Thermo Pride CHX3-75N User manual

TWO STAGE CONDENSING GAS FURNACE
INSTALLATION AND OPERATION MANUAL
MODELS:
FOR USE WITH NATURAL GAS OR LP GAS (PROPANE)
CHX3-75N CDX3-75N
CHX3-100N CDX3-100N
CHX3-125N CDX3-125N
: IF YOU DO NOT FOLLOW THE SAFETY PRECAUTIONS BELOW AND IN THIS
MANUAL, A FIRE OR EXPLOSION MAY RESULT CAUSING PROPERTY DAMAGE, PERSONAL
INJURY, OR LOSS OF LIFE.
DO NOT STORE OR USE GASOLINE OR OTHER FLAMMABLE VAPORS 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 NEIGHBOR’S PHONE. FOLLOW THE GAS
SUPPLIER’S INSTRUCTIONS.
• IF YOU CANNOT REACH YOUR GAS SUPPLIER; CALL THE FIRE DEPARTMENT.
INSTALLATION AND SERVICE MUST BE PERFORMED BY A QUALIFIED INSTALLER, SERVICE
AGENCY OR THE GAS SUPPLIER. (REFERRED TO IN THESE INSTRUCTIONS AS A QUALIFIED
HEATING CONTRACTOR).
PLEASE READ THESE INSTRUCTIONS PRIOR TO INSTALLATION, INITIAL FIRING, AND BEFORE
PERFORMING ANY SERVICE OR MAINTENANCE. THESE INSTRUCTIONS MUST BE LEFT WITH
THE HOMEOWNER AND SHOULD BE RETAINED FOR FUTURE REFERENCE BY QUALIFIED
SERVICE PERSONNEL.
THERMO PRODUCTS, LLC.
BOX 217
NORTH JUDSON, IN 46366
PHONE: [phone] MADE IN USA
MG-1035
ECN 5222-MA 110815

All installations and services must be performed by qualified service personnel.
I. SAFETY INFORMATION
This and the following page contain reproductions of the various warning and instruction labels placed on
the Thermo Pride Two Stage Condensing Gas Furnaces. Please read and comply with the contents of
these labels.
i

All installations and services must be performed by qualified service personnel.
This and the previous page contain reproductions of the various warning and instruction labels placed on
the Thermo Pride Two Stage Condensing Gas Furnaces. Please read and comply with the contents of
these labels.
The following safety information should be read, understood, and followed by the installer.
WARNING: If you do not follow these instructions exactly, a
fire or explosion may result causing property damage,
personal injury or loss of life.
390540
1. Set thermostat to lowest setting, and, if equipped, set the operating
mode to "COOL" or "OFF".
2. If service is to be performed, turn off all electric power to the
appliance.
3. To turn off gas control valve, remove the burner compartment cover.
4. Move the gas control switch to the "OFF" position.
5. Replace the burner compartment cover.
1. STOP! Read the safety information above on this label.
2. Set the thermostat to the lowest setting.
3. Turn off all electric power to the appliance.
4. This appliance is equipped with a hot surface igniter that
automatically lights the burner. Do not try to light the burner by
hand.
5. Move the gas control switch to the "OFF" position.
6. Wait five (5) minutes to clear out any gas. Then smell for gas,
including near the floor or ground. If you smell gas, STOP! Follow
"B" in the safety information above on this label. If you don't smell
gas, go to the next step.
7. Move the gas control switch to the "ON" position.
8. Turn on all electric power to the appliance.
9. Set thermostat to desired setting, and, if equipped, set the operating
mode to "HEAT".
10.If appliance will not operate, follow the instructions "To Turn Off
Gas To Appliance" and call your service technician or gas supplier.
A. This appliance does not have a pilot. It is equipped with a hot
surface igniter that automatically lights the burner. Do not try to
light the burner by hand.
B. BEFORE OPERATING smell all around the appliance area for gas.
Be sure to smell next to the base of unit because some gas is
heavier than air and will settle on the floor or ground.
WHAT TO DO IF YOU SMELL GAS
? Do not try to light any appliance.
? Do not touch any electric switch; do not use any phone in your
building.
? Immediately call your gas supplier from a neighbor's phone.
Follow the gas supplier's instructions.
? If you cannot reach your gas supplier, call the fire department.
C. Use only your hand to move the gas control switch. Never use tools.
If the switch will not move by hand, don't try to repair it, call a
qualified service technician. Force or attempted repair may result in
a fire or explosion.
D. Do not use this appliance if any part has been underwater.
Immediately call a qualified service technician to inspect the
appliance and to replace any part of the control system and any gas
control which has been underwater.
ii

