LAARS MS-080 User Manual
Installation and Operation Instructions Document 2155
Installation and Operation
Instructions for
™
Mighty Stack
Water Heater
Model MS-080
Sizes 199, 300, 399
FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician,
qualified in hot water water heater 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. For indoor installations, as an
additional measure of safety, Laars strongly recommends installation of suitable Carbon Monoxide
detectors in the vicinity of this appliance and in any adjacent occupied spaces.
WARNING
If the information in this manual is not
followed exactly, a fire or explosion may
result causing property damage, personal
injury or loss of life.
Do not store or use gasoline or other
flammable vapors and liquids in the vicinity of
this or any other appliance.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not
use any phone in your building.
• Immediately call your gas supplier from
a nearby phone. Follow the gas supplier's
instructions.
• If you cannot reach your gas supplier, call
the fire department.
Installation and service must be performed
by a qualified installer, service agency, or gas
supplier.
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
trouvez.
• Appelez immédiatement votre fournisseur de
gaz depuis un voisin. Suivez les instructions
du fournisseur.
• Si vous ne pouvez rejoindre le fournisseur de
gaz, appelez le sservice des incendies.
L’installation et l’entretien doivent être assurés par
un installateur ou un service d’entretien qualifié ou
par le fournisseur de gaz.
AVERTISSEMENT
H2350400-
Page 2
Laars Heating Systems
TABLE OF CONTENTS
SECTION 1.
General Information
1.1 Introduction ...................................................... 3
1.2 Model Identication .......................................... 4
1.3 Warranty .......................................................... 4
1.4 Dimensions ...................................................... 4
1.5 Locating the Appliance..................................... 4
1.6 Locating Appliance for Correct Horizontal Vent/
Ducted Air Distance From Outside Wall .......... 6
SECTION 2.
Venting and Combustion Air
2.1 Combustion Air ................................................ 7
2.1.1 Combustion Air From Room ............................ 7
2.1.2 Intake Combustion Air...................................... 8
2.2 Venting ............................................................. 8
2.2.1 Vent Categories ............................................... 8
2.2.2 Category I Vent ................................................ 8
2.2.3 Common Venting Systems .............................. 8
2.2.4 Category III Vent .............................................. 9
2.3 Locating Vent & Combustion Air Terminals ...... 9
2.3.1 Side Wall Vent Terminal ................................... 9
2.3.2 Side Wall Combustion Air Terminal ................ 12
2.3.3 Vertical Vent Terminal .................................... 12
2.3.4 Vertical Combustion Air Terminal ................... 12
2.4 Common Vent Test ........................................12
2.5 Vent Terminals for Outdoor Units ................... 13
SECTION 3.
Gas Supply and Piping
3.1 Gas Supply and Piping .................................. 15
SECTION 4.
Water Connections
4.1 Water System Piping ..................................... 16
4.2 Hot Water Supply Piping ................................ 16
4.3 Water Flow Requirements ............................. 16
4.4 Combined Water Heating (potable)
and Space Heating ........................................ 16
4.5 Freeze Protection .......................................... 16
SECTION 6.
Operating Instructions
6.1 Filling the Water Heater System .................... 20
6.2 Operating Temperature Control ..................... 20
6.3 External Water Heater Operations ................. 20
6.4 Sequence of Operation .................................. 20
6.5 Ignition Control Reaction to Air Flow/
Blocked Vent Pressure Switch ....................... 20
6.6 Operating the Burner and Set-Up .................. 21
6.6.1 Set-Up for 0 to 2500 Feet Altitude ................. 21
6.6.2 High Altitude Adjustment and Set-Up............. 22
6.7 Shutting Down the Mighty Stack .................... 22
6.8 To Restart the Mighty Stack ........................... 22
SECTION 7.
