53
8
Field wiring
(continued)
Outdoor temperature sensor
1. Mount the sensor on an exterior wall, shielded from
direct sunlight or fl ow of heat or cooling from other
sources.
2. Route sensor wires through a knockout at the rear of the
boiler (see FIG. 8-2).
3. Connect the outdoor temperature sensor (FIG. 8-3) to
the outdoor sensor terminals on the connection board
to enable outdoor reset operation of the FTXL. If fi xed
temperature operation is required, do not install outdoor
sensor.
DHW (Domestic Hot Water)
thermostat
Connect storage indirect water heater (DHW) thermostat
(FIG. 8-3) to the DHW thermostat terminals on the
connection board. If a tank sensor is connected (see DHW
Tank Sensor below) the tank thermostat is ignored.
DHW tank sensor
By installing a tank sensor, the SMART SYSTEM control can
perform the tank thermostat function. The SMART SYSTEM
control automatically detects the presence of this sensor, and
generates a DHW call for heat when the tank temperature
drops 6°F (3°C) below the tank set point, and fi nishes the call
for heat when the tank temperature reaches the tank set point.
The tank sensor included with the Lochinvar Squire® indirect
DHW tanks (TST20015) is the only sensor suitable for use
with the SMART SYSTEM control. Connect the sensor leads
to the Tank Sensor terminals on the low voltage connection
board (FIG. 8-3).
Failure to use the correct sensor may
result in the tank temperature being either
above or below the set point.
WARNING
If TST20015 is not compatible with the indirect tank, a
tank thermostat can be used to control the boiler. The
tank thermostat should be installed per the manufacturer’s
instructions and wired to the DHW Thermostat terminals on
the low voltage connection board (FIG. 8-3).
Installation & Operation Manual
Louver proving switch
1. When the operation of the louvers needs to be verifi ed
before the boiler fi res, remove the jumper wire from
these terminals and connect them to the normally open
contacts on its proving switch (FIG. 8-3).
High gas pressure switch
1. If a switch is provided to detect excessive gas pressure,
remove the jumper wire from the terminals on the
connection board, and then connect them to its normally
closed contacts (FIG. 8-3).
Low gas pressure switch
1. If a switch is provided to detect low gas pressure, remove
the jumper wire from the terminals on the connection
board and connect them to its normally open contacts
(FIG. 8-3).
2. If both a high and low gas pressure switch is used, connect
their respective contacts in series, and connect them to the
terminals on the connection board (FIG. 8-3).
Variable speed system pump
If a variable speed pump is used in the primary loop, and
a 0-10V signal is available from the pump speed control,
this signal can be used by the SMART SYSTEM control to
anticipate changes in the building heat load. By connecting this
0 - 10V signal to the 0 - 10V SYS PUMP IN terminals, the boiler
(or cascade) can modulate up and down as the primary fl ow
increases and decreases.
Boiler pump speed output
This 0 - 10V output is available to control the speed of a variable
speed boiler pump. The SMART SYSTEM control will vary the
speed of this pump in order to maintain a minimum
T across
the heat exchanger, as well as prevent high limit lockouts when
the fl ow in the primary loop is extremely low. NOTE: This
feature is to be used with Primary / Secondary piping systems
only. A system supply sensor MUST be installed. Connect this
output to the 0 - 10V input on the boiler pump speed control.
Rate output
This output provides a 0 - 10V signal that is proportional to the
fi ring rate of the boiler. This may be used by a BMS system to
monitor the actual rate of the boiler.
ModBus/BACnet
When an optional ModBus or BACnet interface module is
installed, the RS-485 cable is connected to these terminals. Use
shielded, 2-wire twisted pair cable. If desired, the shield can
be connected to ground by installing a jumper wire between
terminals 1 and 3 on connector X5 on the optional ModBus or
BACnet interface module.
Flow switch
1. A
fl ow switch is used to guarantee fl ow through the boiler
before allowing it to fi re. The fl ow switch must be installed
at the boiler outlet.
2. Remove the jumper wire from the terminals on the
connection board and connect these terminals to the
normally open contacts on the fl ow switch (FIG. 8-3).
System supply sensor
1. By installing the system supply sensor into the supply of the
primary loop, the temperature of the system supply can be
controlled. The SMART SYSTEM control automatically
detects the presence of this sensor, and controls the boiler
fi ring rate to maintain the system supply temperature to
the set point (if outlet sensor control is currently selected).