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18.8 Frost prevention alarm
The internal unit of the air conditioner determines whether to enter the antifreeze mode according to the
respective water temperature probes of Zone1 / zone2 / poor:
Cooling Antifreeze
To prevent the water freezing and damaging the heat exchanger, the microprocessor shuts down the compressor
if the temperature measured by the heat exchanger outlet temperature sensor is less than 3°C. The frost
prevention temperature set point can be modified by an authorized service center only and only after verifying
that the water circuit contains antifreeze. Tripping of this alarm shuts down the compressor but not the pump,
which remains active. To reset normal functions, the outlet water temperature must rise to more than 5°C. Reset
is manual.
When the unit is in shutdown or standby mode, the anti-freezing function is effective
If any condition is met after the corresponding relationship between ambient temperature and inlet and outlet
water temperature is met, start the unit water pump. When the inlet and outlet temperatures of the unit are greater
than 5°C for 1 minute, turn off the water pump and exit the antifreeze mode.
When the water pump can not meet the exit conditions after continuous operation for 10 minutes: that is, the
inlet and outlet temperatures of the unit are less than 5°C, a forced start-up signal is sent to the external unit.
Regardless of whether E28 is started or not and whether there is a two-way valve signal, the external unit is
forced to start-up and run, tset = 25°C (during ambient temperature control, set the water ambient temperature of
25°C and set the mode of the corresponding area). At the same time, E28 receives the "anti freezing" command,
that is, open all electric valves and thermoelectric valves.
18.9
Water flow alarm
The microprocessor provides for management of a water flow alarm controlled by a pressure diference switch
fitted as standard on the appliance to be installed on the water delivery piping.
This safety device may trip after the first 60 seconds of pump operation when the water flow is up to speed.
Tripping of this alarm shuts down the compressor but not the pump, which remains active. To reset normal
functions, the alarm contact must be deactivated for at least 15 seconds.
When electrical current exceeds to setting value and condenser temperature over than 62°C, system will shut
down, but not returns to normal operation until the condenser temperature decreased less than 52°C.
18.10 Oil return control
This control is mainly to recover the refrigerant oil remaining in the indoor unit, in order to prevent the compressor
folding parts from being worn / burned together due to insufficient refrigerant oil in the compressor.
1. Low frequency oil return logic
After start-up, the frequency is less than 35Hz and runs for 1 hour (the frequency is greater than 50Hz for 1
minute, the timing is cleared, and the time is cleared after defrosting (the frequency limit is effective. When the oil
return conflicts with refrigeration and antifreeze, antifreeze takes priority), and the frequency increases to the oil
return frequency of 50Hz and runs for 1 minute (the frequency limit is effective,)
2. High frequency oil return logic:
The compressor operates at 80Hz and above for more than 3 hours (the frequency ≤ 70Hz lasts for 5 minutes
and then counts again). When the maximum frequency drops to 70Hz and operates for 3 minutes, the timing is
cleared.
