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When the unit is switched on (or when it is reset), and where no heat has been requested, the system runs
through the following procedure:
●
5 second safety pause
●
3-way valve activated for 15 seconds
●
circulator activated for 60 seconds
●
circulator and 3-way valve switched off
This cycle is run every 24 hours and 24 hours after the last heat request. The above operations ensure that the
components are put in motion at least once a day.
HEATING
The heating start-up cycle, after a period of inactivity, is as follows:
●
3-way valve activated for 15 seconds
●
pump activated
●
air pressure switch contacts checked (they must be closed)
●
fan switched on
●
when heat is requested pre-ventilation begins
●
ignition transformer switched on and gas valve opened
●
sif flame detection reveals normal operation the fan runs for a few seconds at maximum power and then
modulation begins
When heat is no longer requested the burner is switched off while the pump continues to run for 3 minutes
(post-circulation time). The 3-way valve is then disactivated.
If the flame is not detected the pre-ventilation/ignition cycle is repeated after a set safety period has elapsed
(repeated up to 3 times, after which the unit is shut down).
HOT WATER PRODUCTION
When hot water is requested the 3-way valve switches immediately to the hot water circuit. When the burner
is switched off the pump continues running for another two minutes after which it shuts down. A hot water
request is detected by a temperature sensor on the hot water circuit heat exchanger; this trips the hot water
production system when the sensor-detected temperature is lower than the phase n
°
1 setting.
Modulation takes place immediately and proceeds as a function of boiler water return temperature.
When producing hot water, the burner goes out when the sensor-detected temperature exceeds set temperatu-
re.
DUAL FUNCTION (HOT WATER + HEATING)
If there is a request for hot water when heating is in progress, the 3-way valve diverts the water flow towards
the hot water heat exchanger (hot water has precedence over heating). When hot water is no longer required
the burner goes out and the pump continues running for another two minutes, then stops. The three-way valve
then diverts the water flow back to the heating circuit.
The pump is then restarted and the heating function put back into operation.
OPERATION
