LAARS Mighty Therm LO-NOx PH User Manual
Installation, Operation and Maintenance Instructions Document 1162A
OUT OF
PRODUCTION
Installation, Operation
and Maintenance
Instructions for
Mighty Therm
™
LO-NOx
Hydronic Boiler
Models HH-PH
Sizes 250/400
For Natural Gas Only
U.S. Reg. 1,483,289
Canada Reg. 333,796
FOR YOUR SAFETY : This product must be installed and serviced by a professional service technician,
qualified in hot water boiler installation and maintenance. Improper installation and/or operation could
create carbon monoxide gas in flue gases which could cause serious injury, property damage, or death.
Improper installation and/or operation will void the warranty.
WARNING
If the information in this manual is not followed exactly, a fire or explosion may result
causing property damage, personal injury or loss of life.
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or
any other appliance.
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.
H0251300A
Page 2
LAARS Heating Systems
TABLE OF CONTENTS
SECTION 1.
General Information
1.1 Introduction.................................................... 3
1.2 Warranty........................................................ 3
SECTION 2.
Installation Instructions
2.1 General Information....................................... 5
2.2 Field Assembly .............................................. 5
2.3 Site Location.................................................. 7
2.3.1 Installation Information .................................. 7
2.3.2 Outdoor Installation .......................................8
2.3.3 Flooring - Typical Installation......................... 8
2.4 Combustion and Ventilation Air Supply .........8
2.4.1 Outdoor Air Supply ........................................ 9
2.4.2 Indoor Air Supply...........................................9
2.4.3 Exhaust Fans or Vents .................................. 9
2.5 Venting (Category I) ......................................9
2.5.1 General Information....................................... 9
2.5.2 Common Venting System2
Venting Multiple Appliances ........................ 10
2.5.3 Inspection of Commonly Vented
Appliances................................................... 11
2.6 Water Flow System ..................................... 12
2.6.1 Freeze Protection ........................................ 12
2.6.2 Pump Requirements.................................... 12
2.6.3 Variable Water Flow Systems ..................... 13
2.6.4 System Pressure Requirements.................. 13
2.6.5 Chilled Water Systems ................................ 15
2.6.6 System to Boiler Piping ............................... 14
2.6.7 Filling the System ........................................ 15
2.6.8 Minimum Boiler Temperature ...................... 15
2.7 Gas Supply and Piping
(Natural Gas Only) ...................................... 15
2.7.1 General Instructions ....................................15
2.8 Electrical Wiring........................................... 16
PRODUCTION
OUT OF
SECTION 3.
Operating Instructions
3.1 Start-Up Procedure ..................................... 17
3.2. Setting the Temperature Controls ............... 17
3.3 Hi-Limit Switch Checkout ............................ 17
3.4 Shut-Down Procedure ................................. 17
SECTION 4.
Maintenance
4.1 General Instructions ....................................24
4.2 Heat Exchanger........................................... 24
4.2.1 Inspecting the Heat Exchanger ................... 24
4.2.2 Cleaning the Heat Exchanger ..................... 24
SECTION 5.
Troubleshooting and Service
5.1 Gas Pressure Tests..................................... 25
5.1.1 Checking the Main Line Gas Pressure ........ 25
5.1.2 Checking the Manifold
Regulated Gas Pressure ............................. 26
5.2 Electrical Troubleshooting ........................... 26
5.2.1 Boiler Does Not Come On........................... 26
5.2.2 Testing the Transformer .............................. 27
5.2.3 Testing the Electrical Power Supply ............ 27
5.2.4 Testing the Manual Reset
Hi-Limit Switch............................................. 27
5.2.5 Testing the Flow Switch............................... 27
5.2.6 Testing the Fusible Link
(flame roll-out switch) .................................. 28
5.2.7 Testing the Fuse.......................................... 28
5.2.8 Testing the Ignition Control..........................28
5.2.9 Combustion Air Blower................................28
5.2.10 Boiler Will Not Shut Off................................ 29
SECTION 6.
