Laars Mighty Therm HH 500 User manual

FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician,
qualified in hot water boiler installation and maintenance. Improper installation and/or operation could
create carbon monoxide gas in flue gases which could cause serious injury, property damage, or death.
Improper installation and/or operation will void the warranty.
WARNING
If the information in this manual is not followed exactly, a fire or explosion may result
causing property damage, personal injury or loss of life.
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or
any other appliance. WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any phone in your building.
• Immediately call your gas supplier from a nearby phone. Follow the gas supplier's
instructions.
• If you cannot reach your gas supplier, call the fire department.
Installation and service must be performed by a qualified installer, service agency, or gas
supplier.
H0117400E
Installation and Operation
Instructions for
Mighty Therm
Hydronic Boilers
Models HH and PH
Sizes 500-1825
These instructions are to be stored in the pocket provided on the boiler
Installation and Operation Instructions Document 1049E

LAARS Heating Systems
Page 2
TABLE OF CONTENTS
SECTION 1.
General Information
1A. Introduction...................................................3
1B. BoilerIdentification .......................................3
1C. Flow Requirements.......................................3
1D. Variable Water Flow Systems.......................4
1E. Warning Regarding Chilled
Water Systems ............................................. 5
1F. FreezeProtection .........................................5
SECTION 2.
Installation
2A. Boiler Placement .......................................... 6
2B. Installation of Indoor Boilers..........................6
2B-1. Combustion Air Supply .................................6
2B-2. Venting ......................................................... 8
2C. Installation of Outdoor Boilers....................... 9
2D. Gas Supply and Piping .................................9
2E. Electrical Wiring.......................................... 10
2F. Water Piping of System .............................. 11
2G. FillingFully-Connected System................... 11
SECTION 3.
Operation
3A. Controls - General ...................................... 12
3B. Initial Start-Up ............................................. 13
3C. To Start Up System .................................... 13
3D. To Turn Off Boiler ....................................... 14
3E. To Shut Down System ................................ 14
SECTION 4.
Maintenance
................................................................... 14
SECTION 5.
Troubleshooting and Analysis of
Service Problems
................................................................... 16
SECTION 6.
Parts Descriptions and
Order Numbers
................................................................... 18
SECTION 7.
Outdoor Parts Descriptions and
Order Numbers
................................................................... 26
SECTION 8.
Optional Parts Descriptions and
Order Numbers
................................................................... 28

MightyThermHydronicBoiler Page 3
SECTION 1.
General Information
1A. Introduction
This manual provides information for the
installation and operation of Laars hydronic boilers. It
is strongly recommended that all application and
installation procedures be reviewed completely before
proceeding with the installation. Consult the Laars
factory, or local factory representative with any
problems or questions regarding this equipment.
Experience has shown that most problems are caused
by improper installation not system design.
Some accessory items are shipped in separate
packages. Verify receipt of all items listed on the
package slip. Inspect everything for possible damage
upon delivery, and inform the carrier of any shortages
or impairments. Any such claims should be filed with
the carrier. The carrier, not the shipper, is responsible
for shortages and damage to the shipment whether
visible or concealed.
IMPORTANT WARNING:
The model HH and PH hydronic boilers must be
installed in accordance with the procedures outlined
in this manual. The warranty does not apply to boilers
not installed or operated in accordance with these
procedures. Consult local building and safety codes
before proceeding with work. The installation must
conform to the requirements of the authority having
jurisdiction or, in the absence of such requirements, to
the latest edition of the National Fuel Gas Code;
ANSI Z223.1, National Electrical Code ANSI/NFPA
70 and/ or in Canada CAN 1 -13149 requirement.
When required by the authority having
jurisdiction, the installation must conform to
American Society of Mechanical Engineers safety
codes for controls and safety devices for automatically
fired boilers No. CSD-1, and in Canada CGA 3.3. Any
modification to the boiler, its gas controls, gas
orifices, wiring or draft diverter may void the Laars
warranty. If field conditions require such
modifications, consult factory.
1B. Boiler Identification
Consult rating plate on the boiler. The following
example simplifies the boiler identification.
1 2 3456
PH 1670 I N 09 L
(1) Basic boiler model (see descriptions below).
(2) Input rate X 1000 BTU/hr.
(3) Indoor (1) or Outdoor (E) installation.
(4) Gas type: Natural (N) or Propane (P).
(5) Ignition system: I.I.D. (09) or continuous pilot
(16). Special option: I.I.D. (04) 115 volts.
(6) Firing modes:
On/Off (C)
2-stage (K)
4-stage (L)
Mechanical Modulation (H)
Motorized Modulation (F)
Motorized On/Off (R)
Motorized 2-stage (T).
Model HH hydronic heating boilers. There must
be a field installed pump to circulate water.
Model PH hydronic heating boilers are basically
the same as the HH models except that the PH boilers
come with integrally mount pumps. Pumps are sized
for pressure drop through the heat exchanger and short
runs of pipe for primary-secondary systems.
Laars hydronic boilers are available in two
configurations: an indoor version and an outdoor
version. Both are available from the factory (see
Figure 1).
1C. Flow Requirements
All low volume hydronic boilers must have
continuous flow through the heat exchanger for proper
operation. The system pump must be capable of
developing sufficient pressure to overcome the
Figure 1. Boiler Configuration.

