General
How the boiler operates
The FTXL uses an advanced stainless steel heat exchanger
and electronic control module that allows fully condensing
operation. The blower pulls in air and pushes fl ue products
out of the boiler through the heat exchanger and fl ue piping.
The control module regulates blower speed to control the
boiler fi ring rate. The gas valve senses the amount of air
fl owing into the boiler and allows only the right amount of
gas to fl ow.
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 valves to regulate
heat input and switches the boiler, Domestic Hot Water
(DHW), DHW recirculation, 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, Modbus, or BACnet, depending on the parameter
settings.
Control inputs and outputs
Room thermostat
There are three (3) heat/loop demand connections available
on this control. These inputs tell the boiler to provide water
for space heating. Each demand connection has its own set
point and outdoor air reset curve. When multiple demands
have a call for heat the control will give priority to the demand
with the highest set point.
Example:
Assume that both heat/loop demand 1 and heat/
loop demand 2 have a call for heat. Demand 1 has a set point
of 110°F. Demand 2 has a set point of 140°F. The boiler will
regulate the system temperature to 140°F until Demand 2 has
been satisfi ed. Once Demand 2 has been satisfi ed the boiler
will provide 110°F water to the system.
SMART SYSTEM Multi-temp loop control
The FTXL boiler is capable of producing up to three (3) set
point temperatures to meet different space heating demands.
This device controls the temperatures of up to three (3)
separate loops, based on the settings for the three (3) heat/
loop demands (reference Lochinvar kit RLY30086).
0 - 10V input (set point or power)
The FTXL can be controlled by a Building Management
System (BMS) using a 0 - 10 VDC signal. The control can be
confi gured by the installer to use this signal to either control
set point or fi ring rate.
The FTXL can also be programmed to accept a call for heat
from a 0 - 10V signal, reference the FTXL 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. When a boiler is programmed for DHW Normal
Mode, the maximum fi ring rate can be limited to match the
input rating of the indirect tank coil.
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. For stand-alone boilers, 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. This function
does not apply to cascade systems.
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 fi ring, 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.
11
Operating information
63
CAUTION
When multiple temperature loops are
used, mixing valves are required for the
protection of any low temperature loops.
Installation & Operation Manual
