Dunkirk Helix VLT Vertical Laser Tube, Wall Hung Modulating Condensing Boiler - Manual (Page 6)

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3 - Cascade – Heating only
Managing Boiler
Boiler is set as Managing (address = 1), controller of this
boiler will drive cascade.
CH mode of managing boiler applies to all other boilers. It
is only required to set CH mode on managing boiler.
• Outdoor temperature sensor connected to MANAGING
boiler is outdoor sensor for cascade operation
• System sensor connected to MANAGING boiler is control
sensor for cascade supply temperature.
• Thermostat connected to MANAGING boiler is CH heat
demand input for cascade system.
Managing boiler calculates required boiler setpoint to
achieve requested cascade setpoint.
Managing boiler provides calculated setpoint to all
dependent boilers.
Power of dependent boilers is Proportional Intergral
Derivative (PID) controlled on basis of calculated setpoint
and dependent boiler supply temperature.
CH Mode
Set CH mode at managing boiler.
CH Setpoint For Boilers
When system temperature is not high enough, setpoint for
all boilers will be adjusted. Boiler setpoint will be increased
when system temperature is below cascade setpoint and
decreased when it is above cascade setpoint temperature.
This is determined as following:
• PID-control loop over system temperature calculates
adjustment of boiler setpoint.
• When system temperature is above cascade setpoint,
calculated boiler setpoint will be decreased by a
maximum of -10ºC (-18ºF). In case system temperature
is below cascade setpoint, calculated boiler setpoint
to all boilers will be increased by a maximum of 20ºC
(36ºF).
• Calculated boiler system setpoint will be limited at 85ºC
(185ºF).
• PID calculation does not start immediately, delay period
allows system to stabilize. Delay period is calculated
by multiplying Start Time delay setting with Start
Modulation Delay Factor (settable).
• Delay period is limited to 60 minutes. Setting Start
Modulation Delay to 0 disables this function.
Dependent Boiler
• Dependent boiler (address = 2-16) always receives its
setpoint from managing boiler.
• Firing rate of ALL boilers is PID controlled by individual
boiler. Individual boiler calculated setpoint is received
from managing boiler to control boiler supply
temperature.
• Managing boiler will operate in cascade system similar
to a dependent boiler, except it will also control external
pumps and analyze data collected by system and
outdoor sensors.
• Maximum dependent boiler temperature is fi xed at 91ºC
(196°F).
4 - Cascade – Domestic Hot Water
Connections:
Wire external tank thermostat to DHW T-T input on
managing boiler terminal block.
Pump for DHW operation is connected to managing boiler
DHW pump high voltage terminals.
Settings:
Set DHW setting, in Installer menu of managing boiler
control, as follows:
• Set DHW mode at 2.
• Set DHW Boiler Assign to ALL in Installer CASCADE
menu of managing boiler.
Control functions as described in boiler's Installation,
Operation and Maintenance Manual, when demand for DHW
is detected.
Dependent Boiler
Dependent boilers (address =2-16) receive DHW setpoint
from managing boiler.
MULTIPLE BOILER GUIDE