HTP Mod Con Installation manual

120 Braley Rd. P.O. Box 429 East Freetown, MA 02717-0429 www.htproducts.com
LP- 205 REV. 9.2.14
Mod Con
INSTALLATION
START-UP
MAINTENANCE
PARTS
Models
300 / 500 / 850
LP / HL / LPHL
Heat Exchanger Bears the ASME “H” Stamp
NOTICE: HTP reserves the right to make product changes or updates without notice and will not be held liable for typographical errors
in literature.
NOTE TO CONSUMER: PLEASE KEEP ALL INSTRUCTIONS FOR FUTURE REFERENCE.
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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LP- 205 REV. 9.2.14
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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LP- 205 REV. 9.2.14
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 Authority Having Jurisdiction, local code authorities, and utility
companies which pertain to this type of water heating equipment.
Authority Having Jurisdiction (AHJ) –The Authority Having Jurisdiction may be a federal, state, local government, or individual such
as a fire chief, fire marshal, chief of a fire prevention bureau, labor department or health department, building official or electrical
inspector, or others having statutory authority. In some circumstances, the property owner or his/her agent assumes the role, and at
government installations, the commanding officer or departmental official may be the AHJ.
NOTE: HTP, Inc. reserves the right to modify product technical specifications and components without prior notice.
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:
Authority Having Jurisdiction, local, state, provincial, and national codes, laws, regulations and ordinances.
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.
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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LP- 205 REV. 9.2.14
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.
The hydronic supply and return connections of these products are for installation in closed loop systems ONLY! Use of this
product in any manner other than described in this manual may result in premature product failure, substantial property damage, severe
personal injury, or death. Damage or failure of this product (or the system in which it is installed) due to unauthorized use IS NOT
COVERED BY WARRANTY.
NOTICE
The CSD-1 ASME Code, Section CW-400 requires that hot water heating and supply boilers have a) a UL 353 temperature control
device, b) at least one (1) temperature-actuated control to shut off the fuel supply when system water reaches a preset operating
temperature, c) a high temperature limit control that prevents the water temperature from exceeding the maximum allowable
temperature by causing a safety shutdown and lockout, and d) its own sensing element and operating switch.
The temperature control system integrated into the 926 control provided with this heating appliance complies with the requirements of
CSD-1 Section CW-400 as a temperature operation control. The control monitors the temperature difference between the inlet and the
outlet sensor, which is affected by boiler water flow. If this temperature difference exceeds 55°F (typically because of low water flow or
very low heat load), the control will reduce the maximum fan speed. If the temperature difference exceeds 60°F, the control will
effectively sense there is little or no water flow or heat load and shut the boiler down. The controller will restart automatically once the
temperature difference has dropped below 55°F and the minimum off time (anti-cycle time) has expired. In addition, if the control
senses that the outlet water temperature has reached 210°F, the boiler is put into a hard lockout and requires manual reset to restart.
TABLE OF CONTENTS
PART 1 –GENERAL SAFETY INFORMATION..........................................................................................................................7
A. PRECAUTIONS..........................................................................................................................................................................7
B. GAS ............................................................................................................................................................................................7
C. IMPROPER COMBUSTION .......................................................................................................................................................7
D. WHEN SERVICING THE BOILER..............................................................................................................................................7
E. BOILER OPERATION.................................................................................................................................................................7
F. BOILER WATER.........................................................................................................................................................................8
G. FREEZE PROTECTION.............................................................................................................................................................8
PART 2 –BEFORE YOU START................................................................................................................................................8
A. WHAT’S IN THE BOX .................................................................................................................................................................8
B. HOW BOILER OPERATES.........................................................................................................................................................8
C. OPTIONAL EQUIPMENT ...........................................................................................................................................................9
PART 3 –PREPARE BOILER LOCATION .................................................................................................................................9
A. BEFORE LOCATING THE BOILER............................................................................................................................................9
B. LEVELING AND DIMENSIONS ................................................................................................................................................10
C. CLEARANCES FOR SERVICE ACCESS.................................................................................................................................12
D. RESIDENTIAL GARAGE INSTALLATION................................................................................................................................12
E. EXHAUST VENT AND INTAKE AIR VENT...............................................................................................................................12
F. PREVENT COMBUSTION AIR CONTAMINATION..................................................................................................................12
G. REMOVING A BOILER FROM A COMMON VENT SYSTEM..................................................................................................13
H. UNCRATING AND MOVING BOILER ......................................................................................................................................14

