ICP 9MPT, 9MPV, A2î, ìA1, 9MPV050F12A Service Manual
...
MULTI POSITION
2-- STAGE
GAS FURNACES
This manual supports condensing gas furnaces manufactured in 2001
Manufactured by:
ã 2001 International Comfort Products Corporation (USA)
*9MPT & *9MPV
“A1 & A2”
Part Number
440 08 2002 02
4/2002
*9MPT -- Dual Certified Venting (1 or 2 pipes)
*9MPV -- Dual Certified Venting (1 or 2 pipes)
Variable Speed
ã 2001 International Comfort Products Corporation (USA)
1136 Heil--Quaker Boulevard, LaVergne, TN 37086
All rights reserved throughout the W orld.
Two- Stage Multi Position Furnace
Service Manual
TABLE OF CONTENTS
1. INTRODUCTION 2............................................................
2. UNIT IDENTIFICATION 2.....................................................
3. FURNACE THEORY OF OPERATION 3........................................
4. ELECTRICAL SUPPLY 4......................................................
5. INTERLOCK SWITCH 5......................................................
6. GAS SUPPLY 5..............................................................
7. L.P. PRESSURE SWITCH 7...................................................
8. HIGH ALTITUDE OPERATION 7...............................................
9. BURNERS 7................................................................
10. CHECKING TEMPERATURE RISE 8..........................................
11. ROOM THERMOSTATS 9....................................................
12. CONTROL WIRING 10.......................................................
13. LIMIT SWITCHES 10.........................................................
14. PRESSURE SWITCHES 12...................................................
15. VENT/COMBUSTION AIR PIPING 13..........................................
16. STANDARD VENT TERMINATION 14..........................................
17. CONCENTRIC VENT TERMINATION 16........................................
18. EXHAUST BLOWER 17......................................................
19. CONDENSATE DRAIN TRAP 17...............................................
20. HONEYWELL ST9162A FAN TIMER/FURNACE CONTROL 18....................
21. ST9162A/SV9541Q TESTING SEQUENCE 19..................................
22. HONEYWELL SV9541Q 2--STAGE GAS VALVE/IGNITION SYSTEM 19............
23. HONEYWELL SV9541Q SYSTEM OPERATION 20..............................
24. CHECKING FLAME CURRENT 22.............................................
25. CAPACITORS 22............................................................
26. BLOWER ASSEMBLY 22.....................................................
27. BLOWER ROTATION 27......................................................
28. HEAT EXCHANGER REMOVAL/REPLACEMENT 38.............................
SV9541Q “SMART VALVE” -- Sequence of Operation 39.............................
SV9541Q “SMART VALVE” -- Trouble shooting 40...................................
SV9541Q “SMART VALVE” -- Electrical Variation 42.................................
TECHNICAL SERVICE DATA (N9MPV) 44.........................................
BLOWER PERFORMANCE DATA (*9MPV) 45......................................
TECHNICAL SERVICE DATA (*9MPT) 52..........................................
BLOWER PERFORMANCE DATA (*9MPT) 53......................................
WIRING DIAGRAM (*9MPV) 54...................................................
WIRING DIAGRAM (*9MPT) 58...................................................
APPENDIX OF HELPFUL INFORMATION 60.......................................
Service
Manual
1. INTRODUCTION
This service manual is designed to be used in conjunction
with the installation manual and/or technical support manual
provided with each furnace.
These furnaces represent the very latest in high efficiency
gas furnace technology. Consequently, they incorporate the
use of certain controls that contain highly sophisticated electronic components which are not user serviceable. there-
fore, it is essential that only competent, qualified, service
personnel attempt to install, service, or maintain this product.
This Service manual was written to assist the professional
HVAC service technician to quickly and accurately diagnose
and repair any malfunction of this product.
This service manual covers several different models in two
(2) families of our new multi--position furnaces; Variable
Speed (D.C.-- Blower Motor) models in the Condensing furnace family, and 2 speed (P.S.C.--Blower Motor) models in
both the Condensing and Non--Condensing furnace families.
The overall operation of all of these models and families is
essentially the same, with the exception of the Blower Motor,
and/or certain control functions which may be unique to a
particular model and/or family.
Two- Stage Multi Position Furnace
ELS”. G ENE RALLY, t he dist inct ion between t hese two
groups is based on a difference in the type of Blower Motor
used. These may not be the only differences, however,
and the differences may vary from model to model within a
particular family or series.
It will be necessary then for you to accurately identify the
unit you are servicing, so you may be certain of a proper
diagnosis and repair. (See Unit Identification, Page 3)
!
The information contained in this manual is
intended for use by a qualified service technician
who is familiar with the safety procedures required
in installation and repair and who is equipped with
the proper tools and test instruments.
Installation or repairs made by the unqualified
persons can result in hazards subjecting the
unqualified person making such repairsto the risk of
injury or electrical shock which can be serious, or
even fatal not only to them, but also to persons being
served by the equipment.
This manual, therefore, will deal with all subjects in a general
nature (I.E. all text will pertain to all models) unless that subject is unique to a particular model or family, in which case
it will be so indicated.