Maintenance
7.1 System Maintenance ..................................... 23
7.2 Appliance Maintenance and
Component Description ................................. 23
7.2.1 Burners .......................................................... 23
7.2.2 Filter ............................................................... 23
7.2.3 Gas Valve ...................................................... 23
7.2.4 Manual Reset High Limit Control ................... 24
7.2.5 Ignition Control............................................... 24
7.2.6 Ignitor ............................................................. 24
7.2.7 Transformer ................................................... 24
7.2.8 Flow Switch .................................................... 24
7.2.9 Heat Exchanger Coil ...................................... 24
SECTION 8.
Trouble Shooting
8.1 Resolving Lockouts........................................ 26
8.2 Delayed Ignition – Possible Causes .............. 26
8.3 High Gas Consumption.................................. 26
SECTION 9.
Replacement Parts
9.1 General Information ....................................... 27
9.2 Parts List ........................................................ 27
SECTION 5.
Electrical Connections
5.1 Main Power .................................................... 18
5.2 Field Wiring ................................................... 18
Mighty Stack
Page 3
SECTION 1.
General Information
In the Commonwealth of Massachusetts, this
appliance must be installed by a licensed plumber or
gas tter.
1.1 Introduction
This manual provides information necessary
for the installation, operation, and maintenance of
Laars Heating Systems’ Mighty Stack copper tube
appliances, sizes 199-399 MBTU/hr. Please read
carefully before installation.
All application and installation procedures
should be reviewed completely before proceeding with
the installation. Consult the Laars Heating Systems
factory, or local factory representative, with any issues
or questions regarding this equipment. Experience
has shown that most operating issues are caused by
improper installation.
The Mighty Stack appliance is protected against
over pressurization. A pressure relief valve is tted to
the outlet header, at the water outlet of the boiler, and
another near the top of the tank.
IMPORTANT: The inlet gas pressure to the appliance
must not exceed 13 in. w.c. (3.2 kPa).
All installations must be made in accordance with:
1) In the U.S., the " National Fuel Gas Code "ANSI
Z223.1/NFPA54, Latest Edition and all applicable
local codes as required by the Authorities Having
Jurisdiction (AHJ), or
2) In Canada, the "Natural Gas and Propane
Installation Code", CSA B149.1, latest edition and all
applicable local codes as required by the AHJ.
All electrical wiring is to be done in accordance with:
1). In the U.S., the "National Electrical Code" (NEC),
ANSI/NFPA 70, latest Edition and all applicable local
codes as required by the AHJ, or
2). In Canada, the “Canadian Electrical Code - Part
1”, CSA STD. C22.1 and all applicable local codes as
required by the AHJ.
This appliance must be electrically grounded in
accordance with the applicable codes and standards
referenced above.
WARNING
To minimize the risk of electric shock, fire or other
hazards which could result in property damage,
injury, or death. The Mighty Stack hydronic,
water heater or water heater must be installed in
accordance with the procedures detailed in this
manual, or the Laars Heating Systems warranty
may 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
Z223.1/NFPA54. In Canada, the installation must
conform to the latest edition of the Natural Gas
and Propane Installation Code, CSA B149.1 and/
or applicable local codes. Where required by
the authority having jurisdiction, the installation
of Mighty Stack appliances must conform to the
Standard for Controls and Safety Devices for
Automatically Fired Water heaters, ANSI/ASME
CSD-1. Any modifications to the water heater, its
gas controls, or wiring may void the warranty. If field
conditions require modifications, consult the factory
representative before initiating such modifications.
