Modine Manufacturing HFG Series Manual

WARNING
Improper installation, adjustment, alteration,
service or maintenance can cause property
damage, injury or death, and could cause
exposure to substances which have been
determined by various state agencies to cause
cancer, birth defects or other reproductive harm.
Read the installation, operating and maintenance
instructions thoroughly before installing or
servicing this equipment.
FOR YOUR SAFETY
The use and storage of gasoline or other
flammable vapors and liquids in open containers
in the vicinity of this appliance is hazardous.
FOR YOUR SAFETY
IF YOU SMELL GAS:
1. Don’t touch electrical switches.
2. Extinguish any open flame.
3. Immediately call your gas supplier.
THIS MANUAL IS THE PROPERTY OF THE OWNER.
PLEASE BE SURE TO LEAVE IT WITH THE OWNER WHEN YOU LEAVE THE JOB.
Inspection on Arrival
1. Inspect unit upon arrival. In case of damage, report it
immediately to transportation company and your local
factory sales representative.
2. Check rating plate on unit to verify that power supply meets
available electric power at the point of installation.
3. Inspect unit upon arrival for conformance with description of
product ordered (including specifications where applicable).
IMPORTANT
The use of this manual is specifically intended
for a qualified installation and service agency.
A qualified installation and service agency must
perform all installation and service of these
appliances.
5-571.4
5H76232A1
Model HFG
Model HFP
April, 2010
INSTALLATION AND SERVICE MANUAL
gas-fired weatherproof duct furnaces
models HFG & HFP
CUS
9900100

5-571.4
2
SPECIAL PRECAUTIONS
THE INSTALLATION AND MAINTENANCE INSTRUCTIONS
IN THIS MANUAL MUST BE FOLLOWED TO PROVIDE SAFE,
EFFICIENT AND TROUBLE-FREE OPERATION. IN ADDITION,
PARTICULAR CARE MUST BE EXERCISED REGARDING
THE SPECIAL PRECAUTIONS LISTED BELOW. FAILURE
TO PROPERLY ADDRESS THESE CRITICAL AREAS COULD
RESULT IN PROPERTY DAMAGE OR LOSS, PERSONAL
INJURY, OR DEATH. THESE INSTRUCTIONS ARE SUBJECT
TO ANY MORE RESTRICTIVE LOCAL OR NATIONAL CODES.
HAZARD INTENSITY LEVELS
1. DANGER: Indicates an imminently hazardous situation
which, if not avoided, WILL result in death or serious injury.
2. WARNING: Indicates a potentially hazardous situation
which, if not avoided, COULD result in death or serious
injury.
3. CAUTION: Indicates a potentially hazardous situation which,
if not avoided, MAY result in minor or moderate injury.
4. IMPORTANT: Indicates a situation which, if not avoided,
MAY result in a potential safety concern.
Table of Contents
Inspection on Arrival ................................................................. 1
General Information/Installation Codes .................................... 1
Special Precautions.................................................................. 2
SI (Metric) Conversion Factors................................................. 3
Unit Location............................................................................. 3
Location Recommendations.............................................. 3
Combustible Material and Service Clearances ................. 3
Unit Lifting................................................................................. 4
Installation ................................................................................ 4
Direction of Airflow............................................................. 4
Duct Installation................................................................. 4
Airflow Distribution............................................................. 4
Venting .............................................................................. 5
Gas Connections............................................................... 5
Electrical Connections....................................................... 7
Start-Up Procedure................................................................... 7
Pilot Burner Adjustment..................................................... 8
Main Burner Adjustment.................................................... 8
Air Shutter Adjustment....................................................... 9
Control Operating Sequence........................................... 10
Variable Air Movement Applications ................................ 11
Gas Control Options........................................................ 12
Dimensional Data .............................................................. 13-14
Performance........................................................................... 15
Air Temperature and External Static Pressure Limits...... 15
Pressure Drop Curves.......................................................16-17
Maintenance........................................................................... 18
Manifold Assembly Removal ........................................... 18
Burner and Pilot Assembly Removal............................... 18
Service & Troubleshooting................................................. 20-21
Automatic Reset High Limit............................................. 20
Replacement Parts Ordering.................................................. 22
Serial Plate Location ....................................................... 22
Model Identification................................................................. 23
Warranty ................................................................................. 24
2
SPECIAL PRECAUTIONS / TABLE OF CONTENTS
IMPORTANT
1. To prevent premature heat exchanger failure, do not locate
ANY gas-fired appliances in areas where corrosive vapors
(i.e. chlorinated, halogenated or acid) are present in the
atmosphere.
2. To prevent premature heat exchanger failure, observe heat
exchanger tubes by looking at the heat exchanger through
field installed access openings in connecting ductwork. If
the bottom of the tubes become red while blower and duct
furnace are in operation, additional baffles must be inserted
between blower and duct furnace to assure uniform air flow
across the heat exchanger.
3. To prevent premature heat exchanger failure, the input to the
appliance, as indicated on the serial plate, must not exceed
the rated input by more than 5%.
4. To prevent premature heat exchanger failure, with all control
systems, a blower starting mechanism must be provided so
that the blower is running or energized within 45 seconds of
the gas control operation.
5. Start-up and adjustment procedures should be performed
by a qualified service agency.
6. To check most of the Possible Remedies in the
troubleshooting guide listed in Table 20.1, refer to the
applicable sections of the manual.
cAUTION
1. Appliances are designed for outdoor installation only. DO
NOT LOCATE APPLIANCES INDOORS.
2. Purging of air from gas supply line should be performed
as described in ANSI Z223.1 - latest edition “National Fuel
Gas Code”, or in Canada in CAN/CGA-B149 codes.
3. Do not reuse any mechanical or electrical component which
has been wet. Such component must be replaced.
dANGER
Appliances must not be installed where they may be exposed
to a potentially explosive or flammable atmosphere.
WARNING
1. All field gas piping must be pressure/leak tested prior to
operation. Never use an open flame. Use a soap solution or
equivalent for testing.
2. Gas pressure to appliance controls must never exceed 14"
W.C. (1/2 psi).
3. To reduce the opportunity for condensation, the minimum sea
level input to the appliance, as indicated on the serial plate,
must not be less than 5% below the rated input, or 5% below
the minimum rated input of dual rated units.
4. Disconnect power supply before making wiring
connections to prevent electrical shock and equipment
damage.
5. All appliances must be wired strictly in accordance with
wiring diagram furnished with the appliance. Any wiring
different from the wiring diagram could result in a hazard to
persons and property.
6. Any original factory wiring that requires replacement must
be replaced with wiring material having a temperature
rating of at least 105°C.
7. Ensure that the supply voltage to the appliance, as indicated
on the serial plate, is not 5% greater than rated voltage.
8. When servicing or repairing this equipment, use only
factory-approved service replacement parts. A complete
replacement parts list may be obtained by contacting
Modine Manufacturing Company. Refer to the rating plate
on the appliance for complete appliance model number,
serial number, and company address. Any substitution of
parts or controls not approved by the factory will be at the
owner's risk.