If you install or perform service on equipment, you
must assume responsibility for any bodily injury or
property damage which may result to you or others.
We will not be responsible for any injury or property
damage arising from improper installation, service
Throughout the manual references may be made to “VARI-
and/or service procedures.
ABLE SPEED MODELS” as well as “TWO SPEED MOD-
2. UNIT IDENTIFICATION
The unit’s rating plate contains important information for the
service technician. It also lists the complete Model Manufacturing and Serial Numbers.
These complete numbers are required to obtain correct re-
MODEL NUMBER IDENTIFICATION GUIDE
* 9 MP T 075 B 12 A 1
Brand Identifier Engineering Rev.
T=Tempstar N=Neture Denotes minor changes
C = Comfortmaker/Keeprite Marketing Digit
H = Heil/Arcoaire X = Evaluation Denotes minor change
Brand Identifier 08 = 800 CFM
8 = Non--Condensing, 80+% Gas Furnace 12 = 1200 CFM
9 = Condensing, 90+% Gas Furnace 14 = 1400 CFM
Installation Configuration 16 = 1600 CFM
UP = Upflow DN = Downflow UH = Upflow/Horizontal 20 = 2000 CFM
HZ = Horizontal DH = Downflow/Horizontal Cabinet Width
MP = Multiposition, Upflow/Downflow/Horizontal B = 15.5² Wide
Major Design Feature F = 19.1² Wide
1 = One (Single) Pipe L= Low NOx T = Two Stage J = 22.8² Wide
2 = Two Pipe N = Single Stage V = Variable Speed L = 24.5² Wide
D = 1 or 2 Pipe P = PVC Vent Input (Nominal MBTUH)
440 08 2002 02
placement parts (example, in certain model families a unit
having a MARKET REVISION of “C” is likely to be equipped
with one or more different components.
Cooling Airflow
2
Two- Stage Multi Position Furnace
Service
Manual
Figure 1
Furnace Vent Pipe
(Vent Pipe Connection through
Side Panel on Some Models)
Vent Pipe Grommet
Manual Gas Valve
Rating Plate
Vent Drain Fitting
Diagnostic Light
Combustion Air Blower
Condensate Trap
3
/4²²²² OD Transition Box
Drain Hose
Component Locations for Four Position Furnaces
5
/8²²²² OD Vent Pipe
Drain Hose
Door Interlock Switch
Air Intake Pipe
(Dual Certified or Direct
Vent furnaces)
Primary Heat Exchanger
Secondary Heat Exchanger
Gas Valve/Ignition Module
Pressure Switches
Plastic Transition Box
Coils Air Baffle
Circulating Air Blower
Fan/Delay Control
3. FURNACE THEORY OF OPERATION
The high efficiencies and lower profile (compared to previous
series) of this furnace have been obtained using design techniques not typical of traditional furnace designs. A brief description of these new design techniques and the purpose
they serve follows.
1. Reducing the height of the furnace while maintaining
the high efficiency of pervious models required working the heat exchanger more efficiencly and yet minimizing the overall size.
The design required to achieve these results is the “SERPENTINE” design, wherein the flue gasses must follow a
serpent shaped passage through the heat exchanger via
convection.
This “Serpentine” path is resistive to normal convective flow,
and requires that a partial vacuum be created at the outlet
of the heat exchanger to maintain the flow of flue products
through the heat exchanger.
2. The serpentine heat exchanger design does not lend
itself well to the ribbon type, or slotted port type burner
found in more traditional design furnaces for the following reasons:
A.The s econdary combustion airflows at right angles to the
burner flame, making it likely to “pull” the flame off a ribbon
or slotted port type burner.
D C Motor Control
(some models)
dwg 25-- 23--29a
B.The flame “height” of a ribbon or slotted port type burner
would make it difficult (if not impossible) to prevent impingement of the flame on the heat exchanger surfaces
whole maintaining the low profile heat exchanger.
For these reasons, an “INSHOT” type burner is used in this
series. The inshot burner (also called a “jet” burner) fires a
flame straight out its end. This burner is designed to fire into
a tube style heat exchanger, making it an ideal application in
the tube--like passages of the serpentine heat exchanger.
3. In order to extract the maximum amount of heat possible from the flue gasses, a secondary heat exchanger (condenser) is connected to the outlet of the primary
heat exchanger. This condenser removes additional
heat from the flue gasses, causing their temperature to
drop below dew point, thus increasing operating efficiency of the furnace, and the term “Condensing Fur-
nace”. This results in the forming of condensation (water) which then must be routed to a drain.
4. The placement of the secondary heat exchanger at the
outlet of the primary heat exchanger creates additional
resistance to the flow of gasses.
5. To overcome the resistance to convective flow of the
Primary and Secondary heat exchangers requires the
use of an Induced Draft Combustion Blower Assembly.
440 08 2002 02
3
Service
Manual
Two- Stage Multi Position Furnace
6. The Combustion Blower Assembly is mounted on the
outlet side of the Secondary heat exchanger, This
blower creates a partial vacuum (negative pressure)
within the heat exchangers drawing the flue products
out of the furnace.
