LAARS Mighty Max HH User Manual

Installation, Operation and Maintenance Instructions Document 2060D

Installation,
Operation and
Maintenance
Instructions for

Mighty Max

Hydronic Boilers

Model HH
Sizes 320M - 1000M

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.

If the information in this manual is not

WARNING

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.

WHA T 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.

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’inst allation et l’entretien doivent être assurés par
un installateur ou un service d’entretien qualifié ou
par le fournisseur de gaz.

AVERTISSEMENT

H2090800D

Page 2

LAARS HEATING SYSTEMS

TABLE OF CONTENTS

SECTION 1.
General Information

1A. Introduction.................................................... 3

1B. Warranty........................................................3

1C. Technical Assistance.....................................3

SECTION 2.
Installation Instructions

2A. General Information....................................... 4

2B. Boiler Placement ........................................... 4

2C. Installation of Outdoor Boilers........................4

2D. Freeze Protection .......................................... 4

2E. Installation of Indoor Boilers...........................5

2E-1. Combustion Air Supply and Ventilation ..........5

2E-2. Removal of Existing Boiler............................. 5

2F. Gas Supply and Piping .................................. 6

2G. Water System Requirements.........................8

2G-1. Flow Requirements........................................8

2G-2. Variable Water Flow Systems........................8

2G-3. System Pressure Requirements ....................9

2G-4. Hot/Chilled Water Systems............................ 9

2G-5. Combined Space Heating/Potable

Water Heating Systems................................. 9

2H. Piping of System to Boiler .............................. 9

2I. Filling the System ........................................ 10

2J. Venting and Combustion Air Information ..... 10

2K. Top-to-Rear Vent Collar Conversion............12

2L. Venting ........................................................ 13

2L-1. Vertical Venting - Category I ........................ 13

2L-2. Vertical Venting - Non Category I.................13

2L-3. Vertical Venting - Non Category 1................13

2L-4. Side Wall Vent Terminal ..............................14

2M. Air for Combustion and Ventilation............... 14

2M-1. Air From Room ............................................ 15

2M-2. Ducted Combustion Air................................15

2M-3. Conversion for Ducted

Combustion Air ............................................ 15

2M-4. Combustion Air Piping ................................. 16

2N. Electrical Wiring ........................................... 16

SECTION 3.
Operating Instructions

3A. Start Up Requirements ................................ 16

3B. Hi-Limit checkout ......................................... 18

3C. Venturi and Gas Pressure

Regulator System ........................................ 18

3C-1. Overall Operation......................................... 18

3C-2. Venturi Adjustment ...................................... 18

3D. To Start Up System ..................................... 19

3D-1. Setting Temperature Controls...................... 20

3E. To Shut Down System ................................. 20

3F. Venturi Combustion Flow System ................ 20

3F-1. Pressure Measurement Ports ...................... 20

3F-2. Venturi Adjustment ...................................... 20

3F-3. Venturi Setup Procedure..............................22

SECTION 4.
Maintenance

4A. General Instructions..................................... 22

4B. Heat Exchanger........................................... 22

4B-1. Inspection of the Heat Exchanger................ 23

4B-1a. External heat Exchanger Inspection ............ 23

4B-1b. Internal Heat Exchanger Inspection ............. 23

4B-2. Cleaning the Heat Exchanger ...................... 23

4B-2a. Cleaning the Heat Exchanger - External...... 23

4B-2b. Cleaning the Heat Exchanger - Internal ....... 23

4C. Gas and Electric Controls ............................ 23

4D. Filter ............................................................ 24

4D-1. Filter Function .............................................. 24

4D-2. Filter Service................................................ 24

SECTION 5.
Troubleshooting

5A. Sequence of Operation................................ 24

5B. Venturi and Gas Pressure

Regulator System ........................................ 26

5B-1. Field Checkout............................................. 26

5C. Electrical Components ................................. 26

5C-1. General Troubleshooting ............................. 26

5C-2. Electrical Troubleshooting ........................... 26

SECTION 6.
Parts List for Mighty Max HH Boiler

6A. General Information..................................... 27

Mighty Max Hydronic Boiler

Page 3

SECTION 1.
General Information

1A. Introduction

This manual contains installation, operation and
maintenance instruction for the Mighty Max hydronic
boiler, Model HH, sizes 320M, 400M, 520M, 625M,
775M and 1000M. Review all application and
installation procedures completely before proceeding
with the installation. Consult the local factory
representative or Laars factory with any questions
regarding this equipment. Experience has shown that
most operating problems are caused by improper
installation. The HH boilers are offered in an indoor
version and an outdoor version (see Figure 1). Table 1
lists the input/output ratings for each boiler size.

The indoor version is convertible for outdoor use
with the installation of a conversion kit. See Section 6,
Parts List, for part number.

1B. Warranty

The Mighty Max HH boilers are sold with a
limited factory warranty. Details are specified on the
back cover of this manual.

Make all warranty claims to an authorized Laars
representative or directly to the factory. Claims must
include the heater serial number and model number
(this information can be found on the rating plate),
installation date, and name of the installer. Shipping
costs are not included in the warranty coverage.

Some accessory items are shipped in separate
packages. Inspect everything for damage immediately
upon delivery, and advise the transporter of any
shortages or damage. Any such claims should be filed
with the transporter. The transporter will not accept a
claim from the shipper, Laars.

The warranty does not cover damage caused by
improper installation, operation, or field modification.

1C. Technical Assistance

Consult the local factory representative or Laars
factory with any questions regarding the specification,
installation, and operation of Laars equipment. An
experienced technical support staff is ready to assist in
assuring the proper performance and application of
Laars products.

Boiler Input Output
Size BTU/h kW BTU/h kW

320M 320,000 94 272,000 80
400M 399,000 17 339,150 99
520M 520,000 152 442,000 130
625M 625,000 183 531,250 156
775M 775,000 227 658,750 193
1000M 1,000,000 293 850,000 249

Table 1. Input/Output Ratings.

INDOOR OUTDOOR

Front Side

(Water Connections)

Figure 1. Mighty Max HH Boiler Configuration.

Rear Side

(Opposite Water

Connections)

Page 4

LAARS HEATING SYSTEMS

SECTION 2.
Installation Instructions

2A. General Information

Install the Mighty Max HH boiler in accordance
with the procedures in this manual (or the Laars
warranty may be voided), local codes, and ordinances.
In the absence of such codes, install the heaters in
accordance with the latest edition of the National Fuel
Gas Code, ANSI Z223.1/National Fire Protection
Association (NFPA) 54. In Canada, the installation
must be in accordance with CAN1-B149.1 or .2 and
local codes. The authority having jurisdiction may
require the installation be in accordance with the
American Society of Mechanical Engineers (ASME)
Safety Codes for Controls and Safety Devices for
Automatically Fired Heaters, CSD-1, and in Canada,
Canadian Gas Association (CGA) 3.3. Any changes to
the boiler, its gas controls, gas orifices or wiring may
void the warranty. If field conditions require change,
consult the factory.

The Mighty Max HH boiler is designed-certified
for installation on a combustible floor. Do not install

the boiler directly on carpeting.

2B. Boiler Placement

2C. Installation of Outdoor Boilers

Caution

Outdoor installations are not recommended in
areas where the danger of snow blockage
exists.

1. Locate the boiler to provide at least the
minimum clearances as listed in Section 2B,
“Boiler Placement.” HH boilers require an
outdoor terminal kit when installed outdoors (see
Section 6, Parts List).

2. Do not locate the boiler in an enclosure or
through-wall recess. Avoid locations where wind
deflection off structures might cause down-draft.
When such wind conditions are possible, locate
the boiler at least 3 feet (.9m) from structures.

3. Never install the boiler under any kind of roof
overhang. Do not locate the boiler below or
adjacent to any doors, windows, louvers, grills,
etc. which communicate in any way with an
inhabited area of a building, even though such
communication might be through another
structure such as a garage or utility room (see
Figure 2).

Clearance From Indoor Outdoor
Combustibles Inches mm Inches mm

Top 18 457 Unobstructed
Water Conn. Side 12 305 12 305
Opposite Side 6 152 6 152
Front Alcove Unobstructed
Rear 6 152 6 152
Vent *6* 152 —
Flooring Combustible Combustible

Service clearance = 24 in. (610mm) at front of boiler.

*1 in. (25mm) if double wall vent is used.

Table 2. Minimum Boiler Clearances

from Combustible Surfaces.

Locate the boiler to provide adequate clearances
on all sides for maintenance and inspection. There
must also be minimum distances maintained from
combustible surfaces (See Table 2).

The boiler must be isolated or otherwise
protected from any source of corrosive chemical
fumes, such as trichlorethylene, perchlorethylene,
chlorine, etc. Install the boiler so that the gas ignition
system components are protected from water
(drippings, spraying, rain, etc.) during operation and
service.

WINDOW

OR GRILL

WRONG

Figure 2. Incorrect Installation of Boiler.

INDOOR

ROOM

2D. Freeze Protection

Boiler installations are not recommended in
areas where the danger of freezing exists unless
proper precautions are made for freeze protection.
Maintaining a mixture of 50% water and 50%
properly inhibited HVAC glycol is the preferred
method of freeze protection for hydronic systems. (Do
not use automotive antifreeze.) 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 recommendation by 15%. Increase the head loss
requirement by 20%. Note: If your application does

Mighty Max Hydronic Boiler

Page 5

not require the full freeze protection of a 50%/50%
mixture, it is beneficial to use a maximum 30% glycol
solution. This mixture will protect the boiler to
temperatures of about 5°F (-15°C), and will serve as
burst protection for boilers that are not in use.

