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The following alarms are possible:
water heater freezing danger according to too low return heat medium temperature;
water heater freezing danger according to too low air temperature downstream from the
water heater;
low return heat medium temperature (cold start is disabled);
low exhaust air temperature to prevent the heat exchanger from freezing;
emergency system shutdown on the signal from fire fighting system.
In case of any listed above alarms the control system stops the fans and the light indicator Alarm,
refer fig. 13 on the controller panel is on. Each alarm code is explained on the controller display, refer
table 3.
All the alarms (except for the alarm U2, low return heat medium, to prevent the water heater from
freezing) are reset automatically during the system restart.
The control system sends an alarm signal whenever water coils freezing danger exists, namely:
Alarm U2 appears if return heat medium temperature is below the set point, Q-04 parameter
(refer the table 3, factory s5°C). The parameter is adjusted in the PLC menu.
Alarm U1 appears if air temperature downstream from the water heater drops below
the minimum set level +3ºС. In this case the freeze protection thermostat is activated.
In case of U1 and U2 failures the light indicator on the control panel is turned on. Simultaneously the
fans shut down and the heat medium regulating valve is 100% open to provide full heat medium
stream through the water heating coils.
After alarm signal the circulation pump is turned on no matter of its previous operation mode.
After the fault is identified and removed unblock the alarm by pressing the start button (1) on the
control panel.
The freezing danger, alarm U1 is detected by the thermostat TS1 located downstream from the
water heating coil. The freezing danger, alarm U2 is detected by TE3 return medium temperature
sensor. Alarm appears if return heat medium temperature or air temperature downstream from the
water heating coils drops down below the set parameter. The freezing danger is detected both in
winter and summer modes.
U3 alarm (Underheating) appears if the return heat medium temperature at the end of the
heating cycle in winter mode is below the set point, Q-03 parameter adjusted from the PLC menu, the
factory setting is +40°C. As this alarm is detected the fans cannot be started and the light indicator
«Alarm» on the control panel is turned on, see fig. 13. To reset underheating alarm, restart the unit. The
light indicator «Alarm» on PLC is turned off and the fans are restarted.