All installations and services must be performed by qualified service personnel.
1. Use only with type of gas approved for this furnace. Refer to furnace rating plate.
2. Connect this furnace to an approved vent system only. Combustion products must be carried
outdoors. Refer to Section III, D thru H, of this manual.
The following pages contain various warnings and cautions found throughout the Thermo Pride
Highboy and Dual Poise Two Stage Condensing Gas Furnace Manual. Please read and comply
with the statements below.
: This furnace is not to be used for temporary heating of buildings or structures under
construction.
: These high efficiency condensing furnaces are not certified for and shall not be
vented into a standard or any type of chimney.
: These furnaces may not be common vented with any other appliance.
: The vent and air intake elbows must be kept away from bushes, shrubs or any
vegetation that may restrict the flow of flue products. It must also be kept clear of any leaves,
weeds or other combustible materials. Keep the vent hood clear of snow. Avoid locating the
terminals in areas where standing water or condensate drippage may be a problem.
: This CHX3/CDX3 furnace has been designed to be installed as a direct vent system.
The failure to install the vent/air intake system as specified in these instructions will void the heat
exchanger warranty and may result in property damage, personal injury or loss of life.
: Outside combustion air must not come from an area that is directly adjacent to a
pool, hot tub or spa. Measures should be taken to prevent the entry of corrosive chemicals or
vapors to the combustion and ventilation air supply. Such chemicals include but are not limited to
chlorinated and/or fluorinated hydrocarbons such as found in refrigerants, aerosol propellants,
dry cleaning fluids, degreasers and removers. Other harmful compounds may come from
bleaches, air fresheners or mastics. Vapors from such products can form acid compounds when
burned in a gas flame. Should acid compounds form in your furnace; it may reduce the life of the
furnace.
: Because of the potential of odorant fade, a gas leak may not be detected by smell. If
this furnace is installed below grade, contact your gas supplier for a gas detector.
: Turn off power to furnace before it is placed into service. The gas piping system
must have been leak tested by a qualified heating contractor.
: It may be necessary to purge the air out of the gas line for initial start-up of the
furnace after installation. This should be done by a qualified heating contractor. If excessive gas
escapes when purging the gas supply at the union, allow the area to ventilate for at least 15
minutes before attempting to start the furnace. LP gas is especially dangerous because the
specific gravity of LP gas allows it to accumulate at floor level at a dangerous concentration. For
remainder of operating instructions, reference Users Information Manual.
: Heat exchanger oil will burn off on initial firing creating an unpleasant odor. To
prevent this odor from occurring more than once, it is suggested that:
1. A window(s) be opened.
2. The thermostat set at highest setting.
3. The furnace remain running at conditions 1&2 for 30 minutes or until odor has dissipated.
iii

All installations and services must be performed by qualified service personnel.
: The CHX3/CDX3 furnace models are sealed combustion design, which does not
require an air shutter adjustment (air shutters are not used) for proper flame characteristics.
Burner box access cover must always be secured with all screws in place and tightened before
operating furnace.
: Personal injury or property damage could result from repair or service of this
furnace by anyone other than a qualified heating contractor. Only the homeowner/user routine
maintenance described in the Users Information Manual may be performed by the user.
iv

All installations and services must be performed by qualified service personnel.
INDEX
SECTION BEGINNING PAGE
I. SAFETY INFORMATION i
II. FURNACE SPECIFICATIONS 1
III. GENERAL INSTALLATION 6
A. CODES AND CLEARANCES 6
B. FURNACE LOCATION 7
B1.CDX3 HORIZONTAL APPLICATION 7
C. REPLACING EXISTING FURNACE FROM A COMMON VENT 9
D. GENERAL REQUIREMENTS FOR VENTING CHX3/CDX3 9
E. SIDEWALL VENTING 11
E1. SINGLE PIPE (SIDEWALL) VENTING OPTION 15
F. INSTALLATION OF OUTSIDE VENT/AIR INTAKE TERMS. 15
G. CONNECTING FURNACE TO ROOF VENT/AIR TERMS. 17
H. CONNECTING FURNACE TO VENT/AIR INTAKE TERMS. 18
I. CONDENSATE DRAIN LINE & TRAP ASSY. 23
J. GENERAL GAS PIPING 26
J1. REQUIREMENTS AND SIZING OF DUCTWORK 27
K.FILTERS 30
L.WIRING 32
IV.STARTINGTHEUNIT 36
A. SEQUENCE OF OPERATIONS 36
B.INITIALSTART-UP 39
C. MEASURING AND ADJUSTING HEAT INPUT RATE 70
D. FURNACE CHECKOUT PROCEDURE 47
V. INSTALLER’S INSTRUCTIONS TO USER 47
VI. TROUBLESHOOTING 48
APPENDIX – A REPLACEMENT PARTS LIST 55
APPENDIX – B WIRING DIAGRAMS 59
WARRANTY 61
v