Replacement Parts
6.1 Ordering Information ................................... 29
6.2 Parts List ..................................................... 29
Mighty Therm LO-NOx Hydronic Boiler
Page 3
SECTION 1.
General Information
1.1 Introduction
This manual provides installation, operating, and
maintenance instructions for Model HH, PH Hydronic
Boilers, Sizes 250 and 400. Review all application and
installation procedures completely before proceeding
with the installation. Experience has shown that most
operating problems are caused by improper
installation.
The boilers are offered in a basic configuration
(see Figure 1). On PH boilers the pump is factory
installed.
WARNING
Mighty Therm hydronic boilers must be installed in
accordance with the procedures detailed in this
manual, or the Laars Heating Systems warranty will
be voided. The installation must conform to the
requirements of the local jurisdiction having
authority, and, in the United States, to the latest
edition of the National Fuel Gas Code, ANSI Z223.
In Canada, the installation must conform to the
latest edition of CSA B149.1 Natural Gas
Installation Code and/or local codes. Any
modifications to the boiler, its gas controls, or wiring
may void the warranty. If field conditions require
modifications consult the factory representative
before initiating such modifications. Improper
installation could result in property damage, injury,
or even death.
PRODUCTION
OUT OF
1.2 Warranty
Laars Heating Systems Mighty Therm boilers are
covered by a limited warranty . The owner should fill
out the warranty registration card and return it to Laars
Heating Systems.
All warranty claims must be made to an
authorized Laars Heating Systems representative or
directly to the factory . Claims must include the serial
number and model (this information can be found on
the rating plate), installation date, and name of the
installer. For specific warranty conditions refer to your
Limited W arranty.
Some accessory items are shipped in separate
packages. Verify receipt of all packages listed on the
packing slip. Inspect everything for damage
immediately upon delivery , and advise the carrier of
any shortages or damage. 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.
MISE EN GARDE
Les appareils de chauffage à eau chaude Mighty
Therm doivent être installés dans le respect des
directives détaillées contenues dans ce manuel, à
défaut de quoi la garantie fournie par Laars Heating
Systems sera annulée. L’installation doit être
conforme à la réglementation locale ou, en
l’absence de réglementation locale, avec le
National Fuel Gas Code, ANSI Z223. Au Canada,
l’installation doit respecter les exigences de la plus
récente édition du Code d’installation du gaz naturel
CSA B149.1, et/ou des codes de la construction
locaux. Toute modification apportée à la chaudière,
aux régulateurs de gaz ou au câblage peut
compromettre la garantie. Si certaines conditions
particulières rendent des adaptations nécessaires,
consulter un représentant du fabricant avant
d’entreprendre ces modifications. Une mauvaise
installation peut entraîner des dommages matériels,
des blessures ou même la mort.
Page 4
LAARS Heating Systems
NOTE:* For outdoor models, add 6 inches (15.2cm) for
outdoor base.
Dimensions shown in inches
(centimeters)
OUT OF
Venting Dimensions
Model Firing Heater
Size Rate Width
PRODUCTION
MBtu/h kW in cm in cm in cm in cm
250 250 73.3 22 1/2 57.2 7 17.8 18 1/4 46.4 25 1/4 64.1
400 399 117.0 31 3/4 80.6 9 22.9 21 1/2 54.6 27 1/2 69.9
All dimensions are nominal.
“W” “V” “H” “H”
Drafthood Vent Outdoor Indoor
Vent Cap Diameter Dim Dim
Figure 1. General Configuration.
Mighty Therm LO-NOx Hydronic Boiler
Page 5
SECTION 2.
Installation Instructions
2.1 General Information
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. Follow the
manufacturer’s maintenance schedule for the
appliance. Follow local regulations with respect to
installation of carbon monoxide (CO) detectors.
MISE EN GARDE
Une mauvaise installation ou un entretien inadéquat
peut être la cause de nausées ou d’asphyxie en
raison de la présence de niveaux dangereux de
monoxyde de carbone dans les résidus de
combustion et peut entraîner des dommages
matériels, des blessures ou même la mort. Suivre
les directives du fabricant au sujet du programme
d’entretien de l’appareil. Suivre les règlements
locaux touchant l’installation de détecteurs de
monoxyde de carbone (CO).
