HTP Mod Con 300 LP Instruction Manual

120 Braley Rd. P.O. Box 429 East Freetown, MA 02717-0429 www.htproducts.com
LP- 205 REV. 3.18.11
Mod Con
INSTALLATION
START-UP
MAINTENANCE
PARTS
Mod Con Models
300 / 500 / 850
LP / HL / LPHL
This manual must only be used by a qualified heating installer/service technician. Read all
instructions in this manual before installing. Perform steps in the order given. Failure to comply
could result in substantial property damage, severe personal injury, or death.
NOTICE: HTP reserves the right to make product changes or updates without notice and will not be held
liable for typographical errors in literature.

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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 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 neighbor’s phone. Follow the gas supplier’s
instructions.
•If you cannot reach your gas supplier, call the fire department. Installation and service must be
provided by a qualified installer, service agency, or the gas supplier.

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The following defined terms are used throughout this manual to bring attention to the presence of
hazards of various risk levels, or to important product information.
DANGER indicates an imminently hazardous situation which, if not avoided, will result in death or serious
injury.
WARNING indicates a potentially hazardous situation which, if not avoided, could result in death or
serious injury.
CAUTION indicates a potentially hazardous situation which, if not avoided, may result in minor or
moderate injury.
CAUTION used without the safety alert symbol indicates a potentially hazardous situation which, if not
avoided, may result in property damage.
FOREWORD
This manual is intended to be used in conjunction with other literature provided with the appliance. This
includes all related control information. It is important that this manual, all other documents included with
this system, and additional publications including the National Fuel Gas Code, ANSI Z223.1-2002, be
reviewed in their entirety before beginning any work.
Installation should be made in accordance with the regulations of the local code authorities and utility
companies which pertain to this type of water heating equipment.
NOTE TO CONSUMER: PLEASE KEEP ALL INSTRUCTIONS FOR FUTURE REFERENCE.
FOR THE INSTALLER
This appliance must be installed by qualified and licensed personnel. The installer should be guided by
the instructions furnished with the boiler, and with local codes and utility company requirements. In the
absence of local codes, preference should be given to the National Fuel Gas Code, ANSI Z223.1-2002.
INSTALLATIONS MUST COMPLY WITH:
Local, state, provincial, and national codes, laws, regulations and ordinances.
This manual must only be used by a qualified heating installer/service technician. Read all instructions in
this manual before installing. Perform steps in the order given. Failure to comply could result in
substantial property damage, severe personal injury, or death.

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The latest version of the National Fuel Gas Code, ANSI Z223.1, from American Gas Association
Laboratories, 8501 East Pleasant Valley Road, Cleveland, OH 44131.
In Canada – CGA No. B149 (latest version), from Canadian Gas Association Laboratories, 55 Scarsdale
Road, Don Mills, Ontario, Canada M3B 2R3. Also, Canadian Electrical Code C 22.1, from Canadian
Standards Association, 5060 Spectrum Way, Suite 100, Mississauga, Ontario, Canada L4W 5N6.
Code for the Installation of Heat Producing Appliances (latest version), from American Insurance
Association, 85 John Street, New York, NY 11038.
The latest version of the National Electrical Code, NFPA No. 70.
NOTE: The gas manifold and controls met safe lighting and other performance criteria when the boiler
underwent tests specified in ANSI Z21.13 – latest edition.
TABLE OF CONTENTS
PART 1 – GENERAL SAFETY INFORMATION..........................................................................................7
A. PRECAUTIONS ....................................................................................................................................7
B. IMPROPER COMBUSTION..................................................................................................................8
C. GAS.......................................................................................................................................................8
D. WHEN SERVICING THE BOILER........................................................................................................8
E. BOILER OPERATION...........................................................................................................................8
F. BOILER WATER...................................................................................................................................8
G. FREEZE PROTECTION.......................................................................................................................8
PART 2 – BEFORE YOU START ................................................................................................................9
A. WHAT’S IN THE BOX...........................................................................................................................9
B. HOW BOILER OPERATES...................................................................................................................9
C. OPTIONAL EQUIPMENT ...................................................................................................................10
PART 3 – PREPARE BOILER LOCATION ...............................................................................................11
A. BEFORE LOCATING THE BOILER ...................................................................................................11
B. LEVELING AND DIMENSIONS..........................................................................................................12
C. CLEARANCES FOR SERVICE ACCESS..........................................................................................14
D. RESIDENTIAL GARAGE INSTALLATION.........................................................................................14
E. EXHAUST VENT AND INTAKE AIR VENT........................................................................................14
F. PREVENT COMBUSTION AIR CONTAMINATION ...........................................................................15
G. REMOVING A BOILER FROM A COMMON VENT SYSTEM...........................................................15
H. UNCRATING AND MOVING BOILER................................................................................................16
PART 4 – BOILER PIPING.........................................................................................................................17
A. GENERAL PIPING INFORMATION ...................................................................................................17
B. RELIEF VALVE...................................................................................................................................17