All installations and services must be performed by qualified service personnel.
II. FURNACE SPECIFICATIONS
CHX3 SERIES
MODEL NO. CHX3-75 CHX3-100 CHX3-125
BTU/HR INPUT (High fire/ Low fire) 75,000 / 52,000 100,000 /
70,000 125,000 / 87,500
BTU/HR OUTPUT (High fire/ Low fire) 71,000 / 49,000 95,000 / 66,000 115,000 /
82,000
HEIGHT OF CASING 44-1/4” 44-1/4” 44-1/4”
WIDTH OF CASING 17” 21” 24”
DEPTH OF CASING 27-1/2” 27-1/2” 27-1/2”
WARM AIR OUTLET 15 x 18 19 x 18 22 x 18
RETURN AIR INLET 25 x 16 25 x 16 25 x 16
DIA. OF FLUE 2” 3” 3”
DIA. OF COMBUSTION
AIR INTAKE 2” 3” 3”
CFM from .2” & .5” w.c.
EXTERNAL STATIC PRESSURE COOLING COOLING COOLING
@COOLING TAP A 1000 1200 1400
@COOLING TAP B 800 1000 1200
@COOLING TAP C 1200 1400 1600
@COOLING TAP D 1400 1600 2000
HEATING HEATING HEATING
@HEATING TAP A (High fire/Low fire) 931 / 760 1243 / 1015 1556 / 1270
TEMPERATURE RISE 70 / 60 70 / 60 70 / 60
BLOWER MOTOR HP .5 .75 1
POWER CHOKES - 2.65 Mh 2.1 Mh
LARGEST RECOMMEDED
AIR CONDITIONER 3.5 Ton 4 Ton 5 Ton
SIZE OF FILTERS 24-3/4” x 15-3/4” 24-3/4” x 15-3/4” 24-3/4” x 19-3/4”
NOTES:
1. BTU output based on annual fuel utilization efficiency rated by manufacturer.
2. On all outlet and inlet dimensions, the first dimension is width.
3. To permit largest recommended air conditioning (at .5 static pressure), selection of the highest motor speed is
required.
1

All installations and services must be performed by qualified service personnel.
CDX3 SERIES
MODEL NO. CDX3-75 CDX3-100 CDX3-125
BTU/HR INPUT (High fire / Low fire) 75,000 / 56,250 100,000 /
75,000 125,000 / 93,750
BTU/HR OUTPUT (High fire / Low fire) 71,000 / 52,000 94,000 / 69,000 116,000 /
87,000
HEIGHT OF CASING 46-1/4” 46-1/4” 46-1/4”
WIDTH OF CASING 17” 21” 24”
DEPTH OF CASING 27-1/2” 27-1/2” 27-1/2”
WARM AIR OUTLET 15 x 18 19 x 18 22 x 18
RETURN AIR INLET 15 x 22 19 x 22 22 x 22
DIA. OF FLUE 2” 3” 3”
DIA. OF COMBUSTION
AIR INTAKE 2” 3” 3”
CFM from .2” & .5” w.c.
EXTERNAL STATIC PRESSURE COOLING COOLING COOLING
@COOLING TAP A 1000 1200 1400
@COOLING TAP B 800 1000 1200
@COOLING TAP C 1200 1400 1600
@COOLING TAP D 1400 1600 2000
HEATING HEATING HEATING
@HEATING TAP C (High fire / Low
fire) 1012 / 826 1340 / 1094 1673 / 1366
TEMPERATURE RISE 65 / 60 65 / 60 65 / 60
BLOWER MOTOR HP .5 .75 1
POWER CHOKES - 2.65Mh 2.1Mh
LARGEST RECOMMEDED
AIR CONDITIONER 3.5 Ton 4 Ton 5 Ton
SIZE OF FILTERS 21-3/4” x 14”(2) 21-3/4” x 14”(2) 21-3/4” x 14”(2)
NOTES:
1. BTU output based on annual fuel utilization efficiency rated by manufacturer.
2. On all outlet and inlet dimensions, the first dimension is width.
3. To permit largest recommended air conditioning (at .5 static pressure), selection of the highest motor
speed is required.
4. Electrical characteristics at 115 volts, 60 Hz., 1 phase (less than 15 amps. for all models).
5. All specifications are subject to change without notice.
2

