Reznor RP 125 Installation and operating instructions

Revision: RP-HRPD-IOM (01-23) 132210-D
MODELS RP AND HRPD
OUTDOOR DUCT FURNACE INSTALLATION, OPERATION,
AND MAINTENANCE
Supersedes: RP-HRPD-IOM (10-22) 132210-C
⚠ DANGER ⚠
FIRE OR EXPLOSION HAZARD
• Failure to follow safety warnings exactly could result in serious injury, death, or property
damage.
• Improper installation,adjustment,alteration, service,or maintenance can cause serious injury,
death, or property damage.
• Installation and service must be performed by a qualified installer, service agency, or the gas
supplier.
• Be sure to read and understand the installation, operation, and service instructions in this
manual.
• Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or
any other appliance.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any phone in your building.
• Leave the building immediately.
• Immediately call your gas supplier from a phone remote from the building. Follow the gas
supplier’s instructions.
• If you cannot reach your gas supplier, call the fire department.
DO NOT DESTROY. PLEASE READ CAREFULLY. KEEP IN A SAFE PLACE FOR FUTURE REFERENCE.
RP HRPD

2RP-HRPD-IOM (01-23) 132210-D
TABLE OF CONTENTS
GENERAL INFORMATION .............................................................................3
References ........................................................................................3
Important Safety Information........................................................................... 3
Important Safety Information—Continued................................................................. 4
Installation Codes ...................................................................................4
Warranty ..........................................................................................4
Dimensions ........................................................................................5
Weights........................................................................................... 7
Clearances ........................................................................................7
Unit Location....................................................................................... 7
Combustion Air Requirements ......................................................................... 7
Hazards of Chlorine ................................................................................. 7
INSTALLATION ......................................................................................8
Uncrating/Unpacking................................................................................. 8
Shipped-Separate Parts .............................................................................. 8
Pre-Installation Modifications ..........................................................................8
High CFM Conversion .............................................................................8
Reverse Airflow Conversion ....................................................................... 11
Mounting .........................................................................................11
Duct Connections ..................................................................................11
Ductwork Requirements .......................................................................... 12
Discharge Air Temperature Sensor Installation.........................................................13
Duct Furnace Airflow .............................................................................15
Duct Furnace Blower Connections ..................................................................15
Bypass Duct Construction .........................................................................16
Piping Connections................................................................................. 18
Gas Supply Pressure............................................................................. 18
Gas Supply Piping............................................................................... 18
Supply Piping Connections ........................................................................ 19
Electrical Connections ..............................................................................21
Control Wiring ..................................................................................21
CONTROLS ........................................................................................22
Thermostat .......................................................................................22
Fan Control .......................................................................................22
Limit Control ......................................................................................22
Combination Gas Valve ............................................................................. 22
Combustion Air Proving Switch........................................................................ 23
Optional Two-Stage Control (Heating Only Application).....................................................23
Optional Two-Stage Control (Makeup Air Application) ...................................................... 23
Optional Ductstat with Capillary Tubing (Options AG3 and AG4) ........................................... 25
Optional Ductstat with Electronic Remote Setpoint Module (Options AG15 and AG17) .......................... 25
Optional Electronic Modulation ........................................................................25
Electronic Modulation Between 50% and 100% Firing Rate (Options AG7, AG8, and AG9) ...................... 25
Computer-Controlled Electronic Modulation Between 50% and 100% Firing Rate (Option AG21).................. 26
Electronic Modulation Between 20–28% and 100% Firing Rate (Options AG39 and AG41) ...................... 26
Electronic Modulation Between 20–28% and 100% Firing Rate (Options AG40 and AG42) ...................... 28
Pilot and Ignition Systems............................................................................28
Burners and Carryover System........................................................................ 29
OPERATION ....................................................................................... 29
Pre-Startup Checklist ...............................................................................29
Startup ..........................................................................................30
Post-Startup Checklist ..............................................................................30

