Daikin E Series, Service Manual

Page: 112 / 453

SiAU18-715 BP Unit Control
Function 99
6.3 SH 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 heat exchanger temperatures and gas pipe temperatures of operating room units are
detected by the gas pipe thermistors, and the electronic expansion valves' flow rates are
corrected so as to adjust the difference between heat exchanger temperature and gas pipe
temperature of each room unit (hereafter referred to as SH) close to the target values.
When SH is higher than target value
→
Opens the valve of that room unit
When SH is lower than target value
→
Closes the valve of that room unit
When the liquid pipe temperature is lower than the heat exchanger temperature, the electronic
expansion valve is opened more than normal opening.
(Protection function to prevent rotor dew condensation)
The gas pipe temperature and indoor heat exchanger temperature are detected at the time of
every sampling time of 40 sec for the cooling SH control.
In order to prevent dew condensation in connection pipe, gas pipe lower-limit temperature is set
as follows.
Outdoor Temperature Gas Pipe Lower-Limit Temperature
-5 -22
0 -17
5 -12
10 -6
15 -1
20 4
25 8
30 8
35 8
40 8
45 8
0
2
4
6
8
10
12
-20 0 20 40 60
Outdoor air temperature
Gas pipe lower-limit temperature
(Q0378)
Gas pipe lower-limit temperature = × DOA - 17 (however 8ºC or lower)
DOA:Outdoor air temperature
240
256