HydroTherm HeatNet KN-20 User manual

is manual is intended only for use by a qualied heating installer/technician. Read and follow this manual, all supplements and re-
lated instructional information provided with the boiler. Install, start and service the boiler only in the sequence and methods given in
this manual and the documents listed above. Failure to do so can result in severe personal injury, death or substantial property damage.
Do not use the boiler during construction. Construction dust and particulate, particularly drywall dust, will cause contamination
of the burner, resulting in possible severe personal injury, death or substantial property damage. e boiler can only be operated with a
dust-free air supply. Follow the instruction manual procedures to duct air to the boiler air intake. If the boiler has been contaminated by
operation with contaminated air, follow the instruction manual guidelines to clean, repair or replace the boiler if necessary.
P/N 42-9551 Copyright 2011 Mestek, Inc.
Hydrotherm®
Gas-fired direct vent
Cast iron boilers
Model KN-20 only
-Series
KN
Field assembly
instructions
Also read and follow:
KN Series Gas Boiler
Installation & Operating
Instructions and KN
HeatNet Control Manual

2P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Hazard icons
You will find the following icons
throughout this manual.
(English/French)
The WARNING icon indicates
a hazard that can cause severe
personal injury, death or
substantial property damage.
The CAUTION icon indicates a
hazard that will or can cause minor
personal or property damage.
The NOTICE icon calls out special
instructions that are important, but
are not related to hazards.
Other manuals
You must read and follow this
manual, the KN Series Gas Boiler
Installation and Operating
Instructions, the KN HeatNet
Control manual and all additional
materials supplied with the boiler.
Failure to do so can result in severe
personal injury, death or substantial
property damage.
Boiler/control installa-
tion and setup
After completing assembly of the
KN boiler, follow all instructions
in the Installation and Operation
Instructions and Control Manual for
installation, start-up and testing.
Contents and information
Read before beginning the installation. . . . . . . . 5
Boiler ratings and specifications . . . . . . . . . . . . 6
Installation site preparation . . . . . . . . . . . . . . . 7
Prepare the boiler . . . . . . . . . . . . . . . . . . . . 10
Water piping. . . . . . . . . . . . . . . . . . . . . . . . 11
Gas piping . . . . . . . . . . . . . . . . . . . . . . . . . 18
Wiring a single boiler . . . . . . . . . . . . . . . . . . 20
Control setup . . . . . . . . . . . . . . . . . . . . . . . 25
Vent piping (and air piping when used) . . . . . . 28
Condensate drain line. . . . . . . . . . . . . . . . . . 29
Fill and test the system . . . . . . . . . . . . . . . . . 30
Starting the boiler . . . . . . . . . . . . . . . . . . . . 32
Annual start-up . . . . . . . . . . . . . . . . . . . . . . 41
Maintenance . . . . . . . . . . . . . . . . . . . . . . . 42
Replacement parts. . . . . . . . . . . . . . . . . . . . 46
Appendix A — suggested wiring. . . . . . . . . . . 48

3
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Customer service and technical support
Direct all questions to your HydroTherm distributor or contact the HydroTherm Customer Service Department at:
260 North Elm Street Westfield, MA 01085.
Always include the model and serial numbers from the rating plate of the boiler in question.
Claims for damage or missing components must be filed immediately against the transportation company by the
consignee.
Read before proceeding
Codes and standards
Code compliances
All aspects of the boiler installation must conform to the requirements of
the authority having jurisdiction, or, in the absence of such requirements,
to the National Fuel Gas Code, ANSI Z223.1/NFPA 54-latest revision.
Where required by the authority having jurisdiction, the installation must
conform to the Standard for Controls and Safety Devices for Automati-
cally Fired Boilers, ANSI/ASME CSD-1.
In Canada, the installation must be in accordance with the requirements
of CSA B149.1 or .2, Installation Code for Gas Burning Appliances and
Equipment.
Before assembling the boiler . . .
Verify boiler rating and gas supply
• Before assembling and installing the boiler, check the ratings to en-
sure that the unit has been sized properly for the job.
• Ensure that the boiler will be set up for the type of gas available at the
installation site.
Verify location is suitable
• Ensure the availability of an adequate electrical supply, uncontami-
nated air for combustion, and that vent (and air) piping can be cor-
rectly installed.
• Ensure the boiler can be connected to system water piping and gas
supply.
• e boiler must not be exposed to dripping or spraying water or to
rain.
• If replacing an existing boiler, nd out what caused the boiler to fail
before installing a new boiler. Correct the problems that led to failure,
or the failure may happen to the new boiler.
Attention:
Use of an approved dust respirator is strongly
recommended when handling the insulating com-
ponents of the boiler.
Electrical shock hazard — Disconnect all electrical
power sources to the boiler before making any electrical
connections.
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and dangerous
operation! Verify proper operation aer servicing.
Failure to comply with the above could result in severe
personal injury, death or substantial property damage.
e electrical connections to this boiler must be made in
accordance with all applicable local codes and the latest
revision of the National Electrical Code, ANSI /NFPA-70.
Installation should also conform to CSA C22.1 Canadian
Electrical Code Part I if installed in Canada. Install a sepa-
rate 120 volt 15 amp circuit for the boiler. A properly rated
shut-o switch should be located at the boiler. e boiler
must be grounded in accordance with the authority having
jurisdiction, or if none, the latest revision of the National
Electrical Code, ANSI/NFPA-70.
Line voltage eld wiring of any controls or other devices
must use copper conductors with a minimum size of
#14awg. Use appropriate wiring materials for units
installed outdoors.
DO NOT open any gas valve, or aempt to re the boiler,
until all boilers have been set up and veried following the
instructions in the KN Series Gas Boiler Installation &
Operating Instructions.
Failure to comply could cause a boiler failure, leading to
possible severe personal injury, death or substantial prop-
erty damage.

