Lochinvar Knight 80 - 285 - Manual (Page 53)

Installation & Operation Manual
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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 input from
boiler sensors and external inputs. 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, or system temperature, depending on the
parameter setting.
Control inputs and outputs
Room thermostat / zone control
This input tells the boiler to provide water for space heating.
Domestic Hot Water (DHW) tank thermostat
This input tells the boiler to provide water for heating an
indirect DHW tank.
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.
DHW priority
The SMART SYSTEM control module allows connection of a
DHW thermostat to the low voltage connection board. When
the DHW thermostat calls for heat, the module activates the
DHW pump, shuts down the boiler pump, and immediately
sets the target outlet water temperature to 180°F. This
provides automatic priority heat allocation to the` indirect
water heater for maximum response and recovery. The DHW
pump continues for 30 seconds after the heating cycle to
deliver the most possible heat.
DHW / space heating (SH) cycling
If a DHW call for heat is received while a space heating call is
in progress, 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. 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.
Anti-cycling
After a space heating demand has been satisfied, the control
will delay the next space heating call 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, system, and DHW pump control
When a space heating call for heat starts and no DHW call is
on, the system and boiler pumps are turned on. As long as the
space heating call for heat is on, the system pump will remain
on. If a DHW call for heat is on, the boiler pump will wait to
turn on until just before the DHW pump turns off. After the
space heating call for heat ends, both pumps will run for an
additional period of time.
When a DHW call for heat starts, the DHW pump is turned
on. If a space heating call for heat was on, the boiler pump
will turn off a few seconds after the DHW pump turns on.
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.