LAARS Mighty Therm PH Installation Manual

Installation and Operation Instructions Document 1049E

Installation and Operation
Instructions for

Mighty Therm

Hydronic Boilers

Models HH and PH

Sizes 500-1825

These instructions are to be stored in the pocket provided on the boiler

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.

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.

H0117400E

Page 2

LAARS Heating Systems

TABLE OF CONTENTS

SECTION 1.
General Information

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

1B. Boiler Identification .......................................3

1C. Flow Requirements.......................................3

1D. Variable Water Flow Systems.......................4

1E. Warning Regarding Chilled

Water Systems ............................................. 5

1F. Freeze Protection ......................................... 5

SECTION 2.
Installation

2A. Boiler Placement ..........................................6

2B. Installation of Indoor Boilers..........................6

2B-1. Combustion Air Supply ................................. 6

2B-2. Venting .........................................................8

2C. Installation of Outdoor Boilers....................... 9

2D. Gas Supply and Piping ................................. 9

2E. Electrical Wiring .......................................... 10

2F. Water Piping of System .............................. 11

2G. Filling Fully-Connected System................... 11

SECTION 3.
Operation

3A. Controls - General ...................................... 12

3B. Initial Start-Up ............................................. 13

3C. To Start Up System .................................... 13

3D. To Turn Off Boiler ....................................... 14

3E. To Shut Down System ................................ 14

SECTION 4.
Maintenance

................................................................... 14

SECTION 5.
Troubleshooting and Analysis of
Service Problems

................................................................... 16

SECTION 6.
Parts Descriptions and
Order Numbers

................................................................... 18

SECTION 7.
Outdoor Parts Descriptions and
Order Numbers

................................................................... 26

SECTION 8.
Optional Parts Descriptions and
Order Numbers

................................................................... 28

Mighty Therm Hydronic Boiler

Page 3

SECTION 1.
General Information

1A. Introduction

This manual provides information for the
installation and operation of Laars hydronic boilers. It
is strongly recommended that all application and
installation procedures be reviewed completely before
proceeding with the installation. Consult the Laars
factory, or local factory representative with any
problems or questions regarding this equipment.
Experience has shown that most problems are caused
by improper installation not system design.

Some accessory items are shipped in separate
packages. Verify receipt of all items listed on the
package slip. Inspect everything for possible damage
upon delivery, and inform the carrier of any shortages
or impairments. Any such claims should be filed with
the carrier. The carrier, not the shipper, is responsible
for shortages and damage to the shipment whether
visible or concealed.

IMPORTANT WARNING:

The model HH and PH hydronic boilers must be
installed in accordance with the procedures outlined
in this manual. The warranty does not apply to boilers
not installed or operated in accordance with these
procedures. Consult local building and safety codes
before proceeding with work. The installation must

conform to the requirements of the authority having
jurisdiction or, in the absence of such requirements, to
the latest edition of the National Fuel Gas Code;
ANSI Z223.1, National Electrical Code ANSI/NFPA
70 and/ or in Canada CAN 1 -13149 requirement.

When required by the authority having
jurisdiction, the installation must conform to
American Society of Mechanical Engineers safety
codes for controls and safety devices for automatically
fired boilers No. CSD-1, and in Canada CGA 3.3. Any
modification to the boiler, its gas controls, gas
orifices, wiring or draft diverter may void the Laars
warranty. If field conditions require such
modifications, consult factory.

1B. Boiler Identification

Consult rating plate on the boiler. The following
example simplifies the boiler identification.

1 2 3456

PH 1670 I N 09 L

(1) Basic boiler model (see descriptions below).
(2) Input rate X 1000 BTU/hr.
(3) Indoor (1) or Outdoor (E) installation.
(4) Gas type: Natural (N) or Propane (P).
(5) Ignition system: I.I.D. (09) or continuous pilot

(16). Special option: I.I.D. (04) 115 volts.