4. ELECTRICAL SUPPLY
!
Electrical shock hazard.
Turn OFF electric power at fuse box or service panel
before making any electrical connections and ensure a proper ground connection is made before
connecting line voltage.
Failure to do so can result in death, personal injury
and/or property damage.
SUPPLY CIRCUIT
The furnace cannot be expected to operate correctly unless
it is properly connected (wired) to an adequately sized (15
amp.) single branch circuit.
7. The Combustion Blower Assembly is mounted on the
outlet side of the Secondary heat exchanger, This
blower creates a partial vacuum (negative pressure)
within the heat exchangers drawing the flue products
out of the furnace.
5. An alternate check would be to check for continuity
from the Neutral to a cold water pipe, (Pipe must be
metal, and must have a continuous, uninterrupted connection to ground) or to a continuous, uninterrupted
connection to ground) or to a driven ground rod.
6. Any readings other than zero Ohms would indicate a
poor ground, or no ground.
Figure 2
Electrical Connections
W2
SUPPLY VOLTAGE
Supply voltage to the furnace should be a nominal 115 volts.
It MUST be between 97 volts and 132 volts. Supply voltage
to the furnace should be checked WITH THE FURNACE IN
OPERATION. Voltage readings outside the specified range
can be expected to cause operating problems. Their cause
MUST be investigated and corrected.
ELECTRICAL GROUND
Grounding of the electrical supply to ALL FURNACES IS
REQUIRED for safety reasons.
POLARITY
CORRECT POLARITY of the line voltage supply to all furnaces is also REQUIRED for safety reasons.
CHECKING GROUNDING AND POLARITY
Grounding may be verified as follows:
1. Turn the power supply “OFF”.
2. Using an Ohmmeter check for continuity between the
Neutral (white) wire and Ground wire (green) of the
supply circuit.
3. With the Ohmmeter set on the R x 1 scale, the reading
should be zero Ohms.
4. A zero Ohm reading indicates that the neutral is
grounded back to the main panel.
W2
W2
Polarity may be verified as follows:
1. Turn the power supply “ON”.
2. Using a Voltmeter check for voltage between the Hot
(Black) and Neutral (White) wire of supply circuit.
3. Reading should be Line (Supply) Voltage.
4. Check for Voltage between the Neutral (White) wire
and Ground wire of the supply circuit.
5. Reading should be zero Volts. (if line voltage is read,
polarity is reversed)
6. A zero Volt reading indicates there is no voltage potential on Neutral wire.
7. Double check by checking for voltage between the Hot
(Black) wire and Ground wire of the supply circuit.
8. Reading should be Line (supply) Vo ltage.(ifzero
volts is read, there is no ground, or polarity is reversed.)
440 08 2002 02
4
Two- Stage Multi Position Furnace
T
5. INTERLOCK SWITCH
The blower compartment door of all models is equipped with
an interlock switch. This switch is “Normally Open” (closes
when the door is on the furnace) and interrupts furnace operation when the door is open. This interlock switch is a safety device, and SHOULD NEVER BE BY--PASSED.
Since this is a single pole switch, (breaking only one side of
the line) proper line voltage is essential to insure that furnace
components are not “HOT” when switch is open. (See
Checking Grounding and Polarity)
6. GAS SUPPLY
Figure 3
Service
Typical Interlock Switch
Manual
10--12--96
On/Off
Switch
Manifold Pressure
Adjustment
OUTLET
INLET
Typical Gas Valve HoneywellFigure 4
Manifold
Adjustment
(Hidden)
LO
HI
INLET
25--22--49a
Diagnostic Light
(on some models)
Pilot
Adjustment
OUTLET
25--22--25a
NATURAL GAS
Inlet (Supply) pressure to the furnace should be checked (at
the gas valve) with ALL OTHER GAS FIRED APPLIANCES
OPERATING. Inlet (Supply) pressure to the furnace under
these conditions MUST be a minimum of 4.5² W.C. (Water
Column). If the inlet pressure is less, it may be an indication
of undersized piping or regulator problems.
L.P. GAS
Inlet (Supply) pressure to the furnace should be checked in
the same manner as for Natural Gas, however with L.P. Gas,
the inlet pressure MUST be a minimum of 11² W.C. If this
cannot be obtained, problems are indicated in either the regulator or pipe sizing.
Tab l e 1 Gas Pressures Below 2000¢¢¢¢
Gas
ype
Recommended Max. Min. Hi Fire Lo Fire
Natural 7² 14² 4.5² 3.5² 1.7²
LP 11² 14² 11² 10² 4.9²
· With Propane gas, the rated input is obtained when the
BTU content is 2,500 BTU per cubic foot and manifold
pressure set at 10²²²² W.C .
· If Propane gas has a different BTU content, orifices
MUST be changed by licensed Propane installer.
· Measured input can NOT exceed rated input.
· Any major change in gas flow requires changing burner
orifice size.