LAARS Heating Systems
Page 4
Design Temperature Rise Across The Boiler
20°F 11°C 25°F 14°C 30°F 17°C 35°F 19°C
Indoor Outdoor Flow H/L Flow H/L Flow H/L Flow H/L
Sizes Sizes GPM l/s Ft. mGPM l/s Ft. mGPM l/s Ft. mGPM l/s Ft. m
500 — 38 2.4 1.4 0.4 31 2.0 1.1 0.3 26 1.6 0.9 0.3 22 1.4 0.6 0.2
— 500 41 2.6 1.7 0.5 33 2.1 1.1 0.3 27 1.7 0.9 0.3 23 1.5 0.7 0.2
600 — 49 3.1 2.3 0.7 39 2.5 1.6 0.5 32 2.0 1.1 0.3 28 1.8 0.9 0.3
— 600 49 3.1 2.3 0.7 39 2.5 1.6 0.5 32 2.0 1.1 0.3 28 1.8 0.9 0.3
715 — 56 3.5 2.5 0.8 45 2.8 1.9 0.6 37 2.3 1.5 0.5 32 2.0 1.0 0.3
— 715 58 3.7 3.2 1.0 47 3.0 2.2 0.7 39 2.5 1.6 0.5 33 2.1 1.1 0.3
850 — 66 4.2 3.4 1.0 53 3.3 2.5 0.8 44 2.8 2.0 0.6 38 2.4 1.4 0.4
— 850 69 4.4 3.6 1.1 55 3.5 3.1 0.9 46 2.9 2.2 0.7 39 2.5 1.6 0.5
1010 — 79 5.0 4.7 1.4 63 4.0 3.4 1.0 53 3.3 2.7 0.8 45 2.8 1.9 0.6
— 1010 82 5.2 5.0 1.5 66 4.2 3.6 1.1 55 3.5 3.1 0.9 47 3.0 2.2 0.7
1200 — 94 5.9 6.5 2.0 75 4.7 4.8 1.5 62 3.9 3.7 1.1 53 3.3 2.6 0.8
— 1200 98 6.2 6.9 2.1 78 4.9 4.9 1.5 65 4.1 3.6 1.1 56 3.5 3.1 0.9
1430 — 112 7.1 8.9 2.7 89 5.6 6.5 2.0 74 4.7 5.0 1.5 64 4.0 3.5 1.1
— 1430 117 7.4 9.5 2.9 93 5.9 6.7 2.0 78 4.9 5.0 1.5 67 4.2 3.7 1.1
1670 — * * * * 102 6.4 8.8 2.7 85 5.4 6.7 2.0 73 4.6 4.7 1.4
— 1670 * * * * 109 6.9 9.1 2.8 91 5.7 6.8 2.1 78 4.9 5.0 1.5
1825 — * * * * 114 7.2 10 3.0 95 6.0 8.0 2.4 81 5.1 5.5 1.7
— 1825 * * * * 119 7.5 10.4 3.2 99 6.2 8.3 2.5 85 5.4 5.7 1.7
*Consult factory for recommendations
resistance of the boiler plus the entire circulating
system at the designated GPM (see Table 1). The
temperature rise across the boiler should never exceed
40°F (22°C). Primary-secondary pumping is the most
effective way to assure proper flow through the boiler
resulting in longer boiler life and greater system
efficiency (see Figure 2).
1D. Variable Water Flow Systems
Heating systems using zone valves, zone pumps
or 3-way valves can experience reduced water flow
through the boiler. This can result in an excessive
water temperature rise and unstable boiler operation.
If the system water flow is variable, it must not be
allowed to fall below 30% of full flow. The boiler
must be equipped with staged or modulated fire with
the temperature sensor installed in the outlet water.
State variable flow when ordering. Laars recommends
primary-secondary pumping for all variable flow
systems. Primary-secondary pumping is mandatory
for variable flow systems where minimum flows are
less than 30% of full flow conditions. The boiler
pump in a primary-secondary system maintains
constant flow through the boiler even though the
system flow is variable. In a primary-secondary
system the pressure drop of the boiler is not added to
the system (see Figure 2).
Table 1. Flow Requirements.
A Special Note About 3-Way Water Valves
3-way water valves (2 position or proportional)
are sometimes used to divert water around a boiler
and control the temperature of water being supplied to
the system. Valves installed in this manner must be
supplied with an end switch or some other suitable
control to shut off the boiler when the flow is reduced
to 30%. The boiler must be supplied with staged or
modulated fire as indicated in Section 1D, Variable
Water Flow Systems.
It is often possible to accomplish excellent water
temperature control without 3-way valves through
proper application of staged or modulated firing
systems. Consult the factory or local Laars
representative for assistance with such systems.
System Pressure Requirements
The model HH and PH boilers are designed to
operate on closed, pressurized systems. A minimum of
12 psi should be maintained on the system where
boiler supply water temperatures are 200°F (93°C) or
less. If higher temperatures are required, the minimum
system pressure should be at least 15 psi above the
water vapor pressure corresponding to the elevated
water temperature.
The hydronic boilers are not suitable for open
systems unless the supply water temperatures are kept
below 180°F (82°C), and minimum of 5 psi static
head is maintained within the boiler.

MightyThermHydronicBoiler Page 5
1E. Warning Regarding Chilled
Water Systems
When a boiler is connected to an air
conditioning system where the same water is used for
heating and cooling, chilled water must be prevented
from entering the boiler. When changing such a
system from cooling to heating, the chilled water
should be allowed to circulate through the building
(after the chiller has been turned off) for a period long
enough for the water to warm up to at least 70°F
(21°C) before the water is allowed to flow into the
boiler. It is equally important to prevent hot water
from entering the chiller. The system shown in Figure
3 is suggested to make sure that the system water is
neither too hot nor too cold when a changeover from
heating to cooling, or vice versa, takes place. When a
boiler is connected to heating coils located in air
handling units (where they may be exposed to
refrigerated air circulation), the boiler piping system
shall be equipped with a flow control valve or other
automatic means to prevent gravity circulation of
chilled water through the boiler. Chilled water in the
boiler will create condensation on the boiler tubes
which will drip on the burners and may extinguish the
pilot.Boilers installed in violation of either of the
above requirements may void the warranty.
1F. Freeze Protection
Boiler installations are not recommended in
areas where the danger of freezing exists unless
proper precautions are taken for freeze protection. The
preferred method of freeze protection is by
maintaining a mixture of no more than 50% properly
inhibited HVAC glycol. This mixture will protect the
boiler to temperatures of about -35°F (-37°C). To get
the desired temperature rise across the boiler when
this mixture is used, increase the water flow by 15%
above the original recommendation. Increase the head
loss requirement by 20%.
Figure 3. Boiler-Chiller Installation.
Figure 2. Typical Schematic for a Primary-Secondary System.
Suggested Wiring Diagram For Tempering System Water
at Change-over From Heating to Cooling.