All installations and services must be performed by qualified service personnel.
INSTALLATION PARTS PACKAGES – CHX3-75
PARTS PACKAGE
#S00S4413 DESCRIPTION PART # QUANTITY
2-3/8” ID radiator hose 410017 1
Thermostat lead bushing 350750 1
PVC trap assembly 320816 1
#8 x ¾ coated TEK screws for
mounting trap & inlet/outlet collars 300283 4
11/16” OD x 1/2” ID vinyl tubing 410060 24”
2 x 4 electrical J-box 350024 1
2 x 4 electrical J-box cover 350020 1
#8 x ½ TEK screws for
mounting 2 x 4 J-box 300208 2
#10-32 x ½ green ground screw 300109 1
#10-32 hex nut 300110 1
3/16” dia. star washer 300270 1
Grounding instructions MG-966 1
Wire nut 300132 2
3” stainless steel hose clamp 300276 2
J-box wire bushing 350016 1
Drain hose grommet 350446 1
Spring clamp, 11/16” 300299 3
Installation notice MG-987 1
PVC tee assembly, 2” dia. 320818 1
CPVC XPVC adapter 320833 1
Gas Conversion Kit AOPS7682 1
INSTALLATION PARTS PACKAGES – CHX3-100-125
PARTS PACKAGE
#S00S4414/4415 DESCRIPTION PART # QUANTITY
2-3/8” ID radiator hose 410017 1
Thermostat lead bushing 350750 1
PVC trap assembly 320816 1
#8 x ¾ coated TEK screws for
mounting trap & inlet/outlet collars 300283 4
11/16” OD x ½” ID vinyl tubing 410060 24”
2 x 4 electrical J-box 350024 1
2 x 4 electrical J-box cover 350020 1
#8 x ½ TEK screws for
mounting 2 x 4 J-box 300208 2
#10-32 x ½ green ground screw 300109 1
#10-32 hex nut 300110 1
3/16” dia. star washer 300270 1
Grounding instructions MG-966 1
Wire nut 300132 2
3” stainless steel hose clamp 300276 2
J-box wire bushing 350016 1
Drain hose grommet 350446 1
Spring clamp, 11/16” 300299 3
Installation notice MG-987 1
3

All installations and services must be performed by qualified service personnel.
PVC tee assembly, 2 x 3” dia. 320817 1
CPVC XPVC adapter 320833 1
Gas Conversion Kit AOPS7683/7419 1
INSTALLATION PARTS PACKAGES – CDX3-75
PARTS PACKAGE
#S00S4416 DESCRIPTION PART # QUANTITY
2-3/8” ID radiator hose 410017 1
Thermostat lead bushing 350750 1
PVC trap assembly 320816 1
#8 x ¾ coated TEK screws for
mounting trap & inlet/outlet collars 300283 6
11/16” OD x ½” ID vinyl tubing 410060 24”
2 x 4 electrical J-box 350024 1
2 x 4 electrical J-box cover 350020 1
#8 x ½ TEK screws for
mounting 2 x 4 J-box 300208 2
#10-32 x ½ green ground screw 300109 1
#10-32 hex nut 300110 1
3/16” dia. star washer 300270 1
Grounding instructions MG-966 1
Wire nut 300132 2
3” stainless steel hose clamp 300276 2
J-box wire bushing 350016 1
Drain hose grommet 350446 1
Spring clamp, 11/16” 300299 3
Installation notice MG-987 1
PVC tee assembly, 2” dia. 320819 1
Pipe 2” dia. PVC 15” 14401 1
Bracket 14406 1
CPVC XPVC adapter 320833 1
Gas Conversion Kit AOPS7682 1
INSTALLATION PARTS PACKAGES – CDX3-100-125
PARTS PACKAGE
#S00S4381 DESCRIPTION PART # QUANTITY
2-3/8” ID radiator hose 410017 1
Thermostat lead bushing 350750 1
PVC trap assembly 320816 1
#8 x ¾ coated TEK screws for
mounting trap & inlet/outlet collars 300283 4
11/16” OD x 1/2” ID vinyl tubing 410060 24”
2 x 4 electrical J-box 350024 1
2 x 4 electrical J-box cover 350020 1
#8 x ½ TEK screws for
mounting 2 x 4 J-box 300208 2
#10-32 x ½ green ground screw 300109 1
#10-32 hex nut 300110 1
3/16” dia. star washer 300270 1
4