Supply Pressure
Important Note:
Manifold
Pressure
An adequately sized gas supply to the furnace is required for
proper operation. Gas piping which is undersized will not provide sufficient capacity for proper operation. Piping should
be sized in accordance with accepted industry standards.
CHECKING INPUT (FIRING) RATE
Once it has been determined that the gas supply is correct
to the furnace, it is necessary to check the input (firing) rate,
This can be done in two (2) ways. First by checking and adjusting (as necessary) the manifold (Outlet) pressure. The
second way is to “Clock” the gas meter.
440 08 2002 02
5
Service
Btu/C
u.F
t
Manual
Two- Stage Multi Position Furnace
!
Fire or explosion hazard.
Turn OFF gas at shut off before connecting
manometer.
Failure to turn OFF gas at shut off before
connecting manometer can result in death,
personal injury and/or property damage.
Gas Pressure Testing DevicesFigure 5
Pressure Connections
3
2
1
0
1
2
3
0
INCHES OF WATER
510
15
MAGNEHELIC
MAX. PRESSURE 15 PSIG
CHECKING MANIFOLD PRESSURE
1. Connect manometer or Magnehelic gauge to the
tapped opening on the outlet side of gas valve. Use a
manometer witha0to12² minimum water column
range.
2. Turn gas ON. Operate the furnace on high fire by using
a jumper wire on the R to W1 & W2 thermostat connections on the fan board.
3. Remove the adjustment cover on the gas valve. Turn
adjusting screw counterclockwise to decrease the
manifold pressure and clockwise to increase. See
Figure 4.
4. Set the manifold pressure to value shown in Table 1 or
Tab l e 2.
5. Operate the furnace on low fire by using a jumper wire
on the R to W1 thermostat connections on the fan
board.
Note: The fourth (4th) DIP switch should be in the on
position to set the low fire manifold pressure. (See wiring digram)
6. Repeat steps 4 and 5 for low fire operation.
7. When the manifold pressures are properly set, replace
the adjustment screw covers on the gas valve.
8. Remove the jumper wires from the thermostat connec-
Typical "U" Tube
Manometer
tions on the fan board. Remove manometer and replace plug in gas valve.
9. Reture fourth (4th) DIP switch to previous setting.
10. Replace the burner compartment door.
MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS
Tab l e 2
HeatValue
.
800 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7
850 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7
900 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.4 1.7
950 3.5 1.7 3.5 1.7 3.5 1.7 3.5 1.7 3.3 1.6 3.2 1.6 3.1 1.5
1000 3.5 1.7 3.4 1.7 3.3 1.6 3.2 1.5 3.0 1.5 2.9 1.4 2.8 1.4
1050 3.2 1.6 3.1 1.5 3.0 1.5 2.9 1.4 2.7 1.3 2.6 1.3 2.5 1.2
1100 2.9 1.4 2.8 1.4 2.7 1.3 2.6 1.3 2.5 1.2 2.4 1.2 2.3 1.1
Orifice Size #42 #42 #42 #42 #42 #42 #42
0-- 1999 2000-- 2999 3000--3999 4000-- 4999 5000-- 5999 6000-- 6999 7000-- 7999
High Low High Low High Low High Low High Low High Low High Low
“CLOCKING” GAS METER (NATURAL GAS)
1. Check with gas supplier to obtain ACTUAL BTU content of gas.
2. Turn “OFF” gas supply to ALL other gas appliances.
High Altitude Pressure Chart
2000--8000 ft. (Natural Gas)
Elevation Above Sea Level
5. Operate furnace on LOW fire, and time how many seconds it takes the smallest (normally 1 cfh) dial on the
gas meter to make one complete revolution.
6. Calculate LOW fire input rate by using ACTUAL BTU
content of gas in formula shown in example.
3. Operate furnace on HIGH fire, and time how many seconds it takes the smallest (normally 1 cfh) dial on the
gas meter to make one complete revolution.
4. Calculate HIGH fire input rate by using ACTUAL BTU
content of gas in formula shown in example.
440 08 2002 02
6
Example
Natural Gas
BTU Content
1,000 3,600 48 75,000
No. of Seconds
Per Hour
1,000 x 3,600 ¸ 48 = 75,000 BTUH
Time Per Cubic
Foot in Seconds
BTU Per
Hour
Two- Stage Multi Position Furnace
7. L.P. PRESSURE SWITCH
Models converted to operate on L.P. Gas will be installed
with an L.P. Pressure Switch. The switch will be located in the
gas supply line (in a “Tee”fitting), just ahead of the gas valve.
The purpose of this switch is to prevent furnace operating under low line (Supply) pressure conditions. Operating under
low line pressure conditions, can create problems such as incomplete combustion, flashback, sooting, etc.
The switch is a “Normally Open” pressure operated switch
that is wired in series with the furnace (Lo--fire) pressure
switch. The L.P. Pressure Switch closes when line (Supply)
pressure is 8.0² W.C. or higher. the L.P. Pressure Switch
Opens if line pressure falls below 6.0²+0.6² W.C. interrupting power to the gas valve.