AVERTISSEMENT
Afin de réduire au minimum les risques de
commotion électrique, de feu ou d’autre nature,
qui pourraient causer des dommages matériels,
des blessures ou des accidents mortels, les
chaudières à eau chaude ou les chauffe-eau Mighty
Stack doivent être installés conformément aux
directives détaillées contenues dans ce manuel,
à défaut de quoi la garantie fournie par Laars
Heating Systems serait annulée. L’installation doit
être conforme aux exigences de la réglementation
locale en vigueur et, aux États-Unis, à l’édition
la plus récente du Natural Fuel Gas Code (Code
pour le gaz combustible naturel) ANSI Z223.1/
NFPA54. Au Canada, l’installation doit respecter
les exigences de la plus récente édition du Code
d’installation du gaz naturel et du propane CSA
B149.1, et/ou des codes locaux de construction en
vigueur. Lorsque la réglementation locale l’exige,
l’installation des appareils électroménagers Mighty
Stack doit respecter les exigences du Standard
for Controls and Safety Devices for Automatically
Fired Water heaters (Code pour les équipements
de commande et de sécurité des chaudières à
combustion automatique), ANSI/ASME CSD-
1. 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.
Page 4
Laars Heating Systems
Model Nomenclature
see Section 1.2 for Model Identification
1 2 3 4 5 6 7 8 9 10 11 12 13
M S 0 8 0 A
SERIES
M S
GALLONS
0 8 0
SIZE
1 9 9
3 0 0
3 9 9
1.2 Model Identication
Consult the rating plate on the unit. The
following information describes the model number
structure.
Model Character Designation
1-2 Model Series Designation
M S = Mighty Stack
3-5 Gallons
080 = 80 Gallons (303 liters)
5-8 Size
1 9 9 = 199,900 BTU/h input
3 0 0 = 299,000 BTU/h input
3 9 9 = 399,900 BTU/h input
9 Fuel
N = Natural Gas
P = Propane
10 Altitude
A = 0-10,000 feet
11 Heat Exchanger / Tank Approvals
2 = HLW Copper Heat Exchanger Only
5 = HLW Cupronickel Heat Exchanger Only
X = HLW (Tank and Copper Heat Exchanger)
Y = HLW (Tank and Cupronickel Heat Exchanger)
12 Pump
N = Normal Water Pump
S = Soft Water Pump
13 Model Revision
1 = Initial Release
1.3 Warranty
Laars Heating Systems’ Mighty Stack appliances
are covered by a limited warranty. The owner should
go to the Laars.com website and register for warranty.
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. Shipping costs are not included in the
warranty coverage.
FUEL
N
P
ALTITUDE
A
HEAT
EXCH.
2
5
X
Y
PUMP
OPTIONS
N
S
REVISION
1
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
led with the carrier. The carrier, not the shipper, is
responsible for shortages and damage to the shipment
whether visible or concealed.
1.4 Dimensions
See Figure 1.
1.5 Locating the Appliance
The appliance should be located to provide
clearances on all sides for maintenance and inspection.
It should not be located in an area where leakage of
any connections will result in damage to the area
adjacent to the appliance or to lower oors of the
structure.
When such a location is not available, it is
recommended that a suitable drain pan, adequately
drained, be installed under the appliance.
The appliance is design certied by CSAInternational for installation on combustible ooring;
in basements; in closets, utility rooms or alcoves.
Mighty Stack Water heaters omust never be
installed on carpeting. The location for the appliance
should be chosen with regard to the vent pipe lengths
and external plumbing. The unit shall be installed
such that the gas ignition system components are
protected from water (dripping, spraying, rain, etc.)
during operation and service (circulator replacement,
control replacement, etc.). When vented vertically, the
Mighty Stack must be located as close as practical to
a chimney or outside wall. If the vent terminal and/
or combustion air terminal terminate through a wall,
and there is potential for snow accumulation in the
local area, both terminals should be installed at an
appropriate level above grade such that blockage of
the terminal from accumulated debris or precipitation
is prevented.
The dimensions and requirements that are shown
in Table 2 should be met when choosing the locations
for the appliance.
Mighty Stack
Page 5
Size A B C D
in. cm in. cm in. cm in. cm
199 33.0 84 4 10 5 13 8.75 22
300 39.0 99 4 10 6 15 15 38
399 43.0 109 6 15 7 18 22 56
*Air and vent connections may be on top or back of the Mighty Stack, and are eld convertible.
Figure 1. Dimensional Data.