2E. Installation of Indoor Boilers

2E-1. Combustion Air Supply and

Ventilation

There are a variety of options available to the
installer when it comes to venting and combustion air;
venting can be vertical or horizontal, it can originate
at the top of the boiler or the back, and combustion air
can be obtained from the room where the boiler is
installed or ducted directly to the boiler from
outdoors. See Sections 2J through 2M for details.

2E-2. Removal of Existing Boiler

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 other appliances
remaining connected to the common venting system
are not in operation.

1. Seal any unused openings in the common

venting system.

2. 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.

3. 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.

4. Place in operation the appliance being inspected.

Follow the lighting instructions. Adjust

thermostat so appliance will operate

continuously.

5. Test for spillage at the draft hood relief opening

if the appliance is equipped with a drafthood,

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 door, windows, exhaust fans,

fireplace dampers and any other gas-burning
appliances 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. 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.

In Canada, at the time the boiler is removed from

common venting system, the common venting system
should be resized so the installation conforms to
CAN/CGA B149.1 or .2.

2E-2. Removal of Existing Boiler

Au moment du retrait d’une chaudière existante,

les mesures suivantes doivent être prises pour chaque
appareil toujours raccordé au système d’evacuation
commun et qui fonctionne alors que d’autres appareils
toujours raccordés au système d’évacuation ne
fonctionnent pas:

1. Sceller toutes les ouvertures non utilisées du
système d’évacuation.

2. Inspecter de façon visuelle le système
d’évacuation pour déterminer la grosseur et
l’inclinaison horiztonale 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 tojours
raccordés et les autres espaces du bâtiment.
Mettre en marche les sécheuses, tous les
appareils non raccordés au système d’évacuation
commun et tous les ventilateurs d’extraction
comme les hottes de cuisinère 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 continue.

5. Faire fonctionner le brûleur principal pendant 5
min ensuite déterminer si le coupe-tirage
déborde à l’ouverture de décharge. Utiliser la
flamme d’une allumette ou d’une chandelle ou la
afumée 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

Page 6

LAARS HEATING SYSTEMS

Distance from Gas Meter or Last Stage Regulator

0-100 feet 100-200 feet 200-300 feet

0-30m 30-60m 60-90m

Natural Propane Natural Propane Natural Propane

Size in.

320M
400M
520M
625M
775M

1000M

Notes: 1. These numbers are based on 1/2 inch (13mm) water column pressure drop.

1.25

1.25

1.50

1.50

2.00

2.00

2. Check supply pressure and local code requirements before proceeding with work.

3. Pipe fittings must be considered when determining gas pipe sizing.

mm

32
32
38
38
51
51

in.

1.25

1.25

1.25

1.25

1.50

1.50

Table 3. Natural Gas and Propane, Pipe Size Requirements.

au systéme d’évacuation est mis à l’air libre de
façon adéquate. Remettre les portes et les
fenêres, 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 êvacuation
commun devrait être corrigé de façon que
l’installation soit conforme au National Fuel
Gas Code, ANSI Z223.1/NFPA 54 et (ou) aux
codes d’installation CAN/CGA-B149. Si la
grosseur d’une section du systéme devrait être
modifié ppour respecter les valeurs minimales
des tableaux pertinents de l’appendice F du

National Fuel Gas Code, ANSI Z223.1/NFPA 54
et (ou) des codes d’installation CAN/CGA-B149.

mm

32
32
32
32
38
38

in.

1.50

1.50

2.00

2.00

2.00

2.50

mm

38
38
51
51
51
64

in.

1.25

1.25

1.50

1.50

1.50

2.00

mm

32
32
38
38
38
51

operate at high altitudes have appropriate
stickers or tags attached.

3. The figures in Table 3 should be used to size the
gas piping from the gas meter to the boiler.
Check local codes for BTU/h capacity required.

4. Install a sediment trap (drip leg) ahead of the gas
controls (see Figure 4). Fit the trap with a
threaded cap which can be removed for cleaning.

5. When required by code, install a second manual
gas shutoff valve. Do not remove manual shutoff
valve supplied with the boiler.

6. Disconnect the boiler and its individual shutoff
valve from the gas supply piping system during
pressure testing of the system at pressures higher
than 1/2 psi (3.5 kPa). Isolate the boiler from the
gas supply piping system by closing its

2F. Gas Supply and Piping

Review the following instructions before

continuing the installation.

1. Gas piping installation must be in accordance
with the latest edition of ANSI Z223.1/NFPA 54.
In Canada, the installation must be in accordance
with CAN1-B149.1 or .2 and all local codes that
apply. See Figure 3 for boiler gas valve

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 psi
(3.5 kPa).

7. Gas supply pressures to the boiler are listed in
Table 4.

Supply Pressure

Water Column

arrangement.

2. Check the rating plate to make sure the boiler is

Minimum 5

fitted for the type of gas being used. Laars
boilers are normally equipped to operate below a
2000 foot (610m) altitude. Boilers equipped to

Maximum 9

Table 4. Gas Supply Pressure Requirements.

in.

1.50

2.00

2.00

2.00

2.50

3.00

mm

38
51
51
51
64
76

Natural Gas Propane Gas
in.

mm
127

229

in.

1.50

1.50

1.50

2.00

2.00

2.50

in.

9

14

mm

38
38
38
51
51
64

mm
229

356

Mighty Max Hydronic Boiler

Air Shutter
Enclosure

Filter
Housing

Automatic,
Regulator
and
Redundant
Gas Valve

Mixture
Plenum

Venturi

Blower
Motor

Filter
Housing

Venturi

Automatic
and
Redundant
Gas Valve

Mixture
Plenum

Air Shutter
Enclosure

Blower
Motor

Regulator

Manual Gas
Valves When
Used On
Canadian Unit
or U.S.Unit
Requiring
CSD-1 Code

Filter
Housing

Venturi

Air Shutter
Enclosure

Mixture
Plenum

Blower
Motor

Automatic
Main
Gas Valves

Page 7

Regulator

Manual Gas
Valves When
Used On
Canadian Unit
or U.S.Unit
Requiring
CSD-1 Code

SIZES:

320M, 400M

SIZES:

520M, 625M

SIZES:

775M, 1000M

Note: The above diagram is a representation. Actual venturi assembly may vary depending on boiler size.

Figure 3. Boiler Gas Valve Arrangement.

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

Gas Supply
Inlet

indication of an undersize gas meter and/or obstructed
gas supply line.

8. Do not exceed the maximum inlet gas pressures

Tee
Fitting

specified. Excessive pressure will result in
damage to the heater's gas controls. The
minimum pressures specified are for gas input

3 In.
(76mm) Min.

Nipple

adjustment.

9. The correct differential gas pressure is stamped
on the rating plate. The regulator is preset at the

Cap

factory, but may need adjustment for altitude per
Section 3.

10. Before operating the heater, test the complete

Figure 4. T-Fitting Sediment Trap Installation.

gas supply system and all connections for leaks
using a soap solution.

To Equipment
Inlet

Caution

Since some leak test solutions (including soap
and water) may cause corrosion or stress
cracking, rinse the piping with water after
testing.

Page 8

LAARS HEATING SYSTEMS

2G. Water System Requirements

2G-1. Flow Requirements

The Model HH boilers must have continuous
flow through the heat exchanger when firing for
proper operation. The system pump must be capable
of developing sufficient pressure to overcome the
resistance of the boiler plus the entire circulating
system at the designated flow (see Table 5). The
temperature rise across the boiler should never exceed
40°F (22°C).

2G-2. Variable Water Flow Systems

There can be reduced water flow through the
boiler in heating systems using zone valves, zone
pumps or 3-way valves. This can result in a high
temperature rise across the boiler. Laars recommends
primary-secondary pumping for all variable flow
systems. The boiler pump in a primary-secondary
system maintains constant flow through the boiler
even though the system flow is variable. In a primary­secondary system the pressure drop of the boiler is not
added to the system (see Figure 5).

TEMPERA TURE RISE IN DEGREES (°F / °C )

10°F

6°C

15°F

MODEL

LPS H/L m

3.41

4.29

5.55

6.69

8.33

10.73

3.4

8.0

2.7

3.7

6.9

11.4

GPM H/L ft.

36
45
58
70
87

113

5.0

11.5

4.0

5.7

9.4

16.5

HH0320M
HH0400M
HH0520M
HH0625M
HH0775M
HH1000M

GPM H/L ft.

54
68

88
106
132
170

11.2

26.2

8.9

12.2

22.5

37.3

Flow High Normal Low

NOTES: Sizes 320M and 400M use 4-pass heat exchangers; 520M, 625M and 775M use 2-pass heat exchangers.

*Pressure drop (head loss) through the boiler, expressed in ft. of H2O.
Shaded area is the recommended flow and temperature rise. Minimum inlet temperature is 105°F.

8°C

LPS H/L m

2.27

2.84

3.66

4.42

5.49

7.13

1.5

3.5

1.2

1.7

2.9

5.0

20°F

GPM H/L ft.

