54
9
Field wiring
Modbus / BACnet
When the optional ModBus / BACnet interface module is
installed, the RS-485 ModBus / BACnet 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 / BACnet interface module.
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 TOUCH control automatically
detects the presence of this sensor, and controls the boiler
firing rate to maintain the system supply temperature to the
set point (if the outlet sensor control is currently selected).
See the Knight XL Service Manual for instructions on how
to use the inlet sensor as the controlling sensor. When the
inlet sensor is programmed as the controlling sensor, it is
vital that the SYSTEM SUPPLY sensor be installed. DO
NOT INSTALL THE SYSTEM SUPPLY SENSOR INTO
THE SYSTEM RETURN.
2. The 100170581 sensor provided with the boiler must be
used for the system sensor.
3. Connect these terminals to the system supply sensor
(FIG. 9-3).
Alarm contacts
The SMART TOUCH control closes another set of contacts
whenever the boiler is locked out or the power is turned off.
This can be used to turn on an alarm, or signal a Building
Management System that the boiler is down.
Wiring of the cascade
When wiring the boilers for Cascade operation, select one
boiler as the Leader boiler. The remaining boilers will be
designated as Members. See “Configuration of the Cascade”
for a detailed explanation of this procedure.
Connect the system supply sensor and outdoor air sensor (if
used) to the Leader boiler. For the Cascade system to work
properly the system supply sensor must be installed. The
location of the system supply sensor should be downstream
of the boiler connections in the main system loop (FIG. 7-4
through 7-8). The system supply sensor should be wired to the
low voltage connection board at the terminals marked for the
system sensor (see FIG. 9-3). The Leader control will use the
water temperature at the system supply sensor to control the
operation of the Cascade.
If outdoor air reset is desired, the outdoor air sensor should
be wired to the low voltage connection board at the terminals
marked for the outdoor air sensor (FIG. 9-3). If the outdoor
air sensor is connected, the Leader control will calculate the
water temperature set point based on the programmed reset
curve parameters. If the outdoor air sensor is not connected,
the Leader control will maintain the fixed water temperature
set point that is programmed into the control.
If a Thermostat or Zone Control enable output is available,
it should be wired to the low voltage connection board on
the Leader boiler at the terminals marked for one of the
heat/loop demands 1-3 (FIG. 9-3). If the boilers are to run
continuously, connect a jumper wire between the R and W
terminals for the heat/loop demand input. This will initiate a
call for heat on the Cascade.
Communication between the Leader boiler and the Member
boilers is accomplished by using shielded, 2-wire twisted pair
communication cable. Connect one of the twisted pair wires
to Cascade terminal A on each of the low voltage connection
boards, and the other wire of the twisted pair to Cascade
terminal B on each of the low voltage connection boards.
Connect the shield wires to one of the shield terminals on
the low voltage connection boards (FIG. 9-3). If more than
two boilers are on the Cascade, daisy chain the wiring from
the Cascade terminals on the second boiler to the Cascade
terminals on the third boiler, then from the third to the forth,
and so on. The connections between boilers can be made in
any order, regardless of the addresses of the boilers. Try to
keep each cable as short as possible.
Boiler management system
1. An external control may be connected to control either
the firing rate or the set point of the boiler. If the
external control uses a set of contacts to enable the boiler,
connect the contacts to the heat/loop demand 1 terminals.
Otherwise, the SMART TOUCH control will be enabled by
the 0-10V signal.
2. Make sure the (-) terminal is connected to the (-) or
common output terminal of the external control, and the
(+) terminal is connected to the 0 - 10 VDC or (+) terminal
of the external control. Make sure that the (-) voltage is not
below ground.
Runtime contacts
The SMART TOUCH control closes a set of dry contacts
whenever the burner is running. This is typically used by
Building Management Systems to verify that the boiler is
responding to a call for heat.
Installation & Operation Manual