5-571.4 3
UNIT LOCATION
Location Recommendations
1. When locating the furnace, consider general space and heating
requirements and availability of gas and electrical supply.
2. Unit must be installed on the positive pressure side of the
circulating blower.
3. Be sure the structural support at the unit location site is
adequate to support the weight of the unit. For proper
operation the unit must be installed in a level horizontal
position.
4. Do not install units in locations where the flue products
can be drawn into the adjacent building openings such as
windows, fresh air intakes, etc.
5. Be sure that the minimum clearances to combustible
materials and recommended service clearances are
maintained. For HFG units, be sure clearances are
maintained to the combustion air/vent cap. For HFP units,
be sure clearances are maintained to the combustion air
inlet louvers and power exhauster discharge cover. Units
are designed for installation on non-combustible surfaces or
combustible surfaces with the minimum clearances shown in
Figure 3.1, Table 3.2, and Table 3.3.
Figure 3.1
Combustible Material and Service Clearances
➀Minimum clearance to combustibles is 0.0'' from bottom of unit mounting rail or
3'' from bottom of sheet metal of unit casing.
➁Minimum clearance to combustible for HFP is 1.0'' from rooftop.
Table 3.2
Combustible Material Clearances
Table 3.3
Service Clearances
HFP
HFG
3
SI (METRIC) CONVERSION FACTORS / UNIT LOCATION
cAUTION
Appliances are designed for outdoor installation only. DO NOT
LOCATE APPLIANCES INDOORS.
IMPORTANT
To prevent premature heat exchanger failure, do not locate
ANY gas-fired appliances in areas where corrosive vapors (i.e.
chlorinated, halogenated or acid) are present in the atmosphere. Clearance to
Combustible Materials
Model Front Front Non-Access Access
Size & Rear (B) & Rear (B) Side (C) Side (A)
HFG HFP HFG/HFP HFG HFP
75 0" 3" 0" 0" 3"
100/125 0" 3" 0" 0" 3"
150/175 3" 3" 0" 0" 3"
200/225 4" 4" 0" 0" 3"
250/300 5" 5" 0" 0" 3"
350/400 11" 11" 0" 0" 3"
AIR FLOW
TOP VIEW
ACCESS
SIDE
B
B
A
C
36"
NON-
ACCESS
SIDE
27"
➀
dANGER
Appliances must not be installed where they may be exposed
to a potentially explosive or flammable atmosphere.
To Convert Multiply By To Obtain
"W.C.
(inches water column) 0.24 kPa
psig 6.893 kpa
°F subtract 32 and then °C
multiply by 0.555
inches 25.4 mm
feet 0.305 meters
CFM 0.028 m3/min
CFH 1.699 m3/min
btu/ft30.0374 mJ/m3
pound 0.453 kg
btu/hr 0.000293 kW/hr
gallons 3.785 liters
SI (METRIC) CONVERSION FACTORS
Table 3.1
➁
Recommended
Service
Clearance
Model Access Non-
Size Side Access
(A) Side (C)
75 18" 6"
100/125 20" 6"
150/175 25" 6"
200/225 27” 6”
250/300 30" 6"
350/400 41" 6"

5-571.4
4
UNIT LIFTING
Lifting holes are provided in the mounting rails of the duct
furnace. When lifting the unit, use spreader bars between the
lifting cables as shown in Figure 4.1 to insure that no damage
will occur to the sheet metal parts of the duct furnace.
Figure 4.1 - Unit Lifting
INSTALLATION
Direction of Airflow
Select proper direction of airflow. If the unit is not provided with
an air distribution baffle (Not provided on models in which the
10th digit of the model number is an “L” for Low Temperature
Rise), the airflow direction is fully reversible without modification
to the duct furnace. See Airflow Reversal Note.
If the unit is provided with an air distribution baffle (Provided on
models in which the 10th digit of the model number is an “H”
for High Temperature Rise), the air baffle must face the air inlet
direction as shown in Figure 4.2. If it is necessary to reverse
the airflow direction, remove the four screws securing the air
distribution baffle, reverse the air distribution baffle to the air
inlet side and replace the screws. See Airflow Reversal Note.
Figure 4.2 - Air Distribution Baffle Location
Baffle location shown on entering air side of duct furnace.
Airflow Reversal Note: If factory installed discharge air
options (thermostat, freeze protection, etc.) were provided,
these options would have to be relocated to the discharge air
side of the duct furnace.
Duct Installation
1. The furnace is designed to accept 90° flanged ductwork.
See Figure 4.3. Provide an airtight seal between the
ductwork and the furnace. Seams with cracks in ductwork
should be caulked and/or taped and be of permanent type.
All duct connections MUST be weathertight to prevent rain
and snow from entering the ductwork.
2. Provide removable access panels on both the upstream
and downstream sides of the ductwork; see Figure 4.3.
These openings should be large enough to view smoke or
reflect light inside the casing to indicate leaks in the heat
exchanger and to check for hot spots on heat exchangers
due to poor air distribution or lack of sufficient air (CFM).
Figure 4.3 - Duct Connections
4
UNIT LIFTING / INSTALLATION
AIR
DISTRIBUTION
BAFFLE
DUCT FURNACE
DUCTWORK
ACCESS
PANEL
90°
FLANGED
DUCTWORK
1/2"
Airflow Distribution
1. Provide uniform air distribution over the heat exchanger.
Use turning vanes where required (see Figure 5.1) to obtain
uniform air distribution. Avoid installing as in “G”, “H” & “J” of
Figure 5.1.
2. A bottom, horizontal discharge type blower should be
installed at least 12" from the furnace (See “A”, Figure 5.1).
3. A top, horizontal discharge type blower should be installed
at least 24" from the furnace (See “B”, Figure 5.1). Provide
air baffle at top of duct to deflect air down to the bottom of
heat exchanger.
IMPORTANT
To prevent premature heat exchanger failure, observe heat
exchanger tubes by looking at the heat exchanger through
field installed access openings in connecting ductwork. If
the bottom of the tubes become red while blower and duct
furnace are in operation, additional baffles must be inserted
between blower and duct furnace to assure uniform air flow
across the heat exchanger.

5-571.4 55
INSTALLATION
Figure 5.1 - Typical Duct & Airflow Installation
RECOMMENCED INSTALLATIONS
Dimensions “B” should never
be less than 1¼2of “A”.
CA
FED
B
12"
Min.
12"
Min.
12"
Min.
12"
Min.
12"
Min.
12"
Min.
24"
Min.
24"
Min.
3" Min.
3" Max.
3" Max.
3" Max.
15° Max. 15° Max.
15° Max.
Air
Baffle
Air
Baffle
Baffle
Baffle
Baffle
B
B
B
BAA
AA
B
Turning
Vanes
Turning
Vanes
Turning
Vanes
Turning
Vanes
Turning
Vanes
3" Min.
Turning
Vanes
3" Max.
3" Min.
Turning
Vanes
SIDE VIEW
SIDE VIEW SIDE VIEW
TOP VIEW
TOP VIEW
TOP VIEW
SIDE VIEW
SIDE VIEWSIDE VIEW
RECOMMENDED INSTALLATIONS
INSTALLATIONS NOT RECOMMENDED
No Air
No Air No Air
G
POOR H POOR J POOR
Venting
1. Installation of venting must conform with local building
codes, or in the absence of local codes, with the National
Fuel Gas Code, ANSI Z223.1 (NFPA 54) - Latest Edition.
In Canada, installation must be in accordance with CAN/
CGA-B149.1 for natural gas units and CAN/CGA-B149.2 for
propane units.
2. For HFG units, do not operate duct furnaces without the
factory supplied vent cap (shipped loose) fastened securely
in place. HFP units are shipped with the power exhauster
discharge cover factory installed.
3. For HFG units, do not modify or obstruct the vent cap
in any manner. For HFP units, do not modify or obstruct
the combustion air inlet louvers or the power exhauster
discharge cover.
4. Do not add any vents other than those supplied by the
manufacturer.
Gas Connections
cAUTION
Purging of air from gas supply line should be performed as
described in ANSI Z223.1 - latest edition “National Fuel Gas
Code”, or in Canada in CAN/CGA-B149 codes.
WARNING
1. All field gas piping must be pressure/leak tested prior to
operation. Never use an open flame. Use a soap solution or
equivalent for testing.
2. Gas pressure to appliance controls must never exceed 14"
W.C. (1/2 psi).
3. To reduce the opportunity for condensation, the minimum sea
level input to the appliance, as indicated on the serial plate,
must not be less than 5% below the rated input, or 5% below
the minimum rated input of dual rated units.
IMPORTANT
To prevent premature heat exchanger failure, the input to the
appliance, as indicated on the serial plate, must not exceed
the rated input by more than 5%.

