Daikin BPMK928B42, Service Manual

Page: 172 / 410

Si18-201 System control
Main Functions 159
3.31 SC Control in Heating Operation
Purpose of the
Function This function ensures appropriate refrigerant distribution when room units are operating in the
heating mode.
Outline The function serves the following two main purposes.
1) Appropriate refrigerant distribution to each room unit
In the case of heating SC control 2, the motorized valves of only operating room units are
regulated. In the case of heating SC control 1, the motorized valves of all room units
including non-operating units are operated.
2) Determination of the location (accumulator, receiver, non-operating room units, operating
room units) to collect refrigerant in accordance with the connection pattern (extended piping,
single-room connection).
"
To ensure appropriate refrigerant distribution to each room unit, each room unit's liquid pipe
temperature and heat exchanger intermediate temperature are detected, and the motorized
valve opening degrees are corrected so SC reaches the target SC (determined based on the
supply capacity and the temperature difference between the discharge pipe temperature and
target discharge pipe temperature).
When SH is higher than target SC
→
Opens the valve of that room unit
When SH is lower than target SC
→
Closes the valve of that room unit
However, the valve operating amount is restricted to prevent a flow rate that exceeds a
certain level at one time.
(For improvement of stability and convergibility performance)
"
The determination of the location (accumulator, receiver, non-operating room units,
operating room units) to collect refrigerant is determined in accordance with the connection
pattern (extended piping, single-room connection).
Non-operating room unit EV : Closed
Operating room unit EV : Open
Outdoor unit EVG : Open
Outdoor unit EVL : Closed
Non-operating room unit EV : Closed
Operating room unit EV : Closed
Outdoor unit EVG : Closed
Outdoor unit EVL : Closed
Discharge pipe temperature < Target discharge temperature
(Wet operation tendency)
SC > Target SC
(High SC provided)
SC < Target SC
(No SC provided)
Close
Refrigerant collected in non-operating
and operating room units
Non-operating room unit EV : Open
Operating room unit EV : Open
Outdoor unit EVG : Open
Outdoor unit EVL : Open
Non-operating room unit EV : Open
Operating room unit EV : Closed
Outdoor unit EVG : Closed
Outdoor unit EVL : Open
Discharge pipe temperature > Target discharge temperature
(High SH provided)
Open
Refrigerant collected in
operating room units
Refrigerant collected
in receiver
Refrigerant collected
in accumulator
(M1056)
Close
Open