Si18-201 System control
Main Functions 157
3.30 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 motorized valves' flow rates are corrected so as to
adjust each room unit's heat exchanger temperature and gas pipe temperature (hereafter
referred to as SH) close to the target values.
When SH is higher than average
→
Opens the valve of that room unit
When SH 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. When the liquid pipe temperature is higher than the
heat exchanger temperature, the motorized valve is opened without providing the above control.
(Protection function to prevent rotor dew condensation)
Details 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.
Gas pipe lower-limit temperature = 0.2 × DOA + 1
Outside Temperature Gas Pipe Lower-Limit Temperature
-5 0
01
52
10 3
15 4
20 5
25 6
30 7
35 8
40 9
45 10
0
2
4
6
8
10
12
-20 0 20 40 60
Outside temperature
Gas pipe lower-limit temperature
(M1049)
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