LAARS Heating Systems
Page 6
SECTION 2.
Installation
2A. Boiler Placement
The boiler must be placed to provide specific
clearances on all sides for maintenance and
inspection. There must also be minimum distances
maintained from combustible surfaces. These
clearances also apply to non-combustible materials,
because the boiler requires air circulation for proper
operation.
Boiler should be mounted on a level surface. An
integral combustible flooring base is provided as
standard equipment on all outdoor models. Indoor
models can be installed on a combustible floor with a
special base assembly which is available from the
factory, or with a base that complies with local code
requirements. See rating plate for part number of the
base assembly.
Do not install boiler on carpeting.
Under the National Fuel Gas Code, ANSI
Z223.1, it is permissible to place the boiler on floors
other than non-combustible when the installation
complies with the American Insurance Code. Figures
5, 6, 7, and 8 show common installation on
combustible flooring.
2B. Installation of Indoor Boilers
1. Locate the boiler to provide adequate
clearance for inspection and service on all sides
(see Table 2). We recommend minimums of 24"
from front (for proper access to and service of
controls) and 18" at water connection end. For
alcove installation, see Figure 9.
2B-1. Combustion Air Supply
1. The boiler location must provide sufficient air
supply for proper combustion and ventilation of
the surrounding area as outlined in the latest
edition of ANSI standard Z223.1 and/or in
Canada CAN 1 - B1 49 requirements, and any
local codes that may be applicable. Inadequate
combustion air supply may result in incomplete
combustion, sooting of the heat exchanger, and
unsafe operation of the boiler.
2. (a.) In the United States, the general
requirements specify that boiler rooms should be
provided with two permanent air supply
openings communicating directly through the
wall to outside air; one within 12 inches
(305mm) of the ceiling, and the other within 12
inches (305mm) of the floor. Each opening
should have a minimum free area of one square
inch per 4,000 BTUH input of the total input
rating of all appliances in the enclosed area. See
Table 3 for recommended air supply for each
model. An improperly ventilated equipment
room can get excessively hot and cause
accelerated deterioration of controls and
electrical components.
Table 2. Minimum Boiler Clearances
From Combustible Surfaces.
Clearance Indoor Outdoor
From inches mm inches mm
Top 30 762 unobstruct
Water Conn. Side 12 305 24 610
Opposite Side 6 152 24 610
Front Alcove Unobstruct
Rear 8 203 24 610
Vent Pipe* 6 152 —
Hot Water Pipes Per Code Per Code
*1" when using type B Vent (refer to Manufacturer's
Instructions
2. Install the boiler on a waterproof floor with an
adequate floor drain and a 6" (152mm)
minimum curb on all four sides to protect the
building if boiler repairs are required. The
manufacturer will not be held liable for any
water damage in connection with this boiler. Table 3. Minimum Recommended
Air Supply to Boiler.
Boiler Each Opening*
Model Sq. Inches Sq. cm
500 125 806.5
600 150 967.8
715 179 1154.9
850 213 1374.3
1010 253 1632.4
1200 300 1935.6
1430 358 2309.8
1670 418 2696.9
1825 457 2948.6
*Net FreeArea in Square Inches
Area indicated is for one of two openings; one at
floor level and one at the ceiling, so the total net
free area could be double the figures indicated.
For special conditions refer to the latest edition of
ANSI Z223.1.
Consult factory if not communicating directly
through the walls with the outdoors.
Note: Check with louver manufacturers for net
free area of louvers. Correct for screen
resistance to the net free area if a screen is
installed. Check all local codes applicable to
combustion air.

MightyThermHydronicBoiler Page 7
(b.) In Canada, consult local building and safety
codes or, in the absence of such requirements,
follow CGA requirements and/or CAN 1 - B149
standard. (Table 3 does not apply).
3. Exhaust Fans or Vents: Any equipment which
exhausts air from the boiler room can deplete the
combustion air supply or reverse the natural
draft action of the venting system.
The boiler must be completely isolated and this
could cause flue products to accumulate in the
room. Additional air must be supplied to
compensate for such exhaust. The information in
Table 3 is not applicable in installations where
exhaust fans or blowers of any type are used.
Such installations must be designed by qualified
engineers.
Figure 4. Base for Combustible Floors.
Figure 5. Typical Boiler Installation on Concrete Slab.
Figure 6. Typical Boiler Installation on Raised Platform
(Wood).
Figure 7. Typical Boiler Installation on Roof Using a
4 x 4 Stringer.
Figure 8. Installation on Concrete Blocks or Tile.

LAARS Heating Systems
Page 8
Figure 9. Alcove Installation.
4. If a blower or fan is used to supply air to the
heater room, the installer should make sure it
does not create drafts which could cause
nuisance shutdowns of the pilot. If a blower is
necessary to provide adequate combustion air to
the boiler, a suitable switch or equivalent must
be wired into the boiler control circuit to prevent
the boiler from firing unless the blower is
operating.
5. The boiler must be completely isolated and
protected from any source of corrosive chemical
fumes such as trichlorethylene, perchlorethylene,
chlorine, etc.
2B-2. Venting
1. Laars boilers have built-in draft diverters for
natural draft operation and must not be
connected to any portion of a mechanical draft
system under positive pressure. The flue outlet
must be connected to a clear, unobstructed vent
of adequate capacity ending above the highest
point of the building with an approved vent cap.
The venting system should be installed
according to the latest edition of ANSI Z223.1
and/or, in Canada, CAN1-13149 requirement
and any local codes having jurisdiction.
IMPORTANT NOTE: Do not use sheet metal
screws at the snap lock joints of Type B gas vents.
2. Do not weld or fasten the vent pipe to the boiler
draft hood. The weight of the stack must not rest
on the boiler. The draft hood and boiler top must
be easily removable for normal boiler service
and inspection.
3. Avoid using long horizontal runs of the vent
pipe, and too many 90° elbows, reductions or
restrictions. Horizontal runs should have at least
a 1/4" rise per foot in the direction of flow. A
vent connector should be supported for the
design and weight of the material used to
maintain clearances and prevent physical
damage and separation of joints.
4. Avoid ending heater vents near air conditioning
or air supply fans. The fans can pick up exhaust
flue products from the boiler and return them
inside the building, creating a possible health
hazard. A minimum of 4 feet (1.2m) horizontal
distance must be maintained from electrical
meters, gas meters, and relief equipment.
5. Always use double-wall or insulated vent pipe
(Type B or equivalent). In cold weather,
uninsulated outside vents can chill the rising flue
products, blocking the natural draft action of the
venting system. This can create a health hazard
by spilling flue products into the boiler room.
6. Avoid oversize vent piping or extremely long
runs of the pipe which may cause excessive
cooling and condensation. Rule of Thumb: The
total length of the vent, including the connector
and any offset, should not exceed 15 feet (4.6m)
for every inch of vent diameter. Longer total
lengths shown in venting tables are based on
maximum capacity, not condensation factors.
7. When the installation of a draft fan is necessary
in connecting a venting system to a Laars boiler,
the installation should be engineered by
competent personnel following good engineering
practices. The draft fan supplier should be
consulted for correct size. The installation
should be in accordance with the latest edition of
ANSI Z223.1 and/or, in Canada, CAN 1-B149
requirement and any local codes having
jurisdiction. When a draft fan is installed, a
suitable draft switch must be wired into the
boiler control circuit at terminal designated
“Field Interlock” to prevent firing of the boiler
unless a positive draft has been established.
8. When an existing boiler is removed from a
common venting system, the common venting
system is likely to be too large for proper venting
of the appliances remaining connected to it.
At the time of removal of an existing boiler, the
following steps shall be followed with each
appliance remaining connected to the common
venting system placed in operation, while the