All installations and services must be performed by qualified service personnel.
Grounding instructions MG-966 1
Wire nut 300132 2
3” stainless steel hose clamp 300276 2
J-box wire bushing 350016 1
Drain hose grommet 350446 1
Spring clamp, 11/16” 300299 3
Installation notice MG-987 1
PVC tee assembly, 2 x 3” dia. 320817 1
PVC tee assembly, 2” dia. 320819 1
Pipe 2” dia. PVC 15” 14401 1
Bracket 14406 1
Reducer 2” x 3” PVC 320067 1
CPVC XPVC adapter 320833 1
Gas Conversion Kit AOPS7683/7419 1
5

All installations and services must be performed by qualified service personnel.
III. GENERAL INSTALLATION
These Category Type IV furnaces are shipped completely assembled and wired (internally). See the
Dealer Receiving and Freight Claim Procedure Section of the price guide for parts shortage or damage.
The furnace and duct system must be adjusted to obtain a temperature rise of 55°F to 85°F through the
furnace after installation. (See rating label located on side panel inside the furnace vestibule). The
installation must conform with local codes, or in the absence of local codes, with the National Fuel Gas
Codes (ANSI Z223.1 or latest edition) and with these instructions.
: This furnace is not to be used for temporary heating of buildings or structures under
construction.
Many of the chemicals used during construction, when burned, form acid bearing condensate that can
substantially reduce the life of the heat exchanger.
It is recommended that a commercially available CO alarm be installed in conjunction with any fossil fuel
burning appliance. The CO alarm shall be installed according to the alarm manufacturer’s installation
instructions and be listed in accordance with latest edition of the UL Standard for Single and Multiple
Station Carbon Monoxide Alarms, UL 2034, or the CSA International Standard, Residential Carbon
Monoxide Alarming Devices, CSA 6.19.
A. CODES AND CLEARANCES
The following items must be considered when choosing the size and location of the furnace.
1. All local codes and/or regulations take precedence over the instructions in this manual and should be
followed accordingly. In the absence of local codes, installation must conform with these instructions,
regulations of the National Fire Protection Association, provisions of National Electrical Code
(ANSI/NFPA70 or latest edition), and the National Fuel Gas Code (ANSI Z223.1 or latest edition).
2. The BTU output capacity of the furnace proposed for installation should be based on a heat loss
calculation made according to the manuals provided by the Air Conditioning Contractors of America
(ACCA) or ASHRAE.
3. MINIMUM CLEARANCES TO COMBUSTIBLE MATERIALS
TABLE 1
MODEL NO. FROM SIDES OF
FURNACE & REAR FRONT TOP OF
PLENUM FROM THE FLUE OR VENT SIDE OF PLENUM
CHX3-75 0 IN. 6 IN. 0 IN. 0 IN. 1 IN.
CHX3-100 0 IN. 6 IN. 0 IN. 0 IN. 1 IN.
CHX3-125 0 IN. 6 IN. 0 IN. 0 IN. 1 IN.
CDX3-75 0 IN. 6 IN. 0 IN. 0 IN. 1 IN.
CDX3-100 0 IN. 6 IN. 0 IN. 0 IN. 1 IN.
CDX3-125 0 IN. 6 IN. 0 IN. 0 IN. 1 IN.
The CHX3-75, 100 and 125 furnaces may be installed on combustible flooring. The furnace shall not be
installed directly on carpeting, tile or other combustible material other than wood flooring.
The CDX3-75, 100 and 125 furnaces are to be installed on non-combustible flooring only. The non-
combustible floor bases model no. 50 DA base for CDX3-75 model no. 100 CA base for the model no.
CDX3-100 and model no. 125 CA base for CDX3-125 are available for the counterflow furnaces to allow
their installations on combustible flooring.
6

