LAARS Mighty Therm VW Installation Manual
Installation and Operation Instructions Document 2052D
Installation and Operation
Instructions for
Mighty Therm
Model VW
Sizes 2000-5000
Volume Water Heaters
FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician,
qualified in hot 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.
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.
H0147700D
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LAARS Heating Systems
TABLE OF CONTENTS
SECTION 1.
General Information
1.1 Introduction...................................................3
1.2 Flow Requirements.......................................3
1.3 Water Chemistry...........................................4
SECTION 2.
Installation
2.1 Heater Placement.........................................4
2.2 Indoor Installation .........................................4
2.2.1 Combustion Air Supply .................................4
2.2.2 Venting ......................................................... 5
2.3 Installation of Outdoor Heater ....................... 6
2.4 Gas Supply and Piping ................................. 6
2.5 Electrical Wiring............................................8
2.6 Water Piping of System ................................ 8
2.7 Water Expansion ..........................................8
2.8 Pump Installation ..........................................9
2.9 Tank Installation ........................................... 9
2.10 Water Pressure .......................................... 10
SECTION 3.
Operation
3.1 Initial Start Up .............................................12
3.2 To Start Up System .................................... 12
3.3 To Turn Off Heater ..................................... 13
3.4 To Shut Down System ................................ 13
SECTION 4.
Maintenance
................................................................... 13
SECTION 5.
Troubleshooting and Analysis of
Service Problems
................................................................... 14
SECTION 6.
Conversion of VW from Indoor
to Outdoor Models
6.1 Conversion Procedure ................................ 16
6.1.1 Section I...................................................... 16
6.1.2 Section II..................................................... 16
SECTION 7.
Parts Description and Order Numbers
7.1 General Information.................................... 19
7.2 Parts List .................................................... 19
Mighty Therm Volume Water Heaters
Page 3
SECTION 1.
General Information
WARNING
The Model VW Volume Water Heater must be
installed in accordance with the procedures outlined
in this manual. Warranty does not apply to heaters
not installed or operated in accordance with these
procedures. Consult local building and safety codes
before proceeding with work. The installation must
conform to the requirements of the authority having
jurisdiction or, in the absence of such requirements,
to the latest edition of the National Fuel Gas Code,
ANSI Z223.1, and/or in Canada, CANI B-149
requirement.
When required by the authority having
jurisdiction, the installation must conform to
American Society of Mechanical Engineers safety
code for controls and safety devices for automatically
fired heaters No. CSD-1, and in Canada CGA 3.3.
Any modification to the water heater, its gas controls,
gas orifices, wiring or draft diverter may void the
Laars warranty. If field conditions require such
modifications, consult factory.
1.1 Introduction
This manual provides information for the
installation and operation of Laars Volume Water
Heaters. It is strongly recommended that all
application and installation procedures be reviewed
completely before proceeding with the installation.
Consult the factory, or local factory representative,
with any problems or questions regarding this
equipment. Experience has shown that most operating
problems are caused by improper installation.
Model VW heaters are available from the factory
in two configurations: An indoor version and an
outdoor version. In addition, the heaters are field
convertible. See Section 6 of this manual.
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.
1.2 Flow Requirements
All low volume hot water heaters 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 heater plus the entire circulating
system at the designed flow rate.
Figure 1 – Heater Configuration - Model VW.
OutdoorIndoor
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LAARS Heating Systems
1.3 Water Chemistry
Laars equipment is designed for use in a wide
variety of water conditions. The water velocity
maintained in the heat exchanger tubes is kept high
enough to prevent scaling from hard water, and at the
same time, low enough to avoid corrosion from soft
water. Most of the urban areas in the country have
water that is compatible with this equipment. In some
areas a water supply will contain a heavy quantity of
scaling chemicals, or the water may be extremely soft
and corrosive. In rare situations, the water will contain
both scaling chemicals and corrosive chemicals such
as calcium, or sodium chloride. These conditions may
be the result of a nearby well or pumping station, and
the particular condition may not be characteristic of
the entire city water system.
If an installer observes damage from these
conditions to any water handling equipment in the
area, a factory representative should be contacted
immediately for assistance in minimizing maintenance
costs. If erosion is present, the pump impeller can be
replaced to reduce water velocity. If scaling
conditions are bad, tube cleaning maintenance
schedules can be established to prevent tube burn-out
and cracking. Neglecting the problem could mean
serious damage to the heater and water system.
Scaling can be recognized as a layer deposited
on the inner walls of the tubes which reduces the inner
diameter of the tube. Scale can be any color or
texture; smooth or rough, granular or amorphous.
Erosion is generally evidenced by pitting, cavitation,
ridges and “islands” on the inner walls of the tubes.
