LP-428 Rev. 6.6.16
35
O. Wiring of Cascade System Communication Bus
NOTE: A termination plug is included in the CAT 3 / CAT 5 Bus
Connection Point labeled J3 in Figure 20. DO NOT REMOVE
THIS PLUG UNLESS INSTRUCTED TO DO SO. Doing so will
aect boiler operation and void warranty.
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 Figure 23 for Cascade Bus
Termination Plug installation detail.
Figure 22 - Wiring Cascade System
Figure 23 - Cascade Termination Plug Detail
create a demand and observe boiler function to verify the
installation is working properly.
NOTE: Installing the optional ow switch will disable the
built-in low water cuto. If a ow switch and a low water
cuto are necessary for the installation, purchase and install
the optional UL353 LWCO (available from HTP, Part # 7350P-
601). In this installation, it is recommended to install the ow
switch kit rst.
N. Optional UL353 Low Water Cut-O Interface Kit
NOTE: This boiler will require 2 interface kits to ensure both
heat exchangers are full of water.
1. If an optional UL353 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.
2. If the optional ow switch is
present on the boiler, then the orange
wire from the LWCO control box
is left unconnected. If the optional
ow switch is not installed on or
connected to the boiler, remove the
wire connected to the low water cut-
o probe on the boiler and connect
it to the orange wire from the newly
mounted LWCO control box.
3. Connect the single red wire from the
control box to the low water cut-o
probe on the boiler.
4. Route the rest of the wires through the hole
provided in the cabinet and down by the main
electrical enclosure.
5. Locate the two pigtails hanging from the main
electrical enclosure. Select the pigtail which has
a white, red, and brown wire in it. If the pigtail is
connected to a gas pressure switch, skip to step 7. If
this pigtail is not connected to a gas pressure switch,
remove the jumper plug from the end of the pigtail
and place the jumper plug into the mating connector
coming from the LWCO control box.
6. Connect the pigtail to the remaining plug coming
from the LWCO control box. Installation is complete.
7. If the pigtail located in step 5 is connected to a gas
pressure switch, disconnect it from the gas pressure
switch and connect the pigtail to the mating connector coming
from the LWCO control box. Connect the gas pressure switch
to the remaining connector from the LWCO control box.
2. Use standard CAT3 or CAT5 computer network patch cables
to connect the communication bus between each of the boilers.
The cable must be of the “straight through” design. 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.
5. Connect the boilers in a daisy chain conguration 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.
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