All installations and services must be performed by qualified service personnel.
These furnaces may be installed in an alcove or in a closet if the minimum clearances to combustible
construction (listed previously) are met. The CDX3 series furnaces may be installed in an attic or crawl
space. Refer to section III, B1 of this installation manual.
The minimum clearances are listed for fire protection. Clearance for servicing the front of the furnaces
and to all points on the furnace requiring access must be 24”*.
*For horizontal furnace installation, refer to section III, B1 of this installation manual.
Equipment must be installed in accordance with regulations of the National Board of Fire
Underwriters. Authorities having jurisdiction should be consulted before installations are made.
B. FURNACE LOCATION
: These high efficiency condensing furnaces are not certified for and shall not be
vented into a standard or any type of chimney.
The following shall be considered for locating the furnace:
1. For best performance locate the furnace so that it is centralized with respect to the duct system and
as near as possible to a floor drain since condensate drainage must be provided.
2. Place the unit so that proper venting can be achieved, with a minimum number of elbows, in accord
with the instructions in this manual.
3. The furnace must be located on a level, dry surface. The furnace must be installed so that the
electrical components are protected from water. If the area becomes wet or damp at times, the
furnace should be raised above the floor using a concrete base, bricks, patio blocks, etc.
NOTICE: Ensure furnace is level after installation to ensure proper drainage and operation.
4. This furnace must be connected to a drain in accordance with these instructions. If it is not practical
to connect the unit to a drain, a condensate pump must be used and can be ordered as an
accessory, part number 350225. If an acid neutralizer kit is required by local code or the customer, it
is available under part number 320095.
B1. CDX3 HORIZONTAL APPLICATION
The CDX3-75, 100, and 125 furnaces may be installed in a horizontal position by placing the furnace on
the left or right side (as viewed from the front in the upright position).
For left or right horizontal applications of the CDX3 series units, the rollout switch located on the burner
box must be moved to the pre-punched mounting holes on the side of the burner box. Screws are
provided in pre-punched holes at the required limit location. Remove these screws and use them to
mount the limit to new location. Utilize previously removed limit mounting screws to fill voided holes at
previous limit location (See Figure 1).
For a right side horizontal application of the CDX3 series units, the hose from the single tap pressure
switch (top switch) is already connected correctly (See Figure 1).
For a left side horizontal application of the CDX3 series units, the hose from the single tap pressure
switch (bottom switch) must be moved to the lower front tap on the face of the collector box. Use the
black cap removed from this tap to plug the original pressure switch tap.
7

All installations and services must be performed by qualified service personnel.
NOTE: The hose, when moved, must be shortened (cut) to ensure that no excess hose exists to cause a
sag, loop, or "water trap".
For a right side horizontal application of the CDX3 series units, the auxiliary limit switch located on the
right side of the house air blower must be moved to the bracket on the opposite (left) side of the blower
(See Figure 1).
NOTE: When the CDX3 is installed as horizontal unit, it is imperative that the auxiliary limit switch and
bracket be located on the upper side of the house air blower; the burner rollout switch located on the
burner box be relocated to the side of the burner box; and that the hose from the single tap pressure
switch be connected to the lower tap on the front of the collector box (See Figure 1).
Figure 1
8

