Harsco Industrial 1004905923 Operating instructions

© 2011 Harsco Corporation, All Rights Reserved
MFD 202
MODU-FIRE®FORCED DRAFT
GAS-FIRED BOILER
2500 - 3000
Model #:_______ Serial #______________________
Start-Up Date: _______________________
Harsco Industrial, Patterson-Kelley
100 Burson Street
East Stroudsburg, PA 18301
Telephone: [phone]
Facsimile: [phone]
www.harscopk.com
C.S.A. Design-Certified
Complies with ANSI Z21.13/CSA 4.9
Gas-Fired Low Pressure Steam and Hot Water Boilers
ASME Code, Section IV
Certified by Harsco Industrial, Patterson-Kelley
C.S.A. Design-Certified
Complies with ANSI Z21.13/CSA 4.9
Gas-Fired Low Pressure Steam and Hot Water Boilers
MODU-FIRE® FD 2500-3000
Rev. 1.01 (2/7/12)

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
2

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
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1INTRODUCTION .........................................................................................................5
2SAFETY.......................................................................................................................5
2.1General ............................................................................................................................5
2.2Training ............................................................................................................................5
2.3Safety Features................................................................................................................6
2.4Safety Labels ...................................................................................................................6
2.5Safety Precautions...........................................................................................................6
3INSTALLATION ...........................................................................................................8
3.1Receiving and Storage.....................................................................................................8
3.2Compliance with Codes ...................................................................................................9
3.3Setup................................................................................................................................9
3.4Electrical Connections....................................................................................................10
3.5Inlet Air and Exhaust Venting.........................................................................................12
3.6Gas Piping......................................................................................................................21
3.7Boiler Water Piping ........................................................................................................23
3.8Burner and Ignition System............................................................................................26
3.9Pre-Start Check List.......................................................................................................26
3.10Safety Checks.............................................................................................................26
3.11Boiler Operating Control .............................................................................................28
3.12Combustion Adjustment..............................................................................................29
4OPERATION..............................................................................................................32
4.1General ..........................................................................................................................32
4.2Lighting and Shut-Down Procedures .............................................................................32
5MAINTENANCE.........................................................................................................33
5.1Maintenance and Inspection Schedule..........................................................................33
5.2Cleaning the Burner .......................................................................................................35
5.3Removing the Heat Exchanger......................................................................................36
5.4After All Repairs or Maintenance ...................................................................................36
5.5Sequence of Operation ..................................................................................................36
5.6Troubleshooting .............................................................................................................37
5.7Manual Reset Error Codes – A## ..................................................................................40
5.8Auto-reset Error Codes – E##........................................................................................41
6PARTS/TECHNICAL SUPPORT ...............................................................................42
6.1Schematic Diagrams......................................................................................................42
7LIMITED WARRANTY ...............................................................................................54
8MODU-FIRE®FORCED DRAFT BOILER FIRE TEST REPORT ..............................55

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
4
Reorder No. 6020-V2WHPK
Improper use may
result in fire or injury.
Read instructions/safety
manual before installing,
operating or servicing boiler.
c
!
WARNING
1998 HCS, Inc. 800-748-0241
If the information in this manual is not followed exactly, a fire or explosion may result
causing property damage, personal injury or loss of life.
Do not store or use gasoline or other flammable vapors or liquids in the vicinity of this or any other appliance.
Installation and service must be performed by a qualified installer, service agency, or the gas supplier.
It is essential to read, understand, and follow the recommendations of this manual
before installing, operating, or servicing this equipment.
Installation and service must be performed by a qualified and knowledgeable individ-
ual who has been trained on the Harsco Industrial, Patterson-Kelley MODU-FIRE®Forced Draft boiler. The same
features which permit this boiler to achieve high-efficiency performance make it unlike most other boilers of this
general size, so it is important to understand how this boiler operates.
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.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
5
1 INTRODUCTION
The MODU-FIRE®Forced Draft gas-fired boiler is a revolutionary advance. Harsco Industrial, Patterson-Kelley
now combines full-modulation burner control and forced draft advances with our time-tested modular hot water
boiler design. The result is a full-modulation boiler utilizing reduced vent sizing for installation and cost
efficiencies. This boiler combines the best of our earlier designs with a new generation of burner, control and
operating technology. You will achieve high part-load efficiencies – but without the complexity you might expect
in this type of high performance boiler. It is high performance made simple and dependable for years of trouble-
free operation.
This manual covers installation and operation of the MODU-FIRE®Forced Draft 2500 & 3000 MFD boiler. The
model numbers may include a prefix to indicate special features or different options. While details may differ
slightly, basic operation is the same for all models. Boilers are built to operate with natural gas or propane. Check
the rating label for the correct gas type and flow rate.
The boiler is only a part of the complete heating system. This boiler may be fully operational and yet, because of
poor circulation, controls, or other operating characteristics, not deliver heat to the desired location. Additional
equipment such as temperature sensors, pumps, flow switches, balancing valves and check valves will be
required for satisfactory operation of any system. Harsco Industrial, Patterson-Kelley cannot be responsible for
the design or operation of such systems and a qualified engineer or contractor must be consulted.