All gas-fired products require correct installation
to assure safe operation. The requirements for boilers
include the following:
1. Field assembly of drafthood or vent cap (see
2. Appropriate site location clearances and flooring.
3. Suf ficient combustion and ventilation air.
4. Adequate venting of combustion products.
5. Adequate water flow.
6. Properly sized gas meter and piping.
7. Proper electrical wiring.
meet these requirements. Review all application and
installation procedures completely before continuing
the installation.
2.2 Field Assembly
with the top assembly in the low-profile configuration
for outdoor installations.
indoor installation when equipped with a special
drafthood, which must be installed without
modification. The part number for the drafthood is on
the boiler rating plate. Follow this procedure to make
the conversion:
PRODUCTION
Section 2.2).
This manual provides the information needed to
The HH, PH boilers are shipped from the factory
The HH, PH boilers are design certified for
OUT OF
1. Remove the top plate, stamped "HOT", by
slipping a fine-blade screwdriver into the slot and
prying it up (see Figure 2).
2. Remove the top by removing all eight screws
connecting it to the jacket (see Figure 3).
3. Remove the rainguard assembly (see Figure 4).
4. Remove the two screws securing the left
vestibule cover (see Figure 5). The cover can be
discarded.
5. Remove the vent cap or drafthood and
accessories from the carton.
NOTE: Vent cap is for outdoor installation, when
required.
6. Place transition plate (with 14" long side)
securely on top of flue collector so flue gases will
not leak (see Figure 6).
7. Remove back portion of rainguard (see Figure 7).
8. Re-install the rainguard (see Figure 8).
9. Replace boiler top and all eight screws (see
Figure 9).
10. Slide the adapter plate up over the bottom of the
stack extension. Fit the stack extension, of the
drafthood or the vent cap, on top of the collar of
the flue transition plate (see Figures 10 and 11).
11. Seat the adapter plate on the top assembly , and
secure it with screws supplied in the kit (see
Figure 12).
12. Attach the clips to the adapter plate by securing
the slotted side of the clips with the screws in the
kit (see Figure 13).
13. Use the holes in the clips as guides to drill three
1/8" dia. holes in the stack.
14. Secure the stack to the clips with the screws
supplied in the kit (see Figure 13).
15. Figure 14 shows a cross-section of the finished
installation.
16. Find the vent damper box which is located in the
boiler package (boiler model 250 only).
17. Install the vent damper directly to the top of the
draft hood outlet. The damper operator should
face to the front of the boiler, and the flow
direction arrow should point upward. Use the
vent damper wire harness to connect the vent
damper to the boiler. The bracket end of the
harness should be connected to the vent damper
actuator (see Figure 16).
18. Plug the wiring for the drafthood switch into the
receptacle on the left side of the vent damper box
(see Figure 15).
19. Do not modify the automatic vent damper device.
The venting system must be arranged so that only
the boiler is served by the vent damper device
supplied with the boiler. Provide at least six
Page 6
LAARS Heating Systems
Figure 2. Figure 3.
Figure 4. Figure 5.
OUT OF
Figure 6. Figure 7. Figure 8. Figure 9.
PRODUCTION
Figure 10. Figure 11.
Figure 13. Figure 14.
Figure 12.
Figure 15. Drafthood
Switch Receptacle.
Mighty Therm LO-NOx Hydronic Boiler
Page 7
inches clearance between the automatic vent
damper and combustible construction, and be
sure to allow access for servicing the damper.
WARNING
Do not force the damper to open or close by moving
the damper blade, turning the shaft, or turning the
position indicator. Doing so can cause an unsafe
condition, leading to property damage, injury or
death.
MISE EN GARDE
Ne pas forcer l’ouverture ou la fermeture du registre
en faisant bouger le volet du registre, en tournant la
tige ou en tournant l’indicateur de pression. Cela
peut engendrer une situation non sécuritaire
susceptible de provoquer des dégâts matériels, des
blessures ou la mort.
