Rinnai REU- A1620WD-IND Operation And Installation Manual page 13

Lock function
To prevent tampering and increase the safety level of the product,
especially for children, it is possible to lock the control panel.
To lock the panel it is necessary to press, and keep pressed for about
five seconds, the 'Priority' keys and the key to increase the temperature
(up arrow) (Fig.1). To unlock the command it is sufficient to repeat the
procedure of blocking commands.
When the panel is locked, the display shows 'LOC' (Fig.2) alternating with
the selected temperature on the display. All connected commands will be
locked and will display the same flashing text.
Fig. 1
Fig. 2
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