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43
AST 14 C 258/00
If at the minimum power the
temperature read by the DHW
probes continues to increase, at
a certain point the boiler
switches off.
PLATE DHW MODULATIONv
(version KC only, P3=1)
Upon an operation request in plate DHW mode with boiler in “DHW” or “DHW+HEATING”,
if the water temperature read by the DHW probe is lower than the set-point value + 3°C, a
consensus is given to the automatic flame control section to start the burner ignition
sequence.
At the end of such sequence the power provided to the burner corresponds to the ignition
power (P6), and then the power to the burner corresponds to the flame modulation value.
The DHW temperature is constantly read, and the ramp is interrupted when reaching the
flame modulation point with a PID type action, until reaching and maintaining the DHW
temperature pre-selected on the boiler or through the remote control.
During the first 20 seconds when the DHW is being drawn, to avoid boiler continuous
“switch on/off", the maximum temperature allowed by the DHW probe to switch off the
burner is set to 15°C higher than the set-point, whereas to switch it on again the
temperature must fall below the set-point + 8°C.
In case of poor thermal yield by the plate exchanger due to possible clogging and
consequent overtemperature of the primary body, another PID type adjustment of the flow
is added to the DHW modulation. Such operation occurs at a flow temperature higher than
81°C and disables when the flow temperature falls below 75°C.
In presence of double modulation, the gas flow rate supplied to the burner corresponds to
the lowest modulation value between the two PID type calculated actions.
During the DHW mode, the pump is powered and the electric diverting valve is in DHW
position, whereas the multifunction relay is in the rest condition.
DHW Output power
Time
