Computherm Q4Z Operating Instructions Manual page 13

Pressing the "A/M" button separates the thermostats
from the zone controller. In this case, the boiler and the
heating zones can only be started manually, without any
temperature inspection. The continuously illuminated blue
LED indicates automatic (thermostat-controlled) mode,
while its switched off state indicates manual mode. This
function might be needed for example, if the battery has
run down in one of the thermostats. In manual mode,
pressing the 1, 2, 3, and/or 4 buttons of the zone controller
unit turns on or off the boiler and opens/closes the zone
valves associated with the heating zones. The operation of
a heating zone is indicated by the illuminated red LED light
associated with it. By pressing the "A/M" button again or
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