3
RP-HRPD-IOM (01-23) 132210-D
GENERAL INFORMATION
•This unit has been tested for capacity and efficiency so as to provide many years of safe and dependable comfort
providing it is properly installed and maintained. With regular maintenance, this unit will operate satisfactorily year
after year. Abuse, improper use, and/or improper maintenance can shorten the life of the appliance and create
unsafe hazards.
•To achieve optimum performance and minimize equipment failure, it is recommended that periodic maintenance
be performed on this unit. The ability to properly perform maintenance on this equipment requires certain tools
and mechanical skills.
•This unit is design-certified to ANSI and CSA standards by the Canadian Standards Association and is approved
for installation in the United States and in Canada. The furnaces are approved for use with either natural gas or
propane. The type of gas for which the furnace is equipped, the correct firing rate, and electrical requirements are
shown on the unit’s rating plate.
•Model HRPD is dual model RP furnaces configured for higher CFM capacity.
References
TABLE OF CONTENTS—CONTINUED
ADJUSTMENTS..................................................................................... 31
Measure and Adjust Manifold (Outlet) Gas Pressure ....................................................... 31
High Elevation (>2,000 Feet/609 Meters) Installations ................................................... 31
Conversion to LP (Propane) .......................................................................33
Burner Air Shutter Adjustment ........................................................................ 33
Adjust Heat Stage Controllers (Model HRPD Units with Option AG41 or AG42) ..................................33
MAINTENANCE..................................................................................... 34
Service Checklist ..................................................................................34
Maintenance Procedures ............................................................................34
Combination Gas Valve Maintenance ................................................................34
Burner Rack Maintenance......................................................................... 35
Cleaning Pilot and Burners ........................................................................36
Spark Ignition System Maintenance .................................................................37
Heat Exchanger Cleaning ......................................................................... 37
TROUBLESHOOTING ................................................................................ 39
INSTALLATION RECORD (TO BE COMPLETED BY INSTALLER)............................................. 40
Table 1. Related Technical Manuals Available from Factory Distributor
Type Form*PN
Replacement parts RP-HRPD-RPB-RPBL-RPL 263984
Maxitrol amplifier replacement kit installation OPT-AG7,8,9,9H 262319
Ignition controller replacement kit installation OPT-IGN-CNTRL 134704
Gas conversion OPT-GC 143147
*Also available at www.reznorhvac.com.
Important Safety Information
Please read all information in this manual thoroughly and become familiar with the capabilities and use of your
appliance before attempting to operate or maintain this unit. Pay attention to all dangers, warnings, cautions, and
notes highlighted in this manual. Safety markings should not be ignored and are used frequently throughout to
designate a degree or level of seriousness.
DANGER: A danger statement describes a potentially hazardous situation that if not avoided, will result in severe
personal injury or death and/or property damage.
WARNING: A warning statement describes a potentially hazardous situation that if not avoided, can result in severe
personal injury and/or property damage.
CAUTION: A caution statement describes a potentially hazardous situation that if not avoided, can result in minor
or moderate personal injury and/or property damage.
NOTE: A note provides important information that should not be ignored.

4RP-HRPD-IOM (01-23) 132210-D
GENERAL INFORMATION—CONTINUED
Important Safety Information—Continued
⚠ DANGER ⚠
• Gas-fired appliances are not designed for use in hazardous atmospheres containing flammable
vapors or combustible dust,in atmospheres containing chlorinated or halogenated hydrocarbons,
or in applications with airborne silicone substances.
• Improper installation,adjustment,alteration,service,or maintenance can cause property damage,
injury, or death. Read these installation, operation, and maintenance instructions thoroughly
before installing or servicing this equipment.
⚠ WARNING ⚠
For your safety, read the warning labels on the unit.
⚠ CAUTION ⚠
These duct furnaces are not certified or approved for use in drying or process applications. If a
duct furnace is to be used in a drying or process application, contact the factory for application
guidelines and for manufacturer’s authorization. Without factory authorization, the warranty is
void and the manufacturer disclaims any responsibility for the duct furnace and/or the application.
NOTES:
• Installation should be done by a qualified agency in accordance with the instructions in this
manual and in compliance with all codes and requirements of authorities having jurisdiction.
• Read this manual and become familiar with the installation requirements of your particular
furnace. If you do not have knowledge of local requirements, check with the local gas company
or any other local agencies who might have requirements concerning this installation.
• The instructions in this manual apply only to duct furnace models RP and HRPD.
Installation Codes
These units must be installed in accordance with local building codes. In the absence of local codes, in the United
States, the unit must be installed in accordance with NFPA/ANSI Z223.1 (latest edition), National Fuel Gas Code.
A Canadian installation must be in accordance with CSA B149.1, Natural Gas and Propane Installation Code. This
code is available from CSA Information Services, 1-800-463-6727. Local authorities having jurisdiction should be
consulted before installation is made to verify local codes and installation procedure requirements.
Warranty
Refer to the limited warranty information on the warranty card in the owner’s envelope. Warranty is void if:
a. Furnaces are used in atmospheres containing flammable vapors or atmospheres containing chlorinated or
halogenated hydrocarbons or any contaminant (silicone, aluminum oxide, etc.) that adheres to the spark
ignition flame sensing probe.
b. Wiring is not in accordance with the diagram furnished with the heater.
c. Unit is installed without proper clearance to combustible materials or without proper ventilation and air for
combustion.
d. Furnace air throughput is not adjusted within the range specified on the rating plate.
e. Duct furnace is installed in a process or drying application without factory authorization (any use in a process
or drying application voids agency certification).

5
RP-HRPD-IOM (01-23) 132210-D
Dimensions
Figure 1. RP Dimensions (Refer to Table 2)
Table 2. RP Dimensions
Dimension
(See Figure 1)
Unit Size
125 150, 175 200, 225 250, 300 350 400
Inches (mm)
A 30-15/16 (786) 36-7/16 (914) 41-15/16 (1065) 50-3/16 (1275) 55-11/16 (1414) 61-3/16 (1554)
B 28-1/2 (648) 34 (864) 39-1/2 (1003) 47-3/4 (1213) 53-1/4 (1353) 58-3/4 (1492)
C 15-1/4 (387) 20-3/4 (527) 26-1/4 (667) 34-1/2 (876) 40 (1016) 45-1/2 (1156)
D 20-5/16 (516) 25-13/16 (656) 31-5/16 (795) 39-9/16 (1005) 45-1/16 (1145) 50-9/16 (1284)
LEFT SIDE VIEW
FRONT VIEW
TOP VIEW
REAR VIEW
3/4 (19)
3/4 (19)
ELECTRIC
CONNECTION
THERMOSTAT
CONNECTION
1-1/8 (29)
1-1/8
(29)
15/16 (24) 15/16 (24)
16-1/4
(413) 10-9/16
(268)
3/4
(19)
3/4
(19)
38-17/32
(979)
8-15/32
(215)
18
(457)
ALTERNATE
ELECTRIC
CONNECTION
ALTERNATE
ELECTRIC
CONNECTION
GAS
CONNECTION
1-21/32 (42)
24-1/4
(616)
1/2
(13)
1/2 (13) 2-1/2 (64)
6-1/32 (153)
25
(635)
26
(660)
CONDENSATE
DRAIN (TWO PER
SIDE, 1/4 (6) DIA)
18-3/32 (460)
4-1/16
(103)
4-1/16
(103) 2-1/2
(64)
3-9/32 (83)
NOTES:
Inches (mm)
Standard airflow may be reversed by changing direction of heat exchanger air baffles.
Burner and control access shown left-hand side. Specify right-hand side for opposite access and connections.