OUT OF
PRODUCTION
2.3 Site Location
2.3.1 Installation Information
WARNING
Improper installation or maintenance can cause
nausea or asphyxiation from carbon monoxide in
flue gases which could result in property damage,
severe injury, or death.
MISE EN GARDE
Une mauvaise installation ou un entretien inadéquat
peut provoquer la nausée ou l’asphyxie en raison
de la présence de niveaux dangereux de monoxyde
de carbone dans les résidus de combustion et peut
entraîner des dommages matériels, des blessures
ou même la mort.
Avoid placing the boiler in locations where it can
cause damage by water or condensate leakage. If this is
not possible, provide a suitable drain pan under the
boiler to catch and divert any leakage. The pan must
not restrict air flow around the boiler.
Locate the boiler to provide adequate clearance
on all sides for inspection, service and to provide
adequate air circulation for proper operation.
Locate the boiler so the clearances from
combustible surfaces shown in Table 1 and Figure 17
are met.
Locate the boiler on a waterproof floor with a
floor drain and a 6 inch (15.2 cm) minimum curb on all
four sides to protect the building if boiler repairs are
needed.
Figure 16. Vent Damper Installation (Model 250 only).
Indoors Outdoors
Clearance from: inch cm inch cm
Top 37 94 Unobstructed
Water conn. side 12 30.5 Unobstructed
Opposite side 6 15.2 6 15.2
Front Alcove Unobstructed
Rear 6 15.2 6 15.2
Vent* 6 15.2 —
Flooring: Combustible
Service clearance = 36 inches (91.4cm) at front of boiler,
and 18 inches (46cm) at water connection side.
*1" (2.5cm) if double wall vent is used.
6" base for outdoor boiler is required.
Table 1. Minimum Boiler Clearances
from Combustible Surfaces.
Page 8
2.3.2 Outdoor Installation
Caution
Outdoor installations are not recommended in areas
where the danger of snow blockage exists.
Avertissement
L’installation à l’extérieur n’est pas recommandée
dans les zones où il y a des risques d’obstruction
par la neige.
1. Locate the boiler in an open, unroofed area. Do
not locate the boiler below or adjacent to any
doors, windows, louvers, grills, etc., which
connect in any way with an inhabited area of a
building, even though the access might be
through another structure such as a garage or
utility room (see Figure 18 and Table 1).
2. There must be a minimum of 4 feet (1.22 m)
horizontally and vertically between the boiler and
any door, window, or gravity inlet to a building
OUT OF
(see Figure 19).
3. Minimum clearance of 4 feet (1.22m) [6 feet
(1.83m) in Canada] horizontally from, and in no
case above or below , unless the minimum
horizontal distance is maintained, from electric
meters, gas meters, regulators and relief
equipment.
4. If the boiler is installed close to a structure,
protect it from rain water runoff with rain gutters
PRODUCTION
on the roof or other measures. Do not locate the
boiler near sprinkler systems that could spray
water on it.
5. Avoid locations where wind deflection off nearby
structures might cause wind loading and
downdraft conditions. Where downdraft
conditions exist, locate the boiler at least 3 feet
(0.91 m) from the structure.
LAARS Heating Systems
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.
REAR
FRONT
* When the ceiling height exceeds 8 feet, you are only allowed to
consider 8 feet when calculating the total volume of the enclosure.
Figure 17. Alcove Installation.
WINDOW
OR GRILL
Figure 18. Incorrect Outdoor Installation.
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
Alcove Installation
(acceptable)
An alcove suitable for the
installation of a heater is a
restricted section of a room not
separated from the room by a door
or partition and which meets the
minimum clearances specified in
this manual.
INDOOR
ROOM
2.3.3 Flooring - T ypical Installation
All outdoor boilers must be installed with the
special base, as a standard part of the boiler. The base,
part number R0368900, is provided in a separate
package. The boiler is designed and certified for
installation on combustible flooring.
the boiler on carpeting.