(6) Firing modes:

On/Off (C)
2-stage (K)
4-stage (L)
Mechanical Modulation (H)
Motorized Modulation (F)
Motorized On/Off (R)
Motorized 2-stage (T).

Figure 1. Boiler Configuration.

Model HH hydronic heating boilers. There must
be a field installed pump to circulate water.

Model PH hydronic heating boilers are basically
the same as the HH models except that the PH boilers
come with integrally mount pumps. Pumps are sized
for pressure drop through the heat exchanger and short
runs of pipe for primary-secondary systems.

Laars hydronic boilers are available in two
configurations: an indoor version and an outdoor
version. Both are available from the factory (see
Figure 1).

1C. Flow Requirements

All low volume hydronic boilers must have
continuous flow through the heat exchanger for proper
operation. The system pump must be capable of
developing sufficient pressure to overcome the

Page 4

Design T emperature Rise Across The Boiler

20°F 11°C 25°F 14°C 30°F 17°C 35°F 19°C

Indoor Outdoor Flow H/L Flow H/L Flow H/L Flow H/L

Sizes Sizes GPM l/s Ft. m GPM l/s Ft. m GPM l/s Ft. m GPM l/s Ft. m

500 — 38 2.4 1.4 0.4 31 2.0 1.1 0.3 26 1.6 0.9 0.3 22 1.4 0.6 0.2

— 500 41 2.6 1.7 0.5 33 2.1 1.1 0.3 27 1.7 0.9 0.3 23 1.5 0.7 0.2

600 — 49 3.1 2.3 0.7 39 2.5 1.6 0.5 32 2.0 1.1 0.3 28 1.8 0.9 0.3

— 600 49 3.1 2.3 0.7 39 2.5 1.6 0.5 32 2.0 1.1 0.3 28 1.8 0.9 0.3

715 — 56 3.5 2.5 0.8 45 2.8 1.9 0.6 37 2.3 1.5 0.5 32 2.0 1.0 0.3

— 715 58 3.7 3.2 1.0 47 3.0 2.2 0.7 39 2.5 1.6 0.5 33 2.1 1.1 0.3

850 — 66 4.2 3.4 1.0 53 3.3 2.5 0.8 44 2.8 2.0 0.6 38 2.4 1.4 0.4

— 850 69 4.4 3.6 1.1 55 3.5 3.1 0.9 46 2.9 2.2 0.7 39 2.5 1.6 0.5

1010 — 79 5.0 4.7 1.4 63 4.0 3.4 1.0 53 3.3 2.7 0.8 45 2.8 1.9 0.6

— 1010 82 5.2 5.0 1.5 66 4.2 3.6 1.1 55 3.5 3.1 0.9 47 3.0 2.2 0.7

1200 — 94 5.9 6.5 2.0 75 4.7 4.8 1.5 62 3.9 3.7 1.1 53 3.3 2.6 0.8

— 1200 98 6.2 6.9 2.1 78 4.9 4.9 1.5 65 4.1 3.6 1.1 56 3.5 3.1 0.9

1430 — 112 7.1 8.9 2.7 89 5.6 6.5 2.0 74 4.7 5.0 1.5 64 4.0 3.5 1.1

— 1430 117 7.4 9.5 2.9 93 5.9 6.7 2.0 78 4.9 5.0 1.5 67 4.2 3.7 1.1

1670 — * * * * 102 6.4 8.8 2.7 85 5.4 6.7 2.0 73 4.6 4.7 1.4

— 1670 * * * * 109 6.9 9.1 2.8 91 5.7 6.8 2.1 78 4.9 5.0 1.5

1825 — * * * * 114 7.2 10 3.0 95 6.0 8.0 2.4 81 5.1 5.5 1.7

— 1825 * * * * 119 7.5 10.4 3.2 99 6.2 8.3 2.5 85 5.4 5.7 1.7

LAARS Heating Systems

*Consult factory for recommendations

Table 1. Flow Requirements.

resistance of the boiler plus the entire circulating
system at the designated GPM (see Table 1). The
temperature rise across the boiler should never exceed
40°F (22°C). Primary-secondary pumping is the most
effective way to assure proper flow through the boiler
resulting in longer boiler life and greater system
efficiency (see Figure 2).