All installations and services must be performed by qualified service personnel.
The horizontal furnace installation should be on a service platform large enough to allow for proper
clearances on all sides and service access to the front of the furnace (See Table 1). If the furnace is
suspended, it must be supported at both ends and in the middle with clearance allowed for removal of
both access doors. Gas supply line contact is only permissible between lines formed by the intersection
of the top and two sides of the furnaces casing and the building joists, studs, or framing (See Figure 1).
Equipment must be installed in accordance with regulations of the National Board of Fire
Underwriters and the National Fuel Gas Code. Authorities having jurisdiction should be consulted
before installations are made.
C. Replacing An Existing Furnace From A Common Vent
: These furnaces may NOT be common vented with any other appliance.
D. General Requirements For Venting Models CHX3 / CDX3
The CHX3 / CDX3 furnace venting system must be installed by a qualified service person in
accordance with local installation codes and these instructions. In the absence of applicable local
codes, conform to the National Fuel Gas Code, NFPA 54 /ANSI Z223.1-2002, or latest edition
thereof.
Installation shall, at least, conform to the following requirements.
1. The exhaust vent / combustion air intake terminations specified by Thermo Products, in this
manual, shall be used.
2. All plastic pipe and pipe fittings sourced to complete the exhaust vent and air intake
systems shall be constructed of rigid PVC (polyvinyl chloride) thermoplastic. All
components shall have a wall thickness equivalent to Schedule 40 series materials.
In addition, all sourced PVC components shall be listed by a nationally recognized testing agency
(e.g. NSF, UL, etc.) as conforming to one (1) or more of the following design standards.
PVC Pipe Designation Design Standard
Cellular Core ASTM-F891
DWV (Drain-Waste-Vent) ASTM-D2665
Schedule 40 ASTM-D1785
3. The exhaust vent pipe and combustion air pipe shall be at least as large as the exhaust vent / air
intake pipe specified by Thermo Products. Size reduction is never permissible. The required
exhaust vent / air intake pipe sizes are:
• nominal 2-inch diameter IPS, Schedule 40 series, PVC thermoplastic pipe, for models
CHX3-75 & CDX3-75, or
• nominal 3-inch diameter IPS, Schedule 40 series, PVC thermoplastic pipe, for models
CHX3-100 / -125 & CDX3-100 / -125.
4. The furnace model series CHX3 / CDX3 shall not be common vented with any other appliance,
including those burning solid fuels.
9

