A.O. Smith AHD 290 - Manual (Page 60)

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2.3 Operation safety
High-pressure switch:
To prevent the compressor from exceeding its range of operation, there is an
integral high-pressure switch, which interrupts when the pressure is 20 bar in the
cooling unit. Activate the red reset button once the cause of the error has been
identified. When the high-pressure switch interrupts, the red LED will flash until
the reset button manually or the pressure has fallen to 15 bar or the cause of
error has been identified. When the high-pressure switch interrupts, the red light
will flash until the reset button on the pressure switch is activated. In order to
prevent a repetition of a pressure switch error, the water may be set 2-3°C lower.
Safety breaker for electrical heating element
If an error occurs at the heater, the safety breaker trips and stops the heater in
order to prevent the tank from being overheated.
When working on the heat pump, always make sure the power
supply is disconnected. Any work on this unit may only be
carried out by trained personnel!
2.4 Warnings
High-pressure switch:
When the pressure switch trips, the red light on the display will light until the pres-
sure switch is reset.