27
34
44
53
65
85

2.8

6.6

2.6

3.3

5.2

9.4

11°C

LPS H/L m

1.70

2.15

2.78

3.34

4.10

5.36

0.9

2.0

0.8

1.0

1.6

2.9

WARNING: This drawing shows suggested
piping configuraiton and valving. Check with
local codes and ordinances for additional
requirements.

Boiler Circulation

12"

Max.

LEGEND:

Thermometer
Temperature

Sensor
Globe Valve
Check Valve
Pressure Reducing Valve

w/Fast Fill Bypass

Purge
Valve

Expansion T ank
with Air Scoop and
Auto Air Vent

3-Way Valve
Valve
Pump

Pump

Table 5. Temperature Rise.

12"

Max.

12"

Max.

Cold Water

Make-Up

System Pump

12"

Max.

Boiler circuit piping must be equal to or larger than
boiler water connection size.

Boiler circulation pump sized for flow through
boiler.

Dotted devices indicate alternate locations.

Figure 5. Primary-Secondary Plumbing.

Mighty Max Hydronic Boiler

Page 9

2G-3. System Pressure Requirements

The Model HH boilers are designed to operate
on closed, pressurized systems. Maintain a minimum
of 12 psi (81.8 kPa) on the system where boiler supply
water temperature is 200°F (93°C) or less. If higher
temperatures are required, the minimum system
pressure should be at least 15 psi (102.2 kPa) above
the water vapor pressure corresponding to the elevated
water temperature.

The Model HH boilers are not suitable for open
systems unless the supply water temperatures are
kept below 180°F (82°C), and a minimum of 5 psi
(34.1 kPa) static head is maintained at the boiler.

2G-4. Hot/Chilled Water Systems

When a boiler is connected to an air
conditioning system where the same water is used for
heating and cooling, you must prevent chilled water
from entering the boiler. When changing such a
system from cooling to heating, allow the chilled
water 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 105°F (41°C)
before the water flows into the boiler. It is equally
important to prevent hot water from entering the
chiller. The system shown in Figure 6 is suggested to
make sure the system water is neither too hot nor too
cold when a changeover takes place. When a boiler is
connected to heating coils located in air handling units
(where they may be exposed to refrigerated air
circulation), install 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 condensate on the boiler tubes.

Boilers installed in violation of the foregoing may
void the warranty.

2G-5. Combined Space Heating/Potable

Water Heating Systems

When using the Mighty Max boiler as a source
of heat for a combined space heating/potable water
heating system, be sure to follow the instructions of
the space heating system.

Do not use water piping, fittings, valves, pumps,
and any other components which are not compatible
with potable water.

Do not connect the heater, which will be used to
supply potable water, to any heating system or
components previously used with a nonpotable water
heating system.

Do not add boiler treatment or any chemicals to
the heating system piping, since the piping contains
water for potable use.

Do not use solder containing lead in the potable
water lines.

Some jurisdictions may require a backflow
preventer in the cold water line. In such cases,

pressure relief valve may discharge water due to
expansion. An expansion tank approved for potable
water will eliminate this condition. Follow the
manufacturer's instructions for installation of the
expansion tank.

Suggested Wiring Diagram For

Tempering System Water at

Changeover From Heating To Cooling

DPDT Manual or Automatic
Change-Over Switch
DPDT - Set at Change-Over
Temperature

115/24V
Transformer

From
Chiller

3-Way Valve No. 1
Change-Over
(Heating and Cooling)

Figure 6. Boiler-Chiller Installation.

Valve Motors
2-Pos
3-Wire - 24V

From
Boiler

3-Way Valve No. 2
To By-Pass
Both Heater and
Chiller

Clock Timer
Auto-Resetting
Set at 15 Minute SPDT

To Boiler
and
Chiller

By-Pass

From
System

To
System

2H. Piping of System to Boiler

1. Be sure to provide gate valves at the inlet and
outlet to the boiler so it can be readily isolated
for service.

2. The pressure relief valve installed in the tapped
opening provided in the outlet header 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. If
the PRV supplied with the boiler is not factory
installed, install it in the front header consistent
with the ANSI/ASME Boiler and Pressure Vessel
Code, Section IV. Pay special attention to relief
valve settings in installations where the boiler is
located on the ground floor of a tall building, or
where the operating temperature of the boiler is
above 210°F (99°C). In both instances, the static
pressure of the system is elevated and could cause
the relief valve to leak and bring considerable raw
water into the system. Where no special setting of
the relief valve is ordered, the factory will furnish
a 75 psi (511.5 kPa) setting. Never reduce the
relief valve opening. If necessary, install the relief
valve in a Tee immediately past the boiler outlet.

Page 10

LAARS HEATING SYSTEMS

Air Changer
and Tank
Drainer

Make-Up
Water
Supply

Check
Valve

Pressure
Reducing
Valve

Blow Down
Valve

Strainer

NOTES: Select Method 1 or 2 when using low water cutoff accessory:

1. Under Method 1, the low water cutoff is furnished by Laars and shipped
as a separate item for fieldinstallation.

2. Under Method 2, electronic low water cutoff isinstalled, wired and tested
on boiler in Laars factory.

3. Preferred locaiton of system pump is shown. Compression tank must
always be on suction side of pump.

Figure 7. Boiler Piping.

To Drain

Method 1

To
System

Pump

Expansion
Tank

Method 2

To
Drain

Thermometer
Temperature
and Pressure
Gauge

3. Provide a boiler installed above radiation level
with a low water cutoff device either as part of
the boiler or at the time of boiler installation (see
Figure 7).

4. Install manual and/or automatic bleeding devices
at high points in the system to eliminate air.
Install a correctly sized expansion or
compression tank with suitable air charger and
tank drainer, as appropriate.

5. Support the weight of all water and gas piping by
suitable hangers or floor stands.

6. Check piping diagrams with local applicable
plumbing, heating and building safety codes.

2I. Filling The System

1. Ensure the system is fully connected. 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 (81.8 kPa) 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 (81.8 kPa) at the
highest point in the heating loop.

4. Open bleeding devices on all radiation units at
the high 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,
check flow switch operation, 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 3A. 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.

13. Check gauge for correct water pressure and also
check water level in the 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 the expansion tank as described in
Steps 4 and 8 above.

IMPORTANT:

The installer is responsible for identifying to the
owner/operator the location of all emergency
shutoff devices.

2J. Venting and Combustion Air

Information

Provisions for venting and supply of air for

venting and combustion must be done in accordance
with these instructions and applicable requirements of
the latest edition of ANSI Z223.1/NFPA 54. In
Canada, installation must be in accordance with CAN/
CGA B149.1 or .2, and applicable local codes.

There are a variety of ways to provide venting

and combustion air for the boiler (see Figure 8).

Mighty Max Hydronic Boiler

Screen Provided

On Vertical Intake

Air Terminal

Category I

Vertical Venting (Category I)

Combustion Air In

Through Louvers

Page 11

For vertically ducted combustion air:

• Combustion air intake must
terminate at least 3 feet (0.91m)
lower than vent termination, if it is
located within a 10 foot (3.05m)
radius.

• Combustion air intake must be at
least 1 foot (0.3m) above roof top
and normal snow levels.

Vertical Venting

with Ducted

Combustion Air

Non-Category I

Horizontal Venting

Any Vent Which Does Not Meet

Category I Combustion Air

Through Louvers

Exhaust Terminal Detail

Wall

Side View

Horizontal

Intake Terminal Detail

(Combustion Air)

Horizontal Venting

Ducted Combustion Air

(Certified As Direct Vent)

NOTE:All views are shown

from rear of heater

Figure 8. Venting and Combustion Air Options.

Wall

Side View

Page 12

LAARS HEATING SYSTEMS

Vent

Collar/Stack

Blank Plate

(Boiler

Jacket)

Adapter Plate

Top Panel

1. Removal of Blank Plate and Adapter
Plate From Boiler

Blank Plate On

Boiler Jacket

Top Panel

Blank Plate On

Flue Collector

3. Blank Plate Placement
Over Stack Top Opening

Blank Plate

(Flue

Collector)

2. Removal of Blank Plate From
Rear of Flue Collector

Figure 9. Top-To-Rear Vent Collar.

The Mighty Max HH boiler is certified as a true
direct vent unit when installed according to the
instructions for horizontal venting and ducted
combustion air. This can be done even if the runs are
vertical.

2K. Top-to-Rear Vent Collar Conversion

The Mighty Max HH boiler is shipped with the
vent collar on top of the heater. Follow this procedure
to convert it for rear connection (see Figure 9).

1. Remove the adapter plate from the top panel.

2. On the boiler jacket, remove the top panel and

ease its lip from under the edge of the bonnet to

gain access to the flue collector.

Vent

Collar/Stack

4. Connecting Vent Collar/Stack
to Flue Collector

3. Remove the vent collar/stack from the flue
collector. Do not damage the vent collar/stack
during removal.

4. Remove the blank plate from the rear of the
jacket.

5. Remove the blank plate from the rear section of
the flue collector. Be careful not to lose the
insulation attached to the plate.

6. Apply high temperature sealant and install the
blank plate (previously removed from the rear
section of the flue collector) on top of the flue
collector.

7. Install the blank plate (previously removed from
the rear of the boiler jacket) over the stack
opening on the top panel of the boiler.