Page 6
Laars Heating Systems
1.6 Locating Appliance for Correct
Horizontal Vent/Ducted Air Distance
From Outside Wall
The forced draft combustion air blower in the
appliance has sufcient power to pull air and vent
properly when the guidelines for horizontal air and
vent are followed (see Table 1).
NOTE: When located on the same wall, the
Mighty Stack combustion air intake terminal must
be installed a minimum of 12" (30cm) below the
exhaust vent terminal and separated by a minimum
of 36 inches (91cm) horizontally.
The air intake terminal must be installed high
enough to avoid blockage from snow, leaves and other
debris.
NOTE: On some models, the vent collar size is
larger than the size of the vent pipe that can be
used. Vent collar size and horizontal pipe diameters
can be found in Table 1. The larger vent collar
size is to accommodate Category I (vertical) vent
systems.
Size
199 5 13 4 10 4 10 50 15 3 CA003101 CA003201
300 6 15 5 13 4 10 50 15 3 CA003102 CA003201
399 7 18 6 15 6 15 50 15 3 CA003103 CA003202
Vent Collar
Size
in cm in cm in cm ft m
Horizontal
Vent Pipe
Diameter
Table 1. Horizontal Vent / Combustion Air Parameters.
Intake
Air Collar
& Pipe
Diameter
Max. Pipe
Length
Max. No.
of Elbows
Side Wall
Vent
Terminal
Part Number
Side Wall
Combustion
Air Terminal
Part Number
Appliance
Surface
Left Side 1 2.5 24 61
Right Side 1 2.5 24 61
Top 1 2.5 12 30
Back 1 2.5 **12** **30**
Front 1 2.5 36 91
Vertical
(Category 1)
Vent
Horizontal
(Category 3)
Vent
*1" (2.5 cm) when b-vent is used.
**When vent and/or combustion air connects to the back,
recommended clearance is 36" (91cm).
Required
Clearance From
Combustible Material
inches cm inches cm
*6* *15.2*
per UL 1738 venting
system supplier's
instructions
Table 2. Clearances.
Recommended
Service Access
Clearance
Mighty Stack
Page 7
SECTION 2.
Venting and Combustion Air
WARNING
For indoor installations, as an additional measure
of safety, Laars strongly recommends installation of
suitable Carbon Monoxide detectors in the vicinity of
this appliance and in any adjacent occupied spaces.
AVERTISSEMENT
Pour des installations intérieures, Laars
recommande fortement, comme mesure de sécurité
supplémentaire, l’installation de détecteurs de
monoxyde de carbone adaptés dans le voisinage
de l’appareil et dans chacune des pièces habitées
adjacentes.
2.1 Combustion Air
Mighty Stack water heaters must have provisions
for combustion and ventilation air in accordance with
the applicable sections addressing requirements for air
for combustion and ventilation of the National Fuel
Gas Code, ANSI Z223.1. In Canada, the applicable
sections of the Natural Gas and Propane Installation
Code (CSA B149.1) must be followed. In all cases any
and all applicable local installation codes must also be
followed.
A Mighty Stack appliance may receive
combustion air from the space in which it is installed,
or it can be ducted directly to the unit from the outside.
Proper ventilation air must be provided in either case.
2.1.1 Combustion Air From Room
In the United States, the most common
requirements specify that the space shall communicate
with the outdoors in accordance with method 1 or 2,
which follow. Where ducts are used, they shall be of
the same cross-sectional area as the free area of the
openings to which they connect.
Method 1: Two permanent openings, one
commencing within 12 inches (30 cm) of the top
and one commencing within 12 inches (30 cm) of
the bottom, of the enclosure shall be provided. The
openings shall communicate directly, or by ducts,
with the outdoors or spaces that freely communicate
with the outdoors. When directly communicating
with the outdoors, or when communicating to the
outdoors through vertical ducts, each opening shall
have a minimum free area of 1 square inch per 4000
Btu/hr (5.5 square cm/kW) of total input rating of all
equipment in the enclosure. When communicating to
the outdoors through horizontal ducts, each opening
shall have a minimum free area of not less than
1 square inch per 2000 Btu/hr (11 square cm/kW) of
total input rating of all equipment in the enclosure.