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LP- 205 REV. 9.2.14
PART 4 –BOILER PIPING........................................................................................................................................................14
A. GENERAL PIPING INFORMATION..........................................................................................................................................14
B. RELIEF VALVE.........................................................................................................................................................................15
C. BACKFLOW PREVENTER.......................................................................................................................................................15
D. SYSTEM WATER PIPING METHODS.....................................................................................................................................15
E. CIRCULATORS ........................................................................................................................................................................16
F. HYDRONIC PIPING WITH CIRCULATORS, ZONE VALVES, AND MULTIPLE BOILERS......................................................16
G. CIRCULATOR SIZING .............................................................................................................................................................17
H. FILL AND PURGE HEATING SYSTEM....................................................................................................................................18
I. FREEZE PROTECTION FLUIDS...............................................................................................................................................19
J. ZONING WITH ZONE VALVES.................................................................................................................................................19
K. ZONING WITH CIRCULATORS ...............................................................................................................................................19
L. MULTIPLE BOILERS ................................................................................................................................................................19
M. BOILER PIPING DETAILS .......................................................................................................................................................20
PART 5 –VENTING, COMBUSTION AIR AND CONDENSATE REMOVAL............................................................................23
A. GENERAL.................................................................................................................................................................................24
B. APPROVED MATERIALS FOR EXHAUST AND INTAKE AIR VENTS....................................................................................24
C. REQUIREMENTS FOR INSTALLATION IN CANADA..............................................................................................................25
D. EXHAUST VENT AND INTAKE AIR VENT PIPE LOCATION..................................................................................................26
E. EXHAUST VENT AND INTAKE AIR VENT SIZING..................................................................................................................29
F. LONGER VENT RUNS .............................................................................................................................................................29
G. EXHAUST VENT AND INTAKE AIR PIPE INSTALLATION.....................................................................................................29
H. BOILER REMOVAL FROM A COMMON VENT SYSTEM .......................................................................................................30
I. SIDEWALL VENTING DIAGRAMS ............................................................................................................................................31
J. VERTICAL VENTING DIAGRAMS............................................................................................................................................33
PART 6 –GAS PIPING..............................................................................................................................................................35
A. GAS CONNECTION .................................................................................................................................................................35
B. GAS PIPING .............................................................................................................................................................................35
C. GAS TABLE..............................................................................................................................................................................36
D. CHECK INLET GAS PRESSURE.............................................................................................................................................36
E. GAS VALVE..............................................................................................................................................................................37
PART 7 –FIELD WIRING..........................................................................................................................................................39
A. INSTALLATION MUST COMPLY WITH:..................................................................................................................................39
B. FIELD WIRING..........................................................................................................................................................................39
C. LINE VOLTAGE WIRING..........................................................................................................................................................39
D. ALARM CONNECTIONS..........................................................................................................................................................40
E. LOW VOLTAGE CONNECTIONS FOR STANDARD BOILER .................................................................................................40
F. THERMOSTAT..........................................................................................................................................................................40
G. OUTDOOR SENSOR...............................................................................................................................................................40
H. INDIRECT SENSOR.................................................................................................................................................................40
I. OPTIONAL 0-10 VOLT BUILDING CONTROL SIGNAL ............................................................................................................41