2 SAFETY
2.1 GENERAL
The MODU-FIRE®Forced Draft gas-fired boiler must be:
Installed in accordance with designs prepared by qualified facility engineers including: structural,
mechanical, electrical, and other applicable disciplines.
Operated and serviced in accordance with a comprehensive safety program determined and established by
the customer. Do not attempt to operate or service the unit until such a program has been established.
Operated and serviced by qualified and knowledgeable personnel in accordance with all applicable codes,
laws, and regulations.
The use of the term “factory-trained personnel” throughout this manual indicates Harsco Industrial, Patterson-
Kelley trained on this specific piece of equipment.
2.2 TRAINING
It is essential to read, understand, and follow the recommendations of this manual before installing, operating, or
servicing this equipment. Failure to do so could result in serious injury, death, and/or property damage.
Proper training is the best protection against accidents. Operating and service personnel must be thoroughly
familiar with the basic construction of the MODU-FIRE®Forced Draft boiler, the use and locations of the controls,
the operation of the boiler, adjustment of its various mechanisms, and all applicable safety precautions. If any of

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
6
the provisions of this manual are not fully and completely understood, contact the Harsco Industrial, Patterson-
Kelley Technical Services Department at [phone].
2.3 SAFETY FEATURES
It is the responsibility of the customer to maintain the safety features of this machine, such as: guards, safety
labels, safety controls, interlocks, lockout devices.
2.4 SAFETY LABELS
The following words are used in this manual to denote the degree of seriousness of the individual hazards.
The safety labels shown below are affixed to the boiler and dual language labels may also be affixed to the boiler.
Although the labels are of high quality, they may become dislodged or unreadable over time. Contact Harsco
Industrial, Patterson-Kelley for replacement labels.
2.5 SAFETY PRECAUTIONS
Provide a suitable location for the boiler, away from normal personnel traffic, with adequate working space,
adequate clearances, proper ventilation and lighting, with a structure sufficiently strong and rigid to support the
weight of the boiler, all piping and accessories.
2.5.1 Electrical Hazards
Shock hazard! Properly lockout/tagout the electrical
service and all other energy sources before working on or
near the machine.
Shock hazard! Boiler is not rated for wash-down service.
Power down unit for at least 10 minutes before servicing
the blower.
indicates an imminently hazardous situation which, if not avoided, will result
in death or serious injury. This signal word is to be limited to the most extreme situations.
indicates a potentially hazardous situation which, if not avoided, could re-
sult in death or serious injury.
indicates a potentially hazardous situation which, if not avoided, may result
in minor or moderate injury. It may also be used to alert against unsafe practices.
NOTICE/NOTE - NOTICE is the preferred signal word to address practices not related to personal
injury. The safety alert symbol is not used with this signal word.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
7
2.5.2 Burn, Fire, and Explosion Hazards
NOTE
Make sure this union is
tight before closing cabinet
cover after servicing boiler.
Reorder No. 8032-02NHAK
c
1998 HCS, Inc. 800-748-0241
NOTE
Reorder No. 8032-01NHPK
c
When opening leak test valves,
always follow instructions in
operation and safety manual.
1998 HCS, Inc. 800-748-0241
Burn, fire, and explosion hazards! Installation must be in strict conformance to all applicable codes and
standards including NFPA 54/ANSI Z223.1 and/or CAN/CSA- B149.1.
Hazard from incorrect fuels! Possible fire, explosion, overheating, and damage. Do not use any fuels except
the design fuel for the unit.
Overfire hazards! High pressure in gas or propane supply could result in overfiring of other devices supplied
from the same source.
Fire and explosion hazards! Close the main gas shutoff before servicing boiler.
Fire and explosion hazards! Do not store or use gasoline or other flammable vapors or liquids in the vicinity
of this or any other gas fired appliance.
Burn hazard! Possible hot surfaces. Do not touch the stack during firing operations. Use only factory
recommended vent components.
Burn hazard! Hot fluids. Use caution. Allow boiler to cool before servicing or draining boiler.
Fire and explosion hazards! Use caution when servicing burner or heat exchanger. Unburned fuel may linger
in the combustion chamber, vent lines, or elsewhere.
Gas leak hazard! Make sure all connections to main burner are tight when reassembling the burner.
Gas leak hazard! All threaded gas connections must be made using a pipe compound that is resistant to
liquefied petroleum. Do not use Teflon tape on threaded gas piping.
Gas leak hazard! Check entire gas train for leaks after installation. If there is a smell of gas, shut down the
boiler, close all gas valves and obtain immediate assistance from factory-trained personnel and/or your local
fire department.
Overfire hazard! Possible fire and explosion from excess gas pressure. Make sure that gas inlet pressure
does not exceed 14 inches W.C. to the boiler main gas valve.
Overfire hazard! Possible fire and explosion. Possible malfunction of regulators and/or gas valves.
Maintain all gas train components in good condition. Do not alter wiring connections. Annual inspection by
factory-trained personnel for proper set-up and operation is recommended.
Overfire and underfire hazards! Possible fire, explosion, overheating, and component failure. Do not attempt
to adjust firing rate of the boiler. The firing rate must be adjusted only by factory-trained personnel.
