Mighty Therm AP User manual

Installation and Operation Instructions Document 3006R
H0067300R
Model AP
Sizes 500 - 1825
These instructions are to be stored in the
pocket provided on the heater.
Installation and Operation
Instructions for
Mighty Therm
Pool Heating Boiler
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.
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.
AVERTISSEMENT
Assurez-vous de bien suivres les instructions
données dans cette notice pour réduire au
minimum le risque d’incendie ou d’explosion ou
pour éviter tout dommage matériel, toute
blessure ou la mort.
Ne pas entreposer ni utiliser d’essence ni
d’autres vapeurs ou liquides inflammables dans
le voisinage de cet appareil ou de tout autre
appareil.
QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ:
• Ne pas tenter d’allumer d’appareils.
• Ne touchez à aucun interrupteur. Ne pas vous
servir des téléphones dansle bâtiment où vous
vous trouvez.
• Appelez immédiatement votre fournisseur de
gaz depuis un voisin. Suivez les instructions
du fournisseur.
• Si vous ne pouvez rejoindre le fournisseur de
gaz, appelez le sservice des incendies.
L’installation et l’entretien doivent être assurés par
un installateur ou un service d’entretien qualifié ou
par le fournisseur de gaz.

LAARS HEATING SYSTEMS
Page 2
TABLE OF CONTENTS
SECTION 1.
General Information
1.1 Introduction ................................................... 3
1.2 Heater Identification ...................................... 3
1.3 Primary/Secondary Pump and Piping ........... 3
1.4 Certifications ................................................. 3
1.5 Engineering Assistance ................................ 3
SECTION 2.
Installation
2.1 Boiler Placement .......................................... 4
2.2 Installation of Indoor Boilers.......................... 4
2.2.1 Combustion Air Supply ................................. 4
2.2.2 Venting ......................................................... 5
2.2.3 Common Venting System
Test Procedure ............................................. 6
2.2.3 Instructions Relatives au Test des
Systèmes à Évent Commun ......................... 6
2.3 Installation of Outdoor Boilers ....................... 7
2.4 Gas Supply and Piping ................................. 7
2.5 Electrical Wiring ............................................ 8
2.6 General Piping Instructions ........................... 9
2.7 Boiler By-Pass Piping ................................... 9
2.8 Temperature Sensor Placement
and Installation ............................................ 10
2.9 Automatic Chlorinators ............................... 10
SECTION 3.
Operation
3.1 Controls - General ...................................... 11
3.2 Initial Start-Up ............................................. 12
3.3 Safety Shutoff Component Checkout.......... 12
3.4 Inlet Temperature and
Temperature Rise Adjustment .................... 13
3.5 Heater Shut Down ...................................... 13
3.6 Spring and Fall Operation
Stand-by Service ........................................ 13
3.7 Winter Operation Complete Shutdown ....... 14
3.8 Time Clock Operation ................................. 14
3.9 Therapeutic Pools (Spas) ........................... 14
SECTION 4.
Maintenance..............................................15
SECTION 5.
Troubleshooting .......................................16
SECTION 6.
Parts Description and Order Numbers ........ 18

Mighty Therm Commercial Pool Heating Boiler Page 3
SECTION 1.
General Information
1.1 Introduction
This manual provides information for the
installation and operation of Laars Model AP pool
heating 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 packages listed on the
packing 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.
The warranty does not apply to heaters 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. In Canada, the installation must conform with the
latest edition of CAN/CGA-B149 requirements.
When required by the authority having
jurisdiction, the installation must conform to
Figure 1. Heater Identification (model nomenclature).
WARNING
The model AP commercial pool heating boiler
must be used on potable water only. For
heating pools containing salt water, a specially
equipped heater must be used; consult your
distributor or factory representative. The pool
heating boiler must be installed in accordance
with the procedures outlined in this manual.
MODEL
AP-POOL
REVISION
P-PUMP (U.S.)
Q-PUMP (CAN)
HEAT EXCHANGER
C-GLASS LINED/COPPER
N-GLASS LINES/CU-NI
K-BRONZE/COPPER
S-BRONZE/CU-NI
VERSION
1- 8 TUBE
B-10 TUBE
I-INDOOR
E-OUTDOOR
FUEL
N-NATURAL
P-PROPANE
IGNITION
04-SPARK 110V
09-SPARK 24V
11-SPARK 24V
16-STND. PILOT
SIZE
BTU/HR X 1000
0500
0600
0715
0850
0999
1010
1200
1430
1670
1825
C
FIRING MODE
ON/OFF
1 2 3 4 5 6 7 8 9 10 11 12 13 14
American Society of Mechanical Engineers safety
codes for controls and safety devices for automatically
fired heaters No. CSD-1, and in Canada CGA 3.3.
Any modification of the heater, its gas controls, gas
orifices, wiring or drafter diverter may void the Laars
warranty. If field conditions require such
modifications, consult factory.
1.2 Heater Identification
Consult rating plate on the heating boiler. Shown
below is a breakdown of the model nomenclature.
Laars commercial pool heating boilers are available in
two configurations: an indoor version and an outdoor
version. Outdoor models are not available in Canada.
1.3 Primary/Secondary Pump and Piping
All models are supplied with integrally mounted
pumps. The 1825 models use a 3/4 HP pump and all
other models are supplied with 1/2 HP pumps. These
pumps are sized for the pressure drop through the heat
exchanger and through the bypass piping as shown in
Figure 10.
Any deviations from the arrangement shown
may increase the head on the pump, reduce flow and
hinder performance (see Section 2.7). For spas see
Section 3.9.
This piping arrangement and the integral pump
allow hot water to be recirculated to the heater inlet,
thus raising the inlet temperature and greatly reducing
condensation.
1.4 Certifications
All models are design-certified by AGA and
CGA for natural or propane gas and conform to
ASME Code requirement for 160 PSI water pressure.
1.5 Engineering Assistance
Consult the factory or distributor regarding any
questions or problems which arise in the specification,
installation or operation of Laars equipment. An
experienced engineering staff is ready to assist in
assuring the proper performance and application of
Laars products.