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LP- 205 REV. 9.2.14
J. OPTIONAL HIGH GAS PRESSURE SWITCH ..........................................................................................................................41
K. OPTIONAL LOW GAS PRESSURE SWITCH ..........................................................................................................................41
L. OPTIONAL FLOW SWITCH......................................................................................................................................................41
M. OPTIONAL UL353 LOW WATER CUT-OFF INTERFACE KIT ................................................................................................42
N. WIRING OF THE CASCADE SYSTEM COMMUNICATION BUS............................................................................................42
O. CASCADE MASTER PUMP AND SENSOR WIRING..............................................................................................................43
P. CASCADE FOLLOWER PUMP AND SENSOR WIRING .........................................................................................................44
PART 8 –START-UP PREPARATION......................................................................................................................................47
A. CHECK / CONTROL WATER CHEMISTRY.............................................................................................................................47
B. FREEZE PROTECTION (WHEN USED) ..................................................................................................................................48
C. FILL AND TEST WATER SYSTEM ..........................................................................................................................................48
D. PURGE AIR FROM WATER SYSTEM.....................................................................................................................................48
E. CHECK FOR GAS LEAKS........................................................................................................................................................49
F. CHECK THERMOSTAT CIRCUIT(S)........................................................................................................................................49
G. CONDENSATE REMOVAL ......................................................................................................................................................49
H. FINAL CHECKS BEFORE STARTING BOILER.......................................................................................................................49
I. CASCADE SYSTEM ..................................................................................................................................................................50
PART 9 –START-UP PROCEDURE.........................................................................................................................................51
A. OPERATING INSTRUCTIONS.................................................................................................................................................51
B. ADJUSTING THE SET POINT..................................................................................................................................................51
C. STATUS MENU........................................................................................................................................................................52
D. TEST MODE.............................................................................................................................................................................53
PART 10 –START-UP PROCEDURES FOR THE INSTALLER...............................................................................................53
A. PROGRAMMING FOR THE INSTALLER.................................................................................................................................53
B. PROGRAM ACCESS................................................................................................................................................................53
C. PROGRAM NAVIGATION ........................................................................................................................................................53
PART 11 –TROUBLESHOOTING ............................................................................................................................................56
A. ERROR CODE..........................................................................................................................................................................56
B. BOILER ERROR.......................................................................................................................................................................56
C. BOILER FAULT ........................................................................................................................................................................56
PART 12 –MAINTENANCE ......................................................................................................................................................59
A. MAINTENANCE PROCEDURES..............................................................................................................................................59
B. COMBUSTION CHAMBER COIL CLEANING INSTRUCTIONS FOR HEATER ......................................................................60
BOILER START-UP REPORT...................................................................................................................................................67
MAINTENANCE REPORT.........................................................................................................................................................67
MAINTENANCE NOTES..................................................................................................................................................................71
HTP CUSTOMER INSTALLATION RECORD FORM......................................................................................................................72

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LP- 205 REV. 9.2.14
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 AND HAVE THIS BOILER SERVICED/INSPECTED ANNUALLY
CAN RESULT IN SUBSTANTIAL PROPERTY DAMAGE, SEVERE PERSONAL INJURY, OR DEATH.
DO NOT USE THIS APPLIANCE IF ANY PART HAS BEEN SUBMERGED IN WATER. Immediately call a qualified service technician.
The appliance MUST BE replaced if it has been submerged. Attempting to operate an appliance that has been submerged could create
numerous harmful conditions, such as a potential gas leakage causing a fire and/or explosion, or the release of mold, bacteria, or other
harmful particulates into the air. Operating a previously submerged appliance could result in property damage, severe personal injury,
or death.
NOTE: Appliance damage due to flood or submersion is considered an Act of God, and IS NOT covered under product warranty.
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.
B. 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.
C. IMPROPER COMBUSTION
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.
Do not obstruct the flow of combustion and ventilating air. Adequate air must be provided for safe operation. Failure to keep the vent
and combustion air intake clear of ice, snow, or other debris could result in property damage, serious personal injury, or death.

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LP- 205 REV. 9.2.14
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.
Consider piping and installation when determining boiler location.
NOTE: Damages resulting from incorrect installation or from use of products not approved by HTP, Inc. ARE NOT covered by warranty.
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.

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LP- 205 REV. 9.2.14
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.
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 # 7350P-601)
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)
PART 3 –PREPARE BOILER LOCATION
Carefully consider installation when determining boiler location. Please read the entire manual before attempting installation. Failure to
properly take factors such as boiler venting, piping, condensate removal, and wiring into account before installation could result in
wasted time, money, and possible property damage and personal injury.
A. BEFORE LOCATING THE BOILER
Incorrect ambient conditions can lead to damage to the heating system and put safe operation at risk. Ensure that the boiler installation
location adheres to the information included in this manual. Failure to do so could result in property damage, serious personal injury, or
death.

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LP- 205 REV. 9.2.14
Failure of boiler or components due to incorrect operating conditions IS NOT covered by product warranty.
1. Installation Area (Mechanical Room) Operating Conditions
Ensure ambient temperatures are higher than 32oF/0oC and lower than 104oF/40oC.
Prevent the air from becoming contaminated by the products, places, and conditions listed in this manual, Part 3, Section F.
Avoid continuously high levels of humidity
Never close existing ventilation openings
The service life of the boiler’s exposed metallic surfaces, such as the casing, as well as internal surfaces, such as the heat exchanger,
are directly influenced by proximity to damp and salty marine environments. In such areas, higher concentration levels of chlorides from
sea spray coupled with relative humidity can lead to degradation of the heat exchanger and other boiler components. In these
environments, boilers must not be installed using direct vent systems which draw outdoor air for combustion. Such boilers must be
installed using room air for combustion. Indoor air will have a much lower relative humidity and, hence, potential corrosion will be
minimized.
This boiler is certified for indoor installations only. Do not install the boiler outdoors. Failure to install this boiler indoors could result in
substantial property damage, severe personal injury, or death.
2. Check for nearby connections to:
System water piping
Venting connections
Gas supply piping
Electrical power
Condensate drain
3. 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.
4. Gas control system components must be protected from
dripping water during operation and service.
5. 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.
Incorrectly-sized expansion tank
6. Clean and flush system when reinstalling a boiler.
NOTE: When installing in a zero clearance location, it may not
be possible to read or view some product labeling. It is
recommended to make note of the boiler model and serial
number.
B. LEVELING AND DIMENSIONS
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.
Figure 1 –Leveling