6RP-HRPD-IOM (01-23) 132210-D
GENERAL INFORMATION—CONTINUED
Dimensions—Continued
Figure 2. HRPD Dimensions (Refer to Table 3)
Table 3. HRPD Dimensions
Dimension
(See Figure 2)
Unit Size
250 300, 350 400 500, 600 700 800
Inches (mm)
A 30-15/16 (786) 36-7/16 (926) 41-15/16 (1065) 50-3/16 (1275) 55-11/16 (1414) 61-3/16 (1554)
B 28-1/2 (724) 34 (864) 39-1/2 (1003) 47-3/4 (1213) 53-1/4 (1353) 58-3/4 (1492)
C 15-1/4 (387) 20-3/4 (527) 26-1/4 (667) 34-1/2 (876) 40 (1016) 45-1/2 (1156)
D 20-5/16 (516) 25-13/16 (656) 31-5/16 (795) 39-9/16 (1005) 45-1/16 (1145) 50-9/16 (1284)
E 3-3/32 (79) 1-21/32 (42)
LEFT SIDE VIEW
FRONT VIEW
TOP VIEW
REAR VIEW
3/4 (19)
3/4 (19)
3/4
(19)
3/4
(19)
50-1/4
(1280)
16-1/4
(413)
1-1/8 (29)
1-1/8
(29)
18
(457)
38-17/32
(979)
10-9/16
(268)
8-15/32
(215)
15/16 (24)
15/16 (24)
1/2 (13)
1/2 (13)
51 (1295)
52 (1321)
CONDENSATE
DRAIN (FOUR PER
SIDE, 1/4 (6) DIA)
18-3/32
(460)
2-1/2
(64)
4-1/16
(103)
4-1/16
(103)
3-9/32 (83)
THERMOSTAT
CONNECTION
ELECTRIC
CONNECTION
ALTERNATE
ELECTRIC
CONNECTION
ALTERNATE
THERMOSTAT
CONNECTION
GAS CONNECTION (APPROX.)
NOTES:
Inches (mm)
Standard airflow may be reversed by changing direction of heat exchanger air baffles.
Burner and control access shown left-hand side. Specify right-hand side for opposite access and connections.

7
RP-HRPD-IOM (01-23) 132210-D
Weights
Before installation, check the supporting structure to ensure that it has sufficient load-carrying capacity to support
the weight of the unit. Refer to Table 4, which lists unit weight based on unit size.
Clearances
Clearance to combustibles is defined as the minimum distance—from the heater to a surface or object—that is
necessary to ensure that a surface temperature of 90°F (50°C) above the surrounding ambient temperature is not
exceeded. For safety, adequate combustion air, and convenient installation and service, ensure that the clearances
listed in Table 5 are provided.
Table 4. Weights
Model
RP Unit Size
125 150, 175 200, 225 250, 300 350 400
HRPD Unit Size
250 300, 350 400 500, 600 700 800
Pounds (kg)
RP 201 (91) 217 (98) 247 (112) 295 (134) 333 (151) 361 (164)
HRPD 402 (182) 434 (196) 494 (224) 590 (268) 666 (302) 722 (328)
Table 5. Clearances
Unit Surface Minimum Clearance (Inches (mm))
Top 36 (915)
Control side 6 (152) + width of furnace
Side opposite controls 6 (152)
Bottom, to combustibles 0 (0)*
Bottom, to noncombustibles 0 (0)
*The unit is certified for installation on a combustible surface when it is equipped with standard heater-mounting rails.
Unit Location
⚠ CAUTION ⚠
Do not locate the heater where it may be exposed to water spray, rain, or dripping water.
•Select a location that complies with the requirements in this manual.
•There are a variety of factors, such as system application, building structure, dimensions, and weight, that contribute
to selecting the location.
•The location must comply with the clearances listed in Table 5.
•A duct furnace is designed for connection to an inlet and an outlet duct and depends on an external air handler.
Combustion Air Requirements
The combustion air and flue gas openings are carefully designed screened openings located on the side of the
unit just above the control access panel. Location of the flue opening directly above the air intakes discourages
recirculation of combustion products.
Hazards of Chlorine
NOTE: Remember, chlorine is heavier than air.This fact should be kept in mind when determining
the installation location of heaters and building exhaust systems.
The presence of chlorine vapors in the combustion air of heating equipment presents a potential corrosion hazard.
Chlorine, found usually in the form of Freon or degreaser vapors, when exposed to flame will precipitate from the
compound and form a solution with any condensation present in the heat exchanger or associated parts. The result
is hydrochloric acid, which readily attacks all metals, including 300 grade stainless steel. Care should be taken to
separate these vapors from the combustion process. This may be done by wise location of the unit with regard to
exhausters or prevailing wind directions.