Mighty Max Hydronic Boiler

r

Page 13

8. Apply high temperature sealant (see Table 6) to
vent collar/stack and install on the rear of the
flue collector.

Term Description

Pipe Type 304, Type 316, or 29-4C

stainless steel, 24 gauge minimum

Joint Sealing 3M Type 433 sealing tape with 400°F

(204°C) rating or high temperature
silicone sealer with 500°F (260°C)
rating, Dow No. 736

Insulation R5 minimum with protective cover

Table 6. Required Horizontal Venting Material.

9. Slip the adapter plate over the vent collar/stack
and install it onto the rear boiler jacket (see
Figure 9).

2L. Venting

Venting must be in accordance with these

instructions and applicable requirements of the latest
edition of ANSI Z223.1/NFPA 54. In Canada,
installation must be in accordance with the latest
edition of CAN/CGA B149.1 or .2, and applicable
local codes.

2L-1. Vertical Venting - Category I

The Mighty Max boiler has a fan-assisted

combustion system, so vertical vents must be installed
in accordance with the special code requirements for
Category I - Fan-Assisted Appliances. These
requirements can be found in the latest edition of
ANSI Z223.1/NFPA 54, Appendix G, Table 1, and in
Canada, CAN/CGA B149.1 or .2, Amendment No. 1.
These codes permit installation as a single appliance
or in combination with other Category I appliances.

However, there are very important requirements for
minimum and maximum vent diameter and length.
Make sure vertically-vented installations comply with
these codes.

NOTE: If a vent cannot be installed in

accordance with the requirements of these codes, it
must be installed as a horizontal vent, even if it is
mainly vertical.

2L-2. Vertical Venting - Non-Category I

When venting does not meet the code
requirements for Category I - Fan-Assisted Vertical
Vents, it can develop positive pressure. Such venting
must be installed in accordance with this section or
Section 2L-3.

The following requirements must be used for
Non-Category I venting:

1. Laars specified vent pipe material (Table 6) and

sizes (Table 7).

2. Pipe insulation and sealing tape.

3. Routing vent pipe through spaces which, except

for the terminal, remain above 60°F (16°C)

during heater operation.

2L-3. Horizontal Venting - Non-Category I

When venting is horizontal, or cannot meet the
code requirements for Category I - Fan-Assisted
Vertical Vents, it can develop positive pressure and
must be installed in accordance with this section.

The following requirements must be used for
Horizontal Venting - Non-Category I:

1. Laars specified vent pipe material (Table 6) and

sizes (Table 7).

2. Laars side wall vent hood.

3. Pipe insulation and sealing tape.

4. Routing vent pipe through spaces which, except

for the terminal, remain above 60°F (16°C)

during heater operation.

Heater

Size

320M
400M
520M
625M
775M

1000M

IMPORTANT: Maximum pipe length allowed is 50 feet (15m), regardless of the number of elbows. Maximum number of elbows allowed is 5.
Vent pipe minimum clearance from combustible surfaces is 6 inches (152mm).

Pipe Diameter M ax Pipe Length

in.

6
7
8
8
9

10

mm

152
178
203
203
229
254

Table 7. Vent Piping Specifications (Combustion Air Exhaust).

ft.

50
50
50
50
50
50

m

15
15
15
15
15
15

Max No.

of Elbows

5
5
5
5
5
5

Side Wall

Vent Terminal

Part Number

D2004500
D2004600
D2004700
D2004700
D2004800
D2006200

Side Wall

Combustion Air

Terminal Part Numbe

20260701
20260702
20260703
20260704
20260705
20526906

Page 14

LAARS HEATING SYSTEMS

Vent Hood

3 (0.9m) Minimum

Vent

Hood

Vent Hood

7 (2.1) Minimum

Above Public

Walkway

Figure 10. Building Exterior.

6 (1.8) Above Any
Outside Air Intake

Within 10 (3.0)

Vent Hood

Vent Hood

1 (0.3) Above Grade

2L-4. Side Wall Vent Terminal

The side wall vent hood must be used when the
heater is vented through a side wall. It provides a
means of installing vent piping through the building
wall, and must be located in accordance with ANSI
Z223.1/NFPA 54 and applicable local codes. In
Canada the installation must be in accordance with
CAN/CGA B149.1 or .2 and local applicable codes
(see Figure 10). Consider the following when
installing the terminal:

1. Locate the vent terminal so that it will not be

damaged by pedestrians and other traffic, and so

the discharge is not objectionable. The National

Fuel Gas Code requires a through-wall vent

terminal be at least 7 feet (2.1m) above grade if

located at a public walkway.

2. Locate the vent terminal so that vent gases

cannot be drawn into air conditioning system

inlets. The National Fuel Gas Code requires that

it be at least 6 feet (1.8m) above any such inlet

that is within 10 feet (3.0m).

3. Locate the vent terminal so that vent gases

cannot enter the building through doors,

windows, gravity inlets or other openings. The

National Fuel Gas Code requires that it be

located at least 4 feet (1.2m) below, 4 feet

4 (1.2)

Minimum

Vent Hood Must Be

Mounted 4 (1.2)

Minimum Below Windows

Dimensions shown in feet (m).

(1.2m) horizontally from, or 3 feet (0.9m) above
such openings.

4. Locate the vent terminal so that it cannot be
blocked by snow. The National Fuel Gas code
requires that it be at least 12 inches (305mm)
above grade, but the installer may determine it
should be higher depending on local conditions.

5. Locate the terminal so the vent exhaust does not
settle on building surfaces and other nearby
objects. Vent products may damage such
surfaces or objects. But the actual construction
of the vent terminal and the flow of vent
products must not be altered.

6. Locate the terminal at least 6 feet (1.8m)
horizontally from any gas or electric metering,
regulating, or relief equipment, or building
opening.

2M. Air for Combustion and Ventilation

The boiler requires air for combustion and the

space around the boiler requires ventilation.
Combustion air can be provided by standard practices
as specified in the installation codes (ANSI Z223.1/
NFPA 54, in Canada, CAN/CGA B149.1 or .2 and
local applicable codes), or ducted directly to the
boiler. Ventilation air must be provided in either case.

4 (1.2)

Minimum

Mighty Max Hydronic Boiler

Page 15

2M-1. Air From Room

Standard requirements for providing air for
combustion and ventilation are provided by ANSI
Z223.1/NFPA 54 and in Canada by CAN/CGA
B149.1 or .2. These codes require passages be
provided for air flow into the space where the boiler is
installed. The size of these passages is based on the
firing rate of the boiler and the path of air flow into
the space. In general, installations which take air from
inside the building require larger passages than those
which take air directly through an outside wall.

Failure to provide adequate combustion and
ventilation air can cause the boiler, and other
appliances occupying the same space, to operate with
dangerous and inefficient combustion, and can cause
overheating of the space. Be sure to provide air
passages in accordance with ANSI Z223.1/NFPA 54,
in Canada, CAN/CGA B149.1 or .2 and local
applicable codes, and do not permit any other
condition, such as an exhaust blower, to affect the air
supply for combustion and ventilation.

2M-2.Ducted Combustion Air

Combustion air can be brought directly to the
boiler through a duct of suitable size and length (see
Table 7). Consult Laars about installations not
covered by Table 7.

Combustion air must be taken from out-of-doors
by means of the Laars side wall terminal.
Locate the terminal within 10 feet (3.0m) of the boiler
vent exhaust terminal, but no closer than 3 feet (0.9m)
(centerline distance).

Do not locate the air inlet terminal near a source
of corrosive chemical fumes (e.g., cleaning fluid,
chlorine compounds, etc.). Locate it so that it will not
be subject to damage by accident or vandalism. It
must be at least 7 feet (2.1m) above a public walkway.

Use single-wall galvanized pipe for the
combustion air duct. Route the duct to the heater as
directly as possible. Seal all joints with tape. Provide
adequate hangers. The heater must not support the
weight of the combustion air duct.

When combustion air is ducted to the boiler,
other provisions must be made for boiler room
ventilation. HH boilers lose less than 1 percent of
their input rating to the room, but other heat sources
may be present. Provide enough ventilation air to meet
comfort specifications. Make sure the ventilation air is
not directed at the boiler, water piping or other
equipment which could be damaged by freezing.

Boiler Size Assembly Number

320 20258101
400 20258102
520 20258103
625 20258104
775 20258105

1000 20258106

Table 8. Combustion Air Assembly.

Louvered

Plate

Inlet

Adapter

Plate

Pipe

2M-3.Conversion for Ducted

Combustion Air

The conversion to ducted combustion air
requires the parts listed in Table 8. Follow these
procedures to convert the heater (see Figure 11):

Ducted Combustion

Air Pipe

Figure 11. Ducted Combustion Air Conversion.

Page 16

LAARS HEATING SYSTEMS

1. Remove the louvered plate from the left side of
the boiler.

2. Remove the adapter plate from the shipping
container.

3. Install the blower motor housing collar in gasket.

4. Slip one end of the inlet pipe over the collar on
the adapter plate.

5. Slide the inlet pipe and adapter plate into the
boiler opening until the pipe is aligned with the
blower motor.

6. Slip the end of the inlet pipe over the blower
motor housing collar.

7. Secure the adapter plate to the side of the boiler
with the 4 screws.

2M-4.Combustion Air Piping

Run piping of the appropriate size between the

air intake terminal and the boiler (see Table 7). Table
9 lists the materials for piping the boiler.

Term Description

Pipe Single-wall galvanized steel pipe,

24 gauge minimum.