Where this condition results from extremely soft
water sources, or as a result of a water softening
program, the internal copper surfaces will be
extremely shiny. Other chemicals, such as chlorine or
chlorides in the water, will result in dark surfaces of
erosion.
In areas where the water supply is extremely
corrosive, it is advisable to order the heater with
cupronickel tubes in the exchanger.
Damage from scaling, corrosion, or erosion is
not covered by the warranty.
SECTION 2.
Installation
2.1 Heater Placement
The heater must be placed to provide clearances
on all sides for maintenance and inspection. There
must also be minimum distances maintained from
combustible surfaces.
All heaters must be installed on a noncombustible flooring. Under no circumstances can
heaters be installed on carpeting.
The National Fuel Code allows a heater to be
placed on other than a non-combustible surface when
such an installation complies with the local codes.
This code specifies the surface under the heater be
protected with hollow masonry no less than 4" thick,
covered with sheet metal at least 20 gauge in
thickness. Such masonry must be laid with ends
unsealed, and joints matched in such a way as to
provide a free circulation of air from side to side
through the masonry (see Figure 2).
Base Must Extend Out
Min. 12" On All Sides
Of Heater Frame
Concrete Blocks Or Tile
Min. 7" High With 3" Min.
Air Openings
Blocks must provide solid base and be braced
so they cannot slip out of place. Air openings
in blocks must be arranged to provide
unobstructed opening through entire width or
length of base.
Figure 2. Non-Combustible Base.
Clearance Indoor Outdoor
From (Inches) (Inches)
Top 24 —
Water Conn. Side 24 24
Opposite Side 24 24
Front 48 48
Rear 24 24
Vent 6 —
Table 1 – Minimum Heater Clearances From
Combustible Surfaces.
Metal Plate
20 Ga. Min.
Under Entire
Heater
2.2 Indoor Installation
2.2.1 Combustion Air Supply
1. The heater location must provide sufficient air
supply for proper combustion, and ventilation of
the surrounding area as outlined in the latest
edition of ANSI standard Z223.1 and in Canada,
CAN1-B149 requirement, and any local codes
that may be applicable. Inadequate combustion
air supply may result in incomplete combustion
and consequent sooting of the heat exchanger
and unsafe operation of the heater.
Mighty Therm Volume Water Heaters
Page 5
2. 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 crosssectional area as the free area of the openings to
which they connect.
Method 1:
Two permanent openings, one commencing
within 12" (30 cm) of the top and one
commencing within 12" (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 directly, or through vertical
ducts, each opening shall have a minimum free
area of 1 square inch per 4000 Btu/hr (550
square mm/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 (1100 square mm/kW) of total
input rating of all equipment in the enclosure.
Method 2:
One permanent opening, commencing within 12"
(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 (734 square mm/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 confined
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, Table 2 does not apply. Consult
local building and safety codes or, in absence of
such requirements, follow CAN/CGA B149.
3. Exhaust Fans or Vents: Any equipment which
exhausts air from the heater room can deplete the
combustion air supply or reverse the natural
draft action of the venting system. This could
cause flue products to accumulate in the heater
room. Additional air must be supplied to
compensate for such exhaust. The information in
Table 2 is not applicable in installations where
exhaust fans or blowers of any type are used.
Such installations must be designed by qualified
engineers.
Indoor Each Opening*
Size (Square Inches)
2000.......................................................... 500
2450.......................................................... 613
3050.......................................................... 763
3500.......................................................... 875
4050......................................................... 1013
4500......................................................... 1125
5000......................................................... 1250
Net Free Area in Square Inches*
*Area indicated is for one of two openings; one at floor
level and one at the ceiling, so the total net free area
would be double the figures indicated. For all other
conditions, refer to latest edition of ANSI Bulletin 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 2– Minimum Recommended Air Supply
To Heater Room.
4. If a blower or fan is used to supply air to the
heater room, the installer should make sure it
does not create drafts which could cause
nuisance shutdowns of the pilot. If a blower is
necessary to provide adequate combustion air to
the heater, a suitable switch or equivalent must
be wired into the heater control circuit to prevent
the heater from firing unless the blower is
operating.
5. The heater must be completely isolated and
protected from any source of corrosive chemical
fumes such as emitted by trichlorethylene,
perchlorethylene, chlorine, etc.
2.2.2 Venting
1. Laars heaters have built-in draft diverters for
natural draft operation and must not be
connected into any portion of a mechanical draft
system under positive pressure. The flue outlet
must be connected to a clear, unobstructed vent
of adequate capacity terminating above the
highest point of the building with an approved
vent cap. The venting system should be installed
according to the latest edition of ANSI Z223.1
and any local codes having jurisdiction, and/or
in Canada follow CAN1-B149 standard.