MightyThermHydronicBoiler Page 9
other appliances remaining connected to the
common venting system are not in operation.
(a) Seal any unused openings in the common
venting system.
(b) Visually inspect the venting system for
proper size and horizontal pitch and
determine there is no blockage or
restriction, leakage, corrosion and other
deficiencies which could cause an unsafe
condition.
(c) Insofar as is practical, close all building
doors and windows and all doors between
the space in which the appliances
remaining connected to the common
venting system are located and other spaces
of the building. Turn on clothes dryers and
any appliance not connected to the common
venting system. Turn on any exhaust fans,
such as range hoods and bathroom
exhausts, so they will operate at maximum
speed. Do not operate a summer exhaust
fan. Close fireplace dampers.
(d) Place in operation the appliance being
inspected. Follow the lighting instructions.
Adjust thermostat so appliance will operate
continuously.
(e) Testfor spillageat thedraft hoodrelief open-
ingafter5minutesofmainburneroperation.
Usetheflameofamatchorcandle,orsmoke
from a cigarette, cigar or pipe.
(f) After it has been determined that each
appliance remaining connected to the
common venting system properly vents
when tested as outlined above, return
doors, windows, exhaust fans, fireplace
dampers and any other gasburning
appliance to their previous conditions of
use.
(g) Any improper operation of the common
venting system should be corrected so the
installation conforms with the latest edition
of the National Fuel Gas Code, ANSI
Z223.1. When resizing any portion of the
common venting system, the common
venting system should be resized to
approach the minimum size as determined
using the appropriate tables in Appendix G
in the National Fuel Gas Code,
ANSI Z223. 1.
2C. Installation of Outdoor Boilers
1. Locate the boiler to provide the minimum
clearances as listed in Table 2, “Boiler
Clearances.” See Service Clearance, 2 B.1.
2. Do not place the boiler in an enclosure or wall
recess. Avoid locations where wind deflection
off structures might cause a down draft. When
such wind conditions are possible, place the
boiler at least three (3) feet (0.9m) from the
structures.
3. Never install the boiler under any kind of roof
overhang. Do not place the boiler below or
adjacent to any doors, windows, louvers, grills,
etc. which connect in any way with an inhabited
area of a building. This includes other structures
such as garages or utility rooms (see Figure 10).
Figure 10. Incorrect Outdoor Installation.
4. Although these models are AGA designed
certified for outdoor installations, such
installations are not recommended in areas
where the danger of freezing exists unless proper
precautions are taken for freeze protection.
Caution
Outdoor installations are not recommended
in areas where the danger of
snow blockage exists.
2D. Gas Supply and Piping
Review the following instructions before
proceeding with the installation.
1. Verify that the boiler is fitted for the proper type
of gas by checking the rating plate. Laars boilers
are normally equipped to operate below a 2000
foot (610m) altitude. Boilers equipped to operate
at higher altitudes have appropriate stickers or
tags attached.
2. Use the figures in Table 4 to provide adequate
gas piping from the gas meter to the boiler.
3. A trap (drip leg) must be provided ahead of the
gas controls (see Figure 11). A manual gas

LAARS Heating Systems
Page 10
shutoff valve must also be provided for service
convenience and safety. Check the local codes.
4. The boiler and its individual shutoff valve must
be disconnected from the gas supply piping
system during any pressure testing of that system
at test pressures in excess of 1/2 psig. The boiler
must be isolated from the gas supply piping
system by closing its individual manual gas
shutoff valve during any pressure testing of the
gas supply piping system at test pressures equal
to or less than 1/2 psig.
5. Provide gas supply pressure to the boiler as
follows:
Natural Gas LPG
Min. (inches Per Rating Plate
water column)
Max. (inches 914
water column)
Note: The boiler and all other gas appliances
sharing the boiler gas supply line must be firing at
maximum capacity to properly measure the inlet
supply pressure. Low gas pressure could be an
indication of an undersized gas meter and/or
obstructed gas supply line.
6. The correct burner manifold gas pressure is
stamped on the rating plate. The regulator is
preset at the factory and normally requires no
further adjustment.
7. The gas manifold and control assembly was
tested and conform to the safe lighting and other
performance criteria specified in the latest
editions of ANSI Z21.13 and CGA 3.3 Low
Pressure Boiler Standard.
8. Before operating the boiler, the complete gas
supply system and all connections must be tested
for leaks using a soap solution. Do not use raw
flame.
Caution
Since some leak test solutions (including soap
and water) may cause corrosion or stress
cracking, the piping must be rinsed with water
after testing, unless it has been determined
that the leak test solution is noncorrosive.
2E. Electrical Wiring
Electrical diagrams are included with the packet
provided with each unit.
WARNING
The boiler must be electrically grounded in
accordance with the most recent edition of the
National Electrical Code, ANSI/NFPA 70. In
Canada, all electrical wiring to the boiler should
be in accordance with the Canadian Electrical
Code, CSA C22.1 Part 1. Do not rely on the
gas or water piping to ground the metal parts
of the heater. Frequently, plastic pipe or
dielectric unions isolate the boiler electrically.
Service and maintenance personnel who work
on or around the boiler may be standing on wet
floors and could be electrocuted by an
underground boiler.
1. Check boiler wiring and pump for correct
voltage, frequency and phase. If the pump circuit
is other than 115V, check to see that the boiler is
provided with an appropriate transformer.
2. Wire the boiler and pump exactly as shown in
the wiring diagram supplied with the boiler.
Table 4. Gas Piping Sizes.
Distance from Gas Meter
or Last Stage Regulator
Size 0-100' 100-200' 200-300'
(0-30.5m) (30.5-61m) (61-91.4m)
500
600
715
850
1010
1200
1430
1670
1825
1-1/2"
1-1/2"
2"
2"
2"
2-1/2"
2-1/2"
2-1/2"
2-1/2"
2"
2"
2"
2-1/2"
2-1/2"
3"
3"
3"
3"
2"
2-1/2"
2-1/2"
2-1/2"
3"
3"
3"
3"
3-1/2"
Note: These figures are for Natural Gas (.65 Sp. Gr.), and are
based on 1/2" water column pressure drop. Check supply
pressure with a manometer, and local code requirements for
variations. For LPG, reduce pipe diameter one size, but maintain
a 1" minimum diameter. A normal number of Tees and elbows
have been taken into allowance.
Figure 11. T-Fitting Sediment Trap Installation.