Joint Sealing Permanent duct tape or aluminum

tape

Insulation Not required, but recommend R5

insulation for cold installations
(consult American Society of
Heating, Refrigerating, and
Air Condditioning Engineers
(ASHRAE) handbook

Table 9. Required Combustion Air Piping Material.

2N. Electrical Wiring

WARNING

Electrically ground the heater in accordance
with the latest edition of ANSI/NFPA 70. In
Canada, use CSA C22.1. Do not rely on the
gas or water piping to ground the metal parts
of the heater. Often, 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
ungrounded boiler.

1. Check boiler wiring and pump for correct
voltage, frequency, and phase.

2. Wire the boiler and pump exactly as shown in
the wiring diagram supplied with the boiler (see
Figure 12).

3. Electrically interlock the pump and boiler so the
boiler cannot come on unless the pump is
running.

4. Connect all field-installed devices (relays,
timers, temperature devices, etc.) to the boiler
wiring at points labeled “Field Interlock” (see
Figure 12).

SECTION 3.
Operation

WARNING

Do not use this appliance if any part has been
under water. Immediately call a qualified
service technician to replace the appliance.

3A. Start Up Requirements

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 ANSI Z21.13 Standard.

Before placing the boiler in operation, check the

automatic safety shutoff devices. Once the boiler is
connected to the gas piping and after all of the
requirements in Section 2 have been met, follow this
procedure:

1. Before beginning the tests, make sure the main
manual gas valve, and any other boiler firing
valves, are in the OFF position.

NOTE: The gas valve is turned off as follows:

• Size 775/1000 Valve is OFF when handle is at

right angle to gas pipe.

• Sizes 520/625 Turn clockwise to OFF and

• Sizes 320/400 Press in gas control knob

slightly and turn clockwise to
OFF. Knob cannot be turned
unless it is pushed in slightly.
Do not force it.

2. Make sure the power switch on the boiler is in
the ON position. Reset all safety devices (high
limit, pressure switch, Low-Water-Cutoff, etc.).

3. Normal Operating Sequence
When the circulation pump is running, the boiler
will turn itself on and off in response to the
water temperature. When the water cools below
the set temperature, the following sequence
occurs:

a. The aquastat powers the ignition control.
b. The ignition control turns on the

combustion fan. After about a 15 second

Mighty Max Hydronic Boiler

Page 17

ATTENTION

IGNITION SYSTEM 20 ON/OFF

SIZES 320-1000, NA TURAL OR PROPANE

Au moment de l’entretien des commandes, étiquetez tous les fils

avant de les débrancher. Les erreurs de câblage peuvent nuire au

bon fonctionnement et être dangereuses.

S’assurer que l’appareil fonctionne adéquatement une fois

l’entretien terminé.

Caution

Figure 12. Wiring Diagram.

Label all wires prior to disconnection when servicing controls.

wiring errors can cause improper and dangerous operation.

Verify proper operation after operation servicing.

Page 18

LAARS HEATING SYSTEMS

Front View of Boiler

Igniter

Junction

Box

NOTE: Sight glass
location may vary.

Figure 13. Periodic Flame Observation.

Sight Glass

For Flame Observation

pre-ignition purge, while the fan clears the
combustion chamber, the igniter is turned
on. The igniter takes about 25 seconds to
heat up. You can see a glow through the
view port (see Figure 13).

NOTE: The manual gas valve must be ON for the

burner to ignite. This valve is turned ON as follows:

• Size 775/1000 Valve is ON when handle is
parallel to as pipe.

• Sizes 320/400 Turn counterclockwise 520/625
to ON.

c. When the igniter is hot, the ignition control

turns on the gas valve and the burner
ignites. You can see the burner flame
through the view port (see Figure 13).

d. The boiler operates until the aquastat

senses that the water is hot enough, and the
burner shuts off. The combustion fan runs
for about one minute to blow all
combustion products out of the boiler.

If the igniter fails to ignite the burner in step 3
(for example, if there is air in the gas line), the
ignition control shuts off the gas valve after a few
seconds of operation. The purge and ignition sequence
is automatically repeated. If there is no ignition in
three tries, the ignition control “locks out” until the
problem is corrected. Contact a qualified service
technician.

3B. Hi-Limit Checkout

After running the boiler for a long enough period
to bring the water temperature within the range of the
hi-limit, slowly back off the high limit setting until the
boiler shuts off. The main burners should re-ignite
when the hi-limit is turned back up to its original
setting and the hi-limit is reset.

3C. Venturi and Gas Pressure Regulator

System

3C-1. Overall Operation

The gas control system of the Mighty Max boiler
is similar to that of a carburetor of a gasoline engine: a
venturi pulls the gas into the combustion air stream
(see Figure 14). In this system, changes in combustion
air flow automatically change the gas flow.

Air

Gas

Orifice

Air/Gas
Mixture

Figure 14. Typical Venturi System.

The flow of air through the venturi creates a
pressure difference. At the narrowest point of the
venturi, the throat, high velocity creates a low
pressure condition which pulls gas in through an
orifice.

For a correct gas/air ratio, the gas pressure must
be the same as the air pressure, but with a slight
negative offset. A special gas regulator (called a
“negative pressure regulator”) which has an equalizer
tube connected to the venturi inlet, maintains the
required gas pressure.

When the system is operating, a combustion fan
forces air into the venturi, creating pressure at the
inlet. The gas regulator sets gas pressure, and gas is
pulled through the orifice. The sizes of the venturi
throat and gas orifice are factory set to provide the
correct air/gas ratio.

3C-2. Venturi Adjustment

The field checkout involves measuring gas and
venturi pressures, and observing the flame through the
sight glass. If necessary, the gas input rate can be
measured by timing the gas meter.

Equalizer

Tube

Negative

Pressure Regulator

Gas

Overall

Operation

Mighty Max Hydronic Boiler

Page 19

Use a single, inclined manometer or digital
manometer with a 4.0 inch water column range. Install
shutoff valves at the gas orifice (regulator outlet) tap
(red), at the venturi inlet tap (blue) and at the venturi
throat tap (yellow). After installing the shutoff valves,
be certain they are closed.

1. With the heater off, connect the positive side of

the manometer to the shutoff valve on the

venturi inlet tap (blue). Open the shutoff valve.

2. Loosen the nut on the blower damper to allow

for adjustment. Turn the boiler on so that the

blower is running and the boiler is not firing. In

this unfired condition, adjust the damper until

the venturi inlet pressure (blue tap) is 1.2 inches

water column.

3. Approximately 40 seconds after the blower starts

the gas valves will open. The boiler is now

firing. If the heater is not running, check all

manual gas valves and heater safety devices.

Ensure proper gas supply pressures according to

the table in Section 2.

4. Now that the boiler is firing, use the blower

damper to readjust the venturi inlet pressure

according to the installation’s altitude in Table

10 (+1.6" w.c. at sea level).

6. Using the toggle switch, turn the heater off. Turn
the heater back on and check the gas pressure
offset after the heater has fired. If the gas offset
pressure is not according to Table 10, adjust the
regulator as needed.

7. While the heater is still running, close the
shutoff valve on the gas orifice tap (red), then
remove the manometer hose from the shutoff
valve. Connect the negative side of the
manometer to the shutoff valve on the venturi
throat tap (yellow). This reading is called the
venturi throat differential pressure and should
appear according to altitude in Table 10 (+2.6"
w.c. at sea level). If it does not appear according
to Table 10, contact a qualified service
technician.

Venturi Inlet

“Low” Side of

Manometer

“High” Side of

Manometer

Tap (Blue)

Elevation Venturi Inlet Gas Throat

Ft. Pressure Pressure Differential

(Blue Tap) Offset Pressure

“WC H20” “WC H20” “WC H20”

SEA LEVEL +1.6 +0.4 +2.6

1000 +1.5 +0.4 +2.5
2000 +1.5 +0.4 +2.4
3000 +1.4 +0.4 +2.3
4000 +1.4 +0.3 +2.2
5000 +1.3 +0.3 +2.2
6000 +1.3 +0.3 +2.1
7000 +1.2 +0.3 +2.0
8000 +1.2 +0.3 +1.9
9000 +1.1 +0.3 +1.9

10000 +1.1 +0.3 +1.8

Table 10. Venturi Pressure Settings.

5. Leaving the positive side of the manometer
connected to the venturi inlet tap (blue), connect
the negative side of the manometer to the shutoff
valve on the gas orifice tap (red). Open the
shutoff valve to take a pressure reading. This
reading is called the gas pressure offset. Using
the regulator only, adjust the gas pressure offset
according to the installation's altitude in Table 5
(+0.4" w.c. at sea level). REPLACE THE
REGULATOR CAP BEFORE TAKING GAS
PRESSURE READINGS. Turn the regulator
screw clockwise to decrease the gas pressure
offset, turn the regulator screw counter­clockwise to increase the offset.

Venturi Throat

Tap (Yellow)

Gas Orifice

Tap (Red)

Figure 15. Measurement of Venturi Throat Pressure
Differential.

After setting all pressures, turn the heater off and
replace each shutoff valve with the factory installed
threaded plugs. The venturi has now been adjusted for
proper operation.

3D. To Start Up System

(See Section 3A for Startup Requirements)

1. Be certain the system pump is running.

2. Set the thermostat or aquastat to its lowest

setting.

