•
The CN17 ON/OFF port is used for receiving the control signal of the solar energy water heating system, this
signal must be a potential free switch signal. When the unit is sending a closing signal, the system will be
blocked for operation and cannot open to heat; when the sending an open circuit signal, the system will be
activated for operation, and the unit will operate according to the preset condition.
•
The CN18 feedback port is used to send "open/stop" feedback to the solar thermal control. The feedback con-
sists of high and low level signals. When the terminal is low level (0V) for outlet, it means that the unit is in
active state; when the terminal is high level (5V) for outlet, it means that the unit is blocked for operation.
Caution! If the water temperature from the solar thermal get overheated, it may trig the built-in
temperature function in the unit.
The automatically reset temperature protection switch (TCO) is triggered when exceeding an operating tempera-
ture of 78°C. This will automatically reset when the temperature get below 78°C.
The manually reset temperature switch is trigged when exceeding a water temperature of 85°C. This switch must
be reset manually.
In either case, one of the above protective functions are triggered, the unit will shutdown, the main supply will be
cut, and the unit will completely shut-off. If integrating the unit with a solar thermal system, take protective
actions to avoid overheating of the unit.
14 – Installation, Service and User Manual VMGFK202
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