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C. BACKFLOW PREVENTER.................................................................................................................18
D. SYSTEM WATER PIPING METHODS...............................................................................................18
E. CIRCULATORS ..................................................................................................................................19
F. HYDRONIC PIPING WITH CIRCULATORS, ZONE VALVES, AND MULTIPLE BOILERS ..............19
G. BOILER PIPING DETAILS .................................................................................................................21
H. CIRCULATOR SIZING........................................................................................................................25
I. FILL AND PURGE HEATING SYSTEM...............................................................................................26
J. FREEZE PROTECTION FLUIDS........................................................................................................27
K. ZONING WITH ZONE VALVES..........................................................................................................27
L. ZONING WITH CIRCULATORS .........................................................................................................28
M. MULTIPLE BOILERS .........................................................................................................................28
PART 5 – VENTING, COMBUSTION AIR AND CONDENSATE REMOVAL...........................................28
A. INSTALLING EXHAUST VENT AND INTAKE AIR VENT..................................................................28
B. GENERAL...........................................................................................................................................29
C. APPROVED MATERIALS FOR EXHAUST VENT AND INTAKE AIR VENT.....................................29
D. REQUIREMENTS FOR INSTALLATION IN CANADA.......................................................................29
E. EXHAUST VENT AND INTAKE AIR VENT PIPE LOCATION ...........................................................32
F. EXHAUST VENT AND INTAKE AIR VENT SIZING ...........................................................................34
G. LONGER VENT RUNS.......................................................................................................................34
H. EXHAUST VENT AND INTAKE AIR PIPE INSTALLATION...............................................................35
I. BOILER REMOVAL FROM A COMMON VENT SYSTEM..................................................................35
J. SIDEWALL VENTING DIAGRAMS .....................................................................................................37
K. VERTICAL VENTING DIAGRAMS .....................................................................................................39
PART 6 – GAS PIPING ..............................................................................................................................41
A. GAS CONNECTION ...........................................................................................................................41
B. GAS PIPING .......................................................................................................................................41
C. GAS TABLE........................................................................................................................................42
D. CHECK INLET GAS PRESSURE.......................................................................................................42
E. GAS VALVE........................................................................................................................................44
PART 7 – FIELD WIRING...........................................................................................................................46
A. INSTALLATION MUST COMPLY WITH:............................................................................................46
B. FIELD WIRING....................................................................................................................................46
C. LINE VOLTAGE WIRING....................................................................................................................46
D. ALARM CONNECTIONS....................................................................................................................47
E. LOW VOLTAGE CONNECTIONS FOR STANDARD BOILER ..........................................................47