1D. Variable Water Flow Systems

Heating systems using zone valves, zone pumps
or 3-way valves can experience reduced water flow
through the boiler. This can result in an excessive
water temperature rise and unstable boiler operation.
If the system water flow is variable, it must not be
allowed to fall below 30% of full flow. The boiler
must be equipped with staged or modulated fire with
the temperature sensor installed in the outlet water.
State variable flow when ordering. Laars recommends
primary-secondary pumping for all variable flow
systems. Primary-secondary pumping is mandatory
for variable flow systems where minimum flows are
less than 30% of full flow conditions. The boiler
pump in a primary-secondary system maintains
constant flow through the boiler even though the
system flow is variable. In a primary-secondary
system the pressure drop of the boiler is not added to
the system (see Figure 2).

A Special Note About 3-Way Water Valves

3-way water valves (2 position or proportional)
are sometimes used to divert water around a boiler
and control the temperature of water being supplied to
the system. Valves installed in this manner must be
supplied with an end switch or some other suitable
control to shut off the boiler when the flow is reduced
to 30%. The boiler must be supplied with staged or
modulated fire as indicated in Section 1D, Variable
Water Flow Systems.

It is often possible to accomplish excellent water
temperature control without 3-way valves through
proper application of staged or modulated firing
systems. Consult the factory or local Laars
representative for assistance with such systems.

System Pressure Requirements

The model HH and PH boilers are designed to
operate on closed, pressurized systems. A minimum of
12 psi should be maintained on the system where
boiler supply water temperatures are 200°F (93°C) or
less. If higher temperatures are required, the minimum
system pressure should be at least 15 psi above the
water vapor pressure corresponding to the elevated
water temperature.

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

Mighty Therm Hydronic Boiler

Page 5

Figure 2. Typical Schematic for a Primary-Secondary System.

1E. Warning Regarding Chilled

Water Systems

When a boiler is connected to an air
conditioning system where the same water is used for
heating and cooling, chilled water must be prevented
from entering the boiler. When changing such a
system from cooling to heating, the chilled water
should be allowed to circulate through the building
(after the chiller has been turned off) for a period long

Suggested Wiring Diagram For Tempering System Water
at Change-over From Heating to Cooling.

Figure 3. Boiler-Chiller Installation.

enough for the water to warm up to at least 70°F
(21°C) before the water is allowed to flow into the
boiler. It is equally important to prevent hot water
from entering the chiller. The system shown in Figure
3 is suggested to make sure that the system water is
neither too hot nor too cold when a changeover from
heating to cooling, or vice versa, takes place. When a
boiler is connected to heating coils located in air
handling units (where they may be exposed to
refrigerated air circulation), the boiler piping system
shall be equipped with 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 condensation on the boiler tubes
which will drip on the burners and may extinguish the
pilot.

Boilers installed in violation of either of the

above requirements may void the warranty.

1F. Freeze Protection

Boiler installations are not recommended in
areas where the danger of freezing exists unless
proper precautions are taken for freeze protection. The
preferred method of freeze protection is by
maintaining a mixture of no more than 50% properly
inhibited HVAC glycol. 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 by 15%
above the original recommendation. Increase the head
loss requirement by 20%.

Page 6

LAARS Heating Systems

SECTION 2.
Installation

2A. Boiler Placement

The boiler must be placed to provide specific
clearances on all sides for maintenance and
inspection. There must also be minimum distances
maintained from combustible surfaces. These
clearances also apply to non-combustible materials,
because the boiler requires air circulation for proper
operation.

Boiler should be mounted on a level surface. An
integral combustible flooring base is provided as
standard equipment on all outdoor models.
models can be installed on a combustible floor with a
special base assembly which is available from the
factory, or with a base that complies with local code
requirements. See rating plate for part number of the
base assembly.

Do not install boiler on carpeting.