It is located (electrically) between the Main Limit Switch and
the furnace (vent) pressure switch. The switcht is located
(electrically) between the Furnace (Lo--fire) pressure switch
and the gas Valve.
8. HIGH ALTITUDE OPERATION
These furnaces are designed to operate in the majority of the
country without modifications. At altitudes over 2,000¢ above
sea level, however, certain measures need to be taken to insure continued, safe reliable operation. For example, units
must be de--rated for altitude (by adjusting manifold pressure and/or changing orifice size) based upon the type of fuel
(I.E. Natural Gas or L.P. gas), Btu content of the gas, and
installed altitude.
Service
Figure 6
ALL UNITS must have a high altitude pressure switch
installed at altitudes above 4,000¢ above sea level.
When servicing a unit installed at altitudes above 2,000¢ insure that it has been properly modified to operate at that altitude. See the sections on Gas pressure, and pressure
switches to obtain specific information for you particular
installation altitude.
Typical L.P . Pressure Switch
Manual
9. BURNERS
Burners used in this series of furnace are of the “INSHOT”
type. Their operation can be compared to that of a torch in
that they produce a hard, sharp, somewhat noisy flame.
Noise should not be an issue, however, because of the
closed burner box design. In order to insure that the burners
are operating properly , and at their design noise level, proper
adjustment of the gas (manifold) pressure is essential. For
further information on manifold pressure adjustments check
the section on “Gas Supply”.
The burners used in this series ARE NOT EQUIPPED WITH
AIR SHUTTERS, as none are required. Proper operation
(flame characteristics) is obtained by insuring that the orifice
size, and manifold pressure are correct for the fuel being
used and the altitude of the installation.
Figure 7
Main Burner
Burner Face
10-- 10--78
440 08 2002 02
7
Service
50Mbt
75Mbtu,100Mb
tu&125Mbt
50Mbt
75Mbtu,100Mb
tu&125Mbt
Manual
10. CHECKING TEMPERATURE RISE
Two- Stage Multi Position Furnace
Figure 8
Thermometer:
Return Air Temp.
Return
Air Flow
The furnace is designed to operate within a certain specified
range of temperature rise.
Operating the furnace outside the specified range may result
in lower efficiency and/or comfort levels, as well as premature combustion component failures.
Simply stated, the temperature rise through the furnace is
the difference in temperature between the return air, and the
supply air.
NOTE: BEFORE CHECKING TEMPERATURE RISE BE
CERTAIN THAT MANIFOLD PRESSURE IS PROPERLY
ADJUSTED.
Checking Temperature Rise
Supply
Air Flow
Thermometer;
Supply Air Temp.
2- STAGE MODELS
Model Fire Range
u
Always check current “Technical Support Manual”
HI 35°F--65°F
LOW 25°F--55°F
HI 40°F--70°F
u
LOW 30°F--60°F
ALLOWABLE TEMPERATURE RISE FOR
VARIABLE SPEED MODELS
Model Fire Range
u
Always check current “Technical Support Manual”
Operate the furnace for 15 minutes before taking temperature readings. Subtract the return air temperature from the
supply air temperature. The result is the temperature rise.
Compare with the allowable rise listed for the model (size)
you are checking.
Temperature Rise can be checked by placing a thermometer
in the return air duct within 6¢ of furnace. Place a second thermometer in the supply duct at lease two (2) ft. away from the
furnace. (This will prevent any false readings caused by radiation from the furnace heat exchanger) Make sure that the
FILTER IS CLEAN and that ALL REGISTERS AND/OR
DAMPERS ARE OPEN.
If the rise is not within the specified range, it will be necessary
to change the heating blower speed. If the rise is too high,
it will be necessary to increase the blower speed. If the
rise is too low, it will be necessary to reduce the blower
speed.
Example:
Supply T emp. 170
Return Temp. 70°
Temperature Rise 100° = Too High
HI 35°F--65°F
LOW 35°F--65°F
HI 40°F--70°F
u
LOW 40°F--70°F
°
ALLOWABLE TEMPERATURE RISE FOR
11. ROOM THERMOSTATS
Room thermostats are available from several different
manufactures in a wide variety of styles. They range from the
very simple and inexpensive Bi--metallic type to the complex.
They are simply a switch (or series of switches) designed to
turn equipment (or components) “ON” or “OFF” at the desired conditions.
440 08 2002 02
Solution: Increase Blower Speed
An improperly operating, or poorly located room thermostat
can be the source of perceived equipment problems. A careful check of the thermostat and wiring must be made then to
insure that it is not the source of problems.
8
Two- Stage Multi Position Furnace
Service
Manual
Figure 9
Thermostat Location
DRAFTS
THERMOSTAT
SUN
SHIELD
5 ft.
LIGHT
LOCATION
The thermostat should not be mounted where it may be affected by drafts, discharge air from registers (hot or cold), or
heat radiated from the sun of appliances. Never install in alcoves, bathrooms or bedrooms.
The thermostat should be located about 5 ft. above the floor
in an area of average temperature, with good air circulation.