Reorder No. 6020-V2WHPK
Improper use may
result in fire or injury.
Read instructions/safety
manual before installing,
operating or servicing boiler.
c
!
WARNING
1998 HCS, Inc. 800-748-0 241

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
8
2.5.3 Crush Hazards
Lifting hazards! Use properly rated lifting equipment to lift and position the boiler. The load is
unbalanced. Test balance before lifting more than 3 ft. above the floor. Do not allow
personnel beneath the lifted load. The approximate weight of the N2500 & N3000 MFD is
1200 lbs.
Bump hazard from overhead piping. Install piping with adequate vertical clearance.
2.5.4 Chemical Hazards
Chemical hazards from cleaning products. Use caution when cleaning the system. The use
of professional assistance is recommended. Use safe procedures for the disposal of all
cleaning solutions.
2.5.5 Pressure Hazards
Pressure hazard! Hot fluids. Install isolation valves on boiler water inlet and outlet. Make
sure isolation valves are closed before servicing boiler.
Pressure hazard! Hot fluids. Test safety relief valve every 30 days during the heating season
and after any prolonged period of inactivity. Do not operate boiler with faulty relief valve.
2.5.5 General Hazards
Tripping hazard! Do not install piping on floor surfaces. Maintain clear path around boiler.
Slip and fall hazard! Use drip pan to catch water while draining the boiler. Maintain dry floor
surfaces.
Slip and fall hazard! Through-the-wall vents shall not terminate over public walkways or over
an area where condensate or vapor could create a nuisance or hazard.
Fall hazard! Do not stand on any part of the boiler.
Catch hazard! Do not wear rings, jewelry, long hair, loose clothing while working on the
boiler.
3 INSTALLATION
Installation and service must be performed by a qualified installer, service agency,
or gas supplier.
3.1 RECEIVING AND STORAGE
3.1.1 Initial Inspection
Upon receiving the boiler, inspect it for signs of shipping damage.Since some damage may be hidden, we
recommend unpacking the boiler, removing the top, front, and side covers and inspect the boiler. Verify that the
total number of pieces shown on the packing slip agrees with those actually received.
General Warning
General Warning
General Warning
General Warning

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
9
3.1.2 Storage Prior to Installation
If the boiler is not installed immediately, it must be stored in a location adequately protected from the weather,
preferably indoors. If this is not possible, then it should remain in the shipping container and be covered by a
tarpaulin or other waterproof covering.
NOTICE! Controls and other equipment that are damaged or fail due to weather exposure are not covered by
warranty.
3.2 COMPLIANCE WITH CODES
The MODU-FIRE®Forced Draft boiler with standard components and many options complies with American
National Standard/CSA Standard ANSI Z21.13/CSA 4.9, latest edition. The heat exchanger is constructed and
stamped in accordance with ASME Boiler and Pressure Vessel Code, Section IV for 160 psig maximum operating
pressure and 250º F maximum operating temperature. Other codes or approvals which apply will be labeled on
the boiler.
Installation of the boiler must conform to all the requirements of all national, state and local codes established by
the authorities having jurisdiction or, in the absence of such requirements, in the U.S. to the National Fuel Gas
Code, NFPA 54/ANSI Z223.1., latest edition, and the specific instructions in this manual. In Canada, the
equipment shall be installed in accordance with the current Installation Code for Gas Burning Appliances and
Equipment, CAN/CSA-B149.1, and applicable Provincial Regulations for the class which should be carefully
followed in all cases. Authorities having jurisdiction should be consulted before installations are made.
Where required by local codes, the installation must conform to American Society of Mechanical Engineers Safety
Code for Controls and Safety Devices for Automatically Fired Boilers (ASME CSD-1).
In the Commonwealth of Massachusetts, see Massachusetts Installation & Owner’s Manual Supplement.
3.3 SETUP
3.3.1 Foundation
Provide a firm, level foundation, preferably of concrete.
NOTICE! The boiler may be installed on a combustible floor; however, the boiler must never be installed on
carpeting.
NOTICE! This boiler is certified for indoor installation only.
3.3.2 Placement
The boiler must be level and upright to function properly. Use shims or other approved structural devices to
properly level boiler.
NOTICE! Note any damage, suspected potential damage, or shortage of materials on the freight bill
and immediately notify the carrier. File all claims for shortage or damage with the carrier. Claims for
hidden damages must be filed with your carrier within 7 days. The boiler carton is equipped with a
“Tip (N) Tell”. If "Tip (N) Tell” arrow point is blue, that indicates that the package has been on its
side or tipped over in transit.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
10
3.3.3 Installation Clearances
If the boiler is to be installed near combustible surfaces, six (6”) inches minimum clearance to the combustible
surface must be maintained.
Failure to provide for the service access clearances, even with non-combustible surfaces, may cause future
problems servicing the boiler.
The boiler must be installed in a space large in comparison to the boiler as described in the National Fuel Gas
Code, NFPA 54/ANSI Z223.1, Latest Edition.
C
AB
C
AB
Clearances from Adjacent Walls, Ceiling,
and Obstructions Side Clearances for a Row of Boilers
† "C" dimension includes clearance to remove
the burner and installation of the air inlet duct.
