7
Electrical connections
40
Louver proving switch
1. When the operation of a louver proving switch needs to
be verified before the boiler fires, remove the jumper wire
from these terminals and connect them to the normally
open contacts on its proving switch (FIG. 7-4).
System supply sensor
1. By installing the system supply sensor into the supply of the
primary loop, the temperature of the primary 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).
2. Connect these terminals to the system supply sensor
(FIG. 7-4).
System return sensor
1. By installing the system return sensor into the return of the
primary loop, the temperature of the primary return can
be sensed when a 3-way valve or other device is installed
ahead of the heater inlet. The SMART TOUCH control
automatically senses the presence of this sensor. If the inlet
sensor is selected as the controlling sensor, the SMART
TOUCH control will adjust the firing rate to hold the
system return temperature to the set point. It is strongly
recommended that the system supply sensor be installed as
well.
2. Connect these terminals to the system return sensor (FIG.
7-4).
Boiler Management System (BMS)
1. An external control may be connected to control either the
firing rate or the set point of the appliance. Connect the 0 -
10 VDC terminals to the 0 - 10 VDC output of the external
control. The SMART TOUCH control can be programmed
to use the enable output of the Boiler Management System,
or use the voltage signal to enable the heater. Connect the
enable terminals to the enable output of the BMS, when
used.
2. Make sure the ground terminal is connected to the ground
output terminal of the external control, and the 0 - 10 VDC
terminal is connected to the 0 - 10 VDC terminal of the
external control.
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.
Alarm contacts
The SMART TOUCH control closes another set of contacts
whenever the heater 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 heaters for Cascade operation, select one
heater as the Leader heater. The remaining heaters will be
designated as Members. See page 49
Configuration of the
Cascade
for a detailed explanation of this procedure.
On boilers, connect the system supply sensor and outdoor air
sensor (if used) to the Leader boiler. The location of the system
supply sensor should be downstream of the boiler connections
in the main system loop (FIG.’s 5-3 and 5-7). The system supply
sensor should be wired to the low voltage connection board at
the terminals marked for the system supply sensor (see FIG.
7-4). 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. 7-4). 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 space heating (SH) set point
that is programmed into the control.
If a Thermostat, Zone Control enable output, or Building
Management System enable output are available, it should be
wired to the low voltage connection board on the Leader boiler
at the enable terminals. If the boilers are to run continuously,
leave the jumper wire between the enable terminals. This will
initiate a call for heat on the Cascade. Also, leave the jumpers on
the enable terminals of all the Member heaters. This will allow
them to run independently should the Leader heater fail.
Communication between the Leader heater and the Member
heaters is accomplished by using shielded, 2-wire twisted pair
communication cable. Connect one of the twisted pair wires
to terminal A on each of the low voltage connection boards,
and the other wire of the twisted pair to terminal B on each of
the low voltage connection boards. Connect the shield wire to
the shield ground terminal on all of the heaters. If more than
two heaters are on the Cascade, daisy chain the wiring from
the Cascade terminals on the second heater to the Cascade
terminals on the third heater, then from the third to the forth,
and so on. The connections can be made in any order, regardless
of the addresses of the heaters. Try to keep each cable as short
as possible.
Installation & Operation Manual