LAARS HEATING SYSTEMS
Page 4
SECTION 2.
Installation
2.1 Boiler Placement
The pool heating boiler must be placed to
provide specific clearances on all sides for
maintenance and inspections. There must also be
minimum distances maintained from combustible
surfaces. These clearances also apply to
noncombustible materials because the pool heating
boiler requires air circulation for proper operation.
The pool heating boiler should be mounted on a
level surface. An integral base for an installation on
combustible flooring is provided as standard
equipment on outdoor models. For indoor models,
special base rails part number 10539000 must be used
for combustible flooring.
Do not install a pool heating boiler on carpeting.
Under the national Fuel Gas Code, ANSI
Z223.1, it is permissible to place the boiler on floors
other than noncombustible when the installation
complies with the American Insurance Code. Figures
2, 3, 4 and 5 show common installation on
combustible flooring.
2.2 Installation of Indoor Boilers
Locate the pool heating boiler to provide
adequate clearance for inspection and service on all
sides. See Table 1. For alcove installation, see
Figure 6.
Install indoor heaters on a waterproof floor with
an adequate floor drain and a 6" (152mm) minimum
curb on all four sides to protect the building if heater
repairs are required. The manufacturer will not be
held liable for any water damage in connection
with this boiler.
2.2.1 Combustion Air Supply
The heater 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 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.
a. Conventional Ventilation
In the United States, these requirements specify
that small 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
(6.5 sq. cm) per 4,000 BTU/hr input of the total input
rating of all appliances in the enclosed area. See Table
2 for recommended air supply for each model. An
improperly ventilated equipment room can get
Clearance Indoor Outdoor
from in. mm in. mm
Top 30 762 unobstructed
Water Conn. side 12* 305 24 610
Pump side 6* 152 24 610
Front Alcove* unobstructed
Rear 8203 24 610
Vent pipe** 6152 - - -
Hot water pipes per code per code
* Water connection and pump side clearances of 24" (610mm)
and front clearances of 48" (1219mm) will allow easier
service access.
** Using type B vent (refer to Manufacturer's Instructions).
Table 1. Minimum boiler clearances from
adjacent surfaces.
Figure 2. Typical Boiler Installation on Concrete Slab.
Figure 3. Typical Boiler Installation on Roof Using
Raised Platform (wood).
excessively hot and cause accelerated deterioration
of controls and electrical components.
In Canada, Table 2 does not apply. Consult local
building codes or, in the absence of such
requirements, follow CGA requirements and/or CAN/
CGA B-149 standard.

Mighty Therm Commercial Pool Heating Boiler Page 5
Figure 4. Typical Boiler Installation on Roof
Using 4x4 Stringer.
Figure 5. Installation on Concrete Blocks or Tile.
b. Forced-Air Ventilation
In the United States: 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. This could cause flue
products to accumulate in the boiler room. Additional
air must be supplied to compensate for such exhaust.
The information in Table 2 is not applicable in
installations where exhaust fans or blowers of any
type are used. Such installations must be designed by
qualified engineers.
In Canada: follow Canadian standard, CAN/
CGA B-149 or local codes.
If a blower or fan is used to supply air to the
boiler 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 interlock must be wired into the heater
control circuit to prevent the heater from firing unless
the blower is operating.
The boiler must be completely isolated and
protected from any source of corrosive chemical fumes
such as trichlorethylene, perchloroethylene, chlorine, etc.
2.2.2 Venting
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, CAN/CGA B-149 and any
local codes having jurisdiction.
Do not weld or fasten the vent pipe to the boiler
drafthood. The weight of the stack must not rest on
the boiler. The drafthood and boiler top must be easily
removable for normal boiler service and inspection.
IMPORTANT NOTE: Do not use sheet metal
screws at the snap lock joints of Type B gas vents.
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" (6mm) 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.
Avoid terminating boiler vents near air
conditioning or air supply fans. The fans can pick up
exhausted flue products from the boiler and return
them inside the building creating a possible health
hazard. A minimum of 4 feet (1.2m), in Canada 6 feet
(1.8m), horizontal distance must be maintained from
electrical meters, gas meters, and relief equipment.
Figure 6. Alcove Installation.
Base must extend out
min. 12" (305mm) on
all sides of
heater frame.
20 ga. min.
galvanized
sheet metal
under entire
heater.
Concrete blocks or tile min. 7" (178mm)
high with 3" (76mm) min. air openings.
Blocks must provide solid base and be braced so they
cannot slip out of place. Air openings in blocks must be
arranged to provide unobstructed opening through entire
width or length of base.
* When the ceiling height exceeds 8 feet, you are only allowed to consider 8
feet when calculating the total volume of the enclosure.
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Water
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CLOSET INSTALLATION
(UNACCEPTABLE)
A closet is any 4 sided enclosure
which is less than 16* times the total
volume of all the gas fired appliances
within the enclosure.
ROOM INSTALLATION
(ACCEPTABLE)
A room is any enclosure which is at
least 16* times greater than the total
volume of all the gas fired appliances
within the enclosure.
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Water
Heater
ALCOVE INSTALLATION
(ACCEPTABLE)
An alcove suitable for the installation
ofawaterheaterisarestrictedsection
of a room not separated from the
room by a door or partition and which
meets the minimum clearances for
thespecific model water heaterlisted
below.

LAARS HEATING SYSTEMS
Page 6
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
systems. This can create a health hazard by spilling
flue products in the boiler room.
Avoid oversized vent piping or extremely long
runs of 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 (25mm) of
vent diameter. Longer total lengths shown in venting
tables are based on maximum capacity, not
condensation factors.
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/CGA B-149 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.
2.2.3 Common Venting System
Test Procedure
At the time of the removal of an existing heater,
the following steps shall be followed with each
appliance remaining connected to the common venting
system. During the testing of each unit, the other
appliances remaining connected to the common
venting system should not be operated.
1. Seal any unused openings in the common
venting system.
2. Visually inspect the venting system for proper
size and horizontal pitch. Determine that there is
no blockage or restriction, leakage, corrosion, or
other deficiencies which could cause an unsafe
condition.
3. Insofar as it is practical, close all building doors
and windows. Also close all doors between the
space in which the appliances remaining
connected to the common venting system are
located and the other spaces of the building.
Turn on any clothes dryer and any appliance not
connected to the common venting system. Turn
on any exhaust fans, including range hoods and
bathroom exhausts, so they will operate at
maximum speed. Do not operate a summer
exhaust fan. Close all fireplace dampers.
4. Place in operation the appliance being inspected.
Follow the lighting instructions for the unit.
Adjust the thermostat so the appliance will
operate continuously.
5. Test for spillage at the draft hood relief opening
after 5 minutes of main burner operation. Use
the flame of a match or candle, or smoke from a
cigarette, cigar, or pipe.
6. 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 gas-burning
appliance to their previous condition of use.
7. Any improper operation of the common venting
system should be corrected so the installation
conforms with the National Fuel Gas Code,
ANSI Z223.1 and/or CAN/CGA B149,
Installation Codes. 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 and/or CAN/CGA
B149 Installation Codes.
2.2.3 Instructions Relatives au Test des Systèmes à
Évent Commun
Au moment du restrait d’une chaudière
existante, les mesures suivantes doivent être prises
pour chaque appareil toujours reccordé au système
d’évacuation ne fonctionnet pas:
1. Sceller toutes les ouvertures non utilisées du
systèmes d’évacuation.
2. Inspecter de façon visuelle le système
d’évacuation pour déterminer la grosseur et
l’inclinaison horizontale qui conviennent et
s’assurer que le système est exempt
d’obstruction, d’étranglement, de fuite, de
corrosion et autres défaillances qui pourraient
présenter des risques.
3. Dans la mesure du possible, fermer toutes les
portes et les fenêtres du bâtiment et toutes les
portes entre l’espace où les appareils toujours
raccordés au système d’évacuation sont installés
et les autres espaces du bâtiment. Mettre en
marche les sécheuses, tous les appareils non
raccordés au système d’évacuation common et
tous les ventilateurs d’extraction comme les
hottes de cuisinière et les ventilateurs des salles
de bain. S’assurer que ces ventilateurs
fonctionnent à la vitesse maximale. Ne pas faire
fonctionner les ventilateurs d’été. Fermer les
registres des cheminées.
4. Mettre l’appareil inspecté en marche. Suivre les
instructions d’allumage. Régler le thermostat de
façon que l’appareil fonctionne de façon
continue.
5. Faire fonctionner le brûleur principal pendant 5
min ensuite, déterminer si le coupe-tirage
déborde à louverture de décharge. Utiliser la

