41
Installation & Operation Manual
7
Field wiring
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 42) 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 52 “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.’s 5-2
through 5-5). The system supply sensor should be wired to the
Low Voltage Connection Board at the terminals marked for the
system 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 (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 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 Enable (FIG. 7-3). If the
boilers are to run continuously, connect a jumper wire between
the R and W terminals for the Enable 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. 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.
When the Member 1 boiler is programmed as an alternate
leader this allows the Member 1 boiler to automatically assume
control of the Cascade should it lose communication with the
Leader boiler. When programmed to YES, it is recommended
that the Member 1 boiler have its own set of external sensors
installed (such as the system supply sensor), to maintain the
same level of temperature control as with the Leader boiler.
Voltage signals (such as 0 - 10V system pump speed input) can
be connected to both boilers.
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.