8RP-HRPD-IOM (01-23) 132210-D
INSTALLATION
NOTE: Before installation,make preparations for necessary supplies,tools,and manpower.
Uncrating/Unpacking
•This furnace was test-operated and inspected at the factory prior to crating and was in operating condition. If
the furnace has incurred any damage in shipment, document the damage with the transporting agency and
immediately contact an authorized Reznor®distributor. If you are an authorized Distributor, follow the FOB freight
policy procedures.
•Check the rating plate for the gas specifications and electrical characteristics of the furnace to ensure that they
are compatible with the gas and electric supplies at the installation site.
Shipped-Separate Parts
•Check to see if there are any field-installed options that need to be connected to the furnace prior to installation.
•Shipped-separate options could include a gas shutoff valve, a vertical vent terminal, a thermostat, an optional
control, and disconnect switch.
•Some gas control options will have parts either shipped loose with the heater or shipped separately. If the unit is
equipped with any of the gas control options listed in Table 6, ensure that these parts are available at the job site.
Table 6. Shipped-Separate Parts for Gas Control Options
Application Option Part(s)
Heating AG7 Thermostat (PN 48033)
Makeup air
AG3, AG4 Control switch (PN 29054)
AG8 Control switch (PN 29054); sensor and mixing tube (PN 48041)
AG9 Control switch (PN 29054); remote temperature selector (PN 48042); sensor and mixing tube (PN 48041)
AG15, AG17 Control switch (PN 29054); remote temperature selector (PN 115848); stage adder module (PN 115849);
discharge air sensor holder (PN 115850); discharge air sensor holder bracket (PN 213612)
AG39, AG41 Remote temperature selector (PN 174849); temperature sensor (PN 133228); mixing tube (PN 90323)
NOTE: If an optional remote console is ordered, the control switch and temperature selector may be mounted on the console.
Pre-Installation Modifications
High CFM Conversion
This unit was factory assembled with the air throughput range listed on the rating plate. If the application requires
a higher CFM than listed on the rating plate, the unit may be converted for lower temperature rise and higher CFM.
The conversion will change the air throughput range as specified in Table 7. Verify the unit size on the heater rating
plate and, after confirming that this conversion is correct for the unit, perform the following procedure:
Table 7. High Air Throughput
RP Unit Size Minimum Maximum
CFM
125 1225 4605
150 1475 5530
175 1720 6450
200 1965 7370
225 2210 8295
250 2455 9215
300 2945 11,060
350 3440 12,900
400 3930 14,745

9
RP-HRPD-IOM (01-23) 132210-D
⚠ DANGER ⚠
• This conversion shall be done by a qualified service agency in accordance with the manufacturer’s
instructions and all applicable codes and requirements of the authority having jurisdiction. If the
information in these instructions is not followed exactly, a fire, an explosion, or the production
of carbon monoxide may cause property damage, personal injury, or loss of life. The qualified
service agency performing this work assumes responsibility for the conversion of this appliance
to provide for higher CFM.
• These instructions are designed to prepare the duct furnace for increased air throughput conversion
prior to installation. If your duct furnace is already installed, for your safety, turn OFF the gas and
electric supply before servicing.
NOTE: Before performing this conversion, determine if airflow is being reversed or if other field-
installed options apply. Perform desired procedure in accordance with Pre-Installation Modifica-
tions section.
1. Remove heat exchanger baffles (see Figure 3):
a. At discharge air side of heat exchanger, remove support bracket screws and slide entire baffle assembly out
of heat exchanger.
b. Reinstall screws to plug holes.
Figure 3. Heat Exchanger Baffle Removal
BAFFLES
SUPPORT BRACKET SCREWS

10 RP-HRPD-IOM (01-23) 132210-D
INSTALLATION—CONTINUED
Pre-Installation Modifications—Continued
High CFM Conversion—Continued
2. Remove side finger baffles (see Figure 4):
a. At entering air side of heat exchanger, locate side finger baffles and remove two side finger baffle screws
from each baffle.
b. Remove both side finger baffles.
Figure 4. Side Finger Baffle Removal
3. Install field conversion label (see Figure 5):
a. Fill in field conversion label (PN 263310) from literature bag.
b. Adhere label to unit on clean dry surface adjacent to rating plate.
4. Test unit for proper operation ensuring that air throughput is in accordance with Table 7.
SCREWS
SIDE FINGER BAFFLE
SCREWS
SIDE FINGER BAFFLE
Figure 5. Field Conversion Label
(date)
(name & address of company making this conversion)
263308