Mighty Therm Commercial Pool Heating Boiler Page 7
flamme d’une chandelle ou la fumée d’une
cigarette, d’une cigare ou d’une pipe.
6. Une fois qu’il a été déterminé, selon la méthode
indiquée ci-dessus, que chaque appareil raccordé
au systéme d’évacuation est mis à l’air libre de
façon adéquate. Remettre les portes et les
fenêtres, les ventilateurs, les registres de
cheminées et les appareils au gaz à leur position
originale.
7. Tout mauvais fonctionnement du systéme
d’évacuation commun devrait être corrigé de
façon que l’installation soit conforme au
National Fuel Gas Code, ANSI.Z223.1 et (ou)
aux codes d’installation CAN/CGA-B149. Si la
grosseur d’une section du système d’évacuation
doit être modifiée, le système devrait être
modifié pour respecter les valeurs minimales des
tableaux pertinents de l’appendice G du National
Fuel Gas Code, ANSI Z2231.1 et (ou) des codes
d’installation CAN/CGA-B149.
2.3 Installation of Outdoor Boilers
(Not available in Canada)
1. Locate the boiler to provide the clearances as
listed in Table 1, “Minimum Boiler Clearances.”
2. Do not place the boiler in an enclosure or wall
recess. Avoid locations where wind deflection
off structures might cause downdraft. When such
wind conditions are possible, place the heater at
least 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 7).
4. Although these models are CSA 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.
Outdoor installations are not recommended in
areas where the danger of snow blockage exists.
WARNING
Liquefied petroleum gas is heavier than air.
Therefore, the pool heating boiler should not
be installed in pits or other locations where gas
could accumulate.
The boiler should be located a safe distance from
Propane gas storage and filling equipment. Consult
local codes and fire protection authorities for advice
on specific installation restrictions.
2.4 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 (609.6m) altitude. Boilers equipped to
operate at higher altitudes have appropriate
stickers or tags attached, also printed
information on rating plate.
2. Use the figures in Table 3 to provide adequate
gas piping from the gas meter to the boiler.
3. A sediment trap (drip leg) must be provided
ahead of the gas controls (see Figure 8). A
manual gas shutoff valve must also be provided
for service convenience and safety. Check the
local codes.
Boiler Each Opening*
Size square inches square 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 Free Area.
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.
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 editon of ANSI Z223.1.
Consult factory if openings do not communicate directly
through the walls with the outdoors.
Table 2. Minimum Recommended Air Supply to Boiler.
Figure 7. Incorrect Outdoor Installation.

LAARS HEATING SYSTEMS
Page 8
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.
The gas manifold and control assembly is
factory tested and conforms to the safe lighting and
other performance criteria specified in the latest
editions of ANSI Z21.13.CSA4.9 Low Pressure Boiler
Standard.
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.
2.5 Electrical Wiring
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 latest edition of CSA
C22.1 Canadian Electrical Code, Part 1. Do not
rely on the gas or water piping to ground the
metal parts of the boiler. Plastic pipe or
dielectric unions often isolate the boiler
electrically. Service and maintenance
personnel who work on or around the heater
may be standing on wet floors and could be
electrocuted by an ungrounded boiler.
Wiring diagrams are included in the information
packet provided with each unit.
1. All Model AP pool heating boilers need 115V
60Hz supply voltage unless specifically ordered
otherwise.
2. The 1825 models are supplied with 3/4 HP pump
motors rated at 115/230V, FLA 8.8/4.4. All
other models are supplied with 1/2 HP pump
motors rated at 115/230V, FLA 5.8/2.9. Consult
the National Electrical Code or the Canadian
Electrical Code regarding branch circuit
requirements for equipment with these motors.
3. The boilers should be wired exactly as shown in
the wiring diagram.
Distance from Gas Meter
Boiler or Last Stage Regulator
Size 0-100' 100-200' 200-300'
0-30.5m 30.5-61m 61-91.4m
500 1½" 2" 2"
600 1½" 2" 2½"
715 2" 2" 2½"
850 2" 2½" 2½"
1010 2" 2½" 3"
1200 2½" 3" 3"
1430 2½" 3" 3"
1670 2½" 3" 3
1825 2½" 3" 3½"
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 Propane Gas, reduce pipe diamter one size. An
average number of tees and elbows have been taken into account.
Table 3. Gas Piping Sizes.
Figure 8. Sediment Trap Installation.
To
Equipment
Inlet
Gas Supply
Inlet
Tee
Fitting
3" (76mm) Min.
Cap
Nipple
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 (3.5kPa).
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 piping system at test pressures equal to or
less than 1/2 psig (3.5kPa).
5. Provide gas supply pressure to the heater as
follows:
Natural Gas Propane Gas
In. W.C. kPa In. W.C. kPa
Max. 10 2.5 14 3.4
Min. 6.5 1.6 11 2.7
NOTE: the heater 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.

