HTP EFT-399 - Manual (Page 56)

56
LP-387 REV. 6.10.14
NOTE: When a 0-10 volt building management system is installed, the return sensor temperature cannot be monitored through the
boiler 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-OFF INTERFACE KIT
If an optional UL 353 Low Water Cut-Off (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-off probe, which is located on the outlet nipple of the boiler.
Follow the complete instructions included in the kit for proper installation.
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.
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, 32, and 33 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 office 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 floor
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.
5. Connect the boilers in a daisy
chain configuration as shown below.
It is best to wire the boilers using the
shortest wire runs rather than trying
to wire them in the order that they are
addressed. The communication bus
jacks on the customer connection
panel are interchangeable so you
can use either one or both in any
order to connect the cable.
If you have connected the boilers to
each other properly, there will be no open communication connection ports.
Figure 32 – LP-387-W