11
RP-HRPD-IOM (01-23) 132210-D
Reverse Airflow Conversion
Duct furnaces are equipped with directional air baffles between the heat exchanger tubes. Facing the control
compartment of the furnace, the standard direction of airflow is from left to right. If the installation site requires airflow
from right to left, the unit may be field-adapted by reversing the position of the directional air baffles (see Figure 6)
as follows:
1. Remove and save baffle screws and lift each airflow baffle slightly and slide forward. Remove all baffles from
heat exchanger.
2. Remove and save top baffle support screws and remove top baffle support. Reposition and secure support on
opposite end of heat exchanger using existing screws.
3. Remove bracket screws and remove bottom baffle support and bracket assembly. Reinstall bracket screws to
plug holes in heat exchanger bottom. Reposition bottom baffle support and bracket assembly on opposite end of
heat exchanger and secure using field-supplied sheet metal screws.
4. Reinstall airflow baffles removed in step 1 and secure using existing screws.
Figure 6. Airflow Baffles
Mounting
⚠ DANGER ⚠
Use a suitable hoist to lift the unit (refer to Weights section). Lifting holes are provided at each of
the four corners of the mounting support rails. Use spreader bars when lifting to prevent chains
or cables from damaging the unit.
⚠ CAUTION ⚠
Furnaces must be level.
Lift the unit using a suitable hoist and spreader bars and set it on a slab or roof where support is adequate.
Duct Connections
⚠ CAUTION ⚠
Joints where ducts attach to furnace must be sealed securely to prevent air leakage into burner
rack area. Leakage can cause poor combustion, poor performance, and pilot problems and can
shorten heat exchanger life.
NOTE: Make adjustments to ductwork as necessary to obtain a temperature rise and static pres-
sure within the ranges specified on the heater rating plate.
BRACKET
SCREWS
TOP BAFFLE
SUPPORT SCREWS
BAFFLE SCREWS
AIRFLOW BAFFLES
BOTTOM BAFFLE SUPPORT
TOP BAFFLE
SUPPORT

12 RP-HRPD-IOM (01-23) 132210-D
INSTALLATION—CONTINUED
Duct Connections—Continued
Ductwork Requirements
• Type: the type of duct installation to be used depends in part on the construction type of the roof (wood joist, steel
bar joist, steel truss, or pre-cast concrete) and ceiling (hung, flush, etc.).
• Material: rectangular duct should be constructed of not lighter than #26 US gauge galvanized iron or #24 B&S
gauge aluminum.
• Size: proper sizing of supply air ductwork is necessary to ensure a satisfactory heating installation. The recognized
authority for such information is the Air Conditioning Contractors Association, 2800 Shirlington Road, Suite 300,
Arlington, VA 22206 (www.acca.org). A manual covering duct sizing in detail may be purchased directly from them.
• Structure: all duct sections 24 inches (610 mm) or wider and over 48 inches (1,219 mm) in length should be
cross-broken on top and bottom and should have standing seams or angle-iron braces.
• Joints: should be S and drive strip or locked.
• Ductwork through masonry walls: no warm air duct should come in contact with masonry walls. Insulate around
all air ducts through masonry walls with not less than 1/2 inch (1 inch is recommended) of insulation.
• Ductwork through unheated space: insulate all exposed warm air ducts passing through an unheated space
with at least 1/2 inch (1 inch is recommended) of insulation.
• Supports: suspend all ducts securely from buildings members. Do not support ducts from unit duct connections.
• Access panels: Install removable access panels (see Figure 7) on both the upstream and downstream sides of
the furnace. The access panels must be accessible when the furnace is in service and should be a minimum of
6 ×10 inches (152 ×254 mm) in size so smoke or reflected light may be observed inside the casing to indicate
the presence of leaks in the heat exchanger. Ensure that the access panels are installed in such a manner so as
to prevent leakage.
• Horizontal discharge duct length: A minimum horizontal duct run of 24 inches (610 mm) is recommended before
turns or branches are made in the duct system to reduce losses at the furnace outlet.
• Supply air duct/furnace horizontal connection: The seal between the furnace and the duct must be mechanical
using U-type flanges on the top and bottom of the connecting duct to to ensure tight joints and an airtight fit. Refer
to Figure 7 and perform the following steps:
a. Ensure that flanges on the furnace (heat exchanger) turn out as shown.
b. Shape duct connection as shown: U-type on top and bottom and L-type on sides.
c. Slide U-channels over furnace top and bottom flanges making connection.
d. Form U-channels to seal sides (see DETAIL A) and drill and lock with sheet metal screws.
• Connection dimensions: connection dimensions (inches (mm)) are shown in Figure 8 and listed in Table 8.
DETAIL A
Figure 7. Connecting Ductwork to Furnace