Mighty Therm Commercial Pool Heating Boiler Page 9
IMPORTANT NOTE: The pool filter pump and
boiler must be electrically interlocked so the boiler
cannot come on unless the pump is running and there
is full flow in the filter piping where the boiler is
connected. If the pool filter pump operation is
intermittent the boiler must be shut off prior to pump
shutdown. See paragraph heading Auxiliary Time
Clock Wiring below. If the backwash operation is
manual the boiler must be shut off manually during
backwashing.
Auxiliary Time Clock Wiring:
If a time clock is used to control the filter pump
operation, a separate switch or relay must be used to
shut off the boiler at least 15 minutes before the filter
pump is shut off. Wire the switch or relay (often
called the Fireman Switch) to the terminals shown in
the wiring diagram as “Field Interlock.”
4. All field installed electrical safety devices and
all field installed controllers (valve end switches,
draft switches, relays, timers) can be connected
to the boiler control to the terminals shown in
the wiring diagram designated “Field Interlock.”
5. Field location of the temperature sensor is
described in Section 2.8.
Where the boiler is installed with a draft fan
refer to the fan manufacturer's wiring diagram. The
draft switch should be wired across the field interlock
terminals in the boiler control panel.
2.6 General Piping Instructions
In addition to the bypass valve “B” and outlet
valve “A” shown in Figures 10 and 11, an inlet valve
“C” should be provided so that the heater can be
readily isolated for service. All valves should be
butterfly or ball style, not gate valves. For spas
application see Section 3.9.
Figure 9. Pressure Relief Valve Location.
Since heater outlet temperatures can reach
150°F (66°C) in some cases, copper or CPVC are
recommended materials for heater connection piping.
PVC material may be used for the inlet valve and the
piping upstream of it.
When pipe, fittings, grids or any other element
of the filter system are made of plastic materials, they
may be damaged by the momentary "back siphoning"
of hot water from the heater when the filter pump
stops running.
The pressure relief valve installed in the tapped
opening provided in the outlet header (see Figure 9),
must be piped, but not connected, 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.
Where no special setting of the relief valve is ordered,
the factory will furnish a 75 psi setting.
The 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 the drain line. Precautions must be taken to
avoid contact with hot water and water damage.
2.7 Boiler By-Pass Piping
Model 500-1825 boilers do not have an internal
bypass valve and MUST BE PIPED AS SHOWN in
Figures 10 and 11. For spas see Section 3.9.
All models are supplied with integral pumps,
These pumps are sized for the pressure drop through
the heat exchanger and through the bypass piping as
shown in Figures 10 and 11.
Any deviations from the arrangement shown
may reduce flow, hinder performance, and will void
the warranty.
2½ inch NPT piping is shown, however, models
500I-1430I and models 500E-1010E may be installed
using 2 inch NPT piping.
All models must be installed in the parallel
arrangement shown. The "secondary" or boiler piping
must tee into the filter piping with the inlet and outlet
connection spaced a maximum of 18" (450mm) apart
(see Figure 11).
To insure that pool inlet water does not exceed
104°F, the filter pump loop must circulate at the
minimum flow rates shown in Table 4.
The outlet valve “A” and the bypass valve “B”
must have a provision for locking the handles in place
(or removing them) after the temperature rise and inlet
temperature adjustments have been made.
Boiler Model Minimum Filter Pump Flow Rate
500-850 90 GPM
1010-1200 110 GPM
1430 140 GPM
1670-1825 180 GPM
Table 4. Minimum Flow to Supply Heater Loop.

LAARS HEATING SYSTEMS
Page 10
Figure 10. Boiler By-Pass Piping.
2.8 Temperature Sensor Placement
and Installation
A temperature sensor with 15 feet (5m) of cable
and an immersion well assembly are supplied with the
boiler. These must be installed in the field. Refer to
Figures 10 through 12.
1. The immersion well body is provided with a 1/2"
NPT. Mount the immersion well on the
underside of the filter circulation piping, just
upstream of the boiler inlet tee as close to the
boiler as possible (see Figure 11). DO NOT
INSTALL in secondary piping or downstream
of the boiler inlet tee.
2. Thread the spring and retainer onto the sensor
cable and secure sensor into the immersion well.
3. Route cable to heater control panel in a location
where it will not be subject to damage. Secure
with nylon cable ties.
2.9 Automatic Chlorinators
A concentration of chlorine in the heater can be
very destructive, therefor the following rules about the
installation and operation of such devices must be
followed:
1. The chlorinator should be installed so it
introduces the gas or solution downstream from
the boiler.
Figure 11. Heater Piping Arrangement.
Suggested By-Pass Loop Fitting
Item Description Material
1 2½" Elbow (See Note) 2½" S-80
2 2½" x 2" Reducing
Bushing (See Note) CPVC
3 2½" Tee (All Sizes) Copper is
optional
4 2½" Tee (See Note)
A, B,
C, D 2½" Ball Valve (See Note)
Note: 2" pipe, fittings and valves are optional for indoor size (500
through 1430) and outdoor size (500 through 1010).

Mighty Therm Commercial Pool Heating Boiler Page 11
Figure 12. Controls Location.
Rating Plate
Manual
Pilot
Valve
Water
Circulating
Pump
Safety
Gas
Valve
Operating/Safety
Gas Valve
Ignition Control
Flow
Switch Pressure
Relief
Valve
Power
(On/Off/Auto)
Switch
Pump Time
Delay Relay
Operating
Control
Terminal Strip
In
Out
Hi-Limit
Manual
Main
Gas Valve
2. The chlorinator should be wired so it cannot
operate unless the filter pump is running.
3. The chlorinator should be provided with an anti-
siphon device so that the draining of the piping
after the pump shuts off will not siphon chlorine
solution into the boiler.
4. When the operation of a chlorinator is such that
it must be installed in the pump suction, or some
other place where the chlorine solution flows
through the heater, corrosion of the heater can
occur. Excessive concentrations of chlorine
caused by improper adjustment or failure of the
chlorination equipment cause this corrosion. The
resulting damage to the heat exchanger is not
covered by heater warranty.
SECTION 3.
Operation
3.1 Controls - General
(see Figures 12 and 13)
1. Electronic Ignition Controls:
a. Intermittent Ignition:
Pilots are automatically lit when the
operating control calls for heat (Systems #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:
An electronic temperature control is provided on
model AP boilers to control the pool water
temperature. The temperature sensor (thermistor)
is located in the filter circulation piping (see
Section 2.8).
3. Boiler Power (On/Off/Auto) Switch:
This provides for constant or automatic pump
operation.
4. High Limit Controls:
The manual reset high limit switch is provided as
standard equipment on all boilers. The
temperature sensing bulb of the switch is always
located in the heater outlet. Burners will
automatically shut down whenever overheating
of water occurs.
5. Flow Switch:
Standard on all AP pool heating boilers. The
switch is mounted in a tee fitting on the outlet
header. This is a paddle type switch which is
deflected by the water flow in the fitting. Any
condition which interrupts or decreases the flow

