Water Control; Automatic Temperature Adjustment - Hitachi RCUE40AG2 Service Manual

Control System

4.2. Water control

4.2.1. Automatic temperature adjustment

Outlet water temperature of Chiller Unit is detected by Thermistor, and based on this value, compressor ON/
−
OFF and the most suitable capacity is determined.
Possible range of water temperature setting (°C):
−
Cooling –10(option)~15, Heating: 35~55 (outlet water temperature control)
Capacity control : 100~15%, stop
−
The minimum range of temperature adjustment (°C): 0,5
−
Restarting of unit after thermo-OFF is done depending on inlet water temperature.
−
Method of outlet temp detection
In case of standard setting: outlet setting temp 7°C, neutral zone (∆T3) 2°C (change of outlet water temp 7~9°C).
Range of stop temp (∆T1) 1°C (stop temp 6°C), range of restart temp 2°C.
1. Load-up I control at over 10°C (The capacity is changed a lot in order to approximate the target temp.
quickly)
2. Load-up II control at 9~10 °C (The capacity is changed moderately)
3. In neutral zone (9~7°C), load is balanced and performance is not changed.
4. Under neutral zone (below 7°C) load-down control is performed and performance is decreased.
5. Stop temp: Compressor is stopped at 6 °C. The inlet temp of that time is saved.
6. When inlet temp becomes 2°C higher than that of at stop, re-start signal is output and unit is re-started after
at least 3 min guard.
7. Control mode after re-start is the same as listed before.
pag. 52
SMGB0003 rev.0-01/2007
Memorizes the inlet
temperature at Thermo-OFF
and re-start at ∆T2
Between setting temp (Tsc) and
range of neutral zone (∆T3),
capacity control balanced by load is
done to keep the temp steady.
Between setting temp (Tsc) and
range of stop (∆T1), load-down is
performed.
After restart, outlet temp. is detected and
the performance is increased by load-up
operation in order that temp. be closer to
set temp. as earlier as possible.