In order to set the desired temperature difference threshold values, a programming mode needs to be entered. This is done by pressing the "Set" button and holding it down for 3 seconds. On entering the programming mode, DTE1 draws a "Blank screen" symbol on its display, as shown in the next drawing.

As soon as the symbol dissapears, user is able to set the START threshold value by pressing "+" or "-" button. After START threshold value was successfully set, a "Set" button should be pressed down briefly, after which the STOP threshold value can be set. After it was set, again the "Set" button should be pressed briefly, which signals the DTE1 that its user is satisfied with threshold value settings. While in programming mode, DTE1 blinks either Start or Stop LED on its housing, signalling which threshold value is currently being set. This is shown in the next two drawings.

START threshold value can be set in range 1'C - 99'C, while STOP threshold value can be set in range 1'C - 98'C. Please note that DTE1 prevents the ΔT_STOP temperature difference value to be set higher than (ΔT_START - 1'C). This is done intentionally as otherwise automatic system regulation would make no sense.

On exiting the programming mode, DTE1 draws the "Blank screen" symbol for a few seconds again. If threshold setting is interrupted at any stage, i.e. if no button is pressed for a minute, DTE1 automatically exits the programming mode and makes no changes to the previously set threshold values. This feature can be used to periodically check the threshold velues set, for example if the user forgot the current settings.

DTE1 provides means to manualy override the internal control logic. Should the user want water to keep circulating the system constantly without interruptions, all one needs to do is to press the "+" key down for a few seconds - a word "On" will be displayed on the display and the pump will be immediately turned constantly on. DTE1 remembers manual override being set by the user so that if sometimes later a power blackout occurs, it will turn the pump on as soon as it estimates that the grid voltage is stable enough for the reliable system operation.

Simmilar goes in case the user wants the pump to be unconditionally turned off, with the exception that the "-" key should be pressed down for a few seconds in this case. The word "Off" appears on the display, the pump turns off and stays that way. Manual override modes are not normal device operation modes but might be useful should for example a sensor failure occur or a maintenance intervention should be done.

Exiting manual override modes is done by pressing down the "Set" key for a few seconds. This activates the programming mode enabling the user to check the previously set temperature difference threshold values and possibly to set the new ones. After tihs, DTE1 will continue normal operation in automatic mode.