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F. THERMOSTAT....................................................................................................................................48
G. OUTDOOR SENSOR.........................................................................................................................49
H. INDIRECT SENSOR...........................................................................................................................49
I. OPTIONAL 0-10 VOLT BUILDING CONTROL SIGNAL......................................................................49
J. OPTIONAL HIGH GAS PRESSURE SWITCH....................................................................................49
K. OPTIONAL LOW GAS PRESSURE SWITCH....................................................................................50
L. OPTIONAL FLOW SWITCH................................................................................................................50
M. OPTIONAL UL353 LOW WATER CUTOFF INTERFACE KIT...........................................................50
N. WIRING OF THE CASCADE SYSTEM COMMUNICATION BUS.....................................................51
O. CASCADE MASTER PUMP AND SENSOR WIRING .......................................................................52
P. CASCADE FOLLOWER PUMP AND SENSOR WIRING...................................................................53
PART 8 – START-UP PREPARATION......................................................................................................56
A. CHECK / CONTROL WATER CHEMISTRY.......................................................................................56
B. FREEZE PROTECTION (WHEN USED)............................................................................................56
C. FILL AND TEST WATER SYSTEM....................................................................................................57
D. PURGE AIR FROM WATER SYSTEM...............................................................................................57
E. CHECK FOR GAS LEAKS..................................................................................................................58
F. CHECK THERMOSTAT CIRCUIT(S) .................................................................................................58
G. CONDENSATE REMOVAL................................................................................................................58
H. FINAL CHECKS BEFORE STARTING BOILER ................................................................................59
I. CASCADE SYSTEM ............................................................................................................................59
PART 9 – START-UP PROCEDURE.........................................................................................................60
A. OPERATING INSTRUCTIONS...........................................................................................................61
B. ADJUSTING THE SET POINT ...........................................................................................................61
C. STATUS MENU ..................................................................................................................................62
D. TEST MODE.......................................................................................................................................63
PART 10 – START-UP PROCEDURES FOR THE INSTALLER ..............................................................63
A. PROGRAMMING FOR THE INSTALLER...........................................................................................63
B. PROGRAM ACCESS..........................................................................................................................64
C. PROGRAM NAVIGATION..................................................................................................................64
PART 11 – TROUBLESHOOTING.............................................................................................................67
A. ERROR CODE....................................................................................................................................67
B. BOILER ERROR.................................................................................................................................67
C. BOILER FAULT ..................................................................................................................................67
PART 12 – MAINTENANCE.......................................................................................................................70

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A. MAINTENANCE PROCEDURES .......................................................................................................70
B. COMBUSTION CHAMBER COIL CLEANING INSTRUCTIONS FOR HEATER...............................71
BOILER START-UP REPORT ...................................................................................................................78
MAINTENANCE REPORT..........................................................................................................................79
MAINTENANCE NOTES ............................................................................................................................82
HTP CUSTOMER INSTALLATION RECORD FORM ........................................................................83
PART 1 – GENERAL SAFETY INFORMATION
A. PRECAUTIONS
This appliance is for indoor installations only. Clearance to combustible materials: 0” top, bottom, sides
and back. Front must have room for service, 24” recommended. (A combustible door or removable panel
is acceptable front clearance.) This appliance has been approved for closet installation. Do not install this
appliance directly on carpeting. This appliance may be installed on combustible flooring. For use with
Category IV vent systems only.
INSTALLER – Read all instructions in this manual before installing. Perform steps in the order given.
USER – This manual is for use only by a qualified heating installer/service technician. Refer to user’s
information manual for your reference. Have this boiler serviced/inspected by a qualified service
technician annually.
FAILURE TO ADHERE TO THE GUIDELINES ON THIS PAGE CAN RESULT IN SUBSTANTIAL
PROPERTY DAMAGE, SEVERE PERSONAL INJURY, OR DEATH.
DO NOT USE THIS APPLIANCE IF ANY PART HAS BEEN UNDERWATER. Immediately call a qualified
service technician. Replace any part of the control unit that has been under water.
NOTE: If the boiler is exposed to the following, do not operate until all corrective steps have been made
by a qualified serviceman:
•FIRE
•DAMAGE
•WATER
Any claims for damage or shortage in shipment must be filed immediately against the transportation
company by the consignee.
Due to low water content of the boiler, improperly sizing the boiler in regard to heating system load will
result in excessive boiler cycling and accelerated component failure. HTP DOES NOT warrant failures
caused by improperly sized boiler applications. DO NOT oversize the boiler to the system. Modular boiler
installations greatly reduce the likelihood of boiler oversizing.