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LP- 205 REV. 9.2.14
Figure 2 –Specifications and Dimensions

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LP- 205 REV. 9.2.14
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.
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.
Check with your local Authority Having Jurisdiction for requirements when installing boiler in a garage. Please read the entire manual
before attempting installation. Failure to properly take factors such as boiler venting, piping, condensate removal, and wiring into
account before installation could result in wasted time, money, and possible property damage and personal injury.
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.
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 1 in 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.
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.
Figure 3

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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 boiler.
This will cause flue gas spillage or boiler 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.
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.
Figure 4 –CO Warning Label

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LP- 205 REV. 9.2.14
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.
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
Failure to follow the instructions in this section WILL VOID the warranty and may result in property damage, serious injury, or death.
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. The boiler
may be connected to a storage tank to supply domestic hot water. HTP offers 60/80/119/175 gallon size storage tanks in either
stainless steel or glass-lined construction. These storage tanks can be directly connected to the boiler supply and return connection.
A. GENERAL PIPING INFORMATION
The building piping system must meet or exceed the piping requirements in this manual.
Use two wrenches when tightening water piping at the appliance. Use one wrench to prevent the appliance return or supply line from
turning. Failure to prevent piping connections from turning could cause damage to appliance components.
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.
Figure 5 –Lifting Detail

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LP- 205 REV. 9.2.14
B. RELIEF VALVE
Connect discharge piping to a safe disposal location following the guidelines on the following page.
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
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.

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LP- 205 REV. 9.2.14
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 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.
The boiler should not be operated as a potable hot water heater. The boiler should not be used as a direct hot water heating device.
Basic steps are listed below that will guide the installation of the boiler.
1. Connect the system return marked “Boiler Return”.
2. Connect the system supply marked “Boiler Supply”.
3. Install purge and balance valve or shut off valve and drain on system return to purge air out of each zone.

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LP- 205 REV. 9.2.14
4. Install a back flow preventer on the cold feed make-up water line.
5. Install a pressure reducing valve on the cold feed make-up water line (15 PSI nominal on the system return). Check temperature and
pressure gauge when operating. It should read a minimum pressure of 12 PSI.
6. Install a circulator as shown in piping details (this section). Make sure the circulator is properly sized for the system and friction loss.
7. Install an expansion tank on the system supply. Consult the tank manufacturer’s instructions for specific information relating to
expansion tank installation. Size the expansion tank for the required system volume and capacity.
8. Install an air elimination device on the system supply.
9. Install a drain valve at the lowest point of the system. NOTE: The boiler cannot be drained completely of water without purging the
unit with an air pressure of 15 PSI.
10. The relief valve is installed at the factory. A pipe discharge line should be installed to discharge 6” above the drain in the event of
pressure relief. The pipe size must be the same size as the relief valve outlet. NEVER BLOCK THE OUTLET OF THE SAFETY
RELIEF VALVE.
G. CIRCULATOR SIZING
The boiler heat exchanger does have a pressure drop which must be considered in system design. Refer to the graph in Figure 6 for
pressure drop through the boiler heat exchanger.
Figure 6 –Heat Exchanger Pressure Drop Chart
The chart below represents the various system design temperature rise through the boiler, along with respective flows and friction loss
which will aid in circulator selection.
Table 3 –Temperature Rise Chart