Do not put pipes, other ducts, equipment, etc.
above the boiler.
* CSA minimum. Actual clearance depends upon
venting requirements.
** Service access need be only on one side of a
boiler or row of boilers. Boilers may be installed immediately
adjacent to each other. However, Harsco Industrial,
Patterson-Kelley recommends this clearance between each
boiler when there is insufficient access at the rear to allow
for service and adjustment.
3.4 ELECTRICAL CONNECTIONS
All field wiring connections for power and controls are in the
junction box on the back of the boiler. The boiler wiring label
is attached to the inside front door of the boiler. An external
electrical disconnect (not supplied with the boiler) with
adequate overload protection is required. The boiler must be
grounded in accordance with local codes or in the absence of
such requirements, in the U.S. with National Electrical
Codes, ANSI/NFPA No. 70 latest edition and in Canada, wire
according to the current Canadian Electrical Code.
Type of Surface Dimensions (inches)
A B C† D
CSA Minimum Clearances to
Combustibles
24 24* 24 24
Recommended Service
Clearances
30 24* 24 24**
DD
Electrical
Connections

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
11
NOTICE! A dedicated earth ground (green wire) is required to avoid nuisance shutdowns. Do not ground
through the conduit. It is also important that proper polarity be maintained.
The junction box at the rear of the boiler contains terminal strips for all customer connections. A detailed
schematic of the connections is shown in 6.1.7. These connections are described as follows:
High Voltage (HV) Terminal Block
The boiler power circuit requires 208-240 volts, single phase, 60 hertz, with a dedicated neutral and ground for
the control circuit as labeled. The voltage from each line (L1, L2) to the neutral must be approximately 120V AC.
Electrical service must be rated for 17 amps minimum. Before starting the boiler, check to ensure that the proper
voltage and amperage are connected to the boiler and that the boiler is connected to a suitable fused disconnect
switch or circuit breaker. There must be less than 1.0V from Neutral (HV-3) to Ground (HV-10)
120VAC Switched Output- This contact closes when the boiler is switched on. This provides 120VAC 5Amp
service to HV12 and HV13. The neutral for this circuit is provided on HV4 and HV5. When the boiler is switched
off, these terminals are switched off as well.
3 Way Valve- This output is normally energized, keeping the three way valve providing heat to the building. The
Domestic Hot Water (DHW) call for heat de-energizes this circuit, causing the 3 way valve to self close, thereby
providing heat to the DHW loop. This output provides 120VAC 0.5Amp service to HV14. The neutral for this
circuit is provided on HV 6.
DHW Pump Relay w/Delay Off - This output is enabled when there is a call for DHW. When the call for heat is
removed, the output remains enabled for a period of time. This output provides 120VAC 0.5Amp service to HV15.
The neutral for this circuit is provided on HV 7.
Circ Pump Relay w/Delay Off - This output is enabled when there is a call for heat. When the call for heat is
removed, the output remains enabled for a period of time. This output provides 120VAC 0.5Amp service to HV16.
The neutral for this circuit is provided on HV 8.
Damper Relay - This output is enabled when the call for heat is enabled. This output provides 120VAC service
to HV17. The neutral for this circuit is provided on HV 9. This circuit is for pilot duty only.
Master Alarm Relay – This contact closes in the event of an alarm output from the boiler control, connecting
HV18 and HV19.
Flame Detected Relay – This contact closes whenever the boiler is firing, connecting HV20 and HV21.
Low Voltage (LV) Strip
Enable/Disable– Use for boiler enable. Closing this circuit allows the boiler to run. Opening this circuit prevents
the boiler from running, provided the remote/local enable switch is in the remote position. This circuit is energized
by the boiler. It has a 24VAC potential. Devices connected to these terminals must be rated for 24VAC
The remote/local switch bypasses the Enable/Disable (LV1 to LV2) when in the local
position. Do not connect safety devices into the Enable/Disable circuit.
Auxiliary Low Water Cutoff – These terminals are used for connection of a secondary low water cutoff used in
the system. This circuit is energized by the boiler. It has a 5V potential. Devices connected to these terminals
must be rated for 5V.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
12
External Interlock - Use for attachment of an additional field safety device to the boiler control circuit. Closing
this circuit allows the boiler to run. Opening this circuit prevents the boiler from running. This circuit is energized
by the boiler with a 5V potential. Devices connected to these terminals must be rated for 5V.
Outdoor Temp Sensor – LV7 and LV8 are connected to the outdoor temperature sensor. The temperature
control must be programmed to run an outdoor air schedule. The outdoor air sensor and programming help are
available from the local Harsco Industrial, Patterson-Kelley Representative. This circuit is energized by the boiler
with a 5V potential. The temperature sensor must be a NTC having 12k@25°C.
DHW Stat/Sensor – LV9 and LV10 are connected to the DHW temperature sensor or thermostat. This circuit is
energized by the boiler with a 5V potential. The temperature sensor must be a NTC having 12k@25°C.
Header Temp Sensor – LV11 and LV12 are connected to the header temperature sensor. This circuit is
energized by the boiler with a 5V potential. The temperature sensor must be a NTC having 12k@25°C.