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B. IMPROPER COMBUSTION
C. GAS
Should overheating occur or gas supply fail to shut off, do not turn off or disconnect electrical supply to
the circulator. Instead, shut off the gas supply at a location external to the appliance.
D. WHEN SERVICING THE BOILER
•To avoid electric shock, disconnect electrical supply before performing maintenance.
•To avoid severe burns, allow boiler to cool before servicing.
E. BOILER OPERATION
•Do not block flow of combustion or ventilation air to boiler.
•Should overheating occur or gas supply fail to shut off, do not turn off or disconnect electrical
supply to circulator. Instead, shut off the gas supply at a location external to the appliance.
•Do not use this boiler if any part has been under water. Immediately call a qualified service
technician to inspect the boiler and replace any part of the control system and any gas control
that has been under water.
F. BOILER WATER
•Do not use petroleum-based cleaning or sealing compounds in a boiler system. These products
may damage gaskets and seals in the system. This can result in substantial property damage.
•Do not use “homemade cures” or “boiler patent medicines”. Substantial property damage,
damage to boiler, and/or serious personal injury may result.
•Continual fresh make-up water will reduce boiler life. Mineral buildup reduces heat transfer,
overheats the stainless steel heat exchanger, and causes failure. Addition of oxygen by make-up
water can cause internal corrosion in system components. Leaks in the boiler or piping must be
repaired at once.
•If you have an old system with cast iron radiators, thoroughly flush the system (without boiler
connected) to remove sediment. The high-efficiency heat exchanger can be damaged by build-up
or corrosion due to sediment.
G. FREEZE PROTECTION
NEVER use any toxic chemical, including automotive, standard glycol antifreeze, or ethylene glycol made
for hydronic (non-potable) systems. These chemicals can attack gaskets and seals in water boilers, are
poisonous if consumed, and can cause injury or death.
Do not obstruct the flow of combustion and ventilating air. Adequate air must be provided for safe
operation.
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 neighbor’s phone. Follow gas supplier’s instructions.
•If you cannot reach your gas supplier, call the fire department. Installation and service must be
provided by a qualified installer, service agency, or the gas supplier.

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Consider piping and installation when determining boiler location.
PART 2 – BEFORE YOU START
A. WHAT’S IN THE BOX
Also included with the boiler:
•Pressure and Temperature Gauge
•Outdoor Sensor
•Intake PVC Tee with Screens
•Exhaust PVC Coupling with Screens
•Installation Manual
•Warranty
•CSD-1 Form
•H-3 Data Sheet
B. HOW BOILER OPERATES
Mod Con condensing technology intelligently delivers highly efficient hydronic heating while maximizing
efficiency by measuring data from the heating system. Outlined below are the features of the system and
how they operate:
Stainless Steel Heat Exchanger - The highly efficient stainless steel heat exchanger is designed to use
the cold return water from the system and extract the last bit of heat before it is exhausted.
Modulating Combustion System - The combustion system will modulate the output of the burner during
operation to match the system demand and achieve the control set point while in operation. The set point
can change by internal or external signals which enhance the overall performance of the system.
Control – The integrated control system monitors the system and regulates fan speed to control boiler
output. This allows the boiler to deliver only the amount of heat energy required and nothing more. The
system can be further enhanced by installing with an indirect water heater to provide domestic hot water.
The control can regulate the output of multiple boilers through its cascade system function. The cascade
system is capable of connecting up to eight boilers together in such a way that they function as one boiler
system. This allows for greater turn down ratios and provides systematic control of the multiple boilers in
an installation to minimize downtime and maximize efficiency.
The cascade system works by establishing one boiler as the master and the other connected boilers as
followers. The master boiler requires a cascade system sensor and a cascade pump in addition to its own
boiler pump. Each of the follower boilers has an individual pump.
System Display and Operational LED Light Indicators – The display allows the user to change the
system parameters and monitor system outputs.
Gas Valve – Senses suction from the blower, allowing gas to flow only if powered and combustion air is
flowing.
All Metal Integrated Venturi – Controls air and gas flow into the burner.