LAARS HEATING SYSTEMS
Page 12
through the secondary loop will shut down the
burners.
6. Low Water Cut Off (optional):
The low water cut off automatically shuts off
boiler whenever water level in the heat
exchanger drops below probe level. It is located
in the inlet header.
3.2 Initial Start-Up
WARNING
Do not use this appliance if any part has been
under water. Immediately call a qualified
service technician to inspect the heater. the
possible damage to a flooded appliance can be
extensive and present numerous safety
hazards. Any appliance that has been under
water must be replaced.
On a newly constructed pool, be sure to run the
filter pump long enough for a complete “turn-over” of
the pool water before starting heater so that dirt and
residue from construction will have been removed.
The filter may clog rapidly during this period, causing
severe cycling of the heater.
1. Before placing the heater in operation, be certain
that the heater is filled with water and that all air
is purged from the system. Open all the valves in
the secondary piping.
2. With the filter pump running, run the heater
pump in manual “CONSTANT PUMP” for
minimum of 10 minutes and listen for the flow
switch to make as the pump is started. Loosen
the pipe plug on the top of the pump scroll
casting to bleed off any air. NOTE: If the system
will be operated in a manner that causes air to be
drawn into the heater and the secondary piping,
an automatic float type air vent should be
permanently installed on top of the pump scroll.
3. To check the heater firing, proceed as follows:
a. Turn off the power switch.
b. Turn off all manual gas valves and wait
five minutes (Figure 14).
c. Set operating control to the lowest setting.
d. After placing the manual pilot gas valve in
the open position and resetting all safety
devices (high limit, low water cutoff, etc.),
the pilot(s) can be lit following the
procedure on the heater rating plate.
e. For standing pilot system, press on pilot
relay knob (see Figure 16), light pilot and
keep relay knob depressed for one minute
then release. Once the pilot is lit, turn
power switch to “AUTO PUMP.”
f. Wait 5 minutes and turn up operating
control until heater fires (for intermittent
ignition system, the pilot will be ignited
automatically). The main burners should
ignite smoothly. Turn the operating control
back to the lowest setting.
NOTE: DO NOT OPERATE HEATER UNTIL
THE FOLLOWING SAFETY CHECKS HAVE
BEEN PERFORMED.
3.3 Safety Shutoff Component Checkout
1. Once the pilot(s) is lit and has been established
for five minutes, the flame failure response time
should be checked as follows:
Systems 4 and 9 - (intermittent ignition). 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. This sequence should be
checked by turning off the manual pilot gas valve (see
Figure 15), 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 heater when so equipped.
System 16 - (electronically supervised standing pilot
system). Extinguish the pilot flame by placing the
manual pilot valve in the closed positions (see
Figure 15), and at the same time, begin recording the
time it takes for the output signal from the electronic
ignition control to be interrupted. The signal
interruption can be detected either with a test light or
a voltmeter. The response time should never exceed
one second.
2. Hi-Limit Checkout. For spas see Section 3.9.
The manual reset high limit is factory preset to
150°F (66°C). Confirm this set point on the unit
and adjust if necessary. After running the heater
in a firing mode for 10 minutes, slowly close the
outlet valve “A” to raise the outlet temperature
as indicated on the outlet thermometer. The high
limit should trip within 2°F (1°C) or 3°F (2°C)
of the 150°F (66°C) setpoint and shut off the
burners. If this does not occur, adjust the set
point on the unit to shut off the burners when the
outlet thermometer reads 150°F (66°C). Open
the outlet valve “A” and push the reset button.
The main burners should reignite.

Mighty Therm Commercial Pool Heating Boiler Page 13
3. Flow Switch: See attached vendor literature.
4. Low Water Cutoff (optional): See attached
vendor literature.
3.4 Inlet Temperature and Temperature
Rise Adjustment
For proper operation the bypass and outlet
valves must be adjusted to obtain the correct heater
temperature rise and the correct inlet temperature.
Please refer to Table 5 which shows these values for
each model. Refer to Section 1.2 and the heater
nameplate to determine the model number of your
heater. Inlet and outlet thermometers are provided on
the unit. For spas see Section 3.9.
1. Make sure that the heater has been firing for at
least 10 minutes and that the operating control is
set at 5° or 10°F (3° or 6°C) above the pool
temperature.
2. Throttling the OUTLET valve “A” will raise the
inlet temperature. Throttling both the OUTLET
valve and the BYPASS valve “B” will increase
the total rise across the heater. Several
adjustments will be necessary to obtain BOTH
the correct temperature rise and the correct inlet
temperature. Wait about 5 minutes between
adjustments for the unit to stabilize.
3. After both temperatures have been set, lock the
handles on the valves or remove the handles to
prevent tampering with or accidental changes to
the valve positions.
4. When the pool has reached the desired operating
temperature check the temperatures again and
adjust if necessary. NOTE: The heater outlet
temperature should not exceed 140°F (60°C).
Reduce heater temp rise if necessary.
POOL OPERATING CONTROL ADJUSTMENT:
5. Adjustable Differential Feature: Remove the
cover from the control box and verify that the
white differential potentiometer is set at about
2°F (1°C). NOTE: a 2°F differential means that,
if the thermostat is set at 80°F, the heater will
come on at 78°F and go off when the pool
reaches 80°F. The 2°F value is a good starting
point for most installations. This differential may
be adjusted up or down to suit individual
applications.
6. The operating control temperature setting can be
adjusted incrementally to obtain the desired pool
operating temperature.
7. An adjustable pump time delay relay is mounted
in the control panel (see Figure 12). This relay
keeps the pump running after the burners shut
off. The delay should be set to 5-6 minutes for
models 500-850 and 9-10 minutes for models
1010-1825.
Figure 13. Safety Components.
Manual Reset
High Limit Flow Switch Low Water Cutoff
(Optional)
Part #E21039
Part #E131 Indoor
Part #E130 Outdoor
Part #20751
Figure 14. Pilot Burners.
Honeywell
(spark ignition, IID) Honeywell (standing pilot)
Part # W00358 (Nat.)
Part # W00344 (Propane)
3.5 Heater Shut Down
1. If heater is firing, turn operating control to
lowest value, wait 10 minutes for pump to stop
running, then turn power switch to off.
2. If heater is not firing, turn power switch to off.
3.6 Spring and Fall Operation
Stand-by Service
Turn the thermostat down to approximately
70°F (21°C). This will prevent the pool and
surrounding ground from becoming chilled and also
permit the pool to be raised to swimming temperature
in a shorter time.
A pool may be maintained at a lower
temperature than 70°F (21°C) with some increased
likelihood of condensation and damage to the unit.
Models 500 through 1010 will maintain an inlet
temperature of 85°F (29°C) to 90°F (32°C) (if the
bypass is properly adjusted) with a pool temperature
of 60°F (16°C). Models 1200 and 1430 can maintain
the above with a pool temperature of 65°F (18°C). For
models 1670 and 1825 pool temperature should be
maintained at 70°F (21°C) or above. See item 3 in the
next section.
Part # W00343 (Nat.)
Part # W20015 (Propane)
W00365
Thermo-
couple

