Daikin BPMK928B42, Service Manual

Page: 168 / 410

Si18-201 System control
Main Functions 155
3.29 Gas Pipe Isothermal Control in Cooling Operation
Purpose of the
Function This function ensures appropriate refrigerant distribution when many room units are operating in
the cooling mode.
Outline The gas pipe temperatures of operating room units are detected by the gas pipe thermistors,
and the motorized valves' flow rates are corrected so as to equalize the temperatures of the gas
pipes.
When gas pipe temperature is higher than average
→
Opens the valve of that room unit
When gas pipe temperature is lower than average
→
Closes the valve of that room unit
However, the closing operation is restricted to prevent the valve operation that results in a flow
rate that exceeds a certain level at one time.
(Protection function to prevent rotor frosting)
Details The gas pipe temperature is detected at every sampling (40 SEC) operation of the gas pipe
isothermal control, and average value DGAV of each gas pipe temperature is obtained.
In order to prevent dew condensation in the connection pipe, when DGAV < Gas pipe lower limit
temp., DGAV = Gas pipe lower limit temp.
Gas pipe lower limit temp. = 0.2 × DOA + 1
0
2
4
6
8
10
12
-20 0 20 40 60
Outside air temperature
Gas pipe lower-limit temperature
(M1048)