Normally, an area in close proximity to the return air grille is
the best choice.
Mercury bulb type thermostats MUST be level to control temperature accurately to the desired set--point. Electronic digital type thermostats SHOULD be level for aesthetics.
HEAT ANTICIPATORS
Heat anticipators are small resistance heaters built into most
electric--mechanical thermostats. Their purpose is to prevent wide swings in room temperature during furnace operation.
In order to accomplish this, the heat output from the anticipator must be the same regardless of the current flowing
through it. Consequently , most thermostats have an adjustment to compensate for varying current draw in the thermostat circuit.
The proper setting of heat anticipators then is important to
insure proper temperature control and customer satisfaction.
The best method to obtain the required setting for the heat
anticipator, is to measure the actual current draw in the con-
trol circuit (“W”) using a low range (0--2.0 Amps) Ammeter.
(See Figure 10) After measuring the current draw, simply
set the heat anticipator to match that value.
Figure 10
Measuring Current Draw
W
Amps
R
Subbase
Ammeter
If a low range ammeter is not available, a “Clamp--on” type
meter may be used as follows:
1. Wrap EXACTLY ten (10) turns of wire around the jaws
of a clamp--on type ammeter.
2. Connect one end of the wire to the “W” terminal of the
thermostat sub--base, and the other to the “R” terminal.
3. Turn power on, and wait approximately 1 minute, then
read meter.
4. Divide meter reading by 10 to obtain correct anticipator
setting.
NOTE: For 2 Stage heating thermostats the above proce-
dure MUST be perform ed twic e. Once for first
stage (W
1), and once f or s econd st age (W2), if
both stages have adjustable heat anticipators.
If an ammeter is not available, a setting of 0.10 amps may
be used for models equipped with the HONEYWELL
SV9541Q Gas Valve/Ignition Control. They should, however, provide satisfactory operation in most cases.
Electronic thermostats do not use a resistance type anticipator. These thermostats use a microprocessor (computer)
that determines a cycle rate based on a program loaded into
it at the factory.
These cycle rates are normally field adjustable for different
types to equipment. The method of adjustment, however,
varies from one thermostat manufacturer to another. Check
with the thermostat manufacturer to find out the proper way
of adjusting the cycle rate.
440 08 2002 02
9
Service
Manual
12. CONTROL WIRING
Control wiring is an important part of the total equipment
installation, since it provides the vital communications link
between the thermostat, and the equipment. It is often
overlooked as the source of equipment malfunctions. Control wiring that is either too long, undersized, or improperly
connected (be it simply loos e, or on the wrong terminal)
can in fact be the source of many equipment problems.
Two- Stage Multi Position Furnace
operation, the furnace will shift from low fire to high fire as
requested by the thermostat. The thermostat heat anticipators should be adjusted to a .10 setting for both types of thermostats.
Low voltage connections to furnace must be made on terminal board to fan control.
ALWA YS check to make sure that the control wiring is connected to the proper terminal(s) of the equipment and thermostat you are using. Remem ber, also, that therm ost at
terminals are not always identified alike by different thermostat manufacturers. Connections MUST be clean and
tight to insure trouble--free operation.
The controls of this series of 2--Stage furnaces ar e designed to provide 2--Stage operation using a Two (2) Stage
Thermostat, ONLY as follows:
The 2--stage furnace control will operate with either a single
stage or a two stage heating thermostat and will provide
2--stage heating operation. For single stage thermostat
installations, the R and W wires from the thermostat connect
to the R and W1 connections on the furnace control. Note:
The fourth (4th) DIP switch must be in the off position, failure
to change DIP switch will result in Lo Fire ONLY operation.
(See furnace wiring digram) See “Furnace Wiring Diagram”
for switch settings. Failure to set DIP switch will result in Lo
fire operation ONLY with single stage thermostat. During operation, the furnace will operate on low fire for 12 minutesIf
the heat request exists for more than 12 minutes. If the heat
request exists for more that 12 minutes, the furnace will automatically shift to the high fire mode for the remaining duration
of the heating cycle. For two stage thermostat installations,
the R, W1 and W2 wires from the thermostat connect to the
R, W1 and W2 connections on the furnace control. During
The ELECTRO NI C CONTROLS used on t his series RESPOND DIFFERENTL Y to certain control wiring practices
which have been generally accepted in the HVAC industry
for many years.
For Example: For years, installers have run a wire from the
“Y” t er m inal of the room thermost at and connec t ed it directly to the contactor coil of a condensing unit. (not making any connection to the furnace with this wire) Then, run
the low voltage “Common” wire from the condensing unit
back to the “C” terminal of the furnace.
With the HONEYWELL ST9162A electronic Fan Timer/
Furnace Control used in the models of this series, however, the “Y” terminal of the furnace does in fact serve a particular purpose. Failure to connect it will result in certain
improper operation as follows:
The COOLING fan speed is energized via the “Y” terminal.
