Sh Control In Cooling Operation - Daikin RMXS-L Series Service Manual

SiUS181631EA
6.3

SH Control in Cooling Operation

Outline This function ensures appropriate refrigerant distribution when many indoor units are operating in
cooling operation.
Details The heat exchanger temperatures and gas pipe temperatures of operating indoor units are
detected by the gas pipe thermistors, and the flow rates of the electronic expansion valve are
corrected so as to adjust the difference between the heat exchanger temperature and gas pipe
temperature of each indoor unit (hereafter referred to as SH) close to the target values.
When SH is higher than target value → Opens the valve of that indoor unit
When SH is lower than target value → Closes the valve of that indoor 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 with a sampling
time of 40 seconds for the cooling SH control.
In order to prevent dew condensation in the connection pipe, the gas pipe lower-limit temperature is
set as follows.
Notes: 1. In SkyAir models, the indoor units are equipped with distribution capillary tubes; as a result, the
2. In SkyAir models, the heat exchanger intermediate position is provided on the liquid connection
Functions and Control
Gas pipe lower limit temperature (˚C) =
(Gas pipe lower limit temperature (˚F) =
Gas pipe lower limit temperature ≤ 8˚C (46.4˚F)
(˚F) (˚C)
50 10
46.4 8
41 5
32 0
23 –5
14 –10
5 –15
–4 –20
–13 –25
–5 0
23 32
heat exchangers may superheat even when the condition is met.
pipe side; as a result, superheated condition is difficult to detect.
240
× outdoor temperature (˚C) – 17
256
240
× outdoor temperature (˚F) – 28.6)
256
5 10 15 20 25
41 50 59 68 77
Outdoor temperature
Branch Provider (BP) Unit Control
30 35 40 45 (˚C)
86 95 104 113 (˚F)
(R19087)
71