LAARS HEATING SYSTEMS
Page 14
Table 5. Temperature Settings.
3.7 Winter Operation
Complete Shutdown
1. To shut down the heater for periods of several
months or more, turn manual main gas valve and
pilot gas valve to "OFF." Where danger of
freezing does not exist, some water should flow
through the heater during the normal filter cycle
all year long, even when the heater is turned off
or shut down completely, if all bypass valves are
opened.
2. If the heater is not protected from freezing
temperatures, it should be completely drained
before the first frost. Drain the heater by
removing the drain plug on the bottom of the
front header casting. Leave the plug out until
ready to use the heater again. Heater must be
level to permit adequate draining. When
compressed air is used to blow out lines, it is
still necessary to follow the above procedure.
Keeping the pool heated and the filter pump
running continuously will not be adequate
protection. If there is a pump failure or an
electrical power failure, the boiler cannot fire
and may freeze and be damaged.
3. Improper Use of Heater: The Laars Pool
Heating Boiler is not designed for continuous
use as an "anti-freezing" device for pools.
Operating the heater with low water
temperatures will cause the fins on the heat
exchanger to be partially blocked with
condensation. Incomplete combustion and
prolonged operation under these conditions will
result in the heat exchanger sooting up. This can
seriously damage the heater and may create a
dangerous fire hazard.
3.8 Time Clock Operation
During the warm-up period, the heater must run
continuously so it can raise the pool temperature from
cold to above 70°F (21°C).
Remove all time clock stops and permit the
heater to raise pool temperature to 70°F (21°C) or
above in one continuous operation.
When the time clock stops are replaced, be sure
to allow the filter pump and the heater to stay on long
enough to keep the pool up to the desired temperature.
3.9 Therapeutic Pools (Spas)
Therapeutic pools or "spa" pools are usually
piped and controlled so that very warm or hot water,
often with air injection, is forced at high velocity into
a confined area of a swimming pool or into a small
separate pool. For the purposes of this manual, any
application in which the water temperature is
maintained above 85°F (30°C) is considered a spa.
SPECIAL SET-UP AND OPERATING
PROCEDURES APPLY TO SPAS.
1. Models 1010I and 1010E and larger should not
be used for spas due to their higher temperature
rises.
2. Since outlet temperatures can approach 140°F
(60°C) units must be piped in a secondary,
parallel loop similar to that shown in Figure 10.
The bypass line between the inlet and outlet can
be deleted or, if it is installed, the BYPASS
valve should be closed with the handle removed.
3. To insure that the spa inlet water does not
exceed 104°F (40°C), the spa filter pump must
circulate at the minimum flow rates shown in
Table 6.
Boiler Model Minimum Filter Pump Flow Rate
500 220 GPM
600 270 GPM
715 320 GPM
850 380 GPM
Table 6. Minimum Filter Pump Flow Rates For Spas.
Note: Maximum Spa Temperature Is
Assumed To Be 100°F (38°C).
4. The high limit stop should be changed to 140°F
(60°C). The set point should then be checked
following the procedure in 3C-2.
5. Use the outlet valve “A” to set the temperature
rise as shown in Table 5. Note there should be
no bypass piping or flow in these installations.
6. Spas are excellent for relaxation, body-
conditioning and for arthritic and rheumatic
problems, but can be hazardous. The Consumer
Product Safety Commission has recommended
the following "Safety Rules for Hot Tubs:"
a. Spa or hot tub water temperature should
never exceed 104°F (40°C). A temperature
of 100°F (38°C) is considered safe for a
healthy adult. Special caution is suggested
for young children.
Heater Size Heater Temp. Rise Inlet Temp Difference*
Indoor Outdoor (TOUT - TIN)(T
INLET - TPOOL)
500 E 14°F 8°C 30°F 17°C
500 I 600 E 16°F 9°C 30°F 17°C
600 I 715 E 19°F 11°C 30°F 17°C
715 I 850 E 23°F 13°C 25°F 14°C
850 I 1010 E 26°F 15°C 25°F 14°C
1200 E 30°F 17°C 25°F 14°C
1010 I 30°F 17°C 25°F 14°C
1200 I 1430 E 35°F 20°C 20°F 11°C
1430 I 37°F 21°C 20°F 11°C
1670 I 1670 E 38°F 21°C 20°F 11°C
1825 I 1825 E 38°F 21°C 20°F 11°C
*ADD this number to pool temperature (TPOOL) to get desired inlet
temperature (TINLET). i.e., for 500 E: If pool temperature is 65°F (18°C),
inlet thermometer should read 95°F (35°C). Field adjustment
tolerance +_1°F (.5°C).
PROCEDURE!

Mighty Therm Commercial Pool Heating Boiler Page 15
b. Drinking of alcoholic beverages before or
during spa or hot tub use can cause
drowsiness which could lead to
unconsciousness and subsequently result in
drowning.
c. Pregnant women beware! Soaking in water
above 102°F (39°C) can cause fetal damage
during the first three months of pregnancy
(resulting in the birth of a brain-damaged or
deformed child). Pregnant women should
stick to the 100°F (38°C) maximum rule.
d. Before entering the spa or hot tub, users
should check the water temperature with an
accurate thermometer; spa or hot tub
thermostats may err in regulating water
temperatures by as much as four degrees
Fahrenheit (2.2°C).
Figure 16. Pilot Safety Relay.
Pilot Reset
Switch
e. Persons with a medical history of heart
disease, circulatory problems, diabetes or
blood pressure problems should obtain
their physician's advice before using spas
or hot tubs.
f. Persons taking medications which induce
drowsiness, such as tranquilizers,
antihistamines or anticoagulants, should
not use spas or hot tubs.
SECTION 4.
Maintenance
1. Lubricate the pump seal every 6 months with
½ oz. of SAE 30 non-detergent oil. Slowly add
to pump oil cup located on top of the bearing
bracket.
2. At start-up and every six (6) months thereafter,
the pilot and main burner flame should be
observed for proper performance (see Figure 17).
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 and call the Laars Service
Department.
3. Inspect the venting system for obstruction,
leakage and corrosion at least once each year.
4. Keep heater area clear and free from
combustible material, gasoline and other
flammable vapors and liquids (see Table 1 for
minimum clearances).
5. Be certain all combustion air and ventilation
openings in the room are unobstructed.
6. 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 with a flashlight by
locating a mirror under the burners. An alternate
method is to remove the venting and top panels
as necessary to inspect the heat exchanger from
above. Also check the vent system for defects at
this time. (If cleaning is required, shut off all
electrical and gas supply to the heater.)
7. To expose the heat exchanger:
Indoor Models: Remove the flue pipe, top of
unit, rear upper jacket, flue collector rear panel
and heat exchanger baffles.
Pilot Relay Manual
Reset Switch
(Standing Pilot Systems) Part # W0030000
Figure 15. Manual Gas Valves.
Pilot Valve
Main Gas Valve
Pilot Valve
Main Gas Valve
ON POSITION
OFF POSITION