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Burner – Constructed of high grade stainless steel, the burner uses premixed air and gas fuel to provide
a wide range of firing rates.
Spark Ignition – The burner is ignited by applying high voltage through the system spark electrode. This
causes the spark from the electrode to ignite mixed gas from the burner.
Supply Water Temperature Sensor – This sensor monitors the boiler outlet water temperature (System
Supply). The control adjusts the boiler firing rate so the supply temperature will match the boiler set point.
Return Water Temperature Sensor – This sensor monitors the boiler return water temperature (System
Return).
Temperature and Pressure Gauge – Allows the user to monitor system temperature and pressure.
Electrical field connections with terminal strips – The electrical cover allows easy access to the line
voltage and low voltage terminals strips which are clearly marked to facilitate wiring of the boiler.
Condensation Collection System – This boiler is a high efficiency appliance, therefore the boiler will
produce condensate. The collection system has a float switch which monitors the condensation level and
prevents condensation from backing up into the combustion system. Inside the collection system there is
a built in trap which seals the combustion system from the connected drain. This condensate should be
neutralized to avoid damage to the drainage system or piping.
Flow Protection – The optional flow switch is designed to protect the boiler in the event of low flow
conditions. The boiler control will also monitor flow through the heat exchanger by monitoring the return
and supply sensors and will shut down the burner before overheating occurs.
Outdoor Sensor – This sensor monitors outdoor temperature. Data from this sensor is monitored by the
control, which adjusts the unit set point to provide greater efficiency.
Indirect Tank Sensor (optional) – Monitors storage tank temperature.
C. OPTIONAL EQUIPMENT
Below is a list of optional equipment available from HTP. These additional options may be purchased
through your HTP distributor.
•System Sensor (Part # 7250P-324)
•Indirect Tank Sensor (Part # 7250P-325)
•4” Stainless Steel Outside Termination Vent Kit (V2000)
•6” Stainless Steel Outside Termination Vent Kit (V3000)
•High and Low Gas Pressure Switch Kit with Manual Reset (Part # 7350P-600)
•U.L. 353 Compliant Low Water Cut-Off Interface Kit with Manual Reset (Part # 7450P-225)
•Alarm System (Part # 7350P-602) (to monitor any failure)
•Stacking Kit (Part # 7350P-603)
•PC Connection Kit (Part # 7250P-320)
•Condensate Neutralizer (Part # 7350P-611)
•Caster Kit (Part # 7350P-604)
•Flow Switch Kit (Part # 7350P-606 for Mod Con 300, Part # 7350P-605 for Mod Con 500/850)

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PART 3 – PREPARE BOILER LOCATION
Before considering location, there are many factors to be addressed. Piping, Venting, and Condensation
Removal are just a few of the important issues covered in detail in this manual. Please read the entire
manual before attempting installation. Doing so could save time and money.
Consider piping and installation when determining boiler location.
A. BEFORE LOCATING THE BOILER
1. Check for nearby connections to:
•System water piping
•Venting connections
•Gas supply piping
•Electrical power
•Condensate drain
2. Check area around boiler. Remove any combustible materials, gasoline, and other flammable liquids.
Failure to keep boiler area clear and free of combustible materials, liquids, and vapors can result in
substantial property damage, severe personal injury, or death.
3. Gas control system components must be protected from dripping water during operation and service.
4. If the boiler is to replace an existing boiler, check for and correct any existing system problems, such
as:
•System leaks
•Location that could cause the system and boiler to freeze and leak.
•Lack of freeze protection in boiler water which will cause system and boiler to freeze and leak.
•Excessive glycol which will affect boiler system operation.
5. Clean and flush system when reinstalling a boiler.

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B. LEVELING AND DIMENSIONS
Figure 1
In order for the condensate to properly flow out of the collection system, the area where you locate the
boiler must be level. The boiler comes equipped with leveling feet. Should you find the floor beneath the
boiler is uneven, adjust the leveling feet with a wrench.

