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76
AST 14 C 257/00
Maximum flow and return deviation check function
(E80 shutdown)
This check is carried out before each burner ignition request different from the
instantaneous DHW.
After pump activation, wait 10 seconds and then check the temperature differential which
must be between the range specified below.
û Tmin < ( Tflow – Treturn – û T_Offset ) < û Tmax
where
û Tmin:
minimum differential value (-8°C)
û Tmax:
maximum differential value (+8°C)
Tflow:
temperature read by the flow probe
Treturn:
temperature read by the return probe
û T_Offset:
probe error differential value (~ 0°C)
When the calculated û T falls within the specified range, the burner receives the
authorisation to ignite. If this does not occur within 60 seconds, the check system forces
boiler shutdown with consequent display of the E80 error (resettable by the user).
During the E80 shutdown, the fan carries out a 6-minute post-ventilation cycle, and the
boiler pump enables its post-circulation function with diverting valve in the position relevant
to the type of request. The multifunction relay performs a post-circulation cycle if it was
energised before the shutdown.
Water flow check function
(E81, E82, E83 and E84 shutdown)
Such function is active only with the burner ON, and constantly monitors the water flow in
the primary exchanger.
For correct boiler operation, the minimum flow rates must comply with the values specified
below.
Output
Flue gas
side
m odules
Water side
m odules
Guaranteed
w ater flow rate
[ kW]
[l/h]
24kW 3+1 2+2
400
28 kW
4+1
3+2
600
32 kW
5+1
3+3
600
This check is based on the difference (û T) between the flow and the return temperatures
according to the fan power. If this difference exceeds the minimum threshold allowed the
burner shuts down.
There are intervention thresholds at different flow rates that progressively reduce burner
operation time at specific switching on/off time.
The intermittence times (ON-OFF) activated during heating, anti-freeze or chimney-sweep
requests differ from those activated during the plate DHW or water heater modes.