DHW Flow Switch – LV13 is energized by the boiler with a 5V potential. This circuit connects through a flow
switch on the domestic side of a domestic hot water system. The flow switch should close upon flow to provide a
closed circuit back to LV14.
Analog Input– Remote signal for controlling the boiler. The boiler can be operated in a remote setpoint or a
remote firing rate control mode. Input 0-10VDC signal only. The temperature control must be programmed to run
with the analog input.
MODBUS®– LV19 and LV20 are used for connecting a MODBUS®building management system. (See the ENVI®
Control Advanced Users Guide for more information)
Cascade – LV21 and LV22 are used to connect between boilers that are part of a Master/Member Network. Up to
24 boilers may be connected together. (See the ENVI®Control Advanced Users Guide for more information)
3.5 INLET AIR AND EXHAUST VENTING
3.5.1 Applicable Codes & Standards
CODES
United States:
NFPA 54/ANSI Z223.1 National Fuel Gas Code
NFPA/ANSI 211 Chimneys, Fireplaces, Vents and Solid Fuel Burning Appliances
Canada
CAN/CSA B149.1 Installation Codes for Gas Burning Equipment
STANDARDS
UL 1738 Venting Systems for Gas-Burning Appliances, Categories II, III, and IV
These codes and standards contain information for the venting of gas fired appliances, including, but not limited to
vent sizing, location, clearance to combustibles, and safe installation practices. The installation must comply with
both the above Federal Codes and with state, provincial and local codes.
Design and installation of venting systems should be done only by qualified and
knowledgeable venting systems personnel and in accordance with vent system manufacturer’s installation
instructions. Installing a boiler or vent system using improper installation methods or materials can result in
serious injury or death due to fire or asphyxiation.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
13
Before connecting a boiler to a venting system, it must be determined whether the
boiler is to be installed in a conventional or Direct Vent configuration. In the US, provisions for combustion and
ventilation air must be in accordance with NFPA 54/ANSI Z223.1, National Fuel Gas Code, latest edition, or
applicable provisions of the local building codes. In Canada, combustion and ventilation air openings shall
comply with CAN/CSA B-149.1 Natural Gas and Propane Installation Code.
For correct installation of vent system, read all of these instructions and refer to vent
manufacturer’s instructions.
Failure to use a proper vent system (types and materials), as described in this manual will void the boiler war-
ranty and may result in rapid deterioration of the venting system, creating a health or life safety hazard.
Faulty vent installation can allow toxic fumes to be released into living areas. This may cause property dam-
age, serious bodily injury or death.
3.5.1.1 Gas Vent Categories
Several codes and standards have categorized appliances in accordance with the flue gas temperature and pres-
sure produced by the appliance. Categories are defined as follows:
Category I An appliance that operates with a non-positive vent static pressure and with a vent tempera-
ture that avoids excessive condensate production in the vent.
Category II An appliance that operates with a non-positive vent static pressure and with a vent tempera-
ture that may cause excessive condensate production in the vent.
Category III An appliance that operates with a positive vent static pressure and with a vent temperature
that avoids excessive condensate production in the vent.
Category IV An appliance that operates with a positive vent static pressure and with a vent temperature
that may cause excessive condensate production in the vent.
Direct Vent An appliance that is constructed and installed so that all air for combustion is derived directly
from outdoors and all flue gases are discharged to the outdoors.
3.5.1.2 Venting Materials for Flue/Exhaust Systems
MODU-FIRE®Forced Draft boilers are Category IV appliances, which vent with a positive exhaust pressure and
with a temperature that is likely to cause condensation in the vent. Therefore, any venting system used with the
MODU-FIRE®Forced Draft boiler must comply with the requirements for Category IV venting systems as speci-
fied in the latest edition of NFPA 54/ANSI Z223.1 in the US or the latest edition of CAN/CSA B-149.1 in Canada.
The venting materials listed below are intended for the venting of gas burning ap-
pliances only. Do not use these venting materials for venting liquid or solid fuel (such as oil, kerosene, wood or
coal) appliances.
Maintain clearances to combustibles as listed in the vent manufacturer’s installation instructions or as set forth
in the codes and standards listed in this section.
Do not use these vent pipes for incinerators of any sort.
3.5.2 Combustion Air
Combustion air must be free from dust, lint, etc. The presence of such materials in the air supplied to the burner
could cause nuisance "Low Air" shutdowns or premature burner failure. The boiler should not be operated during
construction while the possibility of drywall dust, demolition dust, etc. exists.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
14
The combustion air supply must be completely free of chemical fumes which may be corrosive when burned in
the boiler. Common chemicals which must be avoided are fluorocarbons and other halogenated compounds,
most commonly present as refrigerants or solvents, such as freon, trichlorethylene, perchlorethylene, chlorine,
etc. These chemicals, when burned, form acids which quickly attack the boiler and the boiler stack. The result is
improper combustion and premature boiler failure.
Under no circumstances shall the boiler room ever be under a negative pressure.
Particular care should be taken when exhaust fans, compressors, air-handling units or other equipment may
rob air from the boiler. Note that this equipment might be in rooms other than the boiler room.
