The operating program will be stored in non-volatile
memory (EPROM) to eliminate chiller failure due to AC
power failure/battery discharge. Programmed setpoints
shall be retained in lithium battery backed RTC memory.
6.8
Protection and Safety Devices
Defrost System (YCAA-H units only)
To prevent excessive ice formation on the air cooled
condenser coils during heat pump operation, YCAA-H
units are provided with an automatic defrost system.
This system is integrated in electronic control system
and is a time/temperature unit which switches operating
mode from heating to cooling whenever the temperature
(sensed by a probe at the coil inlet) drops below
approximately -4°C.
During the defrosting cycle, the compressor operates
normally but the electric fan are shut off. Defrosting
cycle is automatically interrupted when coil is de-iced,
and the unit returns to heating mode.
Both circuits are defrosted simultaneously.
Low Water Temperature Protection
Units are provided with low water temperature
protection. Protection consists of an electric resistance
in contact with refrigerant/water heat exchanger which
is activated (even with machine off) when water
temperature drops below 4°C, and a low water
temperature alarm which also stops the machine if
outlet water temperature goes below 4°C. During the
cold season, it is advisable to drain water from lines so
as to prevent damage resulting from ice in the water
circuit lines.
If it is not possible to drain the lines, do not turn off the
power supply to the unit, so that the anti-freezing
resistance (which functions to -3°C) can switch on when
necessary.
Compressor Protection
Compressors are provided with a housing oil heater to
prevent excessive oil thinning in the compressor
housing from impairing lubrication with the consequent
risk of seizure.
Compressor motor windings are also provided with
thermal protection.
Flow Switch
To ensure correct operation, it is necessary to install a
flow switch which prevents unit from operating if there is
insufficient water circulation.
Follow the manufacturer's instructions
carefully when installing flow switch.
The flow switch should be installed on circulation pump
delivery before the unit inlet and on a straight, horizontal
section of line away from bends, valves or other items
which could interfere with water flow upstream or
down-stream of flow switch.
Stepless Fan Speed Regulation
An electronic stepless fan speed regulation device is
fitted to enable operation with outside air at
temperatures down to -5°C with standard control or
-18°C with ISN control.
Water Differential Pressure Switch
The switch stops the unit if it does not detect a sufficient
pressure drop on the heat exchanger.
(09/03)
035B09012-100 Rev. 4
6
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5
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