Lochinvar Sunc 1.0, Installation & Operation Manual

Page: 40 / 68

40
Installation & Operation Manual
7
Field wiring
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. Connect these terminals to the system supply sensor
(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 39) or using
the voltage applied to the 0 - 10 VDC input. Reference
the SYNC Service Manual for more details.
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 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. Note that these
contacts will close momentarily at the end of each call for heat
or at least every 24 hours.
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 48 “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 5-5
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 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 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
0 - 10 VDC input.
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 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
wires to one of the 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 Sequencing
terminals on the second boiler to the Sequencing 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
A system supply sensor (factory supplied)
MUST BE installed for proper boiler
operation.
NOTICE
A system supply sensor (factory supplied)
MUST BE installed for proper boiler
operation.
NOTICE
DO NOT INSTALL THE SYSTEM
SUPPLY SENSOR INTO THE SYSTEM
RETURN.