3.5.2.1 Air Inlet Requirements – United States (NFPA 54/ANSI Z223.1 & NFPA/ANSI 211)
When air is supplied from inside the building, the total required volume shall be the sum of the required volume for
all the appliances located in the mechanical room. Adjacent rooms furnished with fixed openings communicating
directly with the mechanical room are considered part of the required volume. The minimum volume is 50 ft3per
1000 Btu/hr (4.8 m3/kW) of installed appliance input capacity.
Openings used to connect indoor spaces to obtain the required minimum volume shall be sized as follows:
When rooms are on the same floor, each opening shall have an area equal to 1 square inch for each 1000
Btu/hr (2200 mm2/ kW) of installed appliance input capacity, but not less than 100 square inches. One open-
ing should commence less than 12 inches above the floor and the other less than 12 inches below the ceiling.
The minimum dimension of air openings shall be 3 inches.
When rooms are on different floors, each opening shall have an area equal to 2 square inches for each 1000
Btu/hr (4400 mm2/ kW) of installed appliance input capacity.
When combustion air is supplied from outside the building, the boiler room shall be provided with one or two
openings to ensure adequate combustion air and proper ventilation.
When using one permanent opening, the opening shall commence within 12 inches of the ceiling and shall com-
municate directly with the outdoors or through a vertical or horizontal duct that communicates to the outdoors.
Minimum free area of the opening is 1 square inch for each 3000 Btu/hr (700 mm2/ kW) of installed appliance
input capacity, and
Not less than the sum of the areas of all vent connectors in the room.
When using two permanent openings, one opening shall commence within 12 inches above the floor and the oth-
er within 12 inches below the ceiling, preferably on opposite walls. The openings shall communicate directly, or
by way of ducts, with free outdoor air. The minimum net free area of the openings shall be calculated in accord-
ance with the following:
When air is taken directly from outside the building, each opening (minimum of two, as outlined above), 1
square inch for each 4,000 Btu per hour (550 mm2/kW) of total boiler input is required.
When air is taken from the outdoors through a vertical duct into the mechanical room, 1 square inch per 4,000
Btu per hour (550 mm2/kW) of total boiler input is required.
When air is taken from the outdoors through a horizontal duct into the mechanical room, 1 square inch per
2,000 Btu per hour (1100 mm2/kW) of total boiler input is required.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
15
NOTICE!
1. The required size of openings for combustion and ventilation air shall be based on the net free area of the
opening.
2. Screens shall be not smaller than ¼”
3. Motorized louvers shall be interlocked with the appliance so that they are proven open prior to main burner
ignition and operation.
Table of US Minimum area of ventilation openings per boiler (sq inches)
MFD
MODEL
AIR SOURCE
INDOOR AIR SUPPLY OUTDOOR AIR SUPPLY
SAME FLOOR DIFF FLOORS ONE OPENING
TWO OPENINGS
DIRECT
VERT
DUCT
HORIZ
DUCT
N2500 2500 5000 833.3 625 625 1250
N3000 3000 6000 1000 750 750 1500
3.5.2.2 Air Inlet Requirements – Canada (CAN/CSA B149.1)
A. Ventilation of the space occupied by fuel burning appliance(s) or equipment shall be supplied by a ventilation
opening at the highest practicable point communicating with the outdoors. The total cross sectional area of
the ventilation opening must be either 10% of the net free area required for combustion air or 10 sq. in. (6500
mm2), whichever is greater.
B. Use the following opening calculation for MACH® condensing boilers or MODU-FIRE®Forced Draft boilers:
When combustion air is supplied for a forced draft burner by natural airflow from the outdoors and there is no
draft regulator or draft hood in the same space, there shall be a permanent opening with a cross sectional ar-
ea not less than 1 sq. in/ 30,000 Btu/Hr (70 mm2/kW) of the total rated input to the burner(s). This opening
must not interfere with the ventilation air opening defined in paragraph A.
C. Use the following opening calculation for P-K THERMIFIC®boilers or other natural draft or fan-assist appli-
ances:
When combustion air is supplied for natural or fan-assisted burners by natural airflow from the outdoors, there
shall be a permanent opening with a cross sectional area not less than 1 sq. in/ 7000 Btu/Hr (321 mm2/kW)
up to and including 1,000,000 Btu/Hr plus 1 sq. in. / 14,000 Btu/Hr (155 mm2/kW) in excess 1,000,000 Btu/Hr.
This opening must be either located at or ducted to a point not more than 18 in. (450 mm) nor less than 6 in.
(150 mm) above floor level. This opening is in addition to the ventilation air opening defined in paragraph A.
D. When combustion air is supplied by natural airflow into a space containing both types of appliances described
in paragraphs B and C, the cross sectional area of the opening shall be not less than the sum of the cross
sectional areas for all appliances in the space as calculated by the applicable method . This opening is in ad-
dition to the ventilation air opening defined in paragraph A.
E. When a duct is used to meet the requirement for combustion air supply, as described in paragraphs A through
D, above, the opening of the duct shall be located so there is no possibility of cold air affecting steam or water
piping, electrical equipment or mechanical equipment.
F. When combustion air is supplied by mechanical means, an airflow-sensing device must be installed. It must
be wired into the pre-ignition limit string to prevent the burner from starting or to stop an operating burner in
case of air supply failure.
