Dunkirk Helix VLT Vertical Laser Tube, Wall Hung Modulating Condensing Boiler - Manual (Page 8)

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7 - Error handling
7.1 Freeze Protection
Frost protection function for cascade relates to system
sensor temperature. When system sensor value is below
10°C (50°F), internal and CH pump of managing boiler
start. Display shows “freeze protection”.
When there is CH call for heat, freeze protection will be
overridden and control will start for CH.
Managing Boiler
• Once cascade freeze protection is activated managing
boiler will operate as individual boiler in freeze
protection mode.
• If boiler supply temperature drops below 5°C
(41°F) burner starts at minimum fi ring derate and
continues fi ring until lowest of both supply and return
temperatures are above 15°C (59°F).
• After burner is switched off, internal and CH pumps run
for post purge period.
Dependent Boiler
• If supply temperature of dependent boiler drops below
freeze protection function, this boiler also starts and will
operate like individual boiler.
7.2 Emergency Mode
Open/Shorted System Sensor
• When system sensor is open or shorted all boilers
will go to permanent heat demand operation and use
Emergensy Setpoint.
• Managing boiler display shows “EMERGENCY MODE” and
system sensor error.
• Emergency mode is default active for each boiler,
however individual boiler can be switched off via “Permit
Boiler Emergency Mode” setting in User Menu of effected
boiler. When not permitted only freeze protection is
active.
Loss Of Cascade Communication
• Loss of cascade communication is detected by
dependent boilers.
• Individual boilers will show error on display when
communication is lost.
• Boiler will go to permanent heat demand operation and
use Cascade Setpoint.
• Set parameter per boiler.
Managing boiler error
When managing boiler is in error mode this boiler is not
used anymore for cascade system. However dependent on
error code pumps connected by managing boiler still can be
controlled for cascade system.
Cascade system can NOT operate with following errors:
A04 - Gas valve relay error,
A05 - Safety relay error
E27 - Water pressure error,
E31 - Low water cutoff.
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