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Figure 2

14
C. CLEARANCES FOR SERVICE ACCESS
See Figure 3 for recommended service
clearances. If you do not provide the
minimum clearances shown, it might not be
possible to service the boiler without
removing it from the space.
Space must be provided with combustion/ventilation air openings correctly sized for all appliances located
in the same space as the boiler. The boiler venting cover must be securely fastened to prevent it from
drawing air from the boiler room. This is particularly important if the boiler is in a room with other
appliances. Failure to comply with the above warnings could result in substantial property damage,
severe personal injury, or death.
D. RESIDENTIAL GARAGE INSTALLATION
PRECAUTIONS
If the boiler is located in a residential garage, per ANSI Z223.1:
•Mount the bottom of the boiler a minimum of 18” above the floor of the garage, to ensure the
burner and ignition devices are well off the floor.
•Locate or protect the boiler so it cannot be damaged by a moving vehicle.
E. EXHAUST VENT AND INTAKE AIR VENT
Vents must be properly supported. The boiler intake and exhaust connections are not designed to carry
heavy weight. Vent support brackets must be within 1’ of the boiler and the balance at 4’ intervals.
Venting must be readily accessible for visual inspection for the first 3’ from the boiler.
The boiler is rated ANSI Z21.13 Category IV (pressurized vent, likely to form condensate in the vent), and
requires a special vent system designed for pressurized venting.
Figure 3

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You must also install air intake piping from outdoors to the boiler flue adaptor. The resultant installation is
categorized as direct vent (sealed combustion). NOTE: To prevent combustion air contamination, see
Table 1in this section when considering exhaust vent and intake air vent termination.
Intake and exhaust vents must terminate near each other and may be vented vertically through the roof or
out a side wall. Intake and exhaust venting methods are detailed in the Venting Section. Do not attempt
installation using any other means. Be sure to locate the boiler so intake and exhaust vent piping can be
routed through the building and properly terminated. The air intake and exhaust vent piping lengths,
routing and termination method must all comply with methods and limits given in the venting section.
F. PREVENT COMBUSTION AIR CONTAMINATION
Install intake piping for the boiler as described in the Venting section. Do not terminate exhaust in
locations that can allow contamination of intake air.
You must pipe outside air to the boiler intake. Ensure that the intake air will not contain any of the
contaminants below. For example, do not pipe intake vent near a swimming pool. Avoid areas subject to
exhaust fumes from laundry facilities. These areas always contain contaminants. Contaminated air will
damage the boiler, resulting in possible substantial property damage, severe personal injury, or death.
PRODUCTS TO AVOID
AREAS LIKELY TO HAVE CONTAMINANTS
Spray cans containing fluorocarbons
Dry cleaning/laundry areas and establishments
Permanent wave solutions
Swimming pools
Chlorinated waxes/cleaners
Metal fabrication plants
Chlorine-based swimming pool chemicals
Beauty shops
Calcium chloride used for thawing
Refrigeration repair shops
Sodium chloride used for water softening
Photo processing plants
Refrigerant leaks
Auto body shops
Paint or varnish removers
Plastic manufacturing plants
Hydrochloric or Muriatic acid
Furniture refinishing areas and establishments
Cements and glues
New building construction
Antistatic fabric softeners used in clothes dryers
Remodeling areas
Chlorine-type bleaches, laundry detergents, and
cleaning solvents
Garages and workshops
Adhesives used to fasten building products
Table 1 – Contaminants
NOTE: DAMAGE TO THE BOILER CAUSED BY EXPOSURE TO CORROSIVE VAPORS IS NOT
COVERED BY WARRANTY.
(Refer to the limited warranty for complete terms and conditions).
G. REMOVING A BOILER FROM A COMMON VENT SYSTEM
Do not install the boiler into a common vent with any other appliance. This will cause flue gas spillage or
appliance malfunction, resulting in possible substantial property damage, severe personal injury, or death.
Failure to follow all instructions can result in flue gas spillage and carbon monoxide emissions, causing
severe personal injury or death.