NEVER store objects on or
NEVER install
around the base of the boiler. For outdoor base
installation, see Figure 20.
2.4 Combustion and Ventilation
Air Supply
All indoor installations must have openings to
outside air for combustion, ventilation and dilution of
flue gases from inside the building (see Figure 21 and
4 ft.
(1.2m)
4 ft.
(1.2m)
10 ft.
(3.0m)
Minimum Clearances
Figure 19. Outdoor Location Installation.
4 ft.
(1.2m)
3 ft.
(0.9m)
Forced Air Inlet
Mighty Therm LO-NOx Hydronic Boiler
5
5
5
12345678901234567890123
1
3
12345678901234567890123
LAARS
UNIT
(Side View)
2345678901234567890123456789012123456789012345678901234567890121234
2345678901234567890123456789012123456789012345678901234567890121234
2345678901234567890123456789012123456789012345678901234567890121234
Figure 20. Base for Outdoor Installation.
Base For Outdoor Unit
Page 9
T able 2 ). Laars does not recommend indoor
installations that do not provide combustion air from
outside the building.
Boiler rooms which are confined spaces require
two permanent air supply openings: one within 12
inches (30.5 cm) of the ceiling, the other within 12
inches (30.5 cm) of the floor.
NOTE: Check with louver manufacturers for net free
area of louvers. If screens or louvers are installed, add
50 percent for each screen/louver to the net free area.
Check the latest edition of ANSI Z223.1 or in Canada
CSA B149 and all local codes applicable to
combustion air.
Required Net Free Opening Area
Directly from Outside
At Top At Bottom
Model in.
250 63 406 63 406
400 100 645 100 645
Note: For screens or louvers, add 50%.
Table 2. Air Openings to Outside.
Vent terminated at
least 2 ft. (61cm)
above any
object within
10 ft. (3.0m)
PRODUCTION
1/4 in. (0.6cm)
Minimum Pitch
Per Foot of
Horizontal Pipe
Notes:
1. The drafthood must sit directly on top of the heater
as shown and must not be altered in any manner.
2. An Underwriters' Laboratories listed vent cap is required to eliminate downdraft and allow the heater
to function properly.
3. Use approved roof fitting.
Figure 21. Indoor Installation and Venting.
2
10 ft.
(3.0m)
2 ft. (61cm)
Drafthood
234567890123456789012
cm
2
in.
2
cm
OUT OF
Listed Vent
Cap
Storm Collar
Roof Jack
Adequate
Air Supply
To Room
Top and
Bottom
2
5 ft.
min.
(1.5m)
2.4.1 Outdoor Air Supply
When combustion air comes directly through an
outside wall, each opening must have a minimum free
area of at least one square inch for each 4,000 BTU/h
input of the total input rating of all appliances in the
enclosed area. (In Canada, refer to CSA B149.1)
2.4.2 Indoor Air Supply
Confined and non-confined areas have different
requirements for installation. Check the latest edition
of ANSI Z223.1 or in Canada CSA B149 and all local
codes applicable to combustion air.
2.4.3 Exhaust Fans or Vents
Any equipment which uses air or removes air
from the boiler room can use up the combustion air
supply or reverse the natural draft action of the venting
system. This could cause flue products to build up in
the boiler room. More air must be supplied to make up
for the decrease.
2.5 V enting (Category I)
2.5.1 General Information
When installed indoors, the drafthood must be
connected to a venting system. The venting system
must be installed by a qualified installer and in
accordance with the latest edition of ANSI Z223.1. In
Canada, the installation must be in accordance with
CSA B149.1, and any local codes that apply.
The vent pipe must have a listed vent cap, and
extend at least 2 feet (0.6 m) above any object within a
10 foot (3.0 m) radius.
NOTE: Do not use sheet metal screws at the snap
lock joints of Type B double-wall gas vents.
Do not weld or bolt 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.
Page 10
LAARS Heating Systems
WARNING
Avoid ending boiler vents near air conditioning or air
supply fans. The fans can pick up exhaust flue
products from the boiler and return them inside the
building, creating a possible health hazard, resulting
in serious injury or death.