Under the National Fuel Gas Code, ANSI
Z223.1, it is permissible to place the boiler on floors
other than non-combustible when the installation
complies with the American Insurance Code. Figures
5, 6, 7, and 8 show common installation on
combustible flooring.

Indoor

2B-1. Combustion Air Supply

1. The boiler 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/or in
Canada CAN 1 - B1 49 requirements, and any
local codes that may be applicable. Inadequate
combustion air supply may result in incomplete
combustion, sooting of the heat exchanger, and
unsafe operation of the boiler.

2. (a.) In the United States, the general
requirements specify that boiler rooms should be
provided with two permanent air supply
openings communicating

directly through the
wall to outside air; one within 12 inches
(305mm) of the ceiling, and the other within 12
inches (305mm) of the floor. Each opening
should have a minimum free area of one square
inch per 4,000 BTUH input of the total input
rating of all appliances in the enclosed area. See
Table 3 for recommended air supply for each
model. An improperly ventilated equipment
room can get excessively hot and cause
accelerated deterioration of controls and
electrical components.

2B. Installation of Indoor Boilers

1. Locate the boiler to provide adequate
clearance for inspection and service on all sides
(see Table 2).
from front (for proper access to and service of
controls) and 18" at water connection end. For
alcove installation, see Figure 9.

Clearance Indoor Outdoor
From inches mm inches mm

Top 30 762 unobstruct
Water Conn. Side 12 305 24 610
Opposite Side 6 152 24 610
Front Alcove Unobstruct
Rear 8 203 24 610
Vent Pipe* 6 152 —
Hot Water Pipes Per Code Per Code

*1" when using type B Vent (refer to Manufacturer's
Instructions

Table 2. Minimum Boiler Clearances

2. Install the boiler on a waterproof floor with an
adequate floor drain and a 6" (152mm)
minimum curb on all four sides to protect the
building if boiler repairs are required. The

manufacturer will not be held liable for any
water damage in connection with this boiler.

We recommend minimums of 24"

From Combustible Surfaces.

Boiler Each Opening*

Model Sq. Inches Sq. cm

500 125 806.5
600 150 967.8
715 179 1154.9

850 213 1374.3
1010 253 1632.4
1200 300 1935.6
1430 358 2309.8
1670 418 2696.9
1825 457 2948.6

*Net Free Area 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 could be double the figures indicated.
For special conditions refer to the latest edition of
ANSI Z223.1.

Consult factory if not communicating directly
through the walls with the outdoors.

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. Minimum Recommended

Air Supply to Boiler.

Mighty Therm Hydronic Boiler

Figure 4. Base for Combustible Floors.

Page 7

Figure 7. Typical Boiler Installation on Roof Using a

4 x 4 Stringer.

Figure 5. Typical Boiler Installation on Concrete Slab.

Figure 6. Typical Boiler Installation on Raised Platform

(Wood).

Figure 8. Installation on Concrete Blocks or Tile.

(b.) In Canada, consult local building and safety
codes or, in the absence of such requirements,
follow CGA requirements and/or CAN 1 - B149
standard. (Table 3 does not apply).

3. Exhaust Fans or Vents: Any equipment which
exhausts air from the boiler room can deplete the
combustion air supply or reverse the natural
draft action of the venting system.

The boiler must be completely isolated and this
could cause flue products to accumulate in the
room. Additional air must be supplied to
compensate for such exhaust. The information in
Table 3 is not applicable in installations where
exhaust fans or blowers of any type are used.
Such installations must be designed by qualified
engineers.

Page 8

Figure 9. Alcove Installation.

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 boiler, a suitable switch or equivalent must
be wired into the boiler control circuit to prevent
the boiler from firing unless the blower is
operating.

5. The boiler must be completely isolated and
protected from any source of corrosive chemical
fumes such as trichlorethylene, perchlorethylene,
chlorine, etc.

