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Installation & Operation Manual
11 Operating information
General
How the boiler operates
The Knight boiler uses an advanced stainless steel heat
exchanger and electronic control module that allows fully
condensing operation. The blower pulls in air and pushes
flue products out of the boiler through the heat exchanger
and flue piping. The control module regulates blower speed
to control the boiler firing rate. The gas valve senses the
amount of air flowing into the boiler and allows only the right
amount of gas to flow.
How the control module operates
The SMART SYSTEM control module receives inputs
from boiler sensors and external devices. The control
module activates and controls the blower and gas valve to
regulate heat input and switches the boiler, Domestic Hot
Water (DHW), and system pumps on and off as needed.
The user programs the module to meet system needs by
adjusting control parameters. These parameters set operating
temperatures and boiler operating modes. Boiler operation
can be based on boiler outlet water temperature, boiler inlet
water temperature, system temperature, a 0-10V signal or
Modbus, depending on the parameter settings.
Control inputs and outputs
Room thermostat
There are three (3) thermostat connections available on this
control. These inputs tell the boiler to provide water for space
heating. Each thermostat connection has its own set point
and outdoor air reset curve. When multiple thermostats have
a call for heat the control will give priority to the demand with
the highest set point.
Example: Assume that both Room Thermostat 1 and Room
Thermostat 2 have a call for heat. RoomThermostat 1 has
a set point of 110°F. Room Thermostat 2 has a set point of
140°F. The boiler will regulate the system temperature to
140°F until Room Thermostat 2 has been satisfied. Once
Room Thermostat 2 has been satisified the boiler will provide
110°F water to the system.
0 - 10V input (set point or power)
The Knight boiler can be controlled by a Building Management
System (BMS) using a 0 - 10 vdc signal. The control can be
configured by the installer to use this signal to either control
set point or firing rate.
The Knight boiler can also be programmed to accept a call for
heat from a 0 - 10V signal, reference the Knight Boiler Service
Manual for a detailed explanation of this procedure.
DHW priority
The SMART SYSTEM control allows the connection of a DHW
thermostat or tank sensor to the low voltage connection board.
When a tank sensor is connected, the DHW thermostat input
is ignored.
DHW / space heating (SH) cycling
If a DHW call for heat is received while a space heating call
is in progress and the DHW is in Normal Mode, the control
will start the DHW pump and shut the boiler pump off. The
system pump will remain on. If the space heating call is still
active while the DHW call is in operation, the control will wait
for 30 minutes (time adjustable by installer) then it will switch
back to the space heating demand. There is a timer to switch
from space heating to DHW and a timer to switch from DHW
to space heating. The control will switch back and forth until
one of the heat demands end.
Programmable controlling sensor
The control module is programmed to use the outlet sensor
as the control sensor by default. If a system supply sensor
is connected, the control automatically uses it as the control
sensor. The control sensor can be changed by the installer to
the inlet sensor. If the inlet sensor is chosen as the controlling
sensor, it is recommended that the system supply sensor be
installed in the system supply in order to provide the best
control of the inlet temperature.
Anti-cycling
After the burner turns off, the control will delay the next burner
cycle for a set time period (time is adjustable by the installer).
The time delay will be bypassed if the inlet water temperature
drops too far during the delay.
Boiler and system pump control
The boiler pump will run whenever the burner is firing, unless
the DHW is programmed for Normal Mode and the boiler is
heating the DHW tank. The boiler pump will run during Freeze
Protection Mode as well. It will continue to run for a short time
after the burner turns off or the Freeze Protection Mode ends.
The system pump will run whenever there is a space heating call
for heat, a DHW call for heat when the DHW is programmed
for Zone Mode, or the boiler goes into Freeze Protection Mode.
It will continue to run for a short time after the end of the heat
demand or the Freeze Protection Mode. The system pump can
be programmed to run continuously if desired, except during
outdoor shutdown.
Temperature control
Modulation
The Knight boiler is capable of modulating its firing rate from
a minimum of 20% to a maximum of 100%. The firing rate is
dictated by the call for heat (i.e., space heating or domestic hot
water), the heating load, ramp delay (if enabled), and various
other temperature limitations.
ƽ CAUTION
When multiple temperature loops are
used, thermostatic mixing valves are
required for the protection of any low
temperature loops.