13
RP-HRPD-IOM (01-23) 132210-D
Figure 8. Ductwork Connection Dimensions (Refer to Table 8)
Table 8. Ductwork Connection Dimensions
Unit Size Dimension G*
RP Models HRPD Models Inches Millimeters
125 250 15-1/4 387
150, 175 300, 350 20-3/4 527
200, 225 400 26-1/4 667
250, 300 500, 600 34-1/2 876
350 700 40 1016
400 800 45-1/2 1156
*See Figure 8.
Discharge Air Temperature Sensor Installation
•Makeup air options AG3 and AG4 (refer to Optional Ductstat with Capillary Tubing (Options AG3 and AG4)
section) have a ductstat with a capillary sensor that is factory-installed in the unit discharge.
•Makeup air options AG8, AG9, AG15, AG17, AG39, AG40, AG41, and AG42 require field-installation of the sensor
in the discharge ductwork.
•Options AG15 and AG17 include a box and sensor holder. Options AG8, AG9, AG39, and AG41 include a sensor
and mixing tube.
•On units with option AG40 or AG42, the discharge sensor is field-supplied.
•Follow the instructions below to install the sensor in the ductwork.
1. Determine distance of sensor from unit:
a. Ensure that there is sufficient distance from outlet to have good mixture of discharge air temperature.
NOTES:
• According to the latest edition of AMCA Standard 201, in straight ducts, the air is typically well
mixed a minimum of five equivalent duct diameters from the discharge of the unit with equivalent
duct diameter defined as equal to the square root of 4AB/3.14 (A and B are duct cross-sectional
dimensions).
• Locate the sensor a minimum of 96 inches (2,435 mm) from the outlet of the unit.
• If the length of the discharge duct is less than 8 feet (2.4 meters), a mixing vane is recommended
for mixing the discharge air. Do not mount the sensor in the ductwork after a split in the supply
as this will cause loss of control in the duct that does not house the sensor.
b. Refer to following formula for calculating sensor placement. This example assumes cross-sectional dimensions
for supply ductwork of 24 ×12 inches (610 ×305 mm):

14 RP-HRPD-IOM (01-23) 132210-D
5 ×�4 × 12 ×24
3.14
=96 ℎ
5 ×�
4 × 305 ×610
3.14 =2435 
DETAIL A: OPTIONS AG8, AG9, AG39, AND AG41 DETAIL B: OPTIONS AG15 AND AG17
INSTALLATION—CONTINUED
Duct Connections—Continued
Discharge Air Temperature Sensor Installation—Continued
2. Determine orientation of sensor:
a. In horizontal ductwork, position sensor in top-middle of duct with sensor probe extending vertically down into
center of air stream.
b. In vertical ductwork, position sensor in middle of duct that corresponds with top-middle of discharge outlet.
3. Secure sensor in ductwork:
a. For units with option AG3 or AG4, sensor is factory-installed.
b. For units with option AG8, AG9, AG15, AG17, AG39, or AG41:
(1) Position of sensor in duct is also important—mixing tube shown in Figure 9, DETAIL A is 12 inches (305
mm) long and holder shown in Figure 9, DETAIL B extends 9-3/16 inches (233 mm) into ductwork.
(2) Turn holder so that element is shielded from direct airflow and will sense air temperature as it flows through
holes in holder.
(3) At selected ductwork location, mark diamond-shaped hole—approximately 1 ×1 inch (25 ×25 mm—
required for sensor holder or round hole required for mixing tube and cut hole no larger than necessary.
(4) For units with option AG8, AG9, AG39, or AG41, slide mixing tube (see Figure 9, DETAIL A) into ductwork
and attach sensor.
(5) For units with AG15 or AG17, push element into clip in holder (see Figure 9, DETAIL B), slide holder into
ductwork, and position holder so that it shields sensor from direct airflow. Secure box portion of holder to
ductwork using four field-supplied #6 sheet metal screws.
c. For units with option AG40 or AG42, install field-supplied sensor in accordance with instructions provided with
sensor.
4. Connect sensor wires:
a. For units with option AG15 or AG17:
(1) Determine where sensor wire should enter box and remove knockout.
(2) Secure field-supplied cable connector to box, connect sensor wire, and install box cover.
b. For all options, ensure that all sensor wires are connected in accordance with wiring diagram provided with unit.
Figure 9. Discharge Air Temperature Sensor and Holder