Table 3 shows data for this sizing method, for each
Mighty Stack model.
Method 2: One permanent opening, commencing
within 12 inches (30 cm) of the top of the enclosure,
shall be permitted. The opening shall directly
communicate with the outdoors or shall communicate
through a vertical or horizontal duct to the outdoors
or spaces that directly communicate with the outdoors
and shall have a minimum free area of 1 square inch
per 3000 Btu/hr (7 square cm/kW) of the total input
rating of all equipment located in the enclosure. This
opening must not be less than the sum of the areas of
all vent connectors in the conned space.
Other methods of introducing combustion and
ventilation air are acceptable, providing they conform
to the requirements in the applicable codes listed
above.
In Canada, consult local building and safety
codes or, in absence of such requirements, follow CSA
B149.1, the Natural Gas and Propane Installation Code.
Size
199 50 323
300 75 484
399 100 645
*Net Free Area in Square Inches / Square cm
Area indicated is for one of two openings; one at oor level
and one at the ceiling, so the total net free area could be
double the gures indicated.
This chart is for use when communicating directly with the
outdoors. For special conditions and alternate methods, refer
to the latest edition of ANSI Z223.1.
Note: Check with louver manufacturers for net free area of
louvers. Correct for screen resistance to the net free area
if a screen is installed. Check all local codes applicable to
combustion air.
Table 3. Combustion Air Openings.
Figure 2. Combustion Air and Vent Through Roof.
Square inches Square cm
Each Opening*
Page 8
Laars Heating Systems
2.1.2 Intake Combustion Air
The combustion air can be ducted through the
wall, or through the roof. When taken from the wall, it
must be taken from out-of-doors by means of the Laars
horizontal wall terminal (see Table 1). When taken
from the roof, a eld-supplied rain cap or an elbow
arrangement must be used to prevent entry of rain
water (see Figure 2).
Use single-wall galvanized pipe, per Table
4, for the combustion air intake (see Table 1 for
appropriate size). Route the intake to the heater as
directly as possible. Seal all joints with tape. Provide
adequate hangers. The unit must not support the
weight of the combustion air intake pipe. Maximum
linear pipe length allowed is 50 feet (15.2m). Three
elbows have been calculated into the 50-foot (15.2m)
linear run. Subtract 10 allowable linear feet (3.0m) for
every additional elbow used (see Table 1). When fewer
than 3 elbows are used, the maximum linear pipe
length allowed is still 50 feet (15.2m).
Term Description
Pipe Single-wall galvanized steel pipe, 24 gauge
minimum (either insulated or non-insulated)
Joint Sealing Permanent duct tape or aluminum tape
Table 4. Required Combustion Air Piping Material.
The connection for the intake air pipe is on the
lter box. The Mighty Stack appliances may have
venting and combustion air ducting attached to the top
or the back. They are shipped with the connections
at the top. For attaching either or both pipes to the
back, the mounting anges are reversible by removing
the mounting screws and orienting the anges in the
desired position. Replace the screws after positioning
anges. Run a bead of silicone around the collar and
slide the pipe over the collar. Secure with sheet metal
screws.
In addition to air needed for combustion, air
shall also be supplied for ventilation, including all air
required for comfort and proper working conditions
for personnel. The Mighty Stack loses less than 1
percent of its input rating to the room, but other heat
sources may be present.
2.2 Venting
2.2.1 Vent Categories
Depending upon desired Mighty Stack venting,
it may be considered a Category I or a Category III
appliance. In general, a vertical vent system will be
a Category I system. However, in rare instances, a
Mighty Stack’s vertical vent system may be considered
Category III. In the U.S., the National Fuel Gas Code
(ANSI Z223.1), or in Canada the Natural Gas and
Propane Installation Code (CSA B149.1), denes a
Category I vent system, and includes rules and tables
to size these vent systems. If the Mighty Stack’s
vertical vent system does not satisfy the criteria for
Category I venting, it must be vented as a Category III
system.