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When removing an existing boiler, the following
steps must be followed.
1. Seal any unused openings in the common venting
system.
2. Visually inspect the venting system for proper size
and horizontal pitch to determine if there is
blockage, leakage, corrosion or other deficiencies
that could cause an unsafe condition.
3. If practical, close all building doors, windows and
all doors between the common venting system and
other spaces in the building. Turn on clothes dryers
and any appliances not connected to the common
venting system. Turn on any exhaust fans, such as
range hoods and bathroom exhausts, at maximum
speed. Do not operate a summer exhaust fan. Close
all fireplace dampers.
4. Place in operation the appliance being inspected.
Follow the lighting instructions. Adjust the thermostat so the appliance will operate continuously.
5. Test for spillage at the draft hood relief opening after 5 minutes of main burner operation. Use the
flame of a match or candle or smoke from a cigarette.
6. After it has been determined that each appliance remaining connected to common venting system
properly vents when tested as outlined, return doors, windows, exhaust fans, fireplace dampers and any
other gas burning appliance to their previous condition of use.
7. Any improper operation of the common venting system should be corrected so the installation
conforms to 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 Z 223.1.
H. UNCRATING AND MOVING BOILER
Uncrating Boiler – Any claims for damage in shipment must be filed immediately against the
transportation company by the consignee.
Cold Weather Handling – If boiler has been stored in a very cold location (below 0oF) before installation,
handle with care until the plastic components come to room temperature.
Figure 4 - CO Warning Label
Figure 5 - CO Warning Label

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Remove all sides of the
shipping crate in order to
allow the boiler to be lifted
into its installation location.
Pick the boiler up by the lift
rings to avoid damage to
the boiler enclosure. Use
either a solid ¾” diameter
black iron pipe or lifting
straps to lift the boiler off of
its shipping crate. The
boiler is very heavy. At least
two individuals are needed
to handle the boiler
properly. If the location is
not level, adjust the boiler’s
leveling feet to ensure a
level boiler and proper flow
of condensate. If surface
flooring is rough, care should be taken not to catch the leveling feet and damage the boiler when sliding it
into position.
PART 4 – BOILER PIPING
Never use dielectric unions or galvanized steel fittings when connecting to a stainless steel storage tank
or boiler. Failure to follow this instruction can lead to premature failure of the boiler system. Such failures
ARE NOT covered by warranty.
Plumbing of this product should only be done by a qualified, licensed plumber in accordance with all local
plumbing codes.
A. GENERAL PIPING INFORMATION
The building piping system must meet or exceed the piping requirements in this manual.
The control module uses temperature sensors to provide both high limit protection and modulating
temperature control. The control module also provides low water protection by sensing the water level in
the heat exchanger. Some codes/jurisdictions may require additional external controls.
B. RELIEF VALVE
Connect discharge piping to a safe disposal location following the guidelines on the following page.
Figure 6

18
To avoid water damage or scalding due to relief valve operation:
•Discharge line must be connected to relief valve outlet and run to a safe place of disposal.
•Terminate the discharge line in a manner that will prevent possibility of severe burns or property
damage should the relief valve discharge.
•Discharge line must be as short as possible and the same size as the valve discharge connection
throughout its entire length.
•Discharge line must pitch downward from the valve and terminate at least 6” above the floor
drain, making discharge clearly visible.
•Discharge line shall terminate plain, not threaded, with a material serviceable for temperatures of
375oF or greater.
•Do not pipe discharge to any location where freezing could occur.
•No shutoff valve may be installed between the relief valve and boiler or in the discharge line. Do
not plug or place any obstruction in the discharge line.
•Test the operation of the relief valve after filling and pressurizing the system by lifting the lever.
Make sure the valve discharges freely. If the valve fails to operate correctly, replace it with a new
relief valve.
•Test relief valve at least once annually to ensure the waterway is clear. If valve does not operate,
turn the boiler “off” and call a plumber immediately.
•Take care whenever operating relief valve to avoid scalding injury or property damage.
•For boilers installed with only a pressure relief valve, the separate storage vessel must have a
temperature and pressure relief valve installed. This relief valve shall comply with Relief Valves
for Hot Water Supply Systems, ANSI Z21.22 CSA4.4
•
FAILURE TO COMPLY WITH THE ABOVE GUIDELINES COULD RESULT IN FAILURE OF RELIEF
VALVE OPERATION, RESULTING IN POSSIBILITY OF SUBSTANTIAL PROPERTY DAMAGE,
SEVERE PERSONAL INJURY, OR DEATH.
C. BACKFLOW PREVENTER
Use a backflow preventer specifically designed for hydronic boiler installations. This valve should be
installed on the cold water fill supply line per local codes (see Boiler Piping Details, Part 4, Section G).
All piping methods shown in this manual use primary/secondary connection to the boiler loop. This is to
avoid the possibility of inadequate flow through the boiler. For other piping methods, consult your local
HTP representative, or refer to Boiler Piping Details in this manual, Part 4, Section G.
D. SYSTEM WATER PIPING METHODS
EXPANSION TANK AND MAKE-UP WATER
1. Ensure that the expansion tank is sized to correctly handle boiler and system water volume and
temperature.
BOILER WATER VOLUME
300
2.9 Gallons
500
4.2 Gallons
850
5.8 Gallons
Table 2