3. Turn off electric power to the appliance.

4. Remove the control access panel.

5. Turn off the manual gas valve.

6. Wait five (5) minutes to clear out any gas, then

smell for gas, including near the floor. Be sure to

smell next to the floor because some gas is

heavier than air and will settle on the floor.

Page 20

Caution

This appliance is equipped with an ignition
device which automatically lights the burner.
Do not try to light the burner by hand.

WHAT TO DO IF YOU SMELL GAS

• Do not try to light any appliance.

• Do not touch any electric switch; do not use any
phone in your building.

• Immediately call your gas supplier from a
neighbor's phone. Follow the gas supplier's
instructions.

If you don't smell gas, go to the next step.

7. Turn on manual gas valves.

8. Rest all safety devices (manual resets on high
limit, low water cutoff, etc.).

9. Replace control access panel.

10. Turn on all electric power to the boiler.

11. Set thermostat to desired setting.

12. If the boiler will not operate, follow the
instructions to turn off gas to boiler and call your
service technician or gas supplier.
a. Turn off main electrical switch.
b. Close all manual gas valves.

3D-1. Setting Temperature Controls

The temperature control differential is factory

set at 15°F. This setting can be adjusted from 1 to
30°F to suit your application. Adjustment is made by
taking the cover off the temperature controller and
turning the potentiometer marked “DIFF”, which is
located just below and to the left of the controller’s
setpoint dial.

To set the temperature and high-limit controls:

a. Set the temperature controller at the system

design temperature.

b. For boilers with the temperature controller bulb

at the boiler inlet, set the high-limit 40°F to 50°F
above temperature controller setting.

c. For boilers with the temperature controller bulb

at the boiler outlet, set the high-limit 15°F to
25°F above temperature controller setting.

3E. To Shut Down System

To shut down the boiler, turn off all manual gas

valves and electrical disconnect switch.

NOTE: There is a filter which needs to be cleaned
prior to setting pressures. See Section 4D-2 “Filter
Service” before proceeding.

3F. Venturi Combustion Flow System

Verifying proper operation of the combustion

flow system has two aspects - air flow and gas flow.
Air flow is checked by measuring pressures at service

LAARS HEATING SYSTEMS

taps on the venturi. Gas flow is checked by evaluating
venturi pressures and the regulator offset pressure.

In a venturi flow system the difference between
various pressures is far more important than their
“gauge” value relative to the room. The gas pressure
offset and the gas orifice pressure differential are
especially important concepts. The following section
describes this setup procedure.

3F-1. Pressure Measurement Ports

Air flow enters the venturi through the filter box
and blower assembly. It is pushed through a
converging section and into the throat, where pressure
is reduced substantially. Gas flow is pulled into the
throat through an orifice. The orifice is located
between the throat and the regulator. Air and gas are
combined in the throat and mix thoroughly as they
proceed through the venturi tailpipe to the burner.

Service taps are provided at three places. One is
located on the chamber with the gas connection, this
tap is called the gas plenum tap. The other is located
above the gas plenum tap, this port is called the
venturi inlet tap. The third tap, gas orifice tap, is
located on the red orifice holder directly before the
gas connects to the venturi. These taps have service
plugs in them. Do not remove any of the plastic
fittings or plastic tubing. To evaluate system operation
requires accurate measurement at these taps. An
inclined manometer with a zero to 6 inches water
column range is ideal. Other instruments may be used,
but the “positive/negative” nature of the readings must
be well understood. Gas pressure offset measurements
are at very low levels (0.4" WC), the instrumentation
must be capable of determining it accurately.

3F-2. Venturi Adjustment

Note that an equalizer tube is connected from a
port on the side of the venturi inlet to the port of the
regulator. This is a very important component which
allows the regulator to track air pressure even when
abnormal conditions occur, such as blockage of the
combustion air. Before firing, confirm that this tube
and the venturi pressure switch tubes are in place and
firmly connected.

The field checkout involves measuring gas and
venturi pressures, and observing the flame through the
sight glass. If necessary, the gas input rate can be
measured by timing the gas meter.

Install shutoff valves at the gas orifice (regulator
outlet) tap (red), at the venturi inlet tap and at the gas
plenum tap. Do not remove any of the plastic fittings
or plastic tubing. After installing the shutoff valves,
be certain they are closed.

a. Unfired Venturi Differential Pressure

NOTE: Turn off the main manual gas valve.

Mighty Max Hydronic Boiler

The difference in pressure between the venturi
inlet tap and the gas plenum tap (see Figure 16). This
measurement is taken by connecting the positive side
of the manometer to the venturi inlet tap and
connecting the negative side of the manometer to the
gas plenum tap. This measurement is taken with the
boiler not firing. It is a temporary setting used to start
the boiler and check for air flow problems.

Page 21

Figure 16. Unfired Venturi Differential Pressure.

b. Gas Offset Pressure

The difference in pressure between the venturi
inlet tap and the outlet of the gas regulator (see
Figure 17). This measurement is taken by connecting
the positive side of the manometer to the venturi inlet
tap and connecting the negative side of the manometer
to the gas orifice tap. This measurement is an
indication of the gas to air ratio and must be
performed while the unit is firing.

c. Gas Orifice Differential Pressure

This measurement is the pressure drop across the
gas orifice. This measurement is taken by connecting
the positive side of the manometer to the gas orifice
tap and the negative side of the manometer to the gas
plenum tap (see Figure 18). This measurement in
conjunction with the gas orifice size is an indication
of the gas firing rate and must be performed while the
unit is firing.

Figure 17. Gas Offset Pressure.

Figure 18. Gas Orifice Differential Pressure.

Page 22

LAARS HEATING SYSTEMS

By setting the gas offset pressure and gas orifice
differential pressure according to Table 11, the correct
input rate and gas to air ratio is achieved.

GAS GAS ORIFICE UNFIRED

ELEVATION, OFFSET DIFFERENTIAL VENTURI

FT PRESSURE PRESSURE DIFFERENTIAL

inch W.C. inch W.C. inch W.C.

SEA LEVEL +0.4 +4.0 +5.8

2000 +0.4 +3.7 +5.3
4000 +0.4 +3.4 +4.9
6000 +0.4 +3.2 +4.6
8000 +0.4 +2.9 +4.2

10000 +0.4 +2.7 +3.9

Table 11. Venturi Pressure Settings.

3F-3. Venturi Setup Procedure

1. Loosen the nut on the blower shutter to allow for

adjustment. Turn the heater on so that the blower

is running and the heater is not firing. Measure

the unfired venturi differential pressure. In this

unfired condition, adjust the shutter until the

unfired venturi differential pressure is according

to Table 1, “Unfired Venturi Differential” (5.8 ±

.3 inches wc at sea level). If this pressure range

can not be achieved, check for blockage in the

combustion air inlet, boiler and venting system.

If there is no obvious cause contact a qualified

Laars service technician.

2. Approximately 40 seconds after the blower starts

the gas valves will open. The heater is now

firing. If the heater is not running, check all

manual gas valves and heater safety devices.

Ensure proper gas supply pressures according to

Table 4 in Section 2.

3. Measure the gas offset pressure. Using the

regulator only, adjust the gas offset pressure

according to the installation’s altitude in Table

11 (+0.4 inches wc. at sea level). REPLACE

THE REGULATOR CAP BEFORE TAKING

GAS PRESSURE READINGS. Turn the

regulator screw clockwise to decrease the gas

offset pressure, turn the regulator screw

counterclockwise to increase the offset.

4. Using the toggle switch, turn the heater off. Turn

the heater back on and check the gas offset

pressure while the heater is firing. If the gas

offset pressure is not according to Table 11,

adjust the regulator as needed.

5. Measure the gas orifice differential pressure.

This pressure must be adjusted according to

Table 1 (4.0 ± .2 inches wc at sea level). Use the

blower shutter to adjust the gas orifice

differential.

6. By adjusting the gas orifice differential, the gas

offset pressure will change. Therefore you must

repeat steps 3-5 until the gas offset and gas
orifice differential pressures are according to
Table 11.

7. After setting all pressures, turn the heater off and
replace each shutoff valve with the factory
installed threaded plugs. The venturi has now
been adjusted for proper operation.

SECTION 4.
Maintenance

4A. General Instructions

1. Oil the water circulating pump in accordance
with the manufacturer's instructions.

2. Oil the blower motor bearings every 6 months.

3. If a strainer is used in a pressure reducing valve
or in the piping, clean it every 6 months in
accordance with the manufacturer's instructions.

4. At startup and every 6 months after, look at the
main burner flame for proper performance. The
burner should not require maintenance in normal
operation. If any malfunction indicates that the
burner needs service (e.g., a flame that is yellow,
or entire burner surface glowing red), call a
professional service technician. Flame
characteristics may be inspected during the first
30 seconds after ignition. Characteristics of a
good flame are:
a. Blue flame color.
b. Dark-colored burner surface with

occasional glowing fibers on surface.

NOTE: After 30 seconds of operation the

combustion chamber will heat up and prevent reliable
flame observation.

5. Inspect the venting system for blockage, leakage,
and corrosion at least once a year.

6. Keep the heater area clear of combustible
material, gasoline, and other flammable liquids
and vapors.

7. Be sure all combustion air and ventilation
openings are not blocked.

8. After installation and first startup, check the heat
exchanger for black carbon soot buildup after the
following periods of operation: 24 hours, 7 days,
30 days, 90 days, and once every 6 months
thereafter.