MISE EN GARDE
Éviter de placer les sorties d’évent près des
appareils de climatisation ou les ventilateurs des
prises d’air. Ces prises d’air peuvent aspirer les
résidus de combustion et les faire pénétrer à
l’intérieur de l’immeuble, ce qui peut représenter
une menace pour la santé et occasionner des
blessures corporelles sérieuses ou même la mort.
Locate unit as close as practical to a chimney or
vent termination. Have horizontal runs sloping
upwards not less than 1/4 inch per foot (21mm/m)
from the boiler to the vent terminal. Support a vent
connector for the design and weight of the material
used to maintain clearances and prevent physical
damage and separate of joints.
Doivent présenter des tronçons horzontaux dont
la pente montante est d’au moins 1/4 po par pied
21mm/m) entre la chaudière et l’évent. Doivent
préciser que les sections horizontales doivent être
supportées pour prévenir le fléchissement.
Always use double-wall or insulated vent pipe
(Type B or equivalent).
In cold weather, uninsulated outside vents can chill
the rising flue products, blocking the natural draft
action of the venting system. This can create a
serious health hazard which can ultimately cause
death by spilling flue products into the boiler room.
Dans les régions froides, les évents non isolés
peuvent occasionner la condensation des résidus
de combustion qui y circulent, ce qui a pour effet de
réduire le tirage naturel du système d’évacuation
des résidus. Cela peut représenter une sérieuse
menace pour la santé, pouvant même provoquer la
mort en causant le refoulement des résidus de
combustion dans la chaufferie.
Avoid oversize vent piping or extremely long
runs of the pipe which may cause too much cooling
and condensation of flue gases.
When the installation of a power vent or draft fan
in the venting system is necessary , qualified personnel
should design the installation following good
PRODUCTION
WARNING
MISE EN GARDE
OUT OF
engineering practices and all applicable codes. A
suitable draft switch must be wired into the boiler
control circuit at the terminal designated Field
Interlock to keep the boiler from firing unless there is a
positive draft.
2.5.2 Common Venting Systems
Venting Multiple Appliances
When installing venting for a Mighty Therm LoNOx boiler or water heater installed as a Category I
fan-assisted appliance with other Category I appliances
through one shared duct called a “common vent”,
special care must be taken by the installer to ensure
safe operation. In the event that the common vent is
blocked, it is possible, especially for fan-assisted
devices, to vent backwards through non-operating
appliances sharing the vent, allowing combustion
products to infiltrate occupied spaces. If the
appliances are allowed to operate in this condition,
serious injury or death may occur.
WARNING
Operation of appliances with a blocked common
vent may lead to serious injury or death. Safety
devices must be implemented to prevent blocked
common vent operation. If safe operation of all
appliances connected to a common vent cannot be
assured, including prevention of spillage of flue
gasses into living spaces, common venting should
not be applied, and appliances should each be
vented separately.
AVERTISSEMENT
Le fonctionnement des appareils avec un système
d’évacuation bloqué peut provoquer des blessures
graves, voire la mort. Des dispositifs de sécurité
doivent être installés pour éviter le blocage des
systèmes d’évacuation. Si le fonctionnement de
tous les appareils connectés à un système
d’évacuation commun ne peut pas être assuré, y
compris la prévention de la dispersion des gaz
toxiques dans les espaces habités, on ne devrait
pas installer un système d’évacuation commun et
chaque appareil devrait être ventilé séparément.
It is for this reason that, in addition to following
proper vent sizing, construction and safety
requirements from the National Fuel Gas Code, ANSI
Z223.1 or in Canada, from CSA B149.1 as well as all
applicable local codes, it is required that installers
provide some means to prevent operation with a
blocked common vent. It is suggested that a blocked
vent safety system be employed such that if the switch
from one appliance trips due to excessive stack spill or
backpressure indicating a blocked vent condition, that
all appliances attached to the vent be locked out and
prevented from operating. As an additional precaution,
it is recommended that a Carbon Monoxide (CO)
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