Important Note: Do not use sheet metal screws
at the snap lock joints of Type B gas vents.
2. Do not weld or fasten the vent pipe to the heater
draft hood. The weight of the stack must not rest
on the heater. The draft hood and heater top
must be easily removable for normal heater
service and inspection.
Page 6
LAARS Heating Systems
Control Wiring for Draft Fan
Figure 3. Draft Inducer/Power Venter.
3. Avoid long horizontal runs of the vent pipe, and
too many 90° elbows, reductions and
restrictions. Horizontal runs should have at least
a 1/4" rise per foot in the direction of flow. A
vent connector shall be supported for the design
and weight of the material employed to maintain
clearances and prevent physical damage and
separation of joints.
4. Avoid terminating heater vents near air
conditioning or air supply fans. The fans can
pick up exhaust flue products from the heater
and return them inside the building, creating a
possible health hazard. A minimum of 4 feet
horizontal distance must be maintained from
electric meters, gas meters, and relief equipment.
5. Always use double-wall or insulated vent pipe
(Type B or equivalent). In cold weather,
uninsulated outside vents can chill the rising flue
products, blocking the natural draft action of the
venting system. This can create a health hazard
by spilling flue products into the heater room.
6. Avoid oversize vent piping or extremely long
runs of the pipe which may cause excessive
cooling and condensation. Rule of Thumb: The
total length of the vent, including the connector
and any offset, should not exceed 15 feet for
every inch of vent diameter. Longer total lengths
shown in venting tables are based on maximum
capacity, not condensation factors.
7. When the installation of a draft fan is necessary
in the venting system to which a Laars heater is
to be connected, the installation should be
engineered by competent personnel following
good engineering practices. The draft fan
supplier should be consulted for correct size.
The installation should be in accordance with the
latest edition of ANSI Z223.1 and any local
codes having jurisdiction. In Canada follow
CAN1-B149 standard. When a draft fan is
installed, a suitable draft switch must be used
and wired into the heater control circuit at
terminal designated “Field Interlock,” to prevent
firing of the heater unless a positive draft has
been established (see Figure 3).
2.3 Installation of Outdoor Heater
Caution
Outdoor installations are not recommended in areas
where the danger of snow blockage exists.
1. Standard outdoor units are shipped with two vent
stacks and vent caps that must be installed on the
vent outlets.
2. Locate the heater to provide the minimum
clearances as listed in Section 2A, “Placement of
Heater.”
3. Do not locate the heater in an enclosure or wall
recess. Avoid location where wind deflection off
structures might cause down draft. When such
wind conditions are possible, locate the heater at
least three (3) feet from the structures.
4. Never install the heater under any kind of roof
overhang. Do not locate the heater 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 4).
Figure 4. Incorrect Outdoor Installation.
2.4 Gas Supply and Piping
Review the following instructions before
proceeding with the installation.
1. Verify that the heater is fitted for the proper type
of gas by checking the rating plate. Laars heaters
are normally equipped to operate below a 2000
foot altitude. Heaters equipped to operate at
higher altitudes have appropriate stickers or tags
attached.
Mighty Therm Volume Water Heaters
Page 7
2. Use the figures in Table 3 to provide adequate
gas piping (check local code for BTU capacity
required). See Table 4.
3. A trap (drip leg) must be provided ahead of the
gas controls (see Figure 5). Where required by
code, provide a second manual gas shutoff valve.
Do not remove manual valve furnished with the
heater.
4. The heater and its individual shutoff valve must
be disconnected from the gas supply piping
system during any pressure testing of that system
at test pressures in excess of 1/2 psig. The heater
must be isolated from the gas supply piping
system by closing its individual manual gas
shutoff valve during any pressure testing of the
gas supply piping system at test pressures equal
to or less than 1/2 psig.
Distance from Gas Meter or Last Stage Regulator
Indoor
Outdoor
Size
Size
2000 –– 2-1/2 2 3 2-1/2 3 3
2450 2200 3 2-1/2 3 2-1/2 3-1/2 3
3050 2800 3 2-1/2 3-1/2 3 3-1/2 3
3500 3200 3 2-1/2 3-1/2 3 4 3-1/2
4050 3600 3-1/2 3 4 3-1/2 4 3-1/2
4500 4000 3-1/2 3 4 3-1/2 5 4
5000 4500 4 3-1/2 4 3-1/2 5 4
NOTES:
These figures are based on 1/2" water column
pressure drop.
Check supply pressure and local code requirements
before proceeding with work.
Pipe fittings must be considered when determining gas
pipe sizing.