4B. Heat Exchanger

Black carbon soot buildup on the external

surfaces of the heat exchanger is caused by one or
more of the following: incomplete combustion,
combustion air problems, venting problems and heater
short cycling. As soon as any buildup is seen, correct
the cause of the buildup. Scale can build up on the

Mighty Max Hydronic Boiler

Page 23

inner surface of the heat exchanger tubes and
restrict the water flow. Inspect the heat exchanger in

accordance with Section 4B-1.

If the heat exchanger needs cleaning, see

Section 4B-2.

4B-1. Inspection of the Heat Exchanger

WARNING

Improper installation or maintenance can
cause nausea or asphyxiation from carbon
monoxide in flue gases which could result in
severe injury, property damage, or death.

4B-1a. External Heat Exchanger

Inspection

1. Disconnect electrical supply to the heater.

2. Turn off the gas supply by closing the manual
gas valve on the heater.

3. On indoor models, remove the vent pipe, top
jacket section, flue collector.

4. On outdoor models, remove outdoor vent
terminal, top jacket section, flue collector.

5. After removing the flue collector, inspect the
finned copper tubing using a flashlight.

6. If there is a buildup of black carbon soot or other
debris on the heat exchanger tubes which may
restrict flue gas passage, refer to Section 4B-2a.

7. If there is no buildup of black carbon soot or other
debris which may restrict flue gas passage
through the heat exchanger, reassemble the heater.

4B-1b. Internal Heat Exchanger Inspection

1. Remove the inlet/outlet header of the heat
exchanger.

2. Remove the return cover of the heat exchanger.

3. Inspect the internal surface of the copper tubes
for signs of scale buildup and erosion.

4. If build-up exists, clean per 4B-2b.

4B-2. Cleaning the Heat Exchanger

4B-2a. Cleaning the Heat Exchanger -

External

1. Disconnect the 120 Vac electrical supply to the
heater.

2. Turn off the gas supply by closing the manual
gas valve on the heater.

3. Disconnect and remove the wires and conduit
from the low water cutoff.

4. Remove the top jacket section, venting and the
flue collector as mentioned in Section 4B-1
“Inspection of the Heat Exchanger”.

5. Isolate the heat exchanger from water supply.

6. Drain the heat exchanger.

7. Disconnect the flange and adapter tee from the
heat exchanger inlet and outlet.

8. Remove temperature sensing probes from the
inlet/outlet header.

9. Remove the heat exchanger from the heater.

10. Remove the heat baffles from the heat
exchanger.

11. Clean the heat exchanger: A light accumulation
of soot or corrosion on the outside of the heat
exchanger can be easily removed after the heat
baffles are removed. Use a wire brush to remove
loose soot and scale from the heat exchanger. Do
not use water or compressed air for cleaning.

NOTE: While the heat exchanger is out of the

heater, inspect the firewall refractory insulation
blocks for cracks, wear and breakage. Replace if
necessary.

4B-2b. Cleaning the Heat Exchanger -

Internal

1. Remove the inlet/outlet header of the heat
exchanger.

2. Remove the return cover of the heat exchanger.

3. Clean the internal surface. (Laars offers a tube
cleaning kit part no. R00100000.)

4. Reassemble in the reverse order.

4C. Gas and Electric Controls

The gas and electric controls on the heaters are

designed for both dependable operation and long life.
Safe operation of the heater depends on their proper
functioning. A professional service technician should
check the following basic items every year, and
replace when necessary.

NOTE: The heat exchangers are heavy and may

require two people to remove to avoid personal injury.

Caution

Black carbon soot buildup on a dirty heat
exchanger can be ignited by a random spark or
flame. To prevent this from happening,
dampen the soot deposits with a wet brush or
fine water spray before servicing the heat
exchanger.

NOTE: the warranty does not cover damage

caused by lack of required maintenance or improper
operating practices.

1. Water temperature controls.

2. Ignition control system.

3. Automatic electric gas valve(s).

4. Flow sensing safety device (when used).

5. Low water cutoffs, including flushing or float
types. (Every six months)

Page 24

LAARS HEATING SYSTEMS

Other maintenance requirements include:

1. Periodic cleaning of filters, when supplied.

2. Lubrication of moving parts (when applicable),
with the correct type and amount of lubricant.

3. Periodic examination of the venting system.

4. Periodic cleaning of vent terminal screens,
where applicable.

5. Cleaning flue gas passageways.

4D. Filter

4D-1. Filter Function

A filter has been designed into the operation of

this Mighty Max boiler. Its function is to filter the
combustion air before it is delivered to the burner
system. The filter is manufactured out of a
polyurethane foam and may be cleaned with a mild
soap and water solution. Clean the filter only after the
filter has been removed from the filter housing (see
Figure 19).

4D-2. Filter Service

(The filter does not need cleaning if this is a first

time heater start-up).

1. Turn the heater off using the toggle switch.

2. Remove the door panel and bonnet from the
jacket.

3. Remove the screws on the filter housing to
expose the filter as shown in Figure 19.

Figure 19. Filter Exposed for Cleaning.

4. Inspect the filter for discoloration due to
contamination or any other forms of debris. If
contamination or debris exists, wash the filter in
a soap/water solution then rinse with water only.
It is important that the
placing it back in the filter housing.

filter be dry before

Caution

The filter has arrows which indicate the
direction of the air flow. Failure to install the
filter correctly may cause blower failure and
dangerous operation.

The filter must be inspected for contamination
one week after start-up. Depending upon the severity
of contamination, a suitable cleaning schedule may be
developed. The factory recommends cleaning the filter
at least once every 30 days. In high contamination
areas, such as construction sites, factories, etc., the
filter may need to be cleaned daily. Failure to do so
could result in lower heat output and potential unsafe
operation.

SECTION 5
Troubleshooting

5A. Sequence of Operation

To troubleshoot the heater properly you must
first understand the sequence of operation of the
heater:

1. Upon a call for heat a 24 Vac signal is sent

through fusible links and high limit(s) to the

ignition control “TH” terminal.

2. The “IND” terminal of the ignition control is

energized for a 15 second pre-ignition purge

period during which the combustion blower

purges the combustion chamber.

3. After the purge period there is a 20 to 35 second

igniter heat up period. The glow of the igniter

can be seen through the boiler sight glass.

4. Then there is a seven second trial for ignition.

During this time the gas valves are energized and

the main burner ignites. The gas valves will

remain energized throughout the call for heat as

long as the ignition control igniter senses a

stable flame.

5. After the call for heat is satisfied the ignition

control closes the gas valves and operates the

blower for a thirty (30) second post purge cycle.

This clears the combustion chamber of

combustion products.

The ignition is attempted three times. If ignition
is not successful, the control shuts down and “locks
out”. It remains in the lockout condition until the
boiler is turned off then back on or 120 Vac power to
the boiler is interrupted.

Mighty Max Hydronic Boiler

Page 25

Figure 20. Troubleshooting Chart.

Page 26

LAARS HEATING SYSTEMS

5B. Venturi and Gas Pressure Regulator

System

5B-1. Field Checkout

See Section 3B “Venturi and Gas Pressure

Regulator System” for proper setup procedure.

5C. Electrical Components

This section describes guidelines for checking
the operation of electrical components installed on the
boiler. Refer to the wiring diagram for correct
connection locations.

5C-1. General Troubleshooting

This section describes guidelines for checking
the electrical components of the boiler. Experience
has shown that most complaints about boilers failing
to fire have nothing to do with the boiler itself.
Usually, one of the protective switches in the boiler
system has shut down operation.

Any of the following can prevent proper
operation. Check these items first:

1. Be sure the boiler has been properly installed

(see Section 2).

2. Make sure the pump is not airlocked, clogged or

otherwise inoperative.

3. Make sure the gas valve is on and there is

sufficient gas pressure in the line. All external

gas valves must be open.

4. Verify that the electrical circuit serving the

boiler is ON.

5. Make sure the toggle switch on the right side of

the boiler is ON.

6. Check the fuse inside the black, twist-lock fuse

holder. If it is burned, replace it with a 2-amp

fuse (part no. E0084400).

7. With the power off inspect all electrical

connections and wiring. Finding a loose

connection or charred wire can save a lot of time

and money.

8. Make sure the temperature controller is set high

enough to call for heat.

9. Make sure none of the manual reset controls, i.e.,

low water cutoff, high limit, etc., have tripped.

Reset any tripped switches.

If the pump is circulating water and the
foregoing items check out okay, the trouble may be in
the boiler control system.

IMPORTANT: Disconnect power to the boiler
before removing or replacing any component or wire
connection. If the power is not disconnected,
“jumping” the gas valve or accidentally grounding the
wire harness or component terminals to the boiler
frame or jacket could cause the ignition control fuse to
blow.

5C-2. Electrical Troubleshooting

Troubleshooting procedures should only be
performed by professional service technicians
qualified in heater maintenance.

Some electrical components are wired in
parallel, so it is necessary to troubleshoot in the order
that they appear on the wiring diagram or the
troubleshooting flow chart (see Figure 20).

NOTE: When testing the safeties between
“MV1” of the ignition control and the gas valve(s)
there is only a seven (7) second trial for ignition
period during which there is power to “MV1”.