All installations and services must be performed by qualified service personnel.
5. All horizontal runs of exhaust vent pipe shall slope upward at least ¼ inch per foot from the outlet
of the furnace (for model CHX3), or the outlet of the drain tee (for the model CDX3), to the vent
termination, beyond the outside wall. This slope will permit proper drainage of the condensate.
Horizontal runs of air intake pipe shall slope downward at least ¼ inch per foot from the outlet of
the last elbow or last horizontal run, before exiting the wall, to the intake termination beyond the
outside wall. This slope will permit proper drainage of any precipitation that enters the intake
pipe.
6. The exhaust vent pipe shall be supported at every joint (no more than 4-feet between supports)
to prevent pipe blockage due to condensate trapped at a local low point, or sag, in the vent
system.
7. The maximum permissible length of piping (consisting of a combination of straight pipe and a
corresponding number of elbows) permitted is:
• 75 equivalent feet, for the exhaust vent system, and
• 70 equivalent feet, for the combustion air intake system.
8. The maximum quantity of Schedule 40 series, type DWV thermoplastic pipe elbows allowed in
each system is listed in Table 2. When counting pipe elbows, all elbows used in the exhaust vent
or combustion air intake systems must be considered. This includes all elbows, or equivalent
pipe fittings, used inside the furnace jacket in addition to those used to construct the termination.
Furthermore, a credit of 5-feet of straight pipe may be taken for each elbow, up to maximum of
three (3) elbows, which is dropped from the maximum permissible number for each system.
Table 2: Maximum Permissible Exhaust Vent and Combustion Air Intake Lengths When Using the
Maximum Quantity of Elbows
Thermoplastic
Pipe Vent Size
(Nominal)
2 in. Diameter IPS 3 in. Diameter IPS
Furnace Model Exhaust or
Intake
Straight
Pipe Length
(ft.)
Maximum Qty.
of Exhaust
Elbows 1, 2
Maximum
Qty. of Intake
Elbows 2
Exhaust or
Intake
Straight Pipe
Length (ft.)
Maximum Qty.
of Exhaust
Elbows 1, 2
Maximum
Qty. of Intake
Elbows 2
CHX3 / CDX3-75 35 8 7 - - -
CHX3 / CDX3-100
CHX3 / CDX3-125 Not Permitted
35 8 7
Superscripts:
1 The drain tee supplied with the model series CHX3 / CDX3 furnaces is considered
equivalent to one (1), 90° elbow.
2 Two (2) 45° elbows can be substituted for one (1), 90° elbow.
Care should be taken to design the shortest possible intake and exhaust systems. Each system
should contain as few elbows as possible to insure the satisfactory operation of the furnace.
However, system length should never be less than 8 ft of pipe with two (2), 90 deg. elbows.
For best overall operation of the combustion system, we recommend the actual equivalent
lengths for both the constructed intake and the exhaust systems have approximately the same
value.
9. Use a saw designed to cut thermoplastic pipe. All cuts should be made at right angles to the pipe
wall. Smooth jagged edges and remove all burrs and strings. All pipe joints must utilize
standard PVC Schedule 40 series, DWV type elbows, couplings, and fittings. Clean all pipe
surfaces at connections using a fine abrasive material or approved PVC cleaner (primer). Secure
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All installations and services must be performed by qualified service personnel.
all pipe joints using suitable permanent PVC pipe solvent cement. Joints are NOT to be made by
simply gluing raw edges of butted together vent pipe.
The piping joints inside the furnace vestibule should be sealed with a silicone caulk, rather than
pipe cement, to allow for disassembly and removal of piping, if necessary, during maintenance.
NOTICE: DO NOT use silicone caulk to seal the pipe sleeve or coupling to the metal air
intake collar on the burner box. Securing the sleeve or coupling to the collar using a screw
is sufficient.
10. Vent connections shall be checked for leakage with the furnace induced draft blower running and
with the vent termination blocked. Use a mild soap and water solution to check for leaks.
11. Vent pipe passing through an unheated space shall be insulated with 1-inch thick, foil-faced
fiberglass insulation, or equivalent, to prevent freezing of condensate within the pipe.
12. No clearance is required from the outer surface of the thermoplastic piping to combustible
materials for fire hazard prevention.
13. Thermo Products does not require screens be installed in the exhaust vent and air intake piping.
However, optional stainless steel screens are available from Thermo Products, should the
homeowner request them.
NOTICE: The CHX3 / CDX3 furnace models may be vented either through the sidewall or the roof.
For sidewall instructions, continue to the following section. For roof venting, refer to Section III G, of
this manual.
E. Direct Venting Through a Sidewall
1. Vent and combustion air pipes may pass through a maximum wall thickness of 18 inches. The
minimum wall thickness is 2 inches. Referring to Figure 2, the maximum distance from the outer
wall to the center of the elbow is 12 inches.
Figure 2: Proper Direct Vent Terminations (RH & LH views) and Vent Termination Only w/o
Outside Combustion Air Intake (RH view).
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All installations and services must be performed by qualified service personnel.
NOTICE: If exterior sidewall building materials are subject to degradation from contact with flue gases or
moisture, a minimum 24-inch diameter shield shall be fabricated from stainless steel or UV-resistant
plastic sheet. The protective shield shall be installed around the vent pipe on the outside wall.
2. The exhaust vent termination elbow shall be installed in accordance with these instructions and
any applicable local codes. Refer to Figures 2 and 3 for typical examples of proper terminations.
a. The exhaust vent termination must be installed in the same atmospheric pressure zone (i.e.
on the same wall) as the air intake termination.
b. The bottom edge of the vent termination elbow must be installed at least 12-inches above the
outlet of intake termination elbow.
c. The horizontal distance between the inlet and exhaust terminations should be minimized,
when possible, and should never exceed 24-inches.
d. The vent and intake systems should utilize the same numbers of elbows and approximately
the same length of straight pipe to reach the outside termination.
Figure 3: Typical Relative Locations of Direct Vent Terminations When Sidewall Venting.
3. Exhaust Vent Terminal Location Clearance Requirements
a. The vent terminal shall be located at least 3-feet above any forced air inlet located within 10-
feet. Refer to Figure 4 for a depiction of the required minimum clearances between vent
terminations and building features according to the National Fuel Gas Code (NFGC).
b. The vent terminal shall be at least 12-inches below, 12-inches horizontally from, or 12-inches
above, any door, window, or gravity air inlet into a building. The bottom of the vent terminal
shall be located at least 12-inches above grade.
c. The vent terminal shall not be located:
• over public walkways or over an area where wetting of surfaces by condensate, or water
vapor, could create a nuisance or hazard,
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All installations and services must be performed by qualified service personnel.
• near soffit vents, crawl space vents, or other areas where condensate or water vapor
could create a nuisance, hazard, or cause property damage, and
• where wetting of components by condensate, or water vapor, could be detrimental to the
operation of pressure regulators, relief valves, or any other equipment.
d. The vent terminal shall be installed a minimum of 14-inches from any obstruction and 3-feet
from an inside corner of an L-shaped structure.
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All installations and services must be performed by qualified service personnel.
Figure 4: NFGC Minimum Clearances Between the Vent Terminal and Various Building Features
Vent Terminal Location Guidelines
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