MightyThermHydronicBoiler Page 11
3. The pump and boiler must be electrically
interlocked so the boiler cannot come on unless
the pump is running.
4. All field installed electrical safety devices and
all field installed devices (draft switches, relays,
timers, outdoor temperature reset devices, etc.)
can be connected to the heater wiring at points
shown in the wiring diagram designated “Field
Interlock.”
2F. Water Piping of System
1. Be sure to provide valves at the inlet and outlet
of the boiler so it can be readily isolated for
service. A butterfly or similar type of valve is
recommended.
2. The pressure relief valve installed in the tapped
opening provided in the outlet header (See
Figure 12), must be piped, but not fastened, to a
drain or floor sink. The drain pipe must be the
same size as the valve outlet and must pitch
downward from the valve.
5. Check piping diagrams with local applicable
plumbing, heating and building safety codes.
6. A boiler installed above radiation level must be
provided with a low water cutoff device either as
part of the boiler or at the time of boiler
installation.
7. Install manual and/or automatic bleeding devices
at high points in the system to eliminate air.
Install a correctly sized air charger and tank
drainer, as appropriate.
2G. Filling Fully-Connected System
1. Close all bleeding devices and open make-up
water valve. Allow system to fill slowly.
2. If make-up water pump is employed, adjust
pressure switch on pumping system to provide a
minimum of 12 psi at the highest point in the
heating loop.
3. If a water pressure regulator is provided on the
make-up water line, adjust the pressure regulator
to provide at least 12 psi at the highest point in
the heating loop.
4. Open bleeding devices on all radiation units at
the highest points in the piping throughout the
system, unless automatic air bleeders are
provided at such points.
5. Run system circulating pump for a minimum of
30 minutes with the boiler shut off.
6. Open all strainers in the circulating system and
check for debris.
7. Recheck all air bleeders as described in Step 4
above.
8. Check liquid level in expansion tank. With the
system full of water and under normal operating
pressure, the level of water in the expansion tank
should not exceed 1/4 of the total, with the
balance filled with air.
9. Start up boiler according to procedure described
in Section 3B. Operate the entire system,
including the pump, boiler, and radiation units
for one (1) hour.
10. Recheck the water level in the expansion tank. If
the water level exceeds 1/4 of the volume of the
expansion tank, open the tank drainer and drain
to that level.
11. Shut down the entire system and vent all
radiation units and high points in the system
piping as described in Step 4 above.
12. Close make-up water valve and check strainer in
pressure reducing valve for sediment or debris
from the make-up water line. Reopen make-up
water valve.
Figure 12. Pressure Relief Valve Location.
Pressure
Relief Valve
Special attention must be given to relief valve
settings in installations where the boiler is
located on the ground floor of a tall building,
The static pressure of the system is elevated and
could cause the relief valve to leak. Where no
special setting of the relief valve is ordered, the
factory will furnish a 75 psi setting. Never
reduce the relief valve openings.
3. Pressure relief valve lever must be tripped at
least once a year to insure that waterways are
clean. When manually operating lever, water
will discharge through drain line. Precautions
must be taken to avoid contact with hot water
and water damage.
4. The weight of all water and gas piping should be
supported by suitable hangers or floor stands.

LAARS Heating Systems
Page 12
13. Check gauge for correct water pressure and also
check water level in system. If the height
indicated above the boiler insures that water is at
the highest point in the circulating loop, then the
system is ready for operation.
14. Within three (3) days of start-up, recheck all air
bleeders and expansion tank as described in
Steps 4 and 8 above.
SECTION 3.
Operation
3A. Controls - General
1. Electronic Ignition Controls:
a. Intermittent Ignition:
Pilots are automatically lit when the
operating aquastat calls for heat (System #4
and #9) The unit performs its own safety
check and opens the main valves only after
the pilot is proven to be lit. Whenever the
pilot flame is interrupted, the main gas
valve closes within 0.8 seconds.
b. Electronically Supervised Standing Pilot
System (System #16):
When pilot flame fails, the ignition control
module responds in less than 0.8 seconds
and provides 100% safety shutdown.
2. Operating Controls:
a. Electrically Operating Controls:
Single, two-stage, four-stage or modulating
aquastats are provided in models HH and
PH boilers to control the desired service
water temperature. The temperature
sensing bulb is located in the boiler inlet.
b. Modu-Snap Valves (Mechanical
Modulation Only):
These valves are furnished in addition to
the main electric gas valve. Each valve has
a remote capillary bulb immersed in a well
at the outlet header to maintain a constant
outlet temperature. Consult Table 5 for
desired temperature setting.
Figure 13. Typical Controls Locations.
Dial No. 123456789
Temp °F 120 135 150 165 180 195 210 225 240
Temp °C 49 57 66 74 82 91 99 107 116
Table 5. Modu-Snap Temperature Settings
3. High Limit Controls:
The manual reset high limit switches are
provided as standard equipment on all
boilers. Automatic reset switches are
optionally provided. The temperature
sensing bulb of the switch is always located
in the boiler outlet. Burners will
automatically shut down whenever
overheating of water occurs.

