37
Installation & Operation Manual
7
Field wiring
(continued)
Auxiliary switch 1 & 2
Additional field supplied limit controls may be connected to
the auxiliary switch inputs. If additional limit controls fail or
open, it will result in a manual reset lockout.
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.
2. For system supply sensor wiring information reference
(FIG. 7-3).
Boiler management system
1. An external control may be connected to control either
the firing rate or the set point of the boiler. Connect the
0 - 10 VDC terminals to the 0 - 10 VDC output of the
external control. The SMART TOUCH control can be
enabled using the Enable output (see page 38) or using
the voltage applied to the 0 - 10 VDC input. Reference
the Crest Service Manual for more details.
2. Make sure terminal #34 on the Low Voltage Connection
Board is connected to the (-) or COM output terminal
of the external control, and 0 - 10 VDC terminal #33 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 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.
System return sensor
1. Install the system return sensor into the return of the
primary
loop.
2. Connect the terminals to the system return sensor as
shown in FIG. 7-3.
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 page 45 “Configuration of the Cascade” for a
detailed explanation of this procedure.
Connect the system supply sensor, system return 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 5-5
and 5-6). The system supply sensor should be wired to the Low
Voltage Connection Board at the terminals marked for the
system supply sensor (see FIG. 7-3). 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 on the Leader boiler
(FIG. 7-3). 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 enable output is available, it should be wired
to the Low Voltage Connection Board on the Leader boiler at
the terminals marked Enable (FIG. 7-3). If the boilers are to
run continuously, connect a jumper wire between the 7 and 8
terminals at the Enable input. This will initiate a call for heat on
the Cascade. If the SMART TOUCH control is being controlled
by a Boiler Management System (BMS), a call for heat may be
initiated by the voltage applied to the BMS 0 - 10 VDC input
instead.
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 Cascade shield ground
terminals on the Low Voltage Connection Boards (FIG. 7-3).
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.
NOTICE
Unless a firing rate is being provided by
a BMS system, a system supply sensor
(factory supplied) MUST BE installed
with Primary/Secondary piping systems
for proper boiler operation.
NOTICE
Unless a firing rate is being provided by a
BMS system, a system supply sensor (factory
supplied) MUST BE installed with Primary/
Secondary piping systems for proper boiler
operation.
NOTICE
DO NOT INSTALL THE SYSTEM
SUPPLY SENSOR INTO THE SYSTEM
RETURN.