4P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Components and special tools required
Special equipment/materials required for assembly
Sealants, lubricants and adhesives supplied with boiler (in hardware box)
Boiler components and shipping information
1. One quart 30-wt motor oil
2. Rubber and leather gloves
3. Rubber or leather mallet
4. Two 2”x4”x12” boards (used for
cushioning when seating push nipples)
5. Two 18-inch pipe wrenches
6. Torque wrench (at least 30 foot-pound
capacity)
7. Deep socket, 11/16” for use with torque
wrench
8. Standard hand tools, wire, nuts, electrical
hand tools
9. 2”x2” steel square stock x 6 inches long,
for driving square-socket pipe plugs
(supplied with boiler in hardware box)
Use gloves when working with
these products as specied in
these instructions and in the
product instructions.
1. Silicone RTV-6500 HiTemp: (3) 10-
oz caulk tubes (for sealing between
sections)
2. Loc-Tite 30557 pipe dope: (1) 16-oz can
(for water and gas piping connections)
3. Hercules Pro Dope: (1) 8-oz jar (for
mixing with 30-wt motor oil, used as
lubricant for push nipples)
4. Res Bond 2300: (1) 11-oz caulk tube (for
sealing burner assembly)
5. Fast-Tack 87: (1) 13-oz spray can (for
securing flue baffles to sections)
Skid 1
Cast iron sections (front, rear and
intermediate)
Push nipples
3” x 8” supply nipple and return
nipple
Pipe plugs
Draw rods and hardware
All-thread rods (7/8”) and cast-iron
draw-up plates for assembling boiler
block
Ceramic flue baffles
Hardware box (bolts, nuts, etc., indi-
vidually packed/labeled by usage)
Skid 2
Base
Burner kit
Ceramic combustion chamber
Drain pan (with inspection cover
plate pre-attached)
Upper casting
4” x 6” boards for section assembly
Skid 3
Jacket components
Jacket insulation
Blower and filter box assembly
Control box assembly
Gas train assembly
Gas train shroud
Components box (igniter, sight
glass, supply and return sensors,
LWCO assembly, etc.)
Flue adapter assembly
Condensate trap assembly

5
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 1 Place 4x6 boards on base
Ignore the palee under the
boiler in the manual images
— it is le in place during
assembly for demonstration
purposes only.
1. Remove base from skid.
2. Place a 4x6 board (supplied) against
each side as a runner shown.
3. Space runner boards with about even
amounts off of each end of the base.
4. The runner boards will be used to
support the boiler block during as-
sembly, then removed afterward.
Step 2 Oil top surface of runner
boards
1. Use a brush to spread 30-wt motor
oil on the runner boards. This will
allow sections to move easily during
draw-up.
Step 3 Position the rear section
Use leather gloves when li-
ing or moving boiler sections.
Sections are heavy and can
cause severe personal injury
or death if mishandled.
Li section using two
people, following the
recommendations shown in
Step13,page8.
1. Identify the rear section — its lower
nipple port is on the right side when
looking at the inside of the section, as
in this photo.
2. Slide the rear section to the end of
the base. Have someone support the
section during the next step.
Step 4 Bolt rear section to base
1. Use 3/8 x 3½” bolts, wedges, split
lock washer and nut on each side as
shown.
2. Point the wedge narrow edge toward
the section.
Tighten bolt rmly, but DO
NOT over-tighten — the
cast iron ange could be bro-
ken if too tight. Tighten only
until the split lock washer has
just aened.