5-571.4
66
INSTALLATION
Gas Connections (continued)
1. Installation of piping must conform with local building codes,
or in the absence of local codes, with the National Fuel Gas
Code, ANSI Z223.1 (NFPA 54) - Latest Edition. In Canada,
installation must be in accordance with CAN/CGA-B149.1 for
natural gas units and CAN/CGA-B149.2 for propane units.
2. Piping to units should conform with local and national
requirements for type and volume of gas handled, and
pressure drop allowed in the line. Refer to Table 9.1 to
determine the cubic feet per hour (cfh) for the type of gas
and size of unit to be installed. Using this cfh value and the
length of pipe necessary, determine the pipe diameter from
Table 6.1. Where several units are served by the same
main, the total capacity, cfh and length of main must be
considered. Avoid pipe sizes smaller than 1/2". Table 6.1
allows for a 0.3" W.C. pressure drop in the supply pressure
from the building main to the unit. The inlet pressure to the
unit must be 6-7" W.C. for natural gas and 11-14" W.C. for
propane gas. When sizing the inlet gas pipe diameter, make
sure that the unit supply pressure can be met after the 0.3"
W.C. has been subtracted. If the 0.3" W.C. pressure drop is
too high, refer to the Gas Engineer’s Handbook for other gas
pipe capacities.
3. The gas piping to the unit can enter the unit from the side
of the unit or from below (curb mounted units). Drill locator
dimples are located in the side and bottom of the unit for
field drilling the hole for the gas pipe entry.
For side piped units
Install a ground joint union with brass seat and a manual
shut-off valve external of the unit casing, and adjacent to the
unit for emergency shut-off and easy servicing of controls,
including a 1/8" NPT plugged tapping accessible for test
gauge connection (See Figure 6.1).
For bottom piped units
Install a ground joint union with brass seat and a manual
shut-off valve internal to the unit casing for easy servicing of
controls, including a 1/8" NPT plugged tapping accessible for
test gauge connection (See Figure 6.2). NOTE: Some local
codes may require a manual shutoff valve external to the unit
casing. In this case, the gas piping must exit the unit through
a side piping hole, followed by the manual shut-off valve,
piped back into the unit corner post, through the unit bottom,
and lead to an additional union and manual shut-off valve.
4. Provide a sediment trap before each unit in the line where
low spots cannot be avoided. (See Figures 6.1 & 6.2).
5. When Pressure/Leak testing, pressures above 14" W.C.
(1/2 psi), close the field installed shut-off valve, disconnect
the appliance and its combination gas control from the gas
supply line, and plug the supply line before testing. When
testing pressures 14" W.C. (1/2 psi) or below, close the
manual shut-off valve on the appliance before testing.
Figure 6.1
Recommended Sediment Trap/Manual Shut-off Valve
Installation - Side Gas Connection
Figure 6.2
Recommended Sediment Trap/Manual Shut-off Valve
Installation - Bottom Gas Connection
➀ Manual shut-off valve is in the “OFF” position when handle is perpendicular to
pipe.
Table 6.1 - Gas Pipe Capacities
Gas Pipe Capacities (Up to 14” W.C. Gas Pressure through Schedule 40 Pipe)
Cubic Feet per Hour with Pressure Drop of 0.3” W.C.
Natural Gas - Specific Gravity - 0.60
Propane Gas - Specific Gravity - 1.50
Length Pipe Diameter
Of Pipe 1/2" 3/4" 1" 1-1/4" 1-1/2" 2"
(feet) Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane
10 132 83 278 175 520 328 1050 662 1600 1008 3050 1922
20 92 58 190 120 350 221 730 460 1100 693 2100 1323
30 73 46 152 96 285 180 590 372 890 561 1650 1040
40 63 40 130 82 245 154 500 315 760 479 1450 914
50 56 35 115 72 215 135 440 277 670 422 1270 800
60 50 32 105 66 195 123 400 252 610 384 1150 725
70 46 29 96 60 180 113 370 233 560 353 1050 662
80 43 27 90 57 170 107 350 221 530 334 990 624
90 40 25 84 53 160 101 320 202 490 309 930 586
100 38 24 79 50 150 95 305 192 460 290 870 548
125 34 21 72 45 130 82 275 173 410 258 780 491
150 31 20 64 40 120 76 250 158 380 239 710 447
GAS
SUPPLY LINE
GAS
SUPPLY LINE
GROUND
JOINT
UNION
W/ BRASS
SEAT
MANUAL GAS
SHUT-OFF VALVE
3"
MIN.
SEDIMENT
TRAP
PLUGGED
1/8" NPT TEST
GAGE CONNECTION
TO
CONTROLS
➀
GAS
SUPPLY LINE GROUND
JOINT
UNION
W/ BRASS
SEAT
MANUAL GAS
SHUT-OFF VALVE
3"
MIN.
SEDIMENT
TRAP
TO
CONTROLS
PLUGGED 1/8"
NPT TEST GAGE
CONNECTION
Through hole
in bottom of unit.
(caulk hole to prevent
water leakage.)
➀

5-571.4 7
Electrical Connections
1. Installation of wiring must conform with local building
codes, or in the absence of local codes, with the National
Electric Code ANSI/NFPA 70 - Latest Edition. Unit must
be electrically grounded in conformance to this code.
In Canada, wiring must comply with CSA C22.1, Part 1,
Electrical Code.
2. All duct furnaces are provided with a wiring diagram located
on the inside door of the electrical junction box. Refer to
this wiring diagram for all wiring connections. For factory
installed options and field installed accessory wiring, refer to
Set A and Set B on the provided wiring diagram.
3. The power supply to the duct furnace should be protected
with a fused disconnect switch.
4. Refer to Table 7.1 to determine the amp draw of the duct
furnace. Size the disconnect switch to cover the amp draw
of the unit.
5. Refer to the unit dimensional drawings on pages 13 and 14
for the location of the drill locator dimples in the side and
bottom of the unit for field drilling the hole for the electrical
conduit entry.
Table 7.1 - Unit Amps
START-UP PROCEDURE
1. Turn off power to the unit at the disconnect switch. Check
that fuses or circuit breakers are in place and sized
correctly. Turn all hand gas valves to the “OFF” position.
2. Check that the supply voltage matches the unit supply
voltage listed on the serial plate. Verify that all wiring is
secure and properly protected. Trace circuits to insure that
the unit has been wired according to the wiring diagram.
3. Check that all electrical and gas connections are
weatherized.
4. For HFG units, check to insure that the vent cap is installed
and free from obstructions. For HFP units, check to
insure that the combustion air inlet louvers and the power
exhauster discharge cover is free from obstructions/damage.
5. Check to see that there are no obstructions to the intake
and discharge of the duct furnace.
6. Perform a visual inspection of the unit to make sure no
damage has occurred during installation.
7. Turn on power to the unit at the disconnect switch. Check to
insure that the voltage between terminals 1 and 2 is 24V.
8. Check the thermostat, ignition control, gas valve, and supply
fan blower motor for electrical operation. If these do not
function, recheck the wiring diagram. Check to insure that
none of the Gas Control Options & Accessories (see page
12) have tripped.
9. Recheck the gas supply pressure at the field installed
manual-shut-off valve. The inlet pressure should be 6" - 7"
W.C. on natural gas or 11" - 14" W.C. on propane. If inlet
pressure is too high, install an additional pressure regulator
upstream of the combination gas control.
10. Open the field installed manual gas shut-off valve.
11. Open the manual main gas valve on the combination gas
control. Call for heat with the thermostat and allow the
pilot to light. (For HFP units, on a call for heat the power
exhauster relay will energize the power exhauster motor.
Once the power exhauster motor reaches full speed, a
centrifugal switch in the motor will close before the pilot can
light.) If the pilot does not light, purge the pilot line. If air
purging is required, disconnect the pilot line at outlet of pilot
valve. In no case should line be purged into heat exchanger.
Check the pilot flame length (See Pilot Burner Adjustment).
12. Once the pilot has been established, check to make sure
that the main gas valve opens. Check the manifold gas
pressure (See Main Burner Adjustment) and flame length
(See Air Shutter Adjustment) while the circulating air blower
is operating.
13. Check to insure that gas controls sequence properly
(See Control Operating Sequence). Verify if the unit has
any additional control devices and set according to the
instructions in the Gas Controls Options.
14. Once proper operation of the duct furnace has been
verified, remove any jumper wires that were required for
testing.
15. Close the electrical compartment door.
16. Replace all exterior panels.
7
INSTALLATION / START-UP PROCEDURE
IMPORTANT
Start-up and adjustment procedures should be performed by a
qualified service agency.
Base Model Supply
(Digits 1-6) Voltage 1 2 3 4 0
(Digit 14)
A 0.35 0.65 1.30 2.17 0.00
B or D 0.19 0.36 0.72 1.20 0.00
HFG (All) C or E 0.17 0.33 0.65 1.09 0.00
F 0.09 0.16 0.33 0.54 0.00
G 0.07 0.13 0.26 0.43 0.00
A 1.75 2.05 2.70 3.57 1.40
B or D 0.89 1.06 1.42 1.90 0.70
HFP C or E 0.83 0.99 1.31 1.75 0.66
75-175 F 0.63➀ 1.25➁ 2.50➂2.72➂ 0.00 ➃
G 0.50➀ 1.00➁ 2.00➂2.17➂ 0.00 ➃
A 2.35 2.65 3.30 4.17 2.00
B or D 1.14 1.31 1.67 2.15 0.95
HFP C or E 1.27 1.43 1.75 2.19 1.10
200-400 F 0.63➀ 1.25➁ 2.50➂2.72➂ 0.00 ➃
G 0.50➀ 1.00➁ 2.00➂2.17➂ 0.00 ➃
Transformer (Digit 15)
➀ Includes a field supplied 250 VA step down transformer from supply voltage to 115V.
➁ Includes a field supplied 500 VA step down transformer from supply voltage to 115V.
➂ Includes a field supplied 1000 VA step down transformer from supply voltage to 115V.
➃ Unit amp draw is included in master unit amp draw.
WARNING
1. Disconnect power supply before making wiring
connections to prevent electrical shock and equipment
damage.
2. All appliances must be wired strictly in accordance with
wiring diagram furnished with the appliance. Any wiring
different from the wiring diagram could result in a hazard
to persons and property.
3. Any original factory wiring that requires replacement must
be replaced with wiring material having a temperature
rating of at least 105°C.
4. Ensure that the supply voltage to the appliance, as indicated
on the serial plate, is not 5% greater than rated voltage.