The following steps should be used when
troubleshooting the boiler:

1. Remove the lower front panel (see Figure 21).

2. Turn the manual gas valve on the heater off.

3. If the heater has locked out turn the toggle

switch off for 5 seconds then back on to reset the

heater.

4. Use the troubleshooting flow chart (see Figure

20) to determine what components and wiring

should be tested first.

5. Test each component by checking for 24 Vac or

120 Vac entering and exiting the device. If there

is voltage entering the safety device, but none

leaving then there is an open circuit and it must

be determined why it is open. When testing

components between “MV1” of the ignition

control and the gas valve install a meter and let

the heater cycle through one complete sequence

of operation. During the sequence of operation

these safeties will only be energized for the

seven second trial for ignition.

6. Turn the manual gas valve on the boiler on and

fire the boiler.

Figure 21. Lower Front Panel Removal.

Mighty Max Hydronic Boiler

Page 27

SECTION 6
Parts List for Mighty Max HH Boiler

6A. General Information

To order or purchase parts for the Laars Mighty
Max HH boiler, contact your nearest Laars contractor
or distributor. If they cannot supply you with what
you need, contact:

Laars Customer Service Department

6000 Condor Drive

Moorpark, California 93021

Telephone [phone]

Telephone [phone]

or

Laars Customer Service Department

20 Industrial Way

Rochester, New Hampshire 03867

Telephone [phone].

In Canada, contact:

Laars Customer Service Department

480 S. Service Road West

Oakville, Ontario, Canada L6K 2H4

Telephone [phone].

Item Description Part Number

1. Base Assembly

320M........................................................... 20157801

400M........................................................... 20157802

520M........................................................... 20157803

625M........................................................... 20157804

775M........................................................... 20157805

1000M......................................................... 20157806

2. Burner and Burner Plenum Weldment

320M........................................................... 20268401

400M........................................................... 20268402

520M........................................................... 20268403

625M........................................................... 20268404

775M........................................................... 20268405

1000M......................................................... 20268406

3. Venturi Assembly

320M........................................................... 20158601

400M........................................................... 20158602

520M........................................................... 20158603

625M........................................................... 20158604

775M........................................................... 20158605

1000M......................................................... 20266400

4. Combustion Chamber Weldment

320M........................................................... 20159101

400M........................................................... 20159102

520M........................................................... 20159103

625M........................................................... 20159104

775M........................................................... 20159105

1000M......................................................... 20159106

5. Gas Train Assembly

320M........................................................... 20254901

400M........................................................... 20254902

Item Description Part Number

520M, 625M......................................20260100 (U.S.)

20260101 (Canada)

775M................................................. 20260200 (U.S.)

20260201 (Canada)

1000M............................................... 20265600 (U.S.)

20265601 (Canada)

Gas Valve

320M, 425M................................................ V2003900

520M, 625M................................................ V2003700

775M, 1000M.............................................. V0046700

Pressure Regulator

520M, 625M................................................V2003800

775M, 1000M..............................................V2003600

Orifice Holder

320M, 400M................................................P2017500

520M, 625M................................................P2017700

775M........................................................... P2018500

1000M......................................................... P2022200

6. Motor, Blower

320M thru 520M Nat. & Prop. Gas .............A2088100

625M, 775M Nat. & Prop. Gas ................... A2087500

1000M Nat. & Propane Gas ....................... A2003900

7. Electrical Controls

High limit Control ...........................................E0015900

Toggle Switch ................................................E0109200

Indicator Light ................................................E0071300

Fusible Link ...................................................E0099403

Transformer ................................................... E0086100

Fuse Holder ................................................... E2000300

Fuse, 2 Amp ..................................................E2043600

Flow Switch....................................................E0013000

Burner Temperature Switch ...........................E2076100

Low Water Cutoff........................................... E2075100

Pump Time Delay .......................................... E2077700

8. Sight Glass .................................................... F0044800

9. Igniter, Hot Surface.......................................W0038001

10. Gasket, Igniter Hot Surface ........................... 20409800

11. Control, Remote Ignition................................ E2101300

12. Control, Temperature .....................................E2101400

13. Display, Temperature..................................... E2101600

14. Heat Exchanger Assy., 2 pass, Copper Tubes

520M........................................................... 20256003

625M........................................................... 20256004

775M........................................................... 20256005

1000M......................................................... 20256006

Heat Exchanger Assy., 2 pass, Cupronickel tubes

520M........................................................... 20104603

625M........................................................... 20104604

775M........................................................... 20104605

1000M......................................................... 20104606

15. Heat Exchanger Assy., 4 pass, Copper Tubes

320M........................................................... 20259601

400M........................................................... 20259602

Heat Exchanger Assy., 4 pass, Cupronickel tubes

320M........................................................... 20104701

400M........................................................... 20104702

Page 28

207121311

211415

38

LAARS HEATING SYSTEMS

5

36

8

10

9

Front View

6

3

2

Right Side View

1

4

Mighty Max Hydronic Boiler

161835

34

Page 29

17

32

31

30

Front ViewRear View

26

19

27

28 25

29

37

23

25

33

39

Right Side ViewLeft Side View

Page 30

LAARS HEATING SYSTEMS

Item Description Part Number

16. Cover, Machined In/Out................................. 20150200

17. Plate, Mach. Adapter

320M, 400M................................................ 20150302

520M, 625M, 775M..................................... 20150306

1000M......................................................... 20150307

18. Flange, Machined

320M, 400M................................................ 20255400

520M, 625m, 775M..................................... 20255401

1000M......................................................... 10391304

19. Cover, Machined Rear................................... 20150100

20. Pressure Switch, Differential 320-775 ........... E0115200

Pressure Switch, Differential 1000 ................E0161400

21. Flue Collector Assembly (with gaskets)

320M........................................................... 20155401

400M........................................................... 20155402

520M........................................................... 20155403

625M........................................................... 20155404

775M........................................................... 20155405

1000M......................................................... 20155406

22. Jacket Assembly (Not Shown)

320M........................................................... 20255201

400M........................................................... 20255202

520M........................................................... 20255203

625M........................................................... 20255204

775M........................................................... 20255205

1000M......................................................... 20255206

23. Covering Plate (side) ..................................... 20256500

24. Collar, Jacket 320-775................................... 20258300

Collar, Jacket 1000........................................ 20266300

25. Bonnet

320M........................................................... 20156801

400M........................................................... 20156802

520M........................................................... 20156803

625M........................................................... 20156804

775M........................................................... 20156805

1000M......................................................... 20156806

26. Panel Top,

320M........................................................... 20157501

400M........................................................... 20157502

520M........................................................... 20157503

625M........................................................... 20157504

775M........................................................... 20157505

1000M......................................................... 20157506

27. Panel, Top Side, Left ..................................... 20152800

28. Panel, Side, Left ............................................ 20152700

29. Panel, Bottom Side, Left................................ 20152900

30. Panel, Access

320M........................................................... 20157401

400M........................................................... 20157402

520M........................................................... 20157403

625M........................................................... 20157404

775M........................................................... 20157405

1000M......................................................... 20157406

Item Description Part Number

31. Panel, Back

320M........................................................... 20157201

400M........................................................... 20157202

520M........................................................... 20157203

625M........................................................... 20157204

775M........................................................... 20157205

1000M......................................................... 20157206

32. Plate, Blank (back)

320M........................................................... 20256201

400M........................................................... 20256202

520M, 625M................................................ 20256203

775M........................................................... 20256204

1000M......................................................... 20256205

33. Panel, Side, Right.......................................... 20157100

34. Panel, Top Side, Right ................................... 20157000

35. Panel, Bottom Side, Right ............................. 20156900

36. Blocked Vent Safety Switch...........................E2103000

37. Cover Plate For Gas Conn.

320M, 400M................................................ 20262701

520M, 625M................................................ 20262702

775M, 1000M.............................................. 20262703

38. Tile Assembly

320M........................................................... 20255101

400M........................................................... 20255102

520M........................................................... 20255103

625M........................................................... 20255104

775M........................................................... 20255105

1000M......................................................... 20255106

39. Outdoor Terminal Kit

320M........................................................... 20254701

400M........................................................... 20254702

520M........................................................... 20254703

625M........................................................... 20254703

775M........................................................... 20254704

1000M......................................................... 20254705

40. Side Wall Vent Terminal (When Used) (Not Shown)

320M...........................................................D2004500

400M...........................................................D2004600

520M...........................................................D2004700

625M...........................................................D2004700

775M...........................................................D2004800

1000M.........................................................D2006200

41. Sidewall Comb. Air Terminal (When Used) (Not Shown)

320M........................................................... 20260701

400M........................................................... 20260702

520M........................................................... 20260703

625M........................................................... 20260704

775M........................................................... 20260705

1000M......................................................... 20526906

Item Description Part Number

Filter A2088700
Filter Gasket S2006100
Filter Housing Gasket, Top S2006200
Filter Housing Gasket, Side S2006300

Mighty Max Hydronic Boiler

Page 31

H2090800D

Waterpik Technologies, Inc.
6000 Condor Drive, Moorpark, CA 93021 • 805.529.2000 • FAX [phone]
20 Industrial Way, Rochester, NH 03867 • 603.335.6300 • FAX [phone]
480 S. Service Road West, Oakville, Ontario, Canada L6K 2H4 • 905.844.8233 • FAX [phone]

www.laars.com Litho in U.S.A. © Laars Heating Systems 0303 Document 2060D