15
RP-HRPD-IOM (01-23) 132210-D
Duct Furnace Airflow
•The duct furnace must be installed on the positive pressure side of the field-supplied blower.
•The air distribution must be even over the entire heat exchanger. Turning vanes should be employed in elbows
or turns in the air inlet to ensure proper air distribution (refer to Duct Furnace Blower Connections section).
•The air throughput must be within the CFM range stated on the heater rating plate.
•If it is determined that the blower CFM is greater than allowed or desirable, refer to the Bypass Duct Construction
section for instructions on determining the correct size of bypass duct required or refer to the High CFM Conversion
section for instructions on converting the furnace for a higher CFM application.
•To determine temperature rise, the inlet and outlet air temperatures should be measured at points not affected by
heat radiating from the heat exchanger. Table 9 and Table 10 list the approved temperature rise range with the
required CFM and the internal pressure drop for each size of unit.
Table 9. Model RP Pressure Drop and Temperature Rise
Unit Size
Temperature Rise*
50°F 60°F 70°F 80°F 90°F
CFM/Pressure Drop
125 1840/0.50 1535/0.33 1315/0.25 1150/0.21 1020/0.18
150 2210/0.38 1840/0.26 1580/0.19 1380/0.15 1225/0.12
175 2580/0.52 2150/0.35 1840/0.26 1610/0.19 1430/0.16
200 2945/0.42 2455/0.28 2105/0.22 1840/0.17 1635/0.14
225 3315/0.53 2765/0.36 2370/0.27 2070/0.22 1840/0.17
250 3685/0.40 3070/0.28 2630/0.23 2300/0.22 2045/0.21
300 4420/0.58 3685/0.39 3160/0.29 2765/0.25 2455/0.22
350 5160/0.65 4300/0.44 3685/0.31 3225/0.25 2865/0.23
400 5895/0.70 4915/0.50 4210/0.30 3685/0.30 3275/0.20
*80% thermal efficient.
Table 10. Model HRPD Pressure Drop and Temperature Rise
Unit
Size
Temperature Rise
40°F 50°F 60°F 70°F 80°F 90°F 100°F
CFM/Pressure Drop
250 4630/1.97 3704/1.26 3086/0.88 2646/0.64 2315/0.49 2058/0.39 1852/0.32
300 5556/1.45 4444/0.92 3704/0.64 3175/0.47 2778/0.36 2469/0.29 2222/0.23
350 6481/2.02 5185/1.29 4321/0.90 3704/0.66 3241/0.51 2881/0.40 2593/0.32
400 7407/1.70 5926/1.09 4938/0.76 4233/0.56 3704/0.43 3292/0.34 2963/0.27
500 9259/1.53 7407/0.98 6173/0.68 5291/0.50 4630/0.38 4115/0.30 3704/0.24
600 11,111/2.14 8889/1.37 7407/0.95 6349/0.70 5556/0.54 4938/0.42 4444/0.34
700 12,963/2.09 10,370/1.34 8642/0.93 7407/0.68 6481/0.52 5761/0.41 5185/0.33
800 14,815/2.09 11,852/1.34 9877/0.93 8466/0.68 7407/0.52 6584/0.41 5926/0.33
Duct Furnace Blower Connections
⚠ WARNING ⚠
The furnace must be installed on the positive pressure side of the air-circulating blower.
•Blowers should be bottom horizontal discharge when coupled to the duct furnace.
•When a top horizontal discharge blower is connected to the duct furnace, ensure that sufficient length of duct is
provided to permit even flow of air at the end of the duct. Or, baffles may be inserted between the blower and the
heater to ensure an even flow of air across the heat exchanger.
•Proper arrangements of blower and duct furnace with respect to angle of approach of the duct connection and the
arrangement of the discharge opening of the blower are shown in Figure 10.

16 RP-HRPD-IOM (01-23) 132210-D
INSTALLATION—CONTINUED
Duct Connections—Continued
Duct Furnace Blower Connections—Continued
STRAIGHT
THROUGH
AIR BLOWER
CONNECTION
BLOWER
CONNECTION
WITH ELBOWS
UP OR DOWN
BLOWER
CONNECTION
WITH ELBOWS
RIGHT OR LEFT
Figure 10. Duct Furnace Blower Connections
Bypass Duct Construction
When the air throughput CFM is greater than desirable or permissible for the unit, a bypass duct (see Figure 11)
may be constructed. Locate the bypass duct on the side of the furnace opposite the controls and 2 inches from the
heat exchanger side panel. Extend the bypass duct 18 inches (457 mm) beyond the furnace on both the inlet and
outlet ends. Determine the correct size of the bypass duct as follows:

17
RP-HRPD-IOM (01-23) 132210-D
Figure 11. Bypass Duct Dimensions
1. Refer to Table 9 or Table 10 to determine pressure drop and allowable CFM for furnace being installed. For
example: model RP unit size 150 @ 50°F temperature rise = pressure drop of 0.38 and CFM of 2,210.
2. Subtract allowable CFM from blower CFM to determine how much air must be diverted through bypass duct. For
example: blower CFM of 3,000 − allowable CFM of 2,210 = bypass CFM of 790.
3. Refer to Table 11 to determine bypass duct size as follows:
a. Go to column closest to pressure drop through heater.
b. Move down to CFM closest (round up) to CFM determined in step 2.
c. Move to left column to determine required bypass duct size. For example: in pressure drop column 0.40, move
down to bypass CFM row 900 and move left to dimension A column 3 inches.
Table 11. Bypass Duct Size
Dimension A
(Inches (mm))*
Pressure Drop Through Furnace
0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
Bypass CFM
3 (76) 490 530 610 700 780 830 900 960 1010
4 (102) 630 750 870 980 1090 1160 1250 1310 1400
5 [phone] 1190 1300 1410 1520 1640 1730 1810
6 (152) 1050 1290 1480 1650 1800 1940 2090 2200 2320
7 (178) 1250 1510 1760 1960 2180 2320 2500 2650 2800
8 (203) 1490 1810 2100 2350 2560 2760 2940 3110 3290
9 (229) 1700 2100 2400 2700 2970 3200 3400 3600 3800
10 (254) 1920 2350 2760 3090 3650 4020 4300 4550 4800
*See Figure 11.
NOTE: Not all capacities are covered above. If your installation is not covered, consult your distributor or the factory representative to
determine the appropriate size of the bypass duct.
Venting Connections
•Locate power-vented furnaces so that flue discharge is not directed at fresh air inlets. The flue discharge openings
are located on the side of the furnace just above the control access panel. The position of this opening discourages
recirculation of combustion products and provides for furnace operation in all normal weather conditions.
• Optional vertical flue discharge (option CC3): These power vented furnaces are certified with 4 feet of vertical
pipe connected as shown in Figure 12, DETAIL A. The distance is measured from the top of the unit to the bottom
of the vent cap. The vent pipe and supports are field-supplied. Optional vertical vent piping provides compliance
with local codes that require either 10-foot horizontal or 4-foot vertical clearance between the flue outlet and the
fresh air intake of the heating system and/or building. The option package (PN 45021) includes the 5-inch vent
cap, the adapter assembly, and the seal plate as shown in Figure 12, DETAIL B. Attach venter seal plate and
oval adapter assembly with sheet metal screws. Use venter seal plate as drill template.