5-571.4
88
START-UP PROCEDURE
Pilot Burner Adjustment
The pilot burner is orificed to burn properly with an inlet
pressure of 6-7" W.C. on natural gas and 11-14" W.C. on
propane gas, but final adjustment must be made after
installation. If the pilot flame is too long or large, it is possible
that it may cause soot and/or impinge on the heat exchanger
causing failure. If the pilot flame is shorter than shown, it may
cause poor ignition and result in the controls not opening the
combination gas control. A short flame can be caused by a
dirty pilot orifice. Pilot flame condition should be observed
periodically to assure trouble-free operation.
To Adjust the Pilot Flame
1. Create a call for heat from the thermostat.
2. Remove the cap from the pilot adjustment screw. For
location, see the combination gas control literature supplied
with unit.
3. Adjust the pilot length by turning the screw in or out
to achieve a soft steady flame 3/4" to 1" long and
encompassing 3/8"-1/2" of the tip of the thermocouple or
flame sensing rod (See Figure 8.1).
4. Replace the cap from the pilot adjustment screw.
Figure 8.1 - Correct Pilot Flame
Main Burner Adjustment
The gas pressure regulator (integral to the combination gas
control) is adjusted at the factory for average gas conditions.
It is important that gas be supplied to the duct furnace in
accordance with the input rating on the serial plate. Actual
input should be checked and necessary adjustments made
after the duct furnace is installed. Over-firing, a result of too
high an input, reduces the life of the appliance and increases
maintenance. Under no circumstances should the input exceed
that shown on the serial plate.
Measuring the manifold pressure is done at the tee in the
manifold (See Figure 9.1).
To Adjust the Manifold Pressure
1. Move the field installed manual shut-off valve to the “OFF”
position.
2. Remove the 1/8" pipe plug in the pipe tee and attach a
water manometer of “U” tube type which is at least 12" high.
3. Move the field installed manual gas shut-off valve to the
“ON” position.
4. Create a high fire call for heat from the thermostat.
5. Determine the correct high fire manifold pressure. For
natural gas 3.5” W.C., for propane gas 10” W.C. Adjust the
main gas pressure regulator spring to achieve the proper
manifold pressure (for location, see the combination gas
control literature supplied with unit).
6. If the unit has Electronic Modulation gas controls
(determine from the Model Identification Digit 12), the low
fire gas pressure needs to be adjusted. Using Figure 9.2 for
item number locations, this is accomplished as follows:
a. Disconnect power.
b. Remove all wires from duct furnace terminal “43” and
remove cover plate (2).
c. Turn on power at the disconnect switch.
d. Remove the maximum adjustment screw (4), spring
(5), and plunger (8). A small magnet is useful for this
purpose. CAUTION - The plunger is a precision part.
Handle carefully to avoid marring or picking up grease
and dirt. Do not lubricate.
e. Using minimum adjusting screw (9), adjust low fire
manifold pressure to 0.56" W.C. for natural gas and
1.6" W.C. for propane gas.
f. Replace plunger and spring retainer, spring, and
maximum adjusting screw in proper order.
g. Using maximum adjustment screw (4), adjust high fire
manifold pressure to 3.5" W.C. for natural gas and 10"
W.C. for propane gas.
h. Disconnect power.
i. Replace cover plate (2) and re-install all wires from
duct furnace terminal “43”.
7. After adjustment, move the field installed manual shut-off
valve to the “OFF” position and replace the 1/8" pipe plug.
8. After the plug is in place, move the field installed manual
shut-off valve to the “ON” position and recheck pipe plugs
for gas leaks with soap solution.
3/4" to 1"

5-571.4 9
Figure 9.1
Checking Manifold Pressure with “U” Tube Manometer
Figure 9.2
Maxitrol Modulating Valve Adjustments
Air Shutter Adjustment
Proper operation provides a soft blue flame with a well-defined
inner core. A lack of primary air will reveal soft yellow-tipped
flames. Excess primary air produces short, well-defined flames
with a tendency to lift off the burner ports. For both natural
and propane gas, the air shutters can be adjusted to control
the burner flame height. The air shutters can be accessed
by reaching behind the manifold tee shown in Figure 9.1. The
larger models may require the removal of the manifold (see
Manifold Assembly Removal).
Natural Gas Flame Control
Control of burner flames on duct furnaces utilizing natural gas
is achieved by resetting the primary air shutters (See Figure
19.1) to either increase or decrease primary combustion air.
Prior to flame adjustment, operate duct furnace for about fifteen
minutes. The main burner flame can be viewed after loosening
and pushing aside the gas designation disc on the side of the
burner box.
To increase primary air, loosen the air shutter set screws and
move the air shutters closer to the manifold until the yellow-
tipped flames disappear. (See Figure 19.1 for air shutter and
heat exchanger support locations.) To decrease primary air,
move the air shutters away from the manifolds until flames no
longer lift from burner ports, but being careful not to cause
yellow tipping. Retighten set screws after adjustment.
Propane Gas Flame Control
An optimum flame will show a slight yellow tip. Prior to flame
adjustment, operate furnace for at least fifteen minutes. Loosen
air shutter set screws and move the air shutters away from the
manifold to reduce the primary air until the yellow flame tips
appear. Then increase the primary air until yellow tips diminish
and a clean blue flame with a well defined inner cone appears.
Table 9.1
Manifold Pressure and Gas Consumption
9
START-UP PROCEDURE
Model Size Type of Gas Natural Propane
Btu/Cu. Ft. 1040 2500
Specific Gravity 0.60 1.53
High Fire Manifold Pressure No. of
Inches of Water Column 3.5 10 Orifices
Cfh 72.1 30.0 1
75 Orifice Drill Size 20 37
Cfh 96.1 40.0 2
100 Orifice Drill Size 30 45
Cfh 120.2 50.0 2
125 Orifice Drill Size 25 42
Cfh 144.2 60.0 3
150 Orifice Drill Size 30 45
Cfh 168.3 70.0 3
175 Orifice Drill Size 27 43
Cfh 192.3 80.0 3
200 Orifice Drill Size 23 40
Cfh 216.3 90.0 3
225 Orifice Drill Size 20 37
Cfh 240.4 100.0 4
250 Orifice Drill Size 25 42
Cfh 288.7 120.0 4
300 Orifice Drill Size 20 37
Cfh 336.5 140.0 6
350 Orifice Drill Size 27 43
Cfh 384.6 160.0 6
400 Orifice Drill Size 23 40
MANIFOLD TEE