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Undersized expansion tanks cause system water to be lost from the relief valve, causing make-up water
to be added. Eventual boiler failure can result due to excessive make-up water addition. SUCH FAILURE
IS NOT COVERED BY WARRANTY.
2. The expansion tank must be located as shown in Part 4, Boiler Piping Details, or following recognized
design methods. See expansion tank manufacturer’s instructions for details. Always install an expansion
tank designed for potable water systems.
3. Connect the expansion tank to the air separator only if the separator is on the suction side of the
circulator. Always install the system fill connection at the same point as the expansion tank connection to
the system.
4. Most chilled water systems are piped using a closed type expansion tank.
DIAPHRAGM (OR BLADDER) EXPANSION TANK
Always install an automatic air vent on top of the air separator to remove residual air from the system.
E. CIRCULATORS
DO NOT install automatic air vents on closed type expansion tank systems. Air must remain in the system
and return to the tank to provide an air cushion. An automatic air vent would cause air to leave the
system, resulting in improper operation of the expansion tank.
DO NOT use the boiler circulator in any location other than the ones shown in this manual. The boiler
circulator location is selected to ensure adequate flow through the boiler. Failure to comply with this
caution could result in unreliable performance and nuisance shutdowns from insufficient flow.
SIZING SPACE HEAT SYSTEM PIPING
1. In all diagrams, the space heating system is isolated from the boiler loop by the primary/secondary
connection.
2. Size the piping and components in the space heating system using recognized design methods.
F. HYDRONIC PIPING WITH CIRCULATORS, ZONE VALVES, AND MULTIPLE BOILERS
The boiler is designed to function in a closed loop hydronic system. The included temperature and
pressure gauge allows the user to monitor system pressure and outlet temperature from the boiler. It is
important to note that the boiler has a minimal amount of pressure drop that must be calculated when
sizing the circulators. Each boiler installation must have an air elimination device that will remove air from
the system.
Install the boiler so the gas ignition system components are protected from water (dripping, spraying,
etc.). Allow clearance for basic service of the boiler circulator, valves, and other components. Observe
minimum 1” clearance around all uninsulated hot water pipes when openings around pipes are not
protected by non-combustible materials.
On a boiler installed above radiation level, some states and local codes require a low water cut off device.
This is provided standard on the Mod Con boiler. Check with local codes for additional requirements. If

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the boiler supplies hot water to heating coils in air handler units, flow control valves or other devices must
be installed to prevent gravity circulation of boiler water in the coils during the cooling cycle. Chilled water
medium must be piped in parallel with the boiler.
Freeze protection for new or existing systems must use glycol specifically formulated for this purpose.
This glycol must include inhibitors that will prevent it from attacking metallic system components. Make
certain that the system fluid is checked for the correct glycol concentration and inhibitor level. The system
should be tested at least once a year and as recommended by the producer of the glycol solution.
Allowance should be made for the expansion of the glycol solution in the system piping. Example: 50% by
volume glycol solution expands 4.8% in volume for the temperature increase from 32oF to 180oF, while
water expands 3% over the same temperature rise.
Never use dielectric unions or galvanized steel fittings when connecting to a stainless steel storage tank
or boiler. Failure to follow this instruction can lead to premature failure of the boiler system. Such failures
ARE NOT covered by warranty.