G. When all combustion air is supplied through a make-up air heater, and the appliance is interlocked to the
heater, the requirements of paragraphs A through F do not apply.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
16
NOTICE!
1. The free area of a combustion air supply opening is calculated by deducting the blockage area of any fixed
louvers, grilles or screens from the total area of the opening.
2. Screens shall be not smaller than ¼”
3. Motorized louvers shall be interlocked with the appliance so that they are proven open prior to main burner
ignition and operation
Table of Canadian Minimum Area of Combustion and Ventilation Air Openings
MFD Required Combustion Air Opening Ventilation Air Opening
Model # Input (Btu/Hr) in
2
mm
2
in
2
mm
2
N2500 2,500,000 83.3 53,763 10 6,452
N3000 3,000,000 100 64,516 10 6,452
3.5.3 Flue Venting
This boiler is not certified for use with Type "B" vent nor with any type of plastic venting.
This boiler is a Category IV appliance (condensing – positive pressure) as it is defined in ANSI Z21.13/CSA 4.9,
latest edition. The vent material must be as described in section 3.5.1.2. The exhaust vent can be run horizontal-
ly or vertically.
Vent installations shall be in accordance with NFPA54/ANSI Z223.1, the National Fuel Gas Code, or CAN/CSA-
B149.1, the Natural Gas and Propane Installation Code, or applicable provisions of the local building codes.
3.5.3.1 VENT SIZING
The vent must be sized in accordance with the ASHRAE Systems and Equipment handbook, Chapter 30 or ac-
cording to the vent manufacturer’s recommendations. When using manufactured venting systems, consult your
vent supplier for correct sizing and structural support requirements.
Table of Vent Design Parameters
MFD Model Frictional
Resistance
Stack
Temperature CO2Natural Gas CO2LP Gas
N2500/N3000 1.0” Max 300°F (gross) 8.5% 10.3%
The vent must be sized according to the vent manufacturer’s recommendations. Consult your vent supplier
for correct sizing and structural support requirements. Design calculations should be based on a positive
pressure at the flue collar, not to exceed 1.0 inch W.C. with a stack temperature of 300° F (gross) and a CO2
level of 8.5% natural gas. The vent should be designed to provide positive pressure at the flue collar at all firing
rates.
NOTICE! Refer to example in section 3.5.5 regarding pressure drop across the boiler.
Do not use a barometric damper with this boiler. This is a positive pressure sys-
tem. Flue gases may leak into the room.
This equipment MUST NOT be used with a heat actuated automatic vent damper.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
17
All boiler venting systems should be designed by a qualified venting professional ex-
perienced in venting system design. The information contained herein should be used as a guide only and is
not intended to be used in lieu of qualified technical expertise.
3.5.3.2 Required Clearances
Provide clearances between combustion air intake, exhaust vent, roof and wall surfaces, doors and window, and
snow line. Refer to Figure below: Termination Clearances – Forced Draft and Direct Vent Installations.
Conventional Vent Systems
The following termination clearance requirements are for conventional, non-direct vent installations.
The vent system shall terminate at least 3 ft above a forced air inlet that is within 10 feet horizontally.
The vent system shall terminate at least 4 ft below, 4 ft horizontally from or 1 ft above any door, operable win-
dow or gravity inlet into any building. The bottom of the vent terminal shall be at least 12 in. above grade or
highest expected snow line (if applicable).
Through the wall terminations shall not terminate over public walkways or over an area where condensate or
vapor could create a nuisance or hazard or could be detrimental to the operation of regulators, relief valves or
other equipment.
Direct Vent (Sealed Combustion) Systems
The vent terminal shall be located at least 12 in. from any air opening into a building. The bottom of the vent
terminal shall be at least 12 in. above grade. Both the vent and air intake terminals must be at least 12 in.
above the highest expected snow line.
Do not locate intake or exhaust terminations directly above a walkway;
dripping of condensation can cause icing of the walking surface. Maintain a minimum clearance of 4
ft (1.22 m) horizontally from any electric or gas meter, regulator or relief equipment.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
18
Through the wall terminations shall not terminate over public walkways or over an area where condensate or
vapor could create a nuisance or hazard or could be detrimental to the operation of regulators, relief valves or
other equipment.
When multiple direct vent appliances are adjacent, the exhaust must terminate at least 10 feet horizontally or
three feet vertically from the air intake of another appliance.
Interior Component Installation Clearances
All vent system components shall be installed so as to maintain the following required minimum clearances:
Vent Type and Clearance Type Combustible Surface Non-Combustible Surface
UL 1738 listed Category IV vent Per manufacturer’s listing Per manufacturer’s listing
3.5.3.3 Flue Connection
The boiler vent should not be connected into any portion of another mechanical
draft system without consulting the vent manufacturer. This boiler operates under a positive vent pressure.
The boiler shall not be connected to any part of a vent system serving a Category I or II appliance, nor shall a
Category I or II appliance be connected to any part of the vent system serving this appliance. Improper inter-
connection of venting systems may result in leakage of flue gases into occupied spaces.