5-571.4
10
➀ After the thermostat calls for heat, the power exhauster relay is energized starting the power exhauster motor. Once the motor has reached full speed, the power
exhauster centrifugal switch closes energizing the gas control circuit.
10
START-UP PROCEDURE
Control Operating Sequence
All Modine weatherproof duct furnaces are supplied with
intermittent pilot ignition systems. These systems are offered
with 100% shut-off with continuous retry for operation on
natural gas and 100% shut-off with lockout for units operating
on propane gas. On all systems, both the main burner and pilot
burner are turned off 100% when the thermostat is satisfied.
For natural gas units, the ignition controller is 100% shut-off
with continuous retry. On a call for heat, the system will attempt
to light the pilot for 70 seconds. If the pilot is not sensed for
any reason, the ignition control will wait for approximately six
minutes with the combination gas control closed and no spark.
After six minutes, the cycle will begin again. After three cycles,
some ignition controllers lockout for approximately one hour
before the cycle begins again. This will continue indefinitely until
the pilot flame is sensed or power is interrupted to the system.
For propane gas units, the ignition controller is 100% shut-off
with lockout. On a call for heat, the system will attempt to light
the pilot for 70 seconds. If the pilot is not sensed for any reason,
the ignition control will lockout, the pilot gas valve shut off and
the sparking discontinued. The system will not attempt to relight
until power has been interrupted to the controls and the controls
are reset via the thermostat.
NOTE: Gas Control Options (see page 12) could change the
listed sequence of operation based on their function.
The descriptions given are for the basic duct furnace.
Single-Stage Gas Controls
Utilizes a single-stage combination gas control, an ignition
control, and a single-stage low voltage thermostat.
1. The thermostat calls for heat. For HFP units, see ➀.
2. The pilot valve opens and the spark ignitor sparks in an
attempt to light the pilot. (If the unit was not provided with a
time delay relay, the blower starts at this time.)
3. Once the pilot is lit, the flame sensor proves the pilot and
stops the spark ignitor from sparking.
4. The main gas valve is opened and the main burner is lit to
100% full fire.
5. If the unit was provided with a time delay relay, the blower
starts after 30 to 45 seconds.
6. The unit continues to operate until the thermostat is
satisfied, at which time both the main and pilot valves close
100%. (If the unit was not provided with a time delay relay,
the blower stops at this time.)
7. If the unit was provided with a time delay relay, the blower
stops after 30 to 45 seconds.
Two-Stage Gas Controls
Utilizes a two-stage combination gas control, an ignition control,
and a two-stage low voltage thermostat. The unit fires at 50%
fire on low stage and 100% fire on high stage.
1. The thermostat calls for low stage heat. For HFP units, see ➀.
2. The pilot valve opens and the spark ignitor sparks in an
attempt to light the pilot. (If the unit was not provided with a
time delay relay, the blower starts at this time.)
3. Once the pilot is lit, the flame sensor proves the pilot and
stops the spark ignitor from sparking.
4. The main gas valve is opened and the main burner is lit to
50% fire.
5. If the unit was provided with a time delay relay, the blower
starts after 30 to 45 seconds.
6. If the temperature at the thermostat continues to fall, the
thermostat will call for high stage heat.
7. The main gas valve is opened completely and the main
burner is lit to 100% full fire.
8. The unit continues to operate until the high stage of the
thermostat is satisfied, at which time the main valve closes
to 50% fire.
9. The unit continues to operate until the low stage thermostat
is satisfied, at which time both the main and pilot valves
close 100%. (If the unit was not provided with a time delay
relay, the blower stops at this time.)
10. If the unit was provided with a time delay relay, the blower
stops after 30 to 45 seconds.
Electronic Modulating Gas Controls
Single Furnace
Utilizes an electronic modulating/regulating gas control,
combination gas valve, an ignition control, modulating amplifier,
and either a modulating room thermostat or modulating
duct thermostat with remote temperature set point adjuster.
The thermostat controls can modulate the gas flow between
40% through 100% full fire. When the thermostat is satisfied,
the amplifier cuts power to the combination gas valve which
prevents gas flow to both the main and pilot burners.
When duct sensing is utilized, a room override thermostat can
be added. When calling for heat, the room override thermostat
provides full fire operation until the space temperature is
satisfied. Control is then returned to the duct sensing control.
In this situation, either the duct sensor or the room override
thermostat can call for heat.
1. The thermostat calls for heat. For HFP units, see ➀.
2. The pilot valve opens and the spark ignitor sparks in an
attempt to light the pilot. (If the unit was not provided with a
time delay relay, the blower starts at this time.)
3. Once the pilot is lit, the flame sensor proves the pilot and
stops the spark ignitor from sparking.
4. The main gas valve is opened and the main burner is lit to
100% full fire.
5. If the unit was provided with a time delay relay, the blower
starts after 30 to 45 seconds.
6. The modulating gas valve can be controlled by either
an electronic modulating room or duct thermostat. The
thermostat can modulate the firing rate between 40%
through 100% full fire. The call for heat is created by a
resistance signal (8000 to 12000 ohms) in the thermostat.
The amplifier converts this resistance into a DC voltage (0
to 12 volts DC with 0 volts high fire and 12 volts low fire).
The output voltage is applied to the modulating gas valve to
control the gas flow to the main burner. As the temperature
drops, the voltage drops causing the modulating valve to
open further. If the discharge air temperature increases,
the voltage increases causing the modulating valve to
close allowing less gas flow to the main burner. For further
information regarding the operation of the electronic
modulating system, consult the literature provided with the
unit.
7. The unit continues to operate in this manner until the
thermostat is satisfied, at which time both the main and
pilot valves close 100%. (If the unit was not provided with a
time delay relay, the blower stops at this time.)
8. If the unit was provided with a time delay relay, the blower
stops after 30 to 45 seconds.
IMPORTANT
To prevent premature heat exchanger failure, with all control
systems, a blower starting mechanism must be provided so
that the blower is running or energized within 45 seconds of
the gas control operation.

