Slant/Fin VGH-299-CH, Installation And Service Manual

Page: 79 / 128

E93.1601EN032.C VGH installation manual 79
12.9.5 A
NTI
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LEGIONELLA PROTECTION
Anti-Legionella protection is enabled for DHW modes with an external tank with a sensor (DHW Mode 1).
To prevent legionella a special function is implemented in the software.
When DHW Mode 1 is selected the Anti-Legionella protection will be checked on the T_DHW_Out sensor.
At least once every 168 hours (7 days) the Anti_Legionella_Sensor must reach a temperature above
Anti_Legionella_Setpoint for a time specified by Anti_Legionella_Burn_Time.
If 7 days have passed and these conditions are not met, the boiler is forced to heat-up the system for Anti-
Legionella. When the Anti_Legionella_Sensor temperature is below Anti_Legionella_Setpoint the control switches
ON the circulators, when the Anti_Legionella_Sensor temperature is above Anti_Legionella_Setpoint
plus 9 °F
( plus 5 °C) the control stops the circulators.
When DHW Mode 1 is selected the boiler setpoint will be at
Anti_Legionella_Setpoint
plus DHW_Store_Supply_Extra.
If the supply temperature drops below the Boiler_Setpoint the boiler is started as well. The boiler is PID controlled
towards the Boiler_Setpoint. When the supply temperature rises above
Boiler_Setpoint
plus DHW_Supp_Hysterese_Up the boiler is switched OFF.
When the Anti_Legionella_Sensor is above Anti_Legionella_Setpoint
minus 5.4 °F ( minus 3 °C) for
Anti_Legionella_Burn_Time the controller goes into post circulation and ends the Anti-Legionella demand. When
the controller has powered up, the Anti_Legionella_Sensor temperature must reach a temperature of
Anti_Legionella_Setpoint (for Anti_Legionella_Burn_Time) within 2 hours, otherwise the boiler is forced into Anti-
Legionella demand.
Every time an Anti-Legionella demand has ended the Anti_Legionella_Active_Counter is incremented to indicate
how many Anti-Legionella actions have been performed. Also the
Anti_Legionella_Wait_Time is started to delay
the next Anti-Legionella cycle.
The Anti-Legionella demand has priority over any DHW and CH demand. However, when the Anti-Legionella
protection is active and there is no heat or burn demand because the Anti_Legionella_Sensor is already at a high
enough temperature CH/DHW demand will be accepted as normal.
Parameters are factory set
Parameter
Factory Setting.
Anti_Legionella_Setpoint
Setpoint for Anti-Legionella demand
140 ºF (60 ºC)
Anti_Legionella_Burn_Time 30 Min.
Anti_Legionella_Wait_Time
Wait time for Anti-Legionella demand.
120 min after cold start, 168 h after first successful Anti-Legionella demand
Table 12. 22