All Mighty Stack vent systems which discharge
horizontally (without the use of a power venter) are
considered Category III vent systems.
2.2.2 Category I Vent
When vented as a Category I appliance, the
vent system must conform to the National Fuel Gas
Code (ANSI Z223.1-Latest Edition) in the U.S., or in
Canada, to the Natural Gas and Propane Installation
Code (CSA B149.1 latest edition). The vent system
must be sized and installed for a Category I FanAssisted Appliance.
If chimney height is greater than 25 feet (7.6m),
or if multiple units are vented into the same vertical
vent, a barometric damper must be installed on each
appliance, such that the ue draft does not exceed
(negative) 0.1 in. w.c.
If using a power venter for any type of Category
I venting, the draft should be set between (negative)
0.01 and 0.05 in. w.c.
2.2.3 Common Venting Systems
Mighty Stack units are Category I fan-assisted
when vented vertically and adhering to all applicable
codes. Mighty Stack units are not allowed to be
vented into a common horizontal vent system, unless
a properly sized vent fan is used, and the common
vent system is properly designed by the vent fan
manufacturer or a qualied engineer. When common
venting Mighty Stack fan-assisted unit with other
appliances through one shared vertical 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 inltrate 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.
Mighty Stack
Page 9
AVERTISSEMENT
Le fonctionnement d’appareils connectés à un
évent commun bouché peut provoquer de sérieuses
blessures corporelles ou la mort. Des dispositifs de
sécurité doivent être mis en place pour empêcher
que les appareils soient utilisés avec un évent
commun bouché. Si un fonctionnement sécuritaire
de tous les appareils reliés à un évent commun et si
la prévention des dégagements accidentels de gaz
de combustion dans des zones habitées ne peuvent
pas être assurés, un évent commun ne doit pas
être mis en place et les appareils doivent être munis
d’évents individuels séparés.
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 the Natural Gas
and Propane Installation Code (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 back pressure indicating a blocked vent
condition, that all appliances attached to the vent be
locked out and prevented from operating. Note that
the Mighty Stack is equipped with a blocked vent
safety (pressure) switch, as shipped. However, this
safety switch has only been designed and tested to
be effective in installations where the Mighty Stack
is vented separately and NOT common vented with
other appliances. As an additional precaution, it is
recommended that a Carbon Monoxide (CO) alarm be
installed in all enclosed spaces containing combustion
appliances. If assistance is required in determining
how a blocked vent safety system should be connected
to a LAARS product, please call Applications
Engineering at the Rochester phone number on the
back cover of this manual.
Refer to the installation and operating
instructions on all appliances to be common vented
for instructions, warnings, restrictions and safety
requirements. If safe operation of all appliances
connected to a common vent cannot be assured,
including prevention of spillage of ue gases into
living spaces, common venting should not be applied,
and appliances should each be vented separately.
2.2.4 Category III Vent
When the Mighty Stack is vented with horizontal
discharge, it must be installed per this installation
manual and the venting system manufacturer’s
installation instructions. The vent system must be
sealed stainless steel, per Table 5.
Route the vent pipe to the heater as directly as
possible. Seal all joints and provide adequate hangers
as required in the venting system manufacturer’s
installation instructions. Horizontal portions of the
venting system must be supported to prevent sagging
and may not have any low sections that could trap
condensate.
The unit must not support the weight of the vent
pipe. Horizontal runs must slope downwards not less
than ¼ inch per foot (2 cm/m) from the unit to the vent
terminal.
L’appareil ne doit pas supporter le poids de la
gaine d’évent. Les parties horizontales doivent être
installées avec une pente de 2 cm/m (1/4 inch par pied)
descendant de l’appareil vers la sortie de l’évent.