5-571.4 1111
START-UP PROCEDURE
Electronic Modulating Gas Controls - Master/Slave
One Master furnace is provided with up to three Slave furnaces
that utilize electronic modulating/regulating gas controls,
combination gas valves, ignition controls, one multiple furnace
modulating amplifier, and either a modulating room thermostat
or modulating duct thermostat with remote temperature adjuster.
The thermostat controls can modulate the gas flow of all the
furnaces between 40% through 100% full fire. The amplifier
sends a signal to all of the gas valves so that they modulate
at the same percentage. When the thermostat is satisfied,
the amplifier cuts power to the combination gas valves which
prevents gas flow to both the main and pilot burners.
When duct sensing is utilized, a room override thermostat can
be added. When calling for heat, the room override thermostat
provides full fire operation until the space temperature is
satisfied. Control is then returned to the duct sensing control.
In this situation, either the duct sensor or the room override
thermostat can call for heat.
The sequence of operation for Electronic Modulating Gas
Controls - Master/Slave is the same as Electronic Modulating
Gas Controls - Single Furnace.
Electronic Modulating Gas Controls -
Building Management Control
(0-10Vdc or 4-20 mA Signal)
Utilizes an electronic modulating/regulating gas control,
combination gas valve, an ignition control, modulating signal
conditioner, and an inverted (0 Vdc or 4mA being high fire and
10 Vdc or 20 mA being low fire) 0-10Vdc or 4-20 mA input
signal provided by a Building Management System (BMS). The
signal conditioner can modulate the gas flow between 40%
through 100% full fire. When the BMS thermostat (field supplied)
is satisfied, the BMS heat contact (field supplied) opens to cut
power to the combination gas valve which prevents gas flow to
both the main and pilot burners.
1. The BMS thermostat (field supplied) calls for heat and
closes the BMS heat contact (field supplied). For HFP units,
see ➀.
2. The pilot valve opens and the spark ignitor sparks in an
attempt to light the pilot. (If the unit was not provided with a
time delay relay, the blower starts at this time.)
3. Once the pilot is lit, the flame sensor proves the pilot and
stops the spark ignitor from sparking.
4. The main gas valve is opened and the main burner is lit to
100% full fire.
5. If the unit was provided with a time delay relay, the blower
starts after 30 to 45 seconds.
6. The modulating gas valve is controlled the BMS thermostat.
The thermostat can modulate the firing rate between
40% through 100% full fire by modulating the input signal
between either 0-10Vdc or 4-20 mA (The signal conditioner
can accept a 0-10 Vdc signal when all the dip switches are
in the “OFF” position and 4-20 mA signal when all the dip
switches are in the “ON” position). The signal conditioner
converts the input signal into a DC voltage (0 to 12 volts
DC with 0 volts high fire and 12 volts low fire). The output
voltage is applied to the modulating gas valve to control the
gas flow to the main burner. As the temperature drops, the
voltage drops causing the modulating valve to open further.
If the discharge air temperature increases, the voltage
increases causing the modulating valve to close allowing
less gas flow to the main burner. For further information
regarding the operation of the electronic modulating
system, consult the literature provided with the unit.
7. The unit continues to operate in this manner until the
thermostat is satisfied, at which time the BMS heat contact
opens resulting in both the main and pilot valves closing
100%. (If the unit was not provided with a time delay relay,
the blower stops at this time.)
8. If the unit was provided with a time delay relay, the blower
stops after 30 to 45 seconds.
Variable Air Movement Applications
When the air mover supplied by others can provide variable
air movement (i.e. 2-speed or variable frequency drive units),
the allowable minimum CFM of the HFG/HFP duct furnace can
be 66% of the minimum listed CFM in Table 15.2 if the unit is
applied as follows:
1. The unit is provided with 2-stage, mechanical modulation,
or electronic modulating gas controls. (see Model
Identification).
2. The unit is provided with a factory installed discharge air
controller.
3. The system does not include a room thermostat.
The factory installed discharge air thermostat will prevent the
unit from firing above the allowable 100°F rise when the unit is
at or above the minimum CFM by monitoring the discharge air
and going to low fire. A room thermostat, because it is located
remote from the unit, could cause the unit to over-fire.
➀ After the thermostat calls for heat, the power exhauster relay is energized starting the power exhauster motor. Once the motor has reached full speed, the power
exhauster centrifugal switch closes energizing the gas control circuit.

5-571.4
1212
START-UP PROCEDURE
Gas Control Options
The unit must be reviewed to determine if any of the listed gas
control options were supplied.
➀Time Delay Relay
The Time Delay Relay is factory installed in the duct furnace
electrical junction box. The standard duct furnace is provided
for instantaneous fan operation. On a call for heat, the blower is
energized at the same time as the gas controls. The optional time
delay relay allows the gas controls to operate for approximately 30
seconds before the blower starts. This allows the heat exchanger
a warm up period so that the initial delivered air coming out of the
ductwork is not cool. The time delay relay also keeps the motor
running for approximately 30 seconds after the call for heat has
been satisfied to remove the residual heat from the heat exchanger.
➁Low Gas Pressure Switch
The low gas pressure switch is factory installed in the duct furnace
above the gas train. The switch monitors the gas pressure
upstream of all the gas controls and shuts off the electric supply
to the ignition controller and combination gas valve if low gas
pressure is experienced. This will shut off all gas flow to the burner.
The switch has an automatic reset so that if the gas pressure
is interrupted and then is returned, the switch will automatically
allow the unit to operate when gas conditions are returned to the
allowable range of the pressure switch. The pressure switch range
is 2" to 14" W.C. and should be set to insure that the minimum inlet
gas pressure is available (6" W.C. for natural gas, 11" W.C. for
propane gas).
➂High Gas Pressure Switch
The high gas pressure switch is factory installed in the duct
furnace above the gas train. The switch monitors the gas pressure
downstream of all the gas controls and shuts off the electric supply
to the ignition controller and combination gas valve if high gas
pressure is experienced right before the manifold. This will shut off
all gas flow to the burner. The switch has a manual reset so that if
the gas pressure is too high, a service person must check the unit
to make sure that none of the gas controls have been damaged
by the high gas pressure and then reset the switch to allow the
unit to operate when gas conditions are returned to the allowable
range of the pressure switch. The pressure switch range is 2" to 16"
W.C. and should be set to insure that the maximum manifold gas
pressure is not exceeded (3.5" W.C. for natural gas, 10" W.C. for
propane gas).
➃Supply Air Fire Stat
The fire stat is factory installed in the duct furnace electrical junction
box with the sensor in the discharge air stream. In case of elevated
temperatures in the supply air, the manual reset switch shuts
down the entire unit. If the limit temperature is exceeded, a service
person must inspect the unit for the cause of the high discharge
temperature, take corrective action, and then reset the switch.
➄Timed Freeze Protection
The timed freeze protection system is factory installed in the duct
furnace electrical junction box with the sensor (30°-75°F adjustable)
factory installed in discharge air stream. On initial start-up, the
timed delay in the system allows the unit to go through the normal
ignition sequence. The timed delay is an automatic reset switch and
adjustable for 1-10 minutes. In the event that the unit fails to fire
after this period, the discharge air sensor will sense the cold air and
will shut down the entire unit.
Figure 12.1 - Location of Gas Control Options
➅Air Flow Proving Switch
The air flow proving switch is factory installed in the duct furnace
electrical junction box. The air flow proving switch monitors the
pressure differential between the duct furnace and the atmosphere.
The purpose of the air flow proving switch is to cut power to the
gas controls if a positive pressure is not measured by the switch.
This could be caused by a lack of air movement through the heat
exchanger.
NOTE: The air flow proving switch will prevent any heat
exchanger warm-up (the unit should not be equipped with
a time delay relay) because the gas controls can not be
energized until air flow is proven.
Setting the Air Flow Proving Switch
The range of the air flow proving switch is adjustable between 0.17"
to 5.0" W.C.
1. Set the thermostat so that there is a call for heat. This should
start the blower and then the burner ignition sequence.
2. Turn the set screw of the pressure switch clockwise until it
stops. This will set the pressure at 5.0" W.C.
3. Turn the screw counter-clockwise until the gas controls light
and then one additional full turn (This is approximately 0.25''
W.C.). This will allow for dirty filters or any other slight static
pressure increases in the system.
➆Manual Reset High Limit
The manual reset high limit switch is factory installed in place
of the standard automatic reset high limit switch located in the
duct furnace electrical junction box. In case of a failure of the
blower motor, blockage of the inlet air, etc., the manual reset
switch prevents the unit from cycling on the high limit. If the limit
temperature is exceeded, a service person must inspect the unit for
the cause of the high discharge temperature, take corrective action,
and then reset the switch.
OPTIONAL
CONTROL RELAY
IGNITION
CONTROLLER ➀
CONTROL
TRANSFORMER
LOW VOLTAGE
TERMINAL STRIP
SUPPLY
POWER
TERMINAL
STRIP
OPTIONAL
DISCHARGE
AIR T-STAT ➄
➃
➁➂
➆
➅
POWER EXHAUSTER
RELAY
POWER
EXHAUSTER
MOTOR
(HFP ONLY)

5-571.4 1313
DIMENSIONAL DATA
Figure 13.1 - HFG Unit Drawing
Model Size 75 100/125 150/175 200/225 250/300 350/400
A 19.22 19.22 19.22 19.22 21.31 24.64
B31.96 34.46 38.72 40.84 43.86 55.38
C18.98 18.98 18.98 22.98 22.98 22.98
E14.20 14.20 14.20 14.20 15.18 18.38
F36.11 36.11 36.11 40.11 40.11 40.11
G25.50 28.00 32.25 34.38 37.40 48.92
Gas Connection Pipe Size 1/2" 1/2" 1/2" 1/2" 3/4" 3/4"
Approx. Unit Shipping 282# 305# 333# 383# 428# 525#
Weight Unit Net 207# 225# 248# 288# 318# 400#
Cap Net 16# 16# 16# 16# 26# 35#
Table 13.1 - Model HFG Dimensions (All dimensions in inches)
Figure 13.2 - Rail or Slab Type Mounting Base
A
33.50
10.26
DRILL LOCATOR
DIMPLES FOR GAS
PIPE ENTRY LOCATION
(FIELD DRILLED HOLE)
37.44
SIDE VIEW REAR VIEW
G
9.00
3.00
F
24.90
22.47
13.00
C
D
8.40
4.70
ELECTRICAL
CONNECTIONS
(both sides)
E
A
B
4.29 BOTTOM DRILL LOCATOR DIMPLES
FOR GAS PIPE ENTRY LOCATION
(FIELD DRILLED HOLE)
6.28
B
G
2.35 LIFTING HOLE
0.75 DIA.
GAS
CONTROL
ACCESS
SIDE
LIFTING
HOLE
1.00 DIA.
37.44 23.10
1.50
1.80 1.75 3.00
1.75
5.42
2.00 1.00
SPREADER
BAR
SPREADER
BAR