18 RP-HRPD-IOM (01-23) 132210-D
Figure 12. Optional Vertical Flue Discharge
Piping Connections
Gas Supply Pressure
The unit is equipped for a maximum gas supply pressure of 1/2 psi, 3.5 kPa, or 14 IN WC.
NOTES:
Supply pressure higher than 1/2 psi requires the installation of an additional service regulator
external to the unit.
PRESSURE TESTING SUPPLY PIPING
• Test pressures above 1/2 psi—disconnect the heater and manual valve from the gas supply line
to be tested. Cap or plug the supply line.
• Test pressures below 1/2 psi—before testing, close the manual valve on the heater.
Gas Supply Piping
⚠ DANGER ⚠
• All components of a gas supply system must be leak tested prior to placing equipment in service.
NEVER TEST FOR LEAKS WITH AN OPEN FLAME. Failure to comply could result in personal
injury, property damage, or death.
• Pipe joint compounds (pipe dope) shall be resistant to the action of liquefied petroleum gas or
any other chemical constituents of the gas being supplied.
•All piping must be in accordance with requirements outlined in the National Fuel Gas Code ANSI/Z223.1 (latest
edition) or the Natural Gas and Propane Installation Code CSA B149.1 (refer to Installation Codes section).
•Gas supply piping installation should conform with good practice and with local codes.
DETAIL BDETAIL A
INSTALLATION—CONTINUED
Venting Connections—Continued

19
RP-HRPD-IOM (01-23) 132210-D
Supply Piping Connections
•Install a ground joint union and manual shutoff valve upstream of the unit control system. The 1/8-inch plugged
tapping in the shutoff valve provides connection for the supply line pressure test gauge. The National Fuel Gas
Code requires the installation of a trap with a minimum 3-inch drip leg. Local codes may require a longer drip leg,
typically 6-inch (see Figure 13, DETAIL A).
•Gas connection location and requirements are shown in Figure 13, DETAIL B.
•Install the gas supply piping so that when the union is disconnected, the supply pipe will not interfere with the
removal of the burner rack (see Figure 13, DETAIL C). The burner rack slides out of the control side of the furnace.
•Seal the opening for the gas supply pipe with the grommet provided.
•After all connections are made, disconnect the pilot supply at the control valve and bleed the system of all air.
Reconnect the pilot line and leak test all connections by brushing on a soap solution.
•Gas connections sizes are listed in Table 13.
Table 12. Gas Supply Line Sizes
Length
of Pipe
(Feet)
Diameter of Pipe (Inches)
1/2 3/4 1 1-1/4 1-1/2 2
Natural
Gas
Propane
Gas
Natural
Gas
Propane
Gas
Natural
Gas
Propane
Gas
Natural
Gas
Propane
Gas
Natural
Gas
Propane
Gas
Natural
Gas
Propane
Gas
Cubic Feet per Hour
20 92 56 190 116 350 214 730 445 1100 671 2100 1281
30 73 45 152 93 285 174 590 360 890 543 1650 1007
40 63 38 130 79 245 149 500 305 760 464 1450 885
50 56 34 115 70 215 131 440 268 670 409 1270 775
60 50 31 105 64 195 119 400 244 610 372 1105 674
70 46 28 96 59 180 110 370 226 560 342 1050 641
80 43 26 90 55 170 104 350 214 530 323 990 604
90 40 24 84 51 160 98 320 195 490 299 930 567
100 38 23 79 48 150 92 305 186 460 281 870 531
125 34 21 72 44 130 79 275 168 410 250 780 476
150 31 19 64 39 120 73 250 153 380 232 710 433
175 28 17 59 36 110 67 225 137 350 214 650 397
200 26 16 55 34 100 61 210 128 320 195 610 372
•The heater is orificed for operation with natural gas having a heating value of 1,000 (±50) BTU per cubic foot or
with propane gas having a heating value of 2,550 (±100) BTU per cubic foot. Sizing of gas supply lines depends
on piping capacity and is based on cubic feet per hour based on a 0.3 IN WC pressure drop, a 0.6 specific gravity
for natural gas at 1,000 BTU per cubic feet, and a 1.6 specific gravity for propane at 2,550 BTU per cubic feet. If
the gas at the installation does not meet this specification, consult the factory for proper orificing.
•Variables for sizing gas supply lines are listed in Table 12. When sizing supply lines, consider possibilities of future
expansion and increased requirements. Refer to National Fuel Gas Code for additional information on line sizing.

20 RP-HRPD-IOM (01-23) 132210-D
INSTALLATION—CONTINUED
Piping Connections—Continued
Supply Piping Connections—Continued
Figure 13. Gas Connections
Table 13. Gas Connection Sizes
Gas Type
RP Unit Size
125–250 300–400
HRPD Unit Size
250–500 600–800
Connection Size (Inches (mm))
Natural gas 1/2 (13) 3/4 (19)
Propane 1/2 (13)
NOTE: The above are not supply line sizes. They are gas connection sizes for a standard unit.
DETAIL A
DETAIL B DETAIL C