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Installation & Operation Manual
56
11 Operating information
High limit operations
When outlet temperature exceeds 200°F (93.3°C), high limit
action occurs. The boiler shuts down until the outlet water
cools down.
Low water cutoff protection
1. The SMART SYSTEM control module uses temperature
sensing of both supply and return areas of the heat
exchanger. If the flow rate is too low or the outlet
temperature too high, the control module modulates and
shuts the boiler down. This ensures boiler shutdown in the
event of low water or low flow conditions.
2. Some codes and jurisdiction may accept these integral
features of the control in lieu of requiring an additional
limit control or low water cutoff. Consult local jurisdiction
to determine. Low water cutoff kits are available (KIT3055
and 3057).
Outdoor reset operation, if used
Target temperature with outdoor reset
This feature improves the system’s efficiency as the outdoor
temperature warms up.
See the Knight XL Service Manual to change the settings.
Reset curve
The reset curve looks at outdoor air temperature and adjusts the
set point.
Cascade
When multiple boilers are installed, they can be wired together
in a cascade sequence. A maximum of eight boilers can be
controlled from a single control. In this application one boiler
would be designated as the Leader control and all others would
be designated as Member controls.
Once the Leader boiler receives a call for heat from a room
thermostat, the control will determine what the set point will be.
If outdoor air reset is desired, connect the outdoor air sensor to
the terminals on the Low Voltage Connection Board on the
Leader boiler. The set point will be calculated based on the
programmed reset curve parameters. See the Knight XL Service
Manual to program the reset curve. If outdoor air reset is not
desired, do not connect the outdoor air sensor. A fixed
temperature set point can be programmed into the control. See
page 52 of this manual to program the set point.
Monitor external limits
Connections are provided on the connection board for
external limits such as flow switch, low water cutoff, gas
pressure switches, and an auxiliary device proving switch.
The SMART SYSTEM will shut off the burner and inhibit
relighting whenever any of these external limits open.
Run-time and alarm outputs
The boiler provides dry contacts for indicating when the
boiler is running, and when it is unable to operate.
Run-time and cycle counting
The control uses two timers to monitor the total hours of
burner operation. One timer monitors the time the boiler
is firing under 50% of rate. The other timer monitors the
time the boiler is firing over 50% rate.
The control uses four (4) ignition counters to monitor the
amount of boiler cycles. The first counter counts all
ignitions of the control. The second counter counts only
ignition attempts that have failed. The third and fourth
counters are the same as the first and second respectively,
but can be reset by the installer.
Service reminder
The control can be programmed for service reminder
notification. This notification will become active when
either a set time frame has expired, or a set amount of
running hours or cycles has expired (all adjustable by the
installer). The display will alternate the standard text on
the display screen with Service Due every 5 seconds. The
service reminder notification can be reset by the installer.
Error logging
The control will hold in memory the last 10 error codes as
well as the last 10 turn-off functions. The date and time of
the occurrence will be recorded as well. Only the 10 most
current occurrences will be held in memory.
Boiler temperature regulation
Operating temperature (target)
The SMART SYSTEM control module senses water
temperature and regulates boiler firing and firing rate to
achieve a target temperature. The target temperature can
be set between 70°F (21°C) and 190°F (88°C).
• Target temperature is fixed when the outdoor
sensor is not installed.
• Target temperature is calculated as described
on this page under “Outdoor Reset Operation”
and “Target Temperature Boost” when the
outdoor sensor is connected.