Reference Table 1 for the size of the Category
III vent system. Up to three elbows can be used with
50 linear feet (15.2m) of pipe. Subtract 10 allowable
linear feet (3.0m) for every additional elbow used.
2.3 Locating Vent & Combustion Air
Terminals
2.3.1 Side Wall Vent Terminal
The appropriate Laars side wall vent terminal
must be used, and is listed in the installation and
operation manual. The terminal provides a means of
installing the 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 CSA B149.1
and local applicable codes. Consider the following
when installing the terminal:
1. Figure 3 shows the requirements for mechanical
vent terminal clearances for the U.S. and Canada.
2. Locate the vent terminal so that vent gases cannot
be drawn into air conditioning system inlets.
3. Locate the vent terminal so that vent gases cannot
enter the building through doors, windows,
gravity inlets or other openings. Whenever
possible, locations under windows or near doors
should be avoided.
4. Locate the vent terminal so that it cannot be
blocked by snow. The installer may determine
that a vent terminal must be higher than the
minimum shown in codes, depending upon local
conditions.
5. Locate the terminal so the vent exhaust does
not settle on building surfaces or other nearby
objects. Vent products may damage such surfaces
or objects.
6. If the water heater or water heater uses ducted
combustion air from an intake terminal located
Term Description
Pipe Must comply with UL Standard 1738 such
as Type AL29-4C Stainless Steel
(either insulated or non-insulated).
Joint
Sealing
Table 5. Required Horizontal Venting Material.
Follow vent manufacturer's instructions.
Page 10
Laars Heating Systems
U.S. Installations (see note 1) Canadian Installations (see note 2)
A= Clearance above grade, veranda, porch, 12 inches (30 cm) 12 inches (30 cm)
deck, or balcony
B= Clearance to window or door that may Direct Vent Only: 12 inches (30 cm)
be opened Other Than Direct Vent: 4 feet (1.2 m) below or 36 inches (91 cm)
to side of opening; 1 foot (30 cm) above opening
C= Clearance to permanently closed window See note 4 See note 5
D= Vertical clearance to ventilated soft located
above the terminal within a horizontal See note 4 See note 5
distance of 2 feet (61cm) from the center line of the terminal
E= Clearance to unventilated soft See note 4 See note 5
F= Clearance to outside corner See note 4 See note 5
G= Clearance to inside corner See note 4 See note 5
H= Clearance to each side of center line See note 4 3 feet (91 cm) within a height 15 feet
extended above meter/regulator assembly above the meter/regulator assembly
I= Clearance to service regulator vent outlet See note 4 3 feet (91 cm)
J= Clearance to non mechanical air supply Direct Vent Only: 12 inches (30 cm)
inlet to building or the combustion air inlet Other Than Direct Vent: 4 feet (1.2 m) below or 36 inches (91 cm)
to any other appliance to side of opening; 1 foot (30 cm) above opening
K= Clearance to a mechanical air supply inlet 3 feet (91 cm) above if within 10 feet (3 m) 6 feet (1.83 m)
horizontally
L= Clearance above paved sidewalk or paved Vent termination not allowed in this location Vent termination not allowed in this
driveway located on public property location
M= Clearance under veranda, porch, deck, See note 4 12 inches (30 cm) (see note 3)
or balcony
Notes:
1. In accordance with the current ANSI Z223.1 / NFPA 54 National Fuel Gas Code.
2. In accordance with the current CSA B149.1, Natural Gas and Propane Installation Code.
3. Permitted only if veranda, porch, deck, or balcony is fully open on a minimum of two sides beneath the oor.
4. For clearances not specied in ANSI Z223.1 / NFPA 54, clearance is in accordance with local installation codes and the requirements of
the gas supplier.
5. For clearances not specied in CSA B149.1, clearance is in accordance with local installation codes and the requirements of the gas
supplier.
Figure 3. Vent Terminal Clearance.