LAARS HEATING SYSTEMS
Page 16
Outdoor Models: Remove vent top assembly,
rear upper jacket, flue collector rear panel and
heat exchanger baffles.
8. To 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 the
manifold pipe and slide out 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.
9. Clean heat exchanger using a wire brush to
remove soot and loose scale from the unit. Clean
fallen debris from bottom of heater. Make sure
burner ports are clear and pilot assembly is free
of debris.
10. Reassemble in reverse order and be sure the heat
exchanger baffles are replaced.
11. The gas and electric controls installed on the
heater are engineered for both dependable
operation and long life, but the proper
functioning of these components is necessary for
safe operation of the heater. It is strongly
recommended that the basic items be checked by
a competent serviceman 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 switch.
12. Low water cutoffs should be inspected every six
(6) months, when provided.
NOTE: The warranty does not cover any
damage caused by lack of required maintenance
or improper operating practices.
13. Pool Water Chemistry
The mineral content of the pool water increases
every day. This is due to the natural evaporation
which removes only distilled water and leaves the
minerals behind. The regular addition of algicidal
and sanitizing chemicals also adds greatly to the
mineral content of the pool. If the concentration
of minerals in the pool is permitted to become too
Figure 17. Main Burner Flame Pattern.
high, the minerals will precipitate out of the water
and deposit onto the walls of the pool, in the filter
and in the tubes of the heat exchanger.
For this reason it is very advantageous to drain
the pool regularly (at least every two years). This
precautionary measure will save the cost of
expensive repairs to the finish, filter system and
heater.
Another important safety precaution - always
keep the pH of the pool water between 7.3 and
7.7. This will add years to the life of the pool
finish, filter system and heater.
Most algicidal and sanitizing chemicals contain
sodium hypochlorite, while others contain
calcium hypochlorite. Sodium is not a scaling
chemical but calcium is. When using calcium
hypochlorite it is especially important to
frequently check the pH of the pool and to
change the pool water when the dissolved solids
indicate an excessive mineral content.
SECTION 5.
Troubleshooting
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 tube manometer or an
accurate gas pressure gauge is acceptable with
proper adapters to 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.
0 to 50 millivolts.
c. Tube cleaning kit consisting of reamer, stainless
steel brush, speed handle and handle extensions.
d. A pool thermometer with a proper range.
e. A pressure gauge with proper range.

Mighty Therm Commercial Pool Heating Boiler Page 17
1. Symptom: heater is pounding, knocking or emitting steam from relief valve
Possible Cause What to Do
A. Low or no water flow A. Is the heater wired into the filter pump circuit so that the heater cannot fire
(most likely). unless the pump is running?
Check to see that all valves in system are open to be sure that water can
circulate through the heater.
Check pool filter, clean if clogged.
Examine heater pump for clogged or frozen impeller.
Check flow switch for proper operation and range setting.
B. Debris from system piping B. Remove header covers. Examine all tubes and waterways. Clean out tubes.
is blocking tubes. Use new gaskets when reassembling.
C. Scale has formed in tubes C. Clean tubes with tube cleaning kit. Determine hardness. Check water flow, and
from high mineral content. clean pool filter.
2. Symptom: heater will not fire
A. Heater not getting power. A. Check to see that power switch is "ON." Use testing device to trace power to
heater power source. Check fuse and secondary voltage in heater control.
B. Operating or safety control has B. Turn off power. Check continuity across terminals of each operating and safety
opened circuit to electric gas valve. 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. Reset pilot safety and all manual reset safety switches. Follow instructions for
start-up.
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 heater inlet, check pressures in following
sequence: (1) downstream from pressure regulator; (2) downstream from electric gas valve.
Replace or adjust as necessary.
F. Electric gas valve operator is F. Disconnect wiring harness at gas valve terminals. Check continuity of actuator
burned out or shorted. coil. If open circuit or short is indicated, replace coil or operator.
G. Pump does not run. G. Operate in manual. Check power to pump from relay, Check that pump/motor
is free to rotate. Replace relay or motor as necessary.
H. Pump runs, but flow switch H. Check continuity across flow switch. Inspect paddle for proper movement.
not closing. Adjust flow range setting.
I. Field interlock open. I. Jumper terminals and isolate problem in other equipment.
3. Symptom: pressure relief valve leaking intermittently or steadily
A. Faulty relief valve. A. Replace with a new relief valve with proper setting (see rating plate).
4. Symptom: soot in flueways or in tubes, or noxious fumes from bad combustion
A. Combustion air supply to heater A. Check air supply opening. Look for debris in screen or louvre which covers
room is inadequate. combustion air opening, or for objects blocking the opening.
B. Stack or vent is blocked or restrictive. B. Look for blocked stack and excessive number of elbows in stack or excessive
length of horizontal runs.
C. Severe downdraft is causing C. Check for (1) proper vent cap on stack; (2) adequate height of stack above
spillage of flue products into room. roof; (3) equipment exhausting air from inside of building; and (4) proper
installation of draft diverter.
D. Gas pressure to burners is excessive. D. Check gas pressure with manometer, and adjust with heater firing at full rate.
E. Heater not fitted for the fuel supplied. E. See nameplate for correct fuel.
F. Heater installed at high altitude F. Installations at altitudes in excess of 2000 ft. above sea level are subject to
without proper derating. jurisdiction of the local inspection authorities. Check orifice size, contact your
dealer or factory for proper size.
5. Symptom: water dripping in firebox
A. Tube in heat exchanger has A. Tube failure is almost always caused by scale formation in the tube, or
overheated and ruptured. inadequate water flow through the heater.
B. Heater is condensing from low B. Check bypass valve adjustment.
inlet temperature.