6P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 5 Prepare section for baffle
Use of an approved dust
respirator is strongly recom-
mended when handling the
insulating components of the
boiler.
1. Spray cast iron heat pin section liber-
ally with spray adhesive supplied with
the boiler.
2. Avoid spraying on the nipple port
machined surfaces.
Step 6 Install baffle
Do not use baes if they
have been broken, cracked,
folded or frayed. Obtain re-
placements before proceed-
ing with the boiler assembly.
1. Place a baffle in the heat pin area of
the front section as shown.
2. The cut-off corner must go to the
lower right.
3. Press into place.
4. Make sure the baffle does NOT
overlap onto the perimeter surfaces
of the section. This would prevent the
section from drawing up correctly.
Step 7 Apply RTV to perimeter
Rubber gloves are recom-
mended for this procedure.
1. Apply a bead of silicone RTV (sup-
plied with boiler) on the perimeter
surfaces of the section and around
the INSIDE edges of the nipple ports.
2. This is necessary to form a seal be-
tween the sections. The seal prevents
flue gases from escaping.
3. Extend the bead all the way from the
top of the section to the bottom.
4. Keep the bead of silicone close to the
INSIDE edge of the nipple ports.
5. This will protect the machined nipple
port surfaces from condensation that
may occur in the flueways.

7
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 8 Push nipple lubricant
Rubber gloves are recom-
mended for this procedure.
1. In a disposable container, mix some
30-wt motor oil with some of the
Hercules Pro Dope supplied with the
boiler.
2. The consistency should be similar to
thick paint and should flow easily.
3. You will need enough to lubricate all
nipple ports and all push nipples —
probably about ½ pint is enough.
Step 9 Lubricate nipple ports
1. Brush the pipe dope/oil mixture on
the inner machined surfaces of the
nipple ports.
2. Avoid getting lubricant on the sili-
cone RTV or on the face of the nipple
ports.
Step 10 Lubricate push nipples
1. Brush the entire outside surface of
each nipple port with the lubricant.
Step 11 Insert push nipples
Avoid scarring or damaging
the push nipple or nipple
port surfaces. e push nip-
ple makes a metal-to-metal
seal with the nipple port. Any
surface defects could cause a
leak.
1. Insert a push nipple into each of the
two nipple ports.
2. Seat each nipple firmly but squarely.
3. Make sure the nipple face is parallel
to the section surface as closely as
possible.
4. DO NOT attempt to assemble sec-
tions if any nipple port is mis-aligned.

8P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 12 Seat the push nipples
1. Place a 2x4 board across the nipple
and strike firmly with a mallet.
2. Do this with several strokes, just so
the push nipple is firmly started.
3. Make sure the board is parallel to the
nipple port surface to prevent rolling
the push nipple.
Step 13 Lifting the sections
Use leather gloves when li-
ing or moving boiler sections.
Sections are heavy and can
cause severe personal injury
or death if mishandled.
Li section using two
people, following the
recommendations shown in
Step13,page8.
1. Lift section, with each person holding
at the bottom of the section.
2. Handlers should lift with their legs to
avoid back strain.
Step 14 Draw up sections
1. Carefully slide the first intermediate
section up to the front.
2. Before pulling the intermediate
section up fully, brush lubricant on
the inside machined surfaces of the
nipple ports as in Step 9, page 7.
3. Use a 2x4 board and mallet to start
the section in place as shown in
Step 17, page 9.
4. Wipe a small amount of motor oil on
the ¾-inch all-thread rods supplied
with the boiler to make pull-up easier.
5. Place a ¾” nut and washer plus a cast
iron plate (supplied with boiler) on
the ¾” rod on each side as shown.
6. Snug finger tight.
Step 15 Pull sections together
1. Use box wrenches (preferred) to pull
the sections together.
2. Alternate from one side to the other
during pull-up to avoid cocking the
nipple ports.
3. When the sections are properly
pulled up, they will be nearly metal-
to-metal.

