44
GAS-FIRED BOILER Boiler Manual
PART 8: FIELD WIRING (CONTINUED)
K. OPTIONAL LOW GAS PRESSURE
SWITCH
1. If an optional low gas pressure switch is
used, it should be installed on the inlet side
of the gas valve. This is normally closed and
will open if the pressure goes above 1½” w.c.
2. Locate the two pigtails hanging from the
electrical box inside of the boiler cabinet.
Remove and discard the jumper plug from
one of the unused pigtails.
3. Connect the low gas pressure switch to the
pigtail that you removed the jumper plug
from.
L. OPTIONAL UL353 LOW WATER CUTOFF
SWITCH
1. If an optional UL353 low water cutoff (LWCO)
switch is used, the control box of the LWCO
should be mounted to the left side of the
boiler cabinet near the low water cutoff
probe, which is located on the outlet nipple
of the boiler.
2. Remove the wire connected to the low water
cutoff 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 cutoff probe on the
boiler.
4. Route the rest of the wires through the
provided hole 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.
M. WIRING OF CASCADE SYSTEM
COMMUNICATION BUS
1. 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.
2. 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 or where
they will 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.
3. Route the communication cables through
one of the knockouts in the cabinet.
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