LAARS HEATING SYSTEMS
Page 18
SECTION 6. Parts Description and Order Numbers
Key Description Size Size Size Size Size Size Size Size Size No 500 600 715 850 1010 1200 1430 1670 1825 Jacket and Combustion Chamber Components 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 {Indoor} 10535501 10535502 10535503 10535504 10535505 10535506 10535507 10535508 10535509 6 Front Support, Flue Collector {Indoor} 10534401 10534402 10534403 10534404 10534405 10534406 10534407 10662108 10662109
7 Tile Cover, Front/Rear {Indoor} 10534201 10534202 10534203 10534204 10534205 10534206 10534207 10661508 10661509
(2) (2) (2) (4) (4) (4) (4) (4) (4)
8 Tile Heat Shield/Spacer, 10560100 - - ------
Front and Rear (2)
9 Tile Heat Shield/Spacer, Front - 10547901 10547902 - - 10547903 10547901 10547904 10547903 10 Tile Heat Shield/Spacer, Front - - - 10548002 10548003 - - - 10548001 11 Tile Heat Shield/Spacer, Front - - - - - 10548101 10548102 10548103 10548104 12 Tile Heat Shield/Spacer, Rear - 10548201 10548202 - - 10548203 10548201 10548204 10548203 13 Tile Heat Shield/Spacer, Rear - - - 10548302 10548303 - - - 10548301 14 Tile Heat Shield/Spacer, Rear - - - - - 10548401 10548402 10548403 10548404 15 Saddle Assembly, End Tile 10533600 10533600 10533600 10533600 10533600 10533600 10533600 10533600 10533600
(2) (2) (2) (2) (2) (2) (2) (2) (2)
16 Lower End Panel/ 10540701 10540701 10540701 10540701 10540701 10540701 10540701 10540701 10540701
Heat Shield Weldment, Right
17 Lower End Panel/ 10540702 10540702 10540702 10540702 10540702 10540702 10540702 10540702 10540702
Heat Shield Weldment, Left
18 Lower Rear Panel 10532901 10532902 10532903 10532904 10532905 10532906 10532907 10532908 10532909
Weldment
19 Middle Rear Panel/ 10540401 10540402 10540403 10540404 10540405 10540406 10540407 10540408 10540409
Heat Shield Weldment
20 End Panel, Upper Right 10531600 10531600 10531600 10531600 10531600 10531600 10531600 10531600 10531600 21 End Panel, Upper Left 10534000 10534000 10534000 10534000 10534000 10534000 10534000 10534000 10534000 22 Upper Rear Panel/ 10540501 10540502 10540503 10540504 10540505 10540506 10540507 10540508 10540509
Heat Shield Weldment
23 Front Panel, Upper 10531501 10531502 10531503 10531504 10531505 10531506 10531507 10531508 10531509 24 Bracket, Support, End Tile 10551000 10551000 10551000 10551000 10551000 10551000 10551000 10551000 10551000
(2) (2) (2) (2) (2) (2) (2) (2) (2)
25 Drafthood, Relief Baffle, Right 10540901 10540902 10540903 10540904 10540905 10540906 10540907 10540908 10540909 26 Drafthood, Relief Baffle, Left 10541001 10541002 10541003 10541004 10541005 10541006 10541007 10541008 10541009 27 Lower Front Panel/ 10554601 10554602 10554603 10554604 10554605 10554606 10554607 10554608 10554609
Heat Shield Weldment
NOTE: Numbers in ( ) represent quantity required for each size. Quantity is one otherwise.

Mighty Therm Commercial Pool Heating Boiler Page 19
Figure 18. Parts Identification.

LAARS HEATING SYSTEMS
Page 20
Key Description Size Size Size Size Size Size Size Size Size No 500 600 715 850 1010 1200 1430 1670 1825 28 Middle Front Panel {Indoor} 10554401 10554402 10554403 10554404 10554405 10554406 10554407 10662008 10662009 29 Sweep Sheet, Flue Collector {Indoor} 10533901 10533902 10533903 10533904 10533905 10533906 10533907 10662208 10662209 30 Control Box Weldment 10545800 10545800 10545800 10545800 10545800 10545800 10545800 10545800 10545800 31 Control Box Cover {Indoor} 10547200 10547200 10547200 10547200 10547200 10547200 10547200 10547200 10547200 32 Base/Tile Support Assembly {Indoor} 10536901 10536902 10536903 10536904 10536905 10536906 10536907 10536908 10536909 33 Tile Assemblies {Refer to Figure 20 for configurations and Part Numbers} Optional Items
Non-Combustible Base {Rail} 10539000 10539000 10539000 10539000 10539000 10539000 10539000 10539000 10539000
(2) (2) (2) (2) (2) (2) (2) (2) (2)
Water System 34 8-Tube Assembly, Copper Tubes/ 10534701 10534702 10534703 10534704 10534705 10534706 10534707 - -
Cast Iron Tubs {Indoor} 8-Tube Assembly, Copper Tubes/ 10542901 10542902 10542903 10542904 10542905 10542906 10542907 - - Bronze Tubs {Indoor} 8-Tube Assembly, CU-NI Tubes/ 10553601 10553602 10553603 10553604 10553605 10553606 10553607 - - Cast Iron Tubs {Indoor} 8-Tube Assembly, CU-NI Tubes/ 10553701 10553702 10553703 10553704 10553705 10553706 10553707 - - Bronze Tubs {Indoor} 10-Tube Assembly, Copper Tube/ - - - ----10665908 10665909 Cast Iron Tubs {Indoor} 10-Tube Assembly, Copper Tube/ - - - ----20001108 20001109 Bronze Tubs {Indoor} 10-Tube Assembly, CU-NI Tubes/ - - - ----20001008 20001009 Cast Iron Tubs {Indoor} 10-Tube Assembly, CU-NI Tubes/ - - - ----10670408 10670409 Bronze Tubs {Indoor}
35 Baffle, Heat Exchanger Front/ 10534301 10534302 10534303 10534304 10534305 10534306 10534307 20020108 20020109
Rear {Indoor} (2) (2) (2) (4) (4) (4) (4) (4) (4)
36 Baffle, Heat Exchanger {8-Tube} 10534601 10534602 10534603 10534604 10534605 10534606 10534607 - -
(7) (14) (14) (14) (14) (28) (28) - -
Baffle, Heat Exchanger {10-Tube} - - - ----10667708 10667709
(28) (14)
Baffle, Heat Exchanger {10-Tube} - - - -----10667702
(14)
NOTE: Numbers in ( ) represent quantity required for each size. Quantity is one otherwise.