5-571.4
1414
DIMENSIONAL DATA
Figure 14.1 - HFP Unit Drawing
INLET LOUVERS
COMBUSTION AIR
DISCHARGE COVER
POWER EXHAUSTER
ELECTRICAL
CONNECTIONS
(both sides)
37.44
10.26
4.70
3.00
F
24.90
22.47
13.00
G
B
D
8.40
C
9.00
33.50
4.29
6.28
9.50
R
1.72
3.00
2.67
4.16
Q
DRILL LOCATOR
DIMPLES FOR GAS
PIPE ENTRY LOCATION
(FIELD DRILLED HOLE)
BOTTOM DRILL LOCATOR
DIMPLES FOR GAS
PIPE ENTRY LOCATION
(FIELD DRILLED HOLE)
SIDE VIEW REAR VIEW
Model Size 75 100/125 150/175 200/225 250/300 350/400
B 31.96 34.46 38.72 40.84 43.86 55.38
C 18.98 18.98 18.98 22.98 22.98 22.98
D 15.18 17.69 21.94 24.06 27.09 38.60
F 36.11 36.11 36.11 40.11 40.11 40.11
G 25.50 28.00 32.25 34.38 37.40 48.92
Q 10.95 10.95 10.95 11.58 11.58 11.58
R 7 7 7 9.9 9.9 9.9
Gas Connection Pipe Size 1/2" 1/2" 1/2" 1/2" 3/4" 3/4"
Approx. Unit Shipping 292# 315# 343# 398# 443# 540#
Weight Unit Net 217# 235# 258# 303# 333# 415#
Table 14.1 - Model HFP Dimensions (All dimensions in inches)
Figure 14.2 - Rail or Slab Type Mounting Base
B
G
2.35 LIFTING HOLE
0.75 DIA.
LIFTING
HOLE
1.00 DIA.
37.44 23.10
1.50
1.80 1.75 3.00
1.75
5.42
2.00 1.00
SPREADER
BAR
SPREADER
BAR

5-571.4 1515
PERFORMANCE
Table 15.1 — Air Temperature Rise - Low Temperature Rise Duct Furnaces ➀ ➁ ➂
Air Temperature Rise Through Unit (°F)
Model Btu/Hr 20 25 30 35 40 45 50 55 60
Size Input Output Max Min
75 75,000 60,000 2778 2222 1852 1587 1389 1235 1111 1010 926
100 100,000 80,000 3704 2963 2469 2116 1852 1646 1481 1347 1235
125 125,000 100,000 4630 3704 3086 2646 2315 2058 1852 1684 1543
150 150,000 120,000 5556 4444 3704 3175 2778 2469 2222 2020 1852
175 175,000 140,000 6481 5185 4321 3704 3241 2881 2593 2357 2160
200 200,000 160,000 7407 5926 4938 4233 3704 3292 2963 2694 2469
225 225,000 180,000 8333 6667 5556 4762 4167 3704 3333 3030 2778
250 250,000 200,000 9259 7407 6173 5291 4630 4115 3704 3367 3086
300 300,000 240,000 11111 8889 7407 6349 5556 4938 4444 4040 3704
350 350,000 280,000 12963 10370 8642 7407 6481 5761 5185 4714 4321
400 400,000 320,000 14815 11852 9877 8466 7407 6584 5926 5387 4938
CFM
Table 15.2 — Air Temperature Rise - High Temperature Rise Duct Furnaces ➀ ➁ ➂
Air Temperature Rise Through Unit (°F)
Model Btu/Hr 20 ➃40 ➃50 ➃60 65 70 75 80 85 90 95 100 ➄
Size Input Output Max Min
75 75,000 60,000 2778 1389 1111 926 855 794 741 694 654 617 585 556
100 100,000 80,000 3704 1852 1481 1235 1140 1058 988 926 871 823 780 741
125 125,000 100,000 4630 2315 1852 1543 1425 1323 1235 1157 1089 1029 975 926
150 150,000 120,000 5556 2778 2222 1852 1709 1587 1481 1389 1307 1235 1170 1111
175 175,000 140,000 6481 3241 2593 2160 1994 1852 1728 1620 1525 1440 1365 1296
200 200,000 160,000 7407 3704 2963 2469 2279 2116 1975 1852 1743 1646 1559 1481
225 225,000 180,000 8333 4167 3333 2778 2564 2381 2222 2083 1961 1852 1754 1667
250 250,000 200,000 9259 4630 3704 3086 2849 2646 2469 2315 2179 2058 1949 1852
300 300,000 240,000 11111 5556 4444 3704 3419 3175 2963 2778 2614 2469 2339 2222
350 350,000 280,000 11111➅6481 5185 4321 3989 3704 3457 3241 3050 2881 2729 2593
400 400,000 320,000 11111➅7407 5926 4938 4558 4233 3951 3704 3486 3292 3119 2963
CFM
➀Ratings are shown for elevations up to 2000 feet. For higher elevations, the input rating should be reduced at the rate of 4% per 1000 feet elevation above sea level. For Canada, in
elevations between 2000 and 4500 feet, the unit must be derated to 90% of the rating listed above.
➁Units approved for use in California by CEC.
➂High air temperature rise units include an air distribution baffle and restrictor change when compared to the low air temperature rise units. Field conversion of a high air
temperature rise to a low air temperature rise unit (or the opposite) requires a factory supplied conversion kit.
➃The certified range of the High Temperature Rise Duct Furnaces is 20°-100°F but it is recommended that they be used from 60°-100°F to reduce the system pressure drop.
➄For Variable Air Movement Applications, see page 11.
➅The maximum CFM for the 350 and 400 results in a 23°F and a 27°F air temperature rise (respectively) based on the maximum unit pressure drop.
Air Temperature and External Static Pressure Limits
The maximum allowable discharge air temperature is 150°F. The maximum allowable air temperature rise for Low Air Temperature
Rise Units is 60°F. The maximum allowable air temperature rise for High Air Temperature Rise Units is 100°F. All duct furnaces are
designed for a maximum allowable static pressure of 3.0" W.C. on the heat exchanger.
Figure 15.1
Recommended Unit Configurations
200,000
BTU/HR
OUTPUT 65
O
F
TEMP. RISE
160,000
BTU/HR
OUTPUT
65
O
F
TEMP. RISE
160,000
BTU/HR
OUTPUT
65
O
F
TEMP. RISE
160,000
BTU/HR
OUTPUT
65
O
F
TEMP. RISE
TANDEM TOP VIEW
SINGLE TOP VIEW PARALLEL TOP VIEW
2279 CFM
60
O
F ENTERING
AIR TEMP.
2279 CFM
20
O
F ENTERING
AIR TEMP.
125
O
F DISCHARGE
AIR TEMP.
150
O
F DISCHARGE
AIR TEMP.
5698 CFM
20
O
F ENTERING
AIR TEMP.
PREHEAT
UNIT REHEAT UNIT
200,000
BTU/HR
OUTPUT 65
O
F
TEMP. RISE
85
O
F DISCHARGE
AIR TEMP.
SEE SERVICE
CLEARANCES

5-571.4
1616
PRESSURE DROP CURVES
Figure 16.1
Low Air Temperature Rise Duct Furnace Pressure Drop vs. CFM Curves
0
0.2
0.4
0.6
0.8
1
1.2
1.4
01000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000
CFM
PRESSURE DROP
(P " W.C.)
75
100/125
150/175
200/225
250/300
350/400
Caution:
Do not exceed the CFM ranges
indicated in Table 15.1