Failure to connect the thermostat “Y” terminal to the “Y”
terminal on the control will result in the failure to energize
the COOLING speed on a call for cooling from the thermostat. (Depending upon the model, either the LOW HEATING speed or the CIRCULATING speed will be energized
instead via the “G” terminal)
For more detailed information about this control, see the
section on the ST9162A control beginning on page 23 of
this manual.
13. LIMIT SWITCHES
Two (2) different kinds of limit switches are used on this series of furnaces. They are the main limit and roll out limit
switches. The main limit, and roll out limit switches are used
on all models.
NOTE: All limit switches are safety devices and other
than for testing purposes, should never be jumped out!
Limit switches are “normally closed” electrical switches, designed to open when their predetermined “limit setting” has
been reached.
It should also be remembered, that when a limit switch
opens, it more than likely is not due to a bad switch! The
cause of the opening limit must be found and corrected, be-
440 08 2002 02
fore the furnace can resume proper operation.
!
Fire hazard.
Limit controls are factory preset and MUST NOT be
adjusted. Use ONLY manufacturer’s authorized
replacement parts.
Failure to do so can result in death, personal injury
and/or property damage.
The specific functions of the two (2) limit switches used in
this series of furnaces are as follows:
10
Two- Stage Multi Position Furnace
Service
Manual
MAIN LIMIT SWITCH
A “Normally Closed” switch located on the front partition of
the furnace. It monitors supply air temperature, and interrupts furnace (burner) operation when a supply air temperature is sensed which would result in the furnace exceeding
Maximum allowable outlet air temperature. While the main
limit is open, combustion blower, and/or the circulating blower will be energized continuously. This control is an “Automatic” reset control, which will reset itself when the temperature sensed drops to a safe level.
If furnace (burner) cycles on this limit switch, (I.E. switch
opens and closes during furnace operation) it is more than
likely due to a high temperature rise through the furnace.
(See checking temperature on page 8 of this manual)
High temperature rise can be caused by either OVER
FIRING (high manifold pressure. incorrect orifices, etc.) or
LOW AIR FLOW (dirty filter, blower speed too low, excessive
static in duct system, etc.)
Figure 11
Typical Limit Switch
If, however , the switch is found to be opening prematurely,
then it should be replaced. When replacing ANY limit switch,
use ONLY a switch of EXACTLY the same temperature setting. Use of a different temperature limit switch can create a
dangerous situation. Some of the main limit switches used
in this series are SIMILAR IN APPEARANCE. DIFFERENT
TEMPERATURE SETTINGS, HOWEVER, ARE USED for
different models. Be certain you have the correct control for
the model you are servicing.
ROLL OUT LIMITS
Those “Normally Closed” unit switches (wired in series with
the Main Limit switch) on the top are mounted on the bottom
(left & right) of the burner box.
The switches are manual reset type. When replacing this
switch, be absolutely certain the correct one is used.
Figure 12
Typical Roll Out Limit Switch
To verify this, the cut--out (opening) point of the switch should
be checked (using a thermocouple type thermometer connected to the face of the switch) as follows:
1. Operate furnace for several minutes.
2. Block return air grille(s) to furnace.
3. Observe temperature at which switch opens (burner
operation ceases).
4. Remove blockage from return grille(s).
5. Observe temperature at which switch closes (burner
operation resumes).
6. Compare readings with the limit setting listed in the
appropriate chart for the model you are servicing.
If switch is opening within the specified range, then it is simply doing its job, and the cause of the over--temperature must
be determined and corrected.
CAUTION
NEVER use an automatic reset roll out switch to replace
a manual reset type roll out switch.
Doing so may cause potentially unsafe and/or intermittent operation.
The roll out switch monitors the temperature inside the burner box, and interrupts furnace (burner) operation when its
temperature indicates flame roll out has occurred.
If the roll out switch has opened, the cause must be determined. Some possible reasons for flame roll out include a restricted primary or secondary heat exchanger or over fired
furnace.
MANUAL RESET SWITCH MODELS
Furnace models which are equipped with a Honeywell
ST9162A Fan timer/furnace control use a manual reset roll
out switch. Once the roll out switch has opened, burner operation will be prevented until the roll out switch is “Manually
Reset” by pressing the red button located on the switch.
While the roll out switch is open, (Depending upon the particular model) the combustion blower and/or circulating blower
will be energized continuously.
440 08 2002 02
11
Service
Manual
14. PRESSURE SWITCHES
Two- Stage Multi Position Furnace
TRANSITION PRESSURE SWITCH
Under normal operating conditions, sufficient pressure is developed by the exhaust (combustion) blower to close the
switch, and permit the burner to operate. As the condensate
drain begins to back--up, however, the pressure begins to reduce. When the pressure drops sufficiently, burner operation
will be prevented until the condition is corrected.
STANDARD PRESSURE SWITCHES - ALL
MODELS
Model
Condensing
50, 75 &100
125
Always check current “Technical Support Manual”for
Part Nos.
Max.
Close
--1.70² W.C.
--2.00² W.C.
Open Part #
--1.50 + 0.10² W. C .
--
--1.80 + 0.10² W.C .