MightyThermHydronicBoiler Page 13
4. Flow Switch:
Standard on all models: Models HH and
PH, the switch is mounted in the outlet
“tee” connection. The flow switch shuts
down all burners in case of pump failure.
5. Low Water Cut Off (Optional):
The low water cut off automatically shuts
off boiler whenever water level drops
below probe. Located at boiler inlet (model
PH) and at return header (model HH).
3B. Initial Start-Up
Lighting: Safe lighting and other performance
criteria were met with the gas manifold and control
assembly provided on the boiler when it underwent
tests specified in the ANSI Z21.13 standard.
Before placing the boiler in operation, be certain
that the boiler is filled with water and all air is purged
from the system. Once the boiler is connected to the
gas supply, the automatic safety shutoff devices must
be checked.
1. Before beginning the tests, make sure the main
manual gas valve, and any other boiler firing
valves are in the “OFF” position.
2. Make sure the boiler’s power switch is in the
“ON” position. After placing the manual pilot
gas valve in the open position and resetting all
safety devices, (high limit, pressure switch, low-
water cutoff, etc.) pilot(s) can be lit following
the procedure located on the boiler rating plate.
3. Once the pilot(s) is lit and has been established
for five minutes, the flame failure response time
should be checked as follows:
Systems 9 and 4 - (Intermittent ignition), natural
gas only: With this system pilots are automatically lit
when the operating controls call for heat. If the pilot
flame fails for any reason, the main valve is shut off
within one second and the pilot spark ignition is
initiated until the pilot flame has been reestablished.
On propane systems, unit locks out for safety. This
sequence should be checked by turning off the manual
pilot gas valve, and, at the same time, monitoring the
audible sparking at the pilot burner and signal
interruption to the main valve.
Caution
Propane gas is heavier than air and sinks to
the ground. Exercise extreme care in lighting
the boiler when so equipped.
System 16 - (Electronically supervised standing
pilot system): Extinguish the pilot flame by placing
the manual pilot valve in the closed position, and at
the same time, begin recording the time it takes for the
output signal from the electronic ignition control to be Figure 14. Gas Manual Valves.
interrupted. The signal interruption can be detected
either with a test light or a voltmeter. The response
time should never exceed one second.
4. With the pilots lit, initial activation of the main
burners can be achieved by slowly opening the
main valve. The result should be a smooth
lighting of the main burners.
Hi-Limit Checkout :
After running the boiler for a long enough
period, bring the water temperature within the range
of the hi-limit and slowly back off the high limit
setting until the boiler shuts off. The main burners
should reignite when the hi-limit is reset and turned
back up to its original setting. The boiler should now
run until it shuts off automatically on operating
aquastat.
3C. To Start Up System:
1. Start Up Boiler
Be certain system pump is running, then proceed
as follows:
a. Turn off main electrical switch.
b. Turn off all manual gas valves and wait
five minutes (see Figure 14).
c. Set operating control to lowest setting.
d. Slowly turn manual gas valve to “ON”.
e. Reset all safety valve switches (manual
reset high limit and low water cut off).

LAARS Heating Systems
Page 14
Figure 16. Main Burner Flame Pattern.
f. Open manual pilot valve. Turn on main
electrical switch.
g. Set temperature controller to desired
temperature. Pilot will light automatically
to ignite main burners whenever the
aquastat calls for heat.
h. For standing pilot system, press on pilot
relay knob (see Figure 15), light pilot and
keep relay knob depressed for one minute
then release. Once the pilot is lit, the power
is supplied through the aquastat to the main
gas valve.
remove drain plug in the bottom of front header cover.
Drain every part of system subject to freezing
temperature.
SECTION 4.
Maintenance
1. Lubricate the water circulating pump (see
instructions found on the pump).
2. If a strainer is employed in a pressure reducing
valve or in piping, clean it every six (6) months.
3. At start-up and every six (6) months thereafter,
the pilot and main burner flame should be
observed for proper performance (see Figure 16).
See attached lighting and shut-down instructions
for proper pilot flame pattern). If flame has the
appearance of “sooting” tips, check for debris
near orifices. Call serviceperson.
Figure 15. Pilot Safety Relay.
2. To set the temperature and high-limit controls:
a. Set the temperature controller at the system
design temperature.
b. Set the high-limit to 40-50°F above
temperature controller setting.
c. Models with Mechanical Modulation
Set the temperature controller (Modu-Snap
valve) dial to the desired water temperature
(see Table 5).
3. Minimum input rates:
The low firing rate setting must be equal to or
greater than the specified minimum input rating
as shown on the appliance rating plate. Laars’
boilers use gas valves which are factory set to
provide an input on low fire that meet or exceed
the specified minimum.
3D. To Turn Off Boiler:
1. Turn off main electric switch.
2. Close all manual gas valves.
3E. To Shut Down System:
To shut down boiler, turn off all manual gas
valves and electrical disconnect switches. Whenever
danger of freezing exists, shut off water supply and
4. Inspect the venting system for obstruction,
leakage and corrosion at least once each year.
5. Keep boiler area clear and free from combustible
material, gasoline and other flammable vapors
and liquids (see Table 2 for minimum
clearances).
6. Be certain all combustion air and ventilation
openings are unobstructed.
7. Check for fouling on the external surfaces of the
heat exchanger every six months. (NOTE: After
installation and first start-up, check the heat
exchanger for fouling after the following periods
of operation: 24 hours, 7 days, 30 days, 90 days,
and once every six months thereafter).
Fouling on the external surfaces of the heat
exchanger is caused by incomplete combustion
and is a sign of combustion air and/or venting
problems. As soon as any fouling is observed,
the cause of the fouling should be corrected (see
Section 5, Troubleshooting Guide). The heat
exchanger can be checked by locating a mirror
under the burners with a flashlight. An alternate
method is to remove the venting and top panel as
necessary to inspect from above. Also check the
vent system for defects at this time.

MightyThermHydronicBoiler Page 15
a. If cleaning is required, shut off all
electrical and gas supply to the heater.
b. To expose the heat exchanger:
Indoor Models:
Remove flue pipe, top of unit, rear upper jacket,
flue collector rear panel and heat exchanger baffles.
Outdoor Models:
Remove vent top assembly, rear upper jacket,
flue collector rear panel and heat exchanger baffles.
c. Remove all burners:
It is usually more convenient to remove the
burner tray assembly. Disconnect sensor
wire, ignition cable (or thermocouple
generator) and pilot gas line. Disconnect
manifold inlet union(s). Remove the four
(4) retaining screws. Grasp burner/pilot
assembly firmly at the front. Push it back,
disengaging it from the gas orifice. Lower
the front of the burner (to avoid damaging
pilot shield) then remove the burner tray.
Caution
Black carbon or green soot on a dirty heat
exchanger can, under certain conditions, be
ignited by a random spark or open flame. To
prevent this unlikely occurrence, dampen the
soot deposits with wet brush or fine water
spray before servicing or cleaning the heat
exchanger.
With a wire brush, remove soot and loose scale
from heat exchanger. Clean fallen debris from bottom
of heater. Make sure burner ports are clear and pilot
assembly is free of debris.
d. Reassemble in reverse order: Be sure the
heat exchanger baffles are replaced.
8. The gas and electric controls installed on boilers
are engineered for both dependable operation
and long life, but the safety of this equipment
completely depends on their proper functioning.
It is strongly recommended that the basic items
be checked by a competent serviceperson every
year and replaced when necessary. The basic
controls are:
a. Water temperature controls.
b. Pilot safety system.
c. Automatic electric gas valve(s).
d. Flow sensing safety device.
9. Low water cutoffs should be inspected every six
(6) months, including flushing of float types.
NOTE: Warranty does not cover any damage
caused by lack of required maintenance or improper
operating practices.
10. Both modulating and stage valve are adjusted at
the factory for minimum permissible rates and
should not be readjusted.

