LP-387 Rev. 7.3.15
40
NOTE: If sensor wires are located in an area with sources of
potential electromagnetic interference (EMI), the sensor
wires should be shielded, or the wires routed in a grounded
metal conduit. If using shielded cable, the shielding should be
connected to the common ground of the boiler.
J. Optional 0-10 Volt Building Control Signal
1. A signal from a
building management
system may be
connected to the boiler
to enable remote
control. This signal
should be a 0-10 volt
positive-going DC
signal. When this
input is enabled using
the installer menu,
a building control
system can be used to
control the set point
temperature of the
boiler. The control
interprets the 0-10 volt
signal as follows; when
the signal is between 0
and 1.5 volts, the boiler
will be in stand¬by mode, not ring. When the signal rises
above 1.5 volts, the boiler will ignite. As the signal continues
to rise towards its maximum of 10 volts, the boiler will
increase in set point temperature. See Part 10 for details on
the setting of function 16.
2. Connect a building management system or other auxiliary
control signal to the terminals marked 16, 0-10 VOLT + and
17, 0-10 VOLT – in the electrical junction box (shown in Figure
29). Caution should be used to ensure that the 0-10 VOLT +
connection does not become connected to ground.
3. Move jumper on connection board (shown in Figure 31)
from A to B.
4. See Function 17 this manual to program the 0-10 volt
signal.
NOTE: When a 0-10 volt building management system
is installed, the return sensor temperature cannot be
monitored through the appliance display.
NOTE: Ensure that the polarity of the connections from the
external modulating boiler controller to the boiler is correct.
Reversed polarity could lead to erratic and/or no response
from the boiler controller.
K. Optional UL353 Low Water
Cut-O Interface Kit
If an optional UL 353 Low Water Cut-
O (LWCO) Interface Kit is used,
the control box of the kit should be
mounted to the left side of the boiler
cabinet near the low water cut-o
probe, which is located on the outlet
nipple of the boiler.
Follow the complete instructions
included in the kit for proper
installation.
L. Wiring of Cascade System Communication Bus
1. A Cascade Bus Termination Plug has been installed on the
customer connection board of this boiler. The purpose of this
plug is to stabilize communication between multiple boilers and
reduce electrical “noise”. See Figures 30 and 31 for Cascade Bus
Termination Plug installation detail.
2. Use standard CAT3 or CAT5 computer network patch cables
to connect the communication bus between each of the boilers.
These cables are readily available at any oce supply, computer,
electronic, department or discount home supply store in varying
lengths. If you possess the skills you can also construct custom
length cables.
3. It is recommended to use the shortest length cable that will
reach between the boilers and create a neat installation. Do not
run unprotected cables across the oor where they may become
wet or damaged. Avoid running communication cables parallel
and close to or against high voltage (120 volt or greater) wiring.
HTP recommends that the maximum length of communication
bus cables not exceed 200 feet.
4. Route the communication cables through one of the
knockouts in the cabinet.
Figure 30 - Wiring Cascade System
Figure 31 - Cascade Termination Plug Detail
NOTE: The control system senses system water temperatures
entering and exiting the heat exchanger to provide protection
against low water conditions. Where local codes or jurisdictions
do not accept a pressure device for low water protection, the
jurisdictions may accept these control functions as a means of
providing low water protection.
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