NOTICE! Make sure that the weight of the vent is not supported by the boiler vent collar. The collar is not
designed to support the weight of the vent. The vent system shall be supported in accordance with the
manufacturer’s instructions. Horizontal vent sections shall be supported in a manner to prevent sags or low
spots where condensate can collect. Structural supports must be connected to building elements of sufficient
strength to withstand the weight of the vent system and any bending forces imposed by the venting system.
This boiler has 10” OD connections for the vent. If venting design permits, this connection may be reduced to 8”
diameter. The connection from the boiler to the vent should be made using an adapter that is designed to fit the
OD of the boiler outlet. The vent manufacturer’s adapter must be sealed to the boiler outlet with sealant listed for
use with the vent material. The connection from the boiler to the vent should be as direct as possible and the
upward slope of any horizontal breaching should be at least ¼ inch per linear foot. Provisions must be made for
supports to prevent contact of the vent with combustible surfaces.
The complete exhaust with drain system is shown in the figures below. The appliance connector should
incorporate provisions to drain condensate formed in the vent system. The first turn from horizontal to vertical
should be made with either a standard tee with condensate drain cap or an elbow with an “inline” drain installed
immediately above the elbow. The condensate drain line from the boiler must be connected to the stack drain
upstream of the stack trap using a material that will withstand condensate corrosion and a maximum temperature
of 400°F. The stack trap shall have a minimum height of 4 inches. The condensate must be routed to a suitable
drain that complies with all local codes.
The boiler condensate drain line can get as hot as the stack. This may be up to
400ºF. This line should be insulated to prevent thermal injury or burns.
Do NOT use copper or plastic for the boiler condensate line, as these may fail and
allow exhaust gas to leak into the room.

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
19
3.5.3.4 Vent Terminations
The vent shall extend at least three (3) feet above the roof, or at least two (2) feet above the highest part of any
structure within ten (10) feet of the vent. This is illustrated in the following diagram. Additionally the boiler vent
shall terminate at least 3 ft above a forced air inlet located within 10 ft.
Building
Sidewall
See 3.6.6 for
termination details
Pitch Towards Boiler
¼” per foot min
Boiler Outlet
10” OD
Tee
w/Drain
Boiler Condensate Drain
(stainless steel or silicone tubing)
Stack Drain
w/Trap
4” min height

MODU-FIRE®Forced Draft Gas-Fired Boiler 2500-3000
20
Reference: NFPA 54/ANSI Z223.1 National Fuel Gas Code
To prevent the possible re-circulation of flue gases, the vent designer must take into consideration such things as
prevailing winds, eddy zones, building configurations, etc. Harsco Industrial, Patterson-Kelley cannot be
responsible for the effects such adverse conditions may have on the operation of the boilers. Dimensions listed
above are minimums and may not be sufficient for conditions at a specific job site. It is important to locate the
exhaust duct in such a way that it does not become blocked due to snow, ice, and/or other natural or man-made
obstructions.
VERTICAL VENTING
Harsco Industrial, Patterson-Kelley does not recommend the use
of a vent cap. A screen termination is not recommended due to
the possibility of ice formation on the screen. Rain is actually
beneficial to the vent internals.
SIDEWALL VENTING – N2500 & N3000 MFD
Harsco Industrial, Patterson-Kelley requires a “T” or 90
degree elbow to be used on the termination end of
sidewall venting on these models. The venting connection
for this “T” or 90 degree elbow should extend a minimum
of 12” from the wall, in addition to other venting
requirements.
3.5.4 Venting for Multiple Boilers
The venting instructions in this manual apply to a single
boiler.
Venting systems for multiple boilers must be designed by experienced and knowledgeable professionals.
The venting system must prevent backflow of exhaust gas through idle boilers.
3.5.5 Sealed Combustion/Direct Vent Systems
The MODU-FIRE®Forced Draft boilers are also certified for operation with a sealed combustion air and pressur-
ized venting system. Such a system employs a sealed combustion air intake duct leading from outdoors and a
sealed exhaust vent terminating outdoors. Air flow through the system is maintained by the combustion air fan.
Intake Duct Materials and Sizes
The air intake duct can be fabricated from PVC, CPVC, single wall galvanized steel, or other suitable materials.
The duct must be rigid enough to maintain the full required cross sectional area under all operating conditions.
Proper sealing of the intake ductwork is necessary to prevent infiltration of air from conditioned space. Joints in
PVC or CPVC must be cemented. For galvanized duct, wrap each joint and seam with adhesive aluminum tape
or other sealant. Connect the air supply duct to the inlet air collar on the boiler. Fasten the duct to the collar with
sheet metal screws and seal with aluminum tape or sealant. The installation of a birdscreen on the intake termi-
nation is recommended. Ensure that the screen does not become blocked with snow, ice, insects etc.
The combined pressure drop of the air supply duct and exhaust
vent must not exceed 1.0” w.c. This combined pressure drop can
be distributed over the intake or exhaust as needed provided that the
air inlet pressure loss does not exceed -0.5” w.c.
Air Requirements – SCFM
MFD MODEL Required SCFM
N2500 583
N3000 700
Thru the roofThru the roof
Thru the Wall
Note:
Elbow and Tee
May be oriented
in any direction
Thru the Wall
Note:
Elbow and Tee
May be oriented
in any direction