LAARS Heating Systems
Page 16
4. PRESSURE RELIEF VALVES LEAKING
INTERMITTENTLY OR STEADILY.
3. BOILER WILL NOT FIRE.
Possible Cause What To Do
A. Electric power is off. A. Check to see that main power
switch is “ON.” Use testing
device to trace power to
boiler junction box.
B. Operating or safety control has B. Turn off power. Use continuity
opened circuit to electric across terminals of each
gas valve. operating and safety control
switch up to the electric gas
valve. Replace defective
control.
C. Pilot flame is out. C. Relight pilot per instruction.
D. Manual reset device has tripped. D. Follow instructions for start-up.
Reset Pilot safety and all
manual reset safety switches
and reset manual safety gas
valve.
E. No gas pressure to burners. E. Trace gas line to service shutoff
cock. If service cock is open,
trace gas line to meter. If no
pressure is present at meter,
call for public utility service. If
gas is present in boiler inlet,
check pressures in following
sequence: (1) downstream from
pressureregulator;
(2) downstream from electric gas
valve. Replace or adjust as
necessary.
F. Electric gas valve operator is F. Disconnect wiring harness at gas
burned out or shortened. valve terminals. Check continuity
to actuator coil. If open circuit or
short is indicated, replace coil or
operator.
Possible Cause What To Do
A. Static pressure in system A. Calculate height of water in
exceeds setting of relief valve. system above boiler. Install new
valve with psi setting 25% above
required static system working
pressure. Do not exceed 160 psi.
B. Expansion tank is waterlogged B. Drain expansion tank, then
(ifinstalled). reopen it to the system. Look for
leaks in expansion tank or
fittings.Calculaterequired
volume of expansion tank in
relation to system to determine
that tank is adequate.
SECTION 5.
Troubleshooting and Analysis of
Service Problems
1. For proper service and problem diagnosis of the
heater and heater system, the following tools are
required:
a. Gas pressure test kit with range from zero
to 14 W.C. Either a slack tub manometer or
an accurate gas pressure gauge is
acceptable with proper adapters which will
connect to the available fittings in the line
and on the gas valve.
b. Multi-meter with the following ranges:
0 to 500 volts A.C.
0 to 1000 ohms continuity.
c. Tube cleaning kit consisting of reamer,
stainless steel brush, speed handle and
handle extensions.
d. Strap on digital temperature gauge to check
temperature rise.
2. In addition, the boiler should be equipped with a
system pressure gauge with proper ranges for
boiler operation.

MightyThermHydronicBoiler Page 17
5. BOILER IS POUNDING, KNOCKING OR EMITTING
STEAM FROM RELIEF VALVES.
Possible Cause What To Do
A. Low or no water flow. A. This condition is usually
caused by lack of adequate
flow through boiler.
Check the following:
(1) Is the boiler wired into
the pump circuit so that the
boiler cannot fire unless
the pump is running?
(2) Check to see that all
valves in system are open
to be sure that water can
circulate through the boiler
and the system.
(3) If the system has
automatic water valves (2-
way or 3-way) that can cut
off the water flow through
the boiler check to see
that they are equipped with
end-switches which shut
the boiler down when the
water flow through the
boiler is reduced by 70%
from full flow.
(4) Examine pump for
clogged impeller.
B. Low or no system pressure. B. Clean strainer in pressure
reducing valve. Look for
closed valve water line or
a leak in the system.
C. Clogged "Y" strainer. C. Remove strainer element
and clean screen.
D. Debris from system piping is D. Remove header covers.
blocking tubes. Examine all tubes and
waterways. Use new
gaskets when reassembling.
Clean out tubes.
E. Scale has formed in tubes. E. This is always caused by
the inflow of raw water into
the system. Clean tubes
with tube cleaning kit.
Determinehardness.
Check for modified flow if
necessary.
7. WATER DRIPPING IN FIREBOX.
Possible Cause What To Do
6. SOOT IN FLUEWAYS OR IN TUBES,
OR NOXIOUS FUMES INDICATIVE
OF BAD COMBUSTION.
Possible Cause What To Do
A. Combustion air supply to A. Check air supply opening.
boiler room is inadequate. Look for debris in screen or
louvre which covers
combustion air opening, or
for material blocking the
opening.
B. Stack or vent is blocked or B. Look for blocked stack and
restrictive. excessive number of elbows in
stack or excessive length of
horizontalruns.
C. Severe down draft is causing C. Check for (1) proper vent cap on
spillage of flue products into stack; (2) adequate height of
room. stack above roof; (3) equipment
exhausting air from inside of
building; and (4) proper
installation of draft diverter.
D. Gas pressure to burners is D. Check gas presssure with
excessive. Manometer, and adjust
with heater firing at full rate.
E. Boiler not fitted for the fuel E. See nameplate for correct
being supplied. fuel.
F. Boiler installed at high F. Installations at altitudes in
altitude withoutproper excess of 2000 ft. above
derating. sea level are subject to
jurisdiction of the local
inspectionauthorities.
Tub in heat exchanger has A tube failure is almost always
overheatedand ruptured. caused by (1) scale formation in the
tube or (2) inadequate water flow
through the boiler.