0-100' 100-200' 200-300'
Nat. L P Nat. L P Nat. LP
5. Provide gas supply pressure to the heater as
follows:
Natural Gas LPG
Min. (inches water column) 7 11
Max. (inches water column) 9 14
Note: The heater and all other gas appliances
sharing the heater gas supply line must be firing at
maximum capacity to properly measure the inlet
supply pressure. Low gas pressure could be an
indication of an undersize gas meter and/or obstructed
gas supply line.
6. The correct burner manifold gas pressure is
stamped on the rating plate. The regulator is preset at the factory, and normally requires no
further adjustment.
7. The gas manifold and control assembly was
tested and conform to the safe lighting and other
performance criteria specified in the latest
editions of ANSI Z21.13 and CGA 3.3 Low
Pressure Heater Standard.
8. Before operating the heater, the complete gas
supply system and all connections must be tested
for leaks using a soap solution. Do not use raw
flame.
Caution
Since some leak test solutions, including soap and
water, may cause corrosion or stress cracking, the
piping must be rinsed with water after testing, unless
it has been determined that the leak test solution is
noncorrosive.
Arrangement of gas train components for on-off,
2-stage and 4-stage firing are shown schematically in
the Gas Piping Diagram (see Figure 6).
Table 3. Gas Line Selection Chart For
Natural and Propane Gas.
Figure 5. T-Fitting Sediment Trap Installation.
* Standard on sizes 3050-5000
** Sizes 2000 & 2450 use one pilot gas valve
Figure 6. Typical Gas Piping Diagram.
Page 8
r
LAARS Heating Systems
2.5 Electrical Wiring
Electrical diagrams are included with the packet
provided with each unit.
WARNING
The heater must be electrically grounded in
accordance with the most recent edition of the
National Electrical Code and ANSI/NFPA 70 , and in
Canada, follow Canadian Electrical Code CSA
C22.1. Do not rely on the gas or water piping to
ground the metal parts of the heater. Many times,
plastic pipe or dielectric unions isolate the heater
electrically. Service and maintenance personnel who
work on or around the heater may be standing on
wet floors and could be electrocuted by a poorly
grounded heater.
1. Check heater wiring and pump for correct
voltage, frequency and phase. If the pump circuit
is other than 115V, check to see that the heater is
provided with an appropriate transformer.
2. Wire the heater and pump exactly as shown in
the wiring diagram supplied with the heater.
3. The pump and heater must be electrically
interlocked so the heater cannot come on unless
the pump is running.
4. All field installed electrical safety devices and
all field installed devices (draft switches, relays,
timers, outdoor temperature reset devices, etc.)
can be connected to the heater wiring at points
shown in the wiring diagram designated “Field
Interlock.”
2.6 Water Piping of System
1. Be sure to provide valves at the inlet and outlet
to the heater so it can be readily isolated for
service.
A butterfly or similar type of valve is
recommended.
2. The pressure relief valve must be installed in the
tapped opening provided in the heater header, or
on the "T" connection on the heater outlet side,
with its outlet piped but not fastened to a drain
or floor sink. Special attention must be given to
relief valve settings in installations where the
heater is located on the ground floor of a tall
building. In both instances, the static pressure of
the system is elevated, and could cause the relief
valve to leak. Where no special setting of the
relief valve is ordered, the factory will furnish a
125 psi setting. Never reduce the relief valve
opening. If necessary, install the relief valve in a
Tee immediately past the heater outlet.
3. The weight of all water and gas piping should be
supported by suitable hangers or floor stands.
4. Check piping diagrams with local applicable
plumbing, heating and building safety codes.
5. All two-temperature systems using temperature
valves must have forced recirculation in the low
temperature building loop.
6. A check valve installed at the hot water inlet to
the tempering valve will prevent cold water from
being drawn in reverse through the tempering
valve into the hot water.
7. When installing a tempering valve, locate it at
the bottom of the antithermosyphon loop at least
24" high to prevent excessive hot water from
entering the mixed water supply (see Figure 7).
Bring the cold water supply up from the floor to
the valve.
8. Keep thermometer bulbs in moving water. Use
of a bushing will cause temperature readings to
be off 10° or more (see Figure 8).
9. Insulate all pipes containing hot water,
especially in unheated areas. Sizing charts
assume this condition exists. Excessive heat loss
of exposed piping adds to gas consumption and
could result in insufficient hot water during peak
demand periods. If pipes are uninsulated, a
larger heater must be used.
2.7 Water Expansion
When cold water is heated, it expands. If no
water is being used during the heat-up period, the
expanded water will normally back up into the city
mains.
Hot
Water
Hot
Water
Storage
Tank
Figure 7. Tempering Valve Installation. Figure 8. Thermometer Bulb.
Floor
Tempered Water
24"
Automatic
Tempering
Valve
Right Wrong
Cold
Wate
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