--
BLOWER PRESSURE SWITCH
An air proving switch (pressure switch) is used on all models
to insure that a draft has been established through the heat
exchanger before allowing burner operation.
To insure continued SAFE, RELIABLE, operation, NEVER
SUBSTITUTE a pressure switch with one that is similar in
appearance. ONLY FACTORY PROVIDED or
AUTHORIZED SUBSTITUTES ARE ACCEPTABLE.
All models installed at altitudes of 4,000¢ above sea level or
higher require replacing the standard pressure switch with a
high altitude pressure switch. The different pressure switch
settings allow continued SAFE, RELIABLE, high altitude
operation.
Note: Transition switch checks lo--fire airflows & blocked
condensate. Blower switch checks Hi--fire airflow.
HIGH ALTITUDE PRESSURE SWITCHES - ALL
MODELS
Model
Condensing
50, 75 &100
125
Always check current “Technical Support Manual”for
Part Nos.
Under normal operating conditions, sufficient negative pressure will be created to close the pressure switch, and keep
it closed to keep furnace operating. Under abnormal conditions, however, such as a restricted vent pipe, or a leak in one
of the heat exchangers, sufficient negative pressure will not
be created. This will result in the switch failing to close or failing to remain closed during furnace operation.
440 08 2002 02
Max.
Close
--1.40² W.C.
--1.70² W.C.
Open Part #
--1.20 + 0.10² W.C .
--
--1.50 + 0.10² W.C .
--
1013165
1013157
Figure 13
Pressure Switches
Blower
(Hi--fi re)
Transition
(Lo--fire)
25--23--72
When servicing a unit whose pressure switch will not close,
or remain closed during operation, the operating pressure of
that furnace should be checked and compared to
approximate operating pressures listed in Tab l e 3 and the
switch setting(s) listed above for the model family you are
servicing.
It is important to remember, that greater negative pressures
are created by the furnace when “Hot” (I.E. upon initial start-up) than when “Cold” (I.E. after furnaces has been in operation for a few minutes). Because of this, furnace pressure
should ONLY be checked when “HOT” to insure accurate
readings.
Tab l e 3 lists approximate operating pressures for Direct
Vent (I.E. Two Pipe) installations of models in this series.
They were obtained in a test lab, under controlled conditions
using two (2) specific vent lengths. They are included in this
manual to provide you with a “Barometer” to gauge our pressures against. The pressures you obtain in the field will differ
slightly from these figures based upon vent length, gas pressure, operating temperature, etc.
Major discrepancies in pressures, will normally cause
problems with pressure switch operation. These Major discrepancies should be investigated as follows:
12
Two- Stage Multi Position Furnace
50Mbtu&
100Mb
t
Table 3 APPROXIMATE OPERATING PRESSURES (INCHES OF W.C.)
@Blower/@Transition
Model Vent Length (High Fire) (Low Fire)
50 Mbtu &
75 Mbtu
u
125 Mbtu
Always check current “Technical Support Manual”for
updated information.
Short -- (5 Ft. No Elbows) --1.80/--2.60 --1.20/--1.90
Long -- (40 Ft. + 5 90° Elbows) --1.30/--2.30 --1.00/--1.80
Short -- (5 Ft. No Elbows) --1.80/--2.60 --1.20/--1.90
Long -- (40 Ft. + 5 90° Elbows) --1.70/--2.50 --1.00/--1.80
Short -- (5 Ft. No Elbows) --1.80/--2.60 --1.30/--2.30
Long -- (40 Ft. + 5 90° Elbows) --1.70/2.50 --1.20/--2.20
2. Leak (lack of restriction) on the Inlet side of the combustion blower.
Service
Manual
Lower (Lesser) Negative Pressures
Lower than normal negative pressures measured at the
Combustion Blower may be caused by:
1. Restriction on the Outlet side of the combustion blower. (I.E. Blocked Flue, Vent too long, Heat Exchanger
leak, etc.)
Figure 14
UPFLOW
*8² Min.
20¢ Max.
in same
atmospheric zone
Vent Pipes MUST be
supported Horizontally
and Vertically
Typical Vent/Combustion Air Piping Installation
Aluminum or non-- rusting shield recommended.
(See Vent Termination Shielding for dimensions).
Inlet Pipe
DISCHARGE AIR
Coupling on ends of exhaust
pipe. Total pipe & coupling
outside structure = 8²
*8² Min.
20¢ Max.
in same atmospheric zone
Higher (Greater) Negative Pressures
Higher than normal negative pressures measured at the
Combustion Blower may be caused by:
1. Restriction on the Inlet side of the combustion blower.
(I.E. Plugged Heat Exchanger, air inlet orifice too
small)
DOWNFLOW
Inlet Pipe
Vent Pipes MUST
be supported
Horizontally and
Vertically
See Vent Termination Shielding
in Vent Section.
*8² Min.
20¢ Max.
in same
atmospheric
zone
Coupling on inside and
outside of wall to
restrain vent pipe
8² Min.
*8² Min.
20¢ Max.
in same
atmospheric zone
* Increase minimