54
Installation & Operation Manual
8
Field wiring
Boiler management system
The United States Energy Policy and Conservation Act
requires residential heating boilers with inputs less than
300,000 Btu/hr be equipped with a control that automatically
adjusts boiler water temperature in relation to heat demand.
An external control may be connected to control the firing
rate or the set point of the boiler provided that either an
external energy management system is installed that reduces
the boiler water temperature as the heating load decreases,
the boiler is not used for any space heating, or the boiler is
part of a modular or multiple boiler system having a total
input of 300,000 Btu/hr or greater.
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 SYSTEM 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 the (-)
voltage is not below ground.
Runtime contacts
The SMART SYSTEM 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 SYSTEM 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 page 63 “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 6-4
and 6-6). The system supply sensor should be wired to the Low
Voltage Connection Board at the terminals marked for the
system sensor (see FIG. 8-4). 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. 8-4). 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 fixed water temperature set
point that is programmed into the control.
If a Thermostat, Zone Control enable output, or Building
Management System 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. 8-4). 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. 8-4). 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.
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 SYSTEM 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). If it is desired to control
the system return temperature, then program the SMART
SYSTEM control to use the inlet sensor as the controlling
sensor. See the Knight Wall Mount Service Manual for
instructions on how to do this. When the inlet sensor
is programmed as the controlling sensor, it is strongly
recommended that the SYSTEM SUPPLY sensor be
installed. DO NOT INSTALL THE SYSTEM SUPPLY
SENSOR INTO THE SYSTEM RETURN.
2. The TST2032 sensor provided with the boiler must be
used for the system sensor.
3. Connect these terminals to the system supply sensor
(FIG. 8-4).