5-571.4 1717
PRESSURE DROP CURVES
Figure 17.1
High Air Temperature Rise Duct Furnace Pressure Drop vs. CFM Curves
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
01000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000
CFM
PRESSURE DROP
(∆P " W.C.)
HFG 75
HFG100/125
HFG150/175
HFG200/225
HFG250/300
Caution:
Do not exceed the CFM ranges
indicated in Table 15.2 OFP200/225
350/400
HFG250/300
150/175
100/125
75
HFG200/225
HFP250/300
HFP200/225

5-571.4
1818
MAINTENANCE
All heating equipment should be serviced before each heating
season to assure proper operations. The following items may be
required to have more frequent service schedule based on the
environment in which the unit is installed, and the frequency of
the equipment operation.
Blower Assembly
The blower assembly includes the bearings, drive sheaves and
belts.
Blower bearings should be checked and lubricated based on the
blower manufacturer’s recommendations. Bearings should also
be checked for any unusual wear and replaced if needed.
Drive sheaves should be checked at the same time the bearings
are inspected. Check to make sure the sheaves are in alignment
and are securely fastened to the blower and motor shafts.
Belt tension should be rechecked shortly after the unit has been
installed to check for belt stretching. After the initial start-up,
monthly checks are recommended.
Filters
If the unit is supplied with a dirty filter switch and light, clean or
replace the filters any time the dirty filter light comes on.
Units which do not have a dirty filter warning light should have
the filters checked monthly. Clean or replace if necessary. In
dirty atmospheres, filter maintenance may be required more
often.
Duct Furnace
When providing annual maintenance for the duct furnace, keep
the unit free from dust, dirt, grease and foreign matter. Pay
particular attention to:
1. The combustion air intake and exhaust vent cap louvered
openings.
2. The burner ports and pilot burner orifices (avoid the use of
hard, sharp instruments capable of damaging surfaces for
cleaning these ports). To check the burner port and pilot
burner orifice, see Burner and Pilot Assembly Removal.
3. The air shutters and main burner orifices (avoid the use of
hard, sharp instruments capable of damaging surfaces for
cleaning these orifices). To check the air shutters and main
burner orifices, see for Manifold Assembly Removal.
The heat exchanger should be checked annually for cracks
and discoloration of the tubes. If a crack is detected, the heat
exchanger should be replaced before the unit is put back into
service. If the tubes are dark gray, airflow across the heat
exchanger should be checked to insure that a blockage has not
occurred or the blower is operating properly.
Electrical Wiring
The electrical wiring should be checked annually for loose
connections or deteriorated insulation.
Gas Piping & Controls
The gas valves and piping should be checked annually for
general cleanliness and tightness.
The gas controls should be checked to insure that the unit is
operating properly.
Manifold Assembly Removal
To remove the manifold
1. Shut off gas and electric supply.
2. Remove the burner side access panel.
3. Disconnect gas manifold at ground union joint.
4. Remove the two screws holding the manifold to the heat
exchanger support.
5. Slide the manifold through the manifold bracket.
6. Clean the orifices and adjust the air shutters as necessary.
7. Follow steps 3-6 in reverse order to install the manifold
assembly.
8. Turn on the electric and gas supply.
9. Check the ground union joint for leaks with a soap solution.
Tighten if necessary.
10. Install the burner side access panel.
Figure 18.1
Manifold Assembly Removal
Burner and Pilot Assembly Removal
To remove the burner
1. Shut off gas and electric supply.
2. Remove the burner side access panel.
3. Disconnect the pilot supply line from the gas valve.
4. Disconnect the ignition cable from the ignition controller
(located in the electrical junction box). Feed the cable
through the bushing in the bottom of the electrical junction
box.
5. Remove the screws holding the burner side access panel.
Attached to the panel are the burner retaining pins that
align the burner.
BURNER SIDE
ACCESS PANEL HEAT EXCHANGER SUPPORT
MANIFOLD
GROUND
UNION
JOINT
ELECTRICAL
JUNCTION
BOX
SERIAL
PLATE

5-571.4 1919
MAINTENANCE
Burner and Pilot Assembly Removal
(continued)
6. Slide the burner assembly out. The pilot is attached to the
burner assembly.
7. Examine the burner and pilot assembly for cleanliness
and/or obstructions as necessary (see Duct Furnace for
cleaning instructions).
8. Replace the burner assembly in reverse order. In replacing
the burner, be certain that the rear burner slots are located
properly on the burner retaining pins. Do not force the
burner side access panel, it will not fit if the burner is not
properly aligned.
9. Reconnect the ignition cable and pilot gas supply line.
10. Install the burner side access panel.
11. Turn on the electric and gas supply.
Figure 19.1
Burner and Pilot Assembly Removal
PILOT
SUPPLY
LINE
HEAT
EXCHANGER
SUPPORT
AIR SHUTTERS
(NOT SHOWN)
ARE LOCATED
ON THE
MANIFOLD
IGNITION
CABLE
PILOT
ASSEMBLY

5-571.4
2020
SERVICE & TROUBLESHOOTING
Pilot does not light
Main burners do not light (Pilot is lit)
Lifting Flames (See Figure 21.1)
Yellow Tipping
(With propane gas, some yellow tipping
is always present.)
Flashback
Floating Flames (See Figure 21.2)
1. Main gas is off.
2. Power supply is off.
3. Air in gas line.
4. Dirt in pilot orifice.
5. Gas pressure out of proper range.
6. Pilot valve does not open.
a. Defective ignition controller.
b. Defective gas valve.
7. No Spark at ignitor.
a. Loose wire connections.
b. Pilot sensor is grounded.
c. Defective ignition controller.
8. Safety device has cut power.
1. Defective valve.
2. Loose wiring.
3. Defective pilot sensor
4. Defective ignition controller.
5. Improper thermostat wiring.
1. Too much primary air.
2. Main pressure set too high.
3. Orifice too large.
1. Insufficient primary air.
2. Dirty orifice.
3. Misaligned orifice.
1. Too much primary air.
2. Main pressure set too high.
3. Orifice too large.
1. Insufficient primary air.
2. Main pressure set too high.
3. Orifice too large.
4. Blocked vent cap.
1. Open manual gas valve.
2. Turn on main power.
3. Purge gas line.
4. Check for plugged pilot orifice and clean
with compressed air if necessary.
5. Adjust to a maximum of 14" W.C.
Minimum for Natural Gas - 6" W.C.
Minimum for Propane Gas - 11" W.C.
6. Check wiring for 24 volts to valve.
a. Replace ignition controller.
b. Replace gas valve.
7.
a. Check all ignition controller wiring.
b. Replace sensor if cracked or worn
c. Replace ignition controller.
8. Check all safety devices (High limit, air
flow proving switch, power exhauster
centrifugal switch - HFP Models Only,
gas pressure switches, etc.) Determine
and correct problem. Reset if necessary.
1. Replace valve.
2. Check wiring to gas valve.
3. Replace pilot sensor.
4. Replace ignition controller.
5. Verify wiring compared to wiring diagram.
1. Reduce primary air.
2. Adjust to a maximum of 14" W.C.
3. Check orifice size with those listed on the
serial plate.
1. Increase primary air.
2. Check orifices and clean with
compressed air if necessary.
3. Check manifold, replace if necessary.
1. Reduce primary air.
2. Adjust to a maximum of 14" W.C.
3. Check orifice size with those listed on the
serial plate.
1. Increase primary air.
2. Adjust to a maximum of 14" W.C.
3. Check orifice size with those listed on the
serial plate.
4. Clean louvers in vent cap.
Trouble Possible Cause Possible Remedy
Table 20.1
Troubleshooting
IMPORTANT
To check most of the Possible Remedies in the troubleshooting
guide listed in Table 20.1, refer to the applicable sections of the
manual.
cAUTION
Do not reuse any mechanical or electrical component which
has been wet. Such component must be replaced.
WARNING
When servicing or repairing this equipment, use only factory-
approved service replacement parts. A complete replacement
parts list may be obtained by contacting Modine Manufacturing
Company. Refer to the rating plate on the appliance for
complete appliance model number, serial number, and
company address. Any substitution of parts or controls not
approved by the factory will be at the owner’s risk.