11
Operating information
(continued)
Temperature control
Modulation
The FTXL is capable of modulating its firing rate from a
minimum of 10% 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.
Ramp delay
For systems with lower flow, the SMART SYSTEM can limit
the firing rate (when enabled) when a space heating call for heat
starts, when the set point is controlled by the BMS, or when
switching from a DHW call for heat to a space heating call for
heat. There are six (6) limits that can be programmed, as well
as six (6) time intervals corresponding to each limit. The sixth
limit will also limit the firing rate for the rest of the call for heat.
Gradient limiting
If during operation of the boiler the outlet water temperature
is rising too quickly, the control will reduce the firing rate to its
lowest setting.
Outdoor air reset
If an outdoor air sensor is connected, the control module will
calculate the set points of the three (3) space heating demands
based on the programmed reset curves. The installer can change
the slope of the reset curves by several adjustable parameters.
The user can limit the maximum set points for each demand
using the space heating set points.
Boost function
If outdoor air reset is active, and any space heating demand
has been active continuously for a set period of time (time
adjustable by installer) and there has been no DHW demands,
the control can increase the set point of that demand by a
fixed number of degrees (adjustable by installer). This process
will continue until the space heating demand ends, the set
point reaches the programmed set point or a maximum of
20 increases has occurred. Once the system heat demand is
satisfied, the set point will revert to the value determined by the
reset curve.
Installation & Operation Manual
60
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. For stand-alone boilers, 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, or the boiler goes into Freeze
Protection Mode. It may be programmed to run during
a DHW call for heat when the DHW is programmed for
Zone 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 and/or a
DHW call for heat.
DHW recirculation pump control
When a DHW recirculation loop is used, the FTXL boiler
can control the recirculation pump. To activate this
function, simply install the DHW recirculation sensor into
the return water from the DHW circulation loop. The
control will turn on the DHW recirculation pump when
the return water drops 10°F (5.5°C) below the DHW tank
set point, and will turn back off when the return water
rises to within 5°F (2.5°C) of the DHW tank set point.
The control will turn the DHW recirculation pump off
whenever DHW night setback is active.