9
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 16 Install baffle
Do not use baes if they
have been broken, cracked,
folded or frayed. Obtain re-
placements before proceed-
ing with the boiler assembly.
1. Before adding additional sections,
install a baffle in the flueway as in
Step 5, page 6 and Step 6, page 6.
2. Place a baffle in the heat pin area of
the front section as shown.
3. The cut-off corner must go to the
lower right.
4. Press into place.
5. Make sure the baffle does NOT
overlap onto the perimeter surfaces
of the section. This would prevent the
section from drawing up correctly.
Step 17 Use 2x4 and mallet
1. To initially seat the push nipple into
the next section, rap with a mallet
and 2x4 at each nipple port.
2. Repeat, alternating from right nipple
port to left to avoid cocking the push
nipples.
Step 18 Install draw rods
e draw rods ARE NOT
used to pull the sections
together, only to keep them
rmly in position.
1. When the section assembly is com-
pleted, slide a draw rod through each
of the four draw rod holes.
2. Apply a washer and nut on each end
and pull up finger tight.
Step 19 Use a torque wrench
DO NOT exceed 30foot-
pounds when tightening
nuts. Higher torque could
cause breakage of the cast
iron.
1. Use a torque wrench to tighten the
nuts on the draw rods.
2. Start with the upper left corner rod
first.
3. Tighten the nut to 15 foot-pounds.
4. Move to the lower right rod. Tighten
the nut to 15 foot-pounds.
5. Repeat with the lower left, then the
upper right rod, both tightened to
15 foot pounds.
6. Repeat this sequence again, but finish
the tightening to 30 foot-pounds for
each nut.

10 P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 20 Bolt boiler to base
Before bolting the boiler to
the base, knock the two 4x6
boards out from under the
block. If necessary, loosen the
two bolts that secure the back
section to the base.
1. Install a bolt, wedge, washer and nut
on side of the front section as done in
Step 4, page 5.
2. Tighten only until the split lock
washer has just flattened.
3. Make sure the back section bolts are
tightened as well.
Step 21 Inspection port plugs
1. Apply pipe dope (supplied with
boiler) to plugs (supplied) and install
in each of the inspection ports at the
lower right side of each section.
Step 22 Prepare condensate pan
Rubber gloves are recom-
mended for this procedure.
e condensate drain pan
is shown here with the
inspection plate and gasket
installed. is can be done
before or aer the conden-
sate drain pan is bolted to the
boiler.
1. Use the silicone RTV supplied with
the boiler to apply a bead on the
condensate pan flange around the
complete perimeter.
2. At each of the four corners, apply a
bead on the flange where the sheet
metal edges meet.
Step 23 Install condensate drain
pan
1. This procedure requires two people
to do correctly.
2. Guide the condensate drain pan
through the front of the base as
shown.
3. When in position, lift the pan straight
up and hold firmly against the bot-
tom of the section assembly.
4. Install each bolt with two flat washers,
one split lock washer and nut (pro-
vided). Insert the bolts from the top.
5. Tighten just until the split lock washer
has flattened.

11
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 24 Install condensate drain
connector
e condensate drain pan
is shown here without the
inspection plate and gasket
installed, to be installed in
Step25,page11.
See Step25,page11 for
details of condensate drain
pan components.
1. The condensate drain connector con-
sists of a plate, O-ring and strainer.
2. Assemble the three parts as shown.
3. Insert the assembly into the bottom
of the condensate drain pan.
4. Look for underneath while assem-
bling to ensure the condensate drain
connector is properly seated.
5. Secure in place with the screws
provided.
Step 25 Install inspection cover
is could be done before
the condensate drain pan
is installed, as shown in
Step22,page10.
e inspection cover is used
for annual inspection of
the section assembly and
condensate handling compo-
nents.
1. Assemble inspection cover flange
and gasket.
2. Position over condensate drain pan
inspection opening.
3. Secure with screws provided.
LEGEND for drawing at right:
30 Hex nuts
31 Inspection cover
32 Inspection cover gasket
33 Condensate drain pan
34 Condensate strainer
35 Condensate drain connector O-ring
36 Condensate drain connector plate
37 Washers
38 Hex bolts
Step 26 Inspect combustion
chamber area for excess silicone 1. Remove any excess silicone that may
have extruded into the interior of the
section assembly.
2. This area must not have any blockage
where the combustion chamber will
be inserted.