2B-2. Venting

1. Laars boilers have built-in draft diverters for
natural draft operation and must not be
connected to any portion of a mechanical draft
system under positive pressure. The flue outlet
must be connected to a clear, unobstructed vent
of adequate capacity ending above the highest
point of the building with an approved vent cap.
The venting system should be installed
according to the latest edition of ANSI Z223.1
and/or, in Canada, CAN1-13149 requirement
and any local codes having jurisdiction.

IMPORTANT NOTE: Do not use sheet metal
screws at the snap lock joints of Type B gas vents.

LAARS Heating Systems

2. Do not weld or fasten the vent pipe to the boiler
draft hood. The weight of the stack must not rest
on the boiler.

The draft hood and boiler top must
be easily removable for normal boiler service
and inspection.

3. Avoid using long horizontal runs of the vent
pipe, and too many 90° elbows, reductions or
restrictions. Horizontal runs should have at least
a 1/4" rise per foot in the direction of flow. A
vent connector should be supported for the
design and weight of the material used to
maintain clearances and prevent physical
damage and separation of joints.

4. Avoid ending heater 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. A minimum of 4 feet (1.2m) horizontal
distance must be maintained from electrical
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 boiler 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 (4.6m)
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 connecting a venting system to a Laars boiler,
the installation should be engineered by
competent personnel following good engineering
practices. The draft fan supplier should be
consulted for correct size. The installation
should be in accordance with the latest edition of
ANSI Z223.1 and/or, in Canada, CAN 1-B149
requirement and any local codes having
jurisdiction. When a draft fan is installed, a
suitable draft switch must be wired into the
boiler control circuit at terminal designated
“Field Interlock” to prevent firing of the boiler
unless a positive draft has been established.

8. When an existing boiler is removed from a
common venting system, the common venting
system is likely to be too large for proper venting
of the appliances remaining connected to it.

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

Mighty Therm Hydronic Boiler

Page 9

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

(a) Seal any unused openings in the common

venting system.

(b) 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.

(c) 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.

(d) Place in operation the appliance being

inspected. Follow the lighting instructions.
Adjust thermostat so appliance will operate
continuously.

(e) Test for spillage at the draft hood relief open-

ing after 5 minutes of main burner operation.
Use the flame of a match or candle, or smoke
from a cigarette, cigar or pipe.

(f) After it has been determined that each

appliance remaining connected to the
common venting system properly vents
when tested as outlined above, return
doors, windows, exhaust fans, fireplace
dampers and any other gasburning
appliance to their previous conditions of
use.

(g) Any improper operation of the common

venting system should be corrected so the
installation conforms with the latest edition
of 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.

2C. Installation of Outdoor Boilers

1. Locate the boiler to provide the minimum
clearances as listed in Table 2, “Boiler
Clearances.”

2. Do not place the boiler in an enclosure or wall
recess. Avoid locations where wind deflection

See Service Clearance, 2 B.1.

off structures might cause a down draft. When
such wind conditions are possible, place the
boiler at least three (3) feet (0.9m) from the
structures.

3. Never install the boiler under any kind of roof
overhang. Do not place the boiler below or
adjacent to any doors, windows, louvers, grills,
etc. which connect in any way with an inhabited
area of a building. This includes other structures
such as garages or utility rooms (see Figure 10).

Figure 10. Incorrect Outdoor Installation.

4. Although these models are AGA designed
certified for outdoor installations, such
installations are not recommended in areas
where the danger of freezing exists unless proper
precautions are taken for freeze protection.

Caution

Outdoor installations are not recommended

in areas where the danger of

snow blockage exists.

2D. Gas Supply and Piping

Review the following instructions before

proceeding with the installation.

1. Verify that the boiler is fitted for the proper type
of gas by checking the rating plate. Laars boilers
are normally equipped to operate below a 2000
foot (610m) altitude. Boilers equipped to operate
at higher altitudes have appropriate stickers or
tags attached.

2. Use the figures in Table 4 to provide adequate
gas piping from the gas meter to the boiler.

3. A trap (drip leg) must be provided ahead of the
gas controls (see Figure 11). A manual gas