LAARS Heating Systems
Page 18
Key Description Model Model Model Model Model Model Model Model Model No 500 600 715 850 1010 1200 1430 1670 1825 1 Top Panel Assembly 10535701 10535702 10535703 10535704 10535705 10535706 10535707 10535708 10535709 2 Spacer, Flue Collector — — 10540800 10540800 10540800 10540800 10540800 10540800 3 End Panel, Flue Collector (left) 10533700 10533700 10533700 10533700 10533700 10533700 10533700 10533700 10533700 4 End Panel, Flue Collector (right) 10533800 10533800 10533800 10533800 10533800 10533800 10533800 10533800 10533800 5 Rear Panel, Flue Collector 10535501 10535502 10535503 10535504 10535505 10535506 10535507 10535508 10535509 6 Rear Panel, Ext., Flue Collector ————— ————————————————————Not Required———————————————— ———— 7 Front Support, Flue Collector 10534401 10534402 10534403 10534404 10534405 10534406 10534407 10534408 10534409 8 Tile Cover, Front & Rear 10534201 10534202 10534203 10534204 10534205 10534206 10534207 10534208 10534209
(2) (2) (2) (4) (4) (4) (4) (4) (4)
9 Baffle, Heat Exch. (Frt & Rear) 10534301 10534302 10534303 10534304 10534305 10534306 10534307 10534308 10534309
(2) (2) (2) (4) (4) (4) (4) (4) (4)
10,11 Baffle, Heat Exchanger 10534601 10534602 10534603 10534604 10534605 10534606 10534607 10534608 10534601
(7) (14) (14) (14) (14) (28) (28) (28) (14)
—— —— —— —— —— —— —— —— 10534602
(14)
12 Return Header (S-00981) 10364300 10364300 10364300 10364300 10364300 10364300 10364300 10364300 10364300
Return Header (S00642)
Bronze 10364301 10364301 10364301 10364301 10364301 10364301 10364301 10364301 10364301 13 Inlet/Outlet Header (S-00943) 10364500 10364500 10364500 10364500 10364500 10364500 10364500 10364500 10364500
Inlet/Outlet Header (S00640) 10364501 10364501 10364501 10364501 10364501 10364501 10364501 10364501 10364501
Bronze 14 Flange, 2" (S00636) 10391302 10391302 10391302 10391302 —— —— —— —— ——
Flange, 2 1/2 “ (S00635) —— —— —— —— 10391303 10391303 10391303 10391303 10391303 Flange, 2 1/2" (S00644), Bronze 10391304 10391304 10391304 10391304 10391304 10391304 10391304 10391304 10391304
15 Flange Gasket S0063700 S0063700 S0063700 S0063700 S0063700 S0063700 S0063700 S0063700 S0063700 16 Header Gasket w/Barrier S0095100 S0095100 S0095100 S0095100 S0095100 S0095100 S0095100 S0095100 S0095100 17 Header Gasket Use S00951 00-Cut Out Barrier 18 Baffle, Water Inlet 10338300 10338300 10338300 10338300 10338300 10338300 10338300 10338300 10338300 19 Barrier, Water 10397500 10397500 10397500 10397500 10397500 10397500 10397500 10397500 10397500 20 Well, Aquastat E0025900 E0025900 E0025900 E0025900 E0025900 E0025900 E0025900 E0025900 E0025900
Well, Aquastat F/4 Stage E0085700 E0085700 E0085700 E0085700 E0085700 E0085700 E0085700 E0085700 E0085700
NOTE: Numbers in ( ) represent quantity required for each size. Quantity is one otherwise.
SECTION 6. Parts Descriptions and Order Numbers

MightyThermHydronicBoiler Page 19
Figure 19. Parts Identification.
NOTE:
Temperature Control Wells -
Inlet/Outlet Header
1. Firing Mode L, K, & C -
2 Dry Wells
2. Firing Mode H
A. Natural Gas Boilers & Heaters
500 thru 850 - 2 Dry Wells
1010 thru 1430 - 3 Dry Wells
1670 thru 1825 - 4 Dry Wells
B. Propane Gas Boilers & Heaters
500 thru 850 - 2 Dry Wells
1010 thru 1852 - 3 Dry Wells

LAARS Heating Systems
Page 20
Key Description Model Model Model Model Model Model Model Model Model No 500 600 715 850 1010 1200 1430 1670 1825 21 Tile, Heat Shield/Spcr, Frt. & Rr. 10560100 —— —— —— —— —— —— —— ——
(2)
22 Tile, Heat Shield/Spacer, Front —— 10547901 10547902 —— —— 10547903 10547901 10547904 10547903 23 Tile, Heat Shield/Spacer, Front —— —— —— 10548002 10548003 —— —— —— 10548001 24 Tile, Heat Shield/Spacer, Front —— —— —— —— —— 10548101 10548102 10548103 10548104 25 Tile, Heat Shield/Spacer, Rear —— 10548201 10548202 —— —— 10548203 10548201 10548204 10548203 26 Tile, Heat Shield/Spacer, Rear —— —— —— 10548302 10548303 —— —— —— 10548301 27 Tile, Heat Shield/Spacer, Rear —— —— —— —— —— 10548401 10548402 10548403 10548404 28 Saddle Assembly, End Tile 10533600 10533600 10533600 10533600 10533600 10533600 10533600 10533600 10533600
(2) (2) (2) (2) (2) (2) (2) (2) (2)
29 Lower End Panel/Heat Shield
Weldment, Right 10540701 10540701 10540701 10540701 10540701 10540701 10540701 10540701 10540701
30 Lower End Panel/Heat
Shield Weldment, Left 10540702 10540702 10540702 10540702 10540702 10540702 10540702 10540702 10540702
31 Lower Rear Panel & Baffle
Rear Weldment 10532901 10532902 10532903 10532904 10532905 10532906 10532907 10532908 10532909
32 Middle Rear Panel/Heat
Shield Weldment 10540401 10540402 10540403 10540404 10540405 10540406 10540407 10540408 10540409
33 End Panel, Upper Right 10531600 10531600 10531600 10531600 10531600 10531600 10531600 10531600 10531600 34 End Panel, Upper Left 10534000 10534000 10534000 10534000 10534000 10534000 10534000 10534000 10534000 35 Upper Rear Panel/Heat
Shield Weldment 10540501 10540502 10540503 10540504 10540505 10540506 10540507 10540508 10540509
36 Front Panel, Upper 10531501 10531502 10531503 10531504 10531505 10531506 10531507 10531508 10531809 37 Brackets, Support, End Tile 10551000 10551000 10551000 10551000 10551000 10551000 10551000 10551000 10551000
(2) (2) (2) (2) (2) (2) (2) (2) (2)
38 Drafthood, Relief Baffle, Right 10540901 10540902 10540903 10540904 10540905 10540906 10540907 10540908 10540909 39 Drafthood, Relief Baffle, Left 10541001 10541002 10541003 10541004 10541005 10541006 10541007 10541008 10541009 40 Lower Right Panel/Heat
Shield Weldment 10554601 10554602 10554603 10554604 10554605 10554606 10554607 10554608 10554609
41 Middle Front Panel 10554401 10554402 10554403 10554404 10554405 10554406 10554407 10554408 10554409 42 Sweep Sheet, Flue Collector 10533901 10533902 10533903 10533904 10533905 10533906 10533907 10533908 10533909 NOTE: Numbers in ( ) represent quantity required for each size. Quantity is one otherwise.