12 P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 27 Install combustion cham-
ber
e combustion chamber
material is fragile, and can be
cracked or gouged with in-
correct handling. HANDLE
CAREFULLY! DO NOT
use the chamber if it is dam-
aged.
Use of an approved dust
respirator is strongly recom-
mended when handling the
insulating components of the
boiler.
1. Insert the chamber into the top of the
section assembly as shown.
2. Position the chamber with the
ROUND hole toward the front and the
SQUARE hole to the rear.
3. The combustion chamber should sit
evenly in the opening, with its FLAT
surface facing up and even with the
surface of the sections.
Step 28 Position the burner gasket
Use of an approved dust
respirator is strongly recom-
mended when handling the
insulating components of the
boiler.
1. Carefully place the burner gasket
on the surface of the combustion
chamber.
Step 29 Apply Resbond adhesive
to the burner gasket
Rubber gloves are recom-
mended for this procedure.
1. Apply a generous bead of Resbond
adhesive (supplied with boiler)
around the entire burner gasket.
2. Position the bead in the center of the
gasket.
3. This adhesive will bond the gasket
to the burner when the burner is
installed.

13
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 30 Burner and manifold
REMOVE THE PILOT
ORIFICE ASSEMBLY
before proceeding. e pilot
orice assembly (shown in
Step37,page15) is factory-
installed in the manifold.
It must be removed before
the manifold is installed to
prevent damage to the pilot
assembly or pilot tube.
1. This illustration shows the manifold
(left) and the burner (right).
2. Orient the burner as shown, with the
double set of bolt notches on the
same side as the blower flange of the
manifold.
3. This will position the pilot tube at the
top as shown in the lower photo.
Step 31 Apply silicone RTV to top
surface of section assembly
Rubber gloves are recom-
mended for this procedure.
1. Apply a generous bead of silicone
RTV completely around the flange
surface of the section assembly.
Step 32 Mark bolt locations
1. Some of the bolt notches in the
burner flange will be used to secure
the manifold.
2. The burner is attached to the section
assembly before the manifold. To
avoid using the wrong bolt notches,
place the burner against the manifold
as shown.
3. Use a marker pen to mark ONLY the
bolt notches NOT required for bolting
the manifold.

14 P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 33 Install the burner
1. Place the burner on top of the section
assembly as shown.
2. The PILOT TUBE must be at the REAR
of the boiler.
Step 34 Install burner bolts
1. Press the burner flange down firmly
and install bolts, washers and nuts
supplied.
2. Place bolts ONLY at the bolt notches
marked in Step 32, page 13.
3. Secure the bolts firmly, but avoid
distorting the burner flange.
Step 35 Position the manifold
1. Place the manifold on top of the
section assembly as shown, with the
blower flange to the FRONT of the
boiler.
Step 36 Install manifold bolts
1. The manifold gasket is pre-attached
to the manifold at the factory.
2. Install a bolt, two flat washers, split
lock washer and nut at each bolt lug
on the manifold.
3. Tighten the bolts only until the split
lock washer is just flattened.

15
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 37 Install pilot assembly
1. Use a flashlight to look down through
the pilot mounting hole at the top
rear of the manifold.
2. The pilot tube (shown in
Step 34, page 14 at the top rear of
the burner) must be aligned with the
hole in the manifold.
3. If the pilot tube is not aligned, use a
screwdriver to reach into the mani-
fold hole and coax the pilot tube into
position.
4. After ensuring the pilot tube is
aligned properly, insert the pilot
orifice assembly as shown.
5. Screw the pilot orifice into the
manifold hole securely. DO NOT over-
tighten.
Step 38 Install burner inspection
port 1. The burner inspection port consists of
a plate, gasket, inspection glass, and
another gasket.
2. Place against the mounting boss on
the top front section.
3. Secure with the bolts and washers
provided.
Step 39 Install plug in front sec-
tion lower nipple port tapping 1. Obtain the 3” flat plug supplied with
the boiler.
2. Apply pipe dope to the tapping and
the plug.
3. Install the plug securely.

16 P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 40 Apply jacket front insula-
tion
Leather gloves are recom-
mended when handling sheet
metal components. ey will
reduce the possibility of cuts
from sheet metal edges.
1. Press jacket front insulation against
the back of the front panel.
Step 41 Mounting hole alignment
1. The installer is pointing to the jacket
panel mounting hole toward the left
center of the jacket front panel.
2. Insert a screwdriver through this hole
and the insulation to help align the
hole to the mounting boss on the
front section while placing the jacket
front panel.
3. Position the jacket front panel on
the section and secure with a bolt
through this hole.
Step 42 Install gas line bracket
1. Install the gas line bracket to the right
front using the bolts provided.