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LP- 205 REV. 9.2.14
The chart below represents the combined flow rates and pipe sizes when using multiple boilers to design the manifold system for the
primary circuit. To size, simply add up the number of boilers and the required flow rates for the system design temperature.
Example: (5) Mod Con 300 boilers with a design of 30oF temperature rise with each boiler having an individual flow rate of 20 GPM. To
correctly size the manifold feeding these boilers, you would need a pipe size of 3”.
Figure 7 –Multiple Boiler Manifold Piping
H. FILL AND PURGE HEATING SYSTEM
Attach the hose to balance and purge hose connector or drain valve and run hose to nearest drain.
Close the other side of the balance and purge valve or the shut off valve after the drain.
Open first zone balance and purge or drain valve to let water flow out the hose. If zone valves are used, open the valves one
at a time manually. (NOTE: You should check the valve manufacturer’s instructions prior to opening valves manually, so as
not to damage the valves.)
Manually operate fill valve regulator. When water runs out of the hose, you will see a steady stream of water (without bubbles).
Close balance and purge valve or drain to stop the water from flowing. Disconnect the hose and connect it to next zone to be
purged.
Repeat this procedure for additional zones (one at a time).
For installation that incorporates standing iron radiation and systems with manual vents at the high points, follow previous section and,
starting with the nearest manual air vent, open until water flows out. Then close vent. Repeat procedure, working your way toward the
furthest air vent. It may be necessary to install a basket strainer in an older system where larger amounts of sediment may be present.
Annual cleaning of the strainer may be necessary.
Upon completion, make sure that the fill valve is in the automatic position and each zone balance and purge or shut off is in an open
position and zone valves are positioned for automatic operation.

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LP- 205 REV. 9.2.14
I. FREEZE PROTECTION FLUIDS
Use only inhibited glycol solutions which are specially formulated for hydronic systems. Ethylene glycol is toxic and can attack gaskets
and seals used in hydronic systems. Glycol mixtures should not exceed 50%.
1. Glycol in hydronic applications is specially formulated for this purpose, and includes inhibitors that prevent the glycol from attacking
metallic system components. Make certain that the system fluid is checked for the correct glycol concentration and inhibitor level.
2. The glycol solution should be tested at least once a year and as recommended by the glycol manufacturer.
3. Anti-freeze solutions expand more than water. For example: A 50% by volume solution expands 4.8% in volume for a temperature
increase from 32oF to 180oF, while water increases 3% over the same temperature rise. Allowances must be made for this expansion in
the system design.
4. A 30% mixture of glycol will result in a BTU output loss of 15% with a 5% increase in head against the system circulator.
5. A 50% mixture of glycol will result in a BTU output loss of 30% with a 50% increase in head against the system circulator.
It is highly recommended that you carefully follow the glycol manufacturer’s recommended concentrations, expansion requirements,
and maintenance recommendations (pH additive breakdown, inhibitor reduction, etc.). Carefully figure the additional friction loss in the
system as well as the reduction in heat transfer coefficients.
J. ZONING WITH ZONE VALVES
1. Connect the boiler to the system as shown in Boiler Piping Details when zoning with zone valves. The primary/secondary piping
shown ensures the boiler loop will have sufficient flow. It also avoids applying the high head of the boiler circulator to the zone valves.
2. Connect DHW (domestic hot water) piping to indirect storage water heater.
K. ZONING WITH CIRCULATORS
1. Connect the boiler to the system when using circulator zoning as shown in Boiler Piping Details. NOTE: The boiler circulator cannot
be used for a zone. It must only supply the boiler loop.
2. Install a separate circulator for each zone.
3. Connect DHW (domestic hot water) piping to indirect storage water heater.
L. MULTIPLE BOILERS
1. Connect multiple boilers as shown in Boiler Piping Details.
2. All piping shown is reverse return to assure balanced flow throughout the connected boilers.
3. Each connected boiler must have its own circulator pump to assure adequate flow.
4. Connect DHW (domestic hot water) piping to indirect storage water heater.
5. The system flow (secondary loop) must be greater than the primary (boiler) loop flow.
Water temperature above 140oF requires the circulator pump to run continuously and water hardness between 5 and 7 grains.
Hardness above 7 grains will damage the heat exchanger and shorten the service life of the boiler.

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LP- 205 REV. 9.2.14
M. BOILER PIPING DETAILS
Figure 8 –Single Boiler Space Heating –Indirect Priority
FIGURE NOTES:
1. This drawing is meant to demonstrate system piping concept only.
2. A mixing valve is recommended if the DHW temperature is set above the factory setting of 119oF.
3. Install a minimum of 12 diameters of straight pipe upstream of all circulators.
4. Install a minimum of 6 diameters of straight pipe up and downstream of all closely spaced tees.
5. Piping shown is Primary/Secondary.
6. The minimum pipe size for connecting an HTP indirect fired water heater is 1”.
7. The minimum pipe size for connecting a Mod Con boiler is 1 ½” for the 300 and 2” for the 500 and 850.
8. System flow (Secondary Loop) must be greater than the boiler’s Primary Loop flow.
9. Installations must comply with all local codes.
10. In Massachusetts, a vacuum relief valve must be installed on the cold water line per 248 CMR.