Mighty Stack
Page 11
on the same wall, locate the vent terminal at least
3 feet (0.9m) horizontally from the combustion
air terminal, and locate the vent terminal at least
1 foot (0.3m) above the combustion air terminal.
WARNING
The outdoor vent terminal gets hot. Unit must be
installed in such a way as to reduce the risk of
burns from contact with the vent terminal.
AVERTISSEMENT
La sortie d’évent à l’extérieur devient très chaude.
Elle doit être installée de façon à réduire le risque
de brûlures au contact de l’extrémité de l’évent.
Important Note: Massachusetts Code
Requirement.
From Massachusetts Rules and Regulations 248
CMR 5.08:
(a) For all side wall horizontally vented gas
fueled equipment installed in every dwelling,
building or structure used in whole or in
part for residential purposes, including those
owned or operated by the Commonwealth and
where the side wall exhaust vent termination
is less than seven (7) feet above nished grade
in the area of the venting, including but not
limited to decks and porches, the following
requirements shall be satised:
1. INSTALLATION OF CARBON MONOXIDE
DETECTORS.
At the time of installation of the side wall
horizontal vented gas fueled equipment, the
installing plumber or gastter shall observe that
a hard-wired carbon monoxide detector with
an alarm and battery back-up is installed on
the oor level where the gas equipment is to be
installed. In addition, the installing plumber or
gastter shall observe that a battery operated or
hard-wired carbon monoxide detector with an
alarm is installed on each additional level of the
dwelling, building or structure served by the side
wall horizontal vented gas fueled equipment.
It shall be the responsibility of the property
owner to secure the services of qualied licensed
professionals for the installation of hard-wired
carbon monoxide detectors.
a. In the event that the side wall horizontally
vented gas fueled equipment is installed
in a crawl space or an attic, the hard-wired
carbon monoxide detector with alarm and
battery back-up may be installed on the next
adjacent oor level.
b. In the event that the requirements of this
subdivision cannot be met at the time of
completion of installation, the owner shall
have a period of thirty (30) days to comply
with the above requirements; provided,
however, that during said thirty (30) day
period, a battery operated carbon monoxide
detector with an alarm shall be installed.
2. APPROVED CARBON MONOXIDE
DETECTORS.
Each carbon monoxide detector as required
in accordance with the above provisions shall
comply with NFPA 720 and be ANSI/UL 2034
listed and IAS certied.
3. SIGNAGE.
A metal or plastic identication plate shall be
permanently mounted to the exterior of the
building at a minimum height of eight (8) feet
above grade directly in line with the exhaust vent
terminal for the horizontally vented gas fueled
heating appliance or equipment. The sign shall
read, in print size no less than one-half (½) inch
in size, “GAS VENT DIRECTLY BELOW.
KEEP CLEAR OF ALL OBSTRUCTIONS”.
4. INSPECTION.
The state or local gas inspector of the side
wall horizontally vented gas fueled equipment
shall not approve the installation unless, upon
inspection, the inspector observes carbon
monoxide detectors and signage installed in
accordance with the provisions of 248 CMR
5.08(2)(a) 1 through 4.
(b) EXEMPTIONS: The following equipment is
exempt from 248 CMR 5.08(2)(a) 1 through 4:
1. The equipment listed in Chapter 10 entitled
“Equipment Not Required To Be Vented” in the
most current edition of NFPA 54 as adopted by
the Board; and
2. Product Approved side wall horizontal vented gas
fueled equipment installed in a room or structure
separate from the dwelling, building or structure
used in whole or in part for residential purposes.
(c) MANUFACTURER REQUIREMENTS –
GAS EQUIPMENT VENTING SYSTEM
PROVIDED. When the manufacturer of
Product Approved side wall horizontally vented
gas equipment provides a venting system
design or venting system components with the
equipment, the instructions provided by the
manufacturer for installation of the equipment
and the venting system shall include:
1. Detailed instructions for the installation of the
venting system design or the venting system
components; and
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