restriction of motorized valve opening degrees of operating room units;
... Restriction of maximum and minimum flow rates based on constant
Restriction of motorized valve opening degrees of non-heating room units;
... Restriction of minimum flow rate based on constant
... Maximum flow rate determined based on flow rates of operating room units
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