17
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 43 Apply jacket rear insula-
tion
Use of an approved dust
respirator is strongly recom-
mended when handling the
insulating components of the
boiler.
1. Press jacket rear insulation against the
back of the rear panel.
Step 44 Install jacket rear panel
e jacket rear panel is sup-
plied with the igniter and
conduit box installed.
Leather gloves are recom-
mended when handling sheet
metal components. ey will
reduce the possibility of cuts
from sheet metal edges.
1. Insert a screwdriver through the left
center jacket mounting hole.
2. Use the screwdriver to help align the
mounting hole with the mounting
boss on the rear section.
3. Secure the jacket rear with the bolts
provided.
4. Apply the upper left bolt and the two
lower bolts.
5. The fourth jacket mounting hole is
under the conduit box. Temporarily
remove this box to install the bolt.
Then re-install the box.

18 P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 45 Install flue adapter
Make sure the ue adapter
condensate nipple is located
at the BOOM when in-
stalled.
Rubber gloves are recom-
mended for this procedure.
1. Apply silicone RTV to the flue adapter
mounting boss.
2. Position the flue adapter on the boss
and insert the four mounting bolts.
The condensate nipple must be
pointed DOWN.
Step 46 Install supply nipple
e boiler is supplied with
two nipples that include
three control tappings. e
nipples are identical, but they
must be positioned dier-
ently.
1. Apply pipe dope to one of the 3-inch
nipples and the upper right tapping
on the rear of the boiler.
2. Install the supply nipple in the tap-
ping.
3. When the nipple is tightened, it must
be in the orientation shown — the
½” tapping must be on top, with a
¾” tapping at the right and at the
bottom.
4. The ½” tapping is used for the 10K
supply sensor.
Step 47 Install supply nipple
e boiler is supplied with
two nipples that include
three control tappings. e
nipples are identical, but they
must be positioned dier-
ently.
1. Apply pipe dope to one of the other
3-inch nipple and the lower left tap-
ping on the rear of the boiler.
2. Install the return nipple in the tap-
ping.
3. When the nipple is tightened, it must
be in the orientation shown — the
½” tapping must be on right, with a
¾” tapping at the bottom and at the
left side.
4. The ½” tapping is used for the 10K
return sensor.
5. The ¾” bottom tapping is used for the
boiler drain.
6. The ¾” side tapping should be
plugged unless used for a special
purpose.

19
P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 48 Install the ignition elec-
trode assembly
Check/adjust the igniter
electrode positioning before
installing. ey are not fac-
tory preset.
1. Check the distance from the ignition
electrode plate to the front end of the
ignition electrode ceramics. It must
be 1½ inches (see dimension “A” in
drawing at right.
2. Check the spacing between the
igniter tips. It must be 1/8 inch (see
drawing at right).
3. If the electrodes are not positioned
correctly, loosen the mounting
screws and adjust.
4. Apply the gasket to the back of the
ignition electrode plate.
5. Bolt the plate to the boiler.
6. Attach the electrode wires to the
electrodes. Then slide the rubber
boots over the connections.
Step 49 Attach the UV scanner
1. Attach the UV scanner to the
threaded boss on the electrode plate
assembly.
Step 50 Mark the gas line nipple
e gas line nipple is factory-
aached to the mounting
brackets. e nipple must
be removed for connection
to the gas train. is step en-
sures the nipple is correctly
placed when re-aached to
the bracket.
1. Use a marker pen to mark the loca-
tion of the two mounting clamps on
the gas line nipple.
2. Mark the gas line nipple to indicate
which end is the top.

20 P/N 42-9551
KN Series Gas-fired direct vent cast iron boilers – Field assembly instructions
Step 51 Mount the control panel
e control panel mounts on
the mounting clip at the top
of the jacket front panel. e
conduit ing and the sensor
hose must be routed through
jacket panel.
1. BX conduit fitting — Hold the control
panel close enough to the jacket
front panel to allow inserting the
conduit fitting through the back of
the panel. Then apply and tighten the
fitting lock nut.
2. Feed the sensor hose through the
grommet-fitted hole in the jacket
panel (see second photo).
3. Then clip the control panel to the
mounting bracket.
Step 52 Attach the gas line nipple
to the gas train 1. Apply pipe dope to the gas line
nipple bottom end. REMOVE any pipe
dope from the inside of the pipe.
Step 53 Tighten gas line nipple
Use two wrenches to prevent
damage to gas train compo-
nents.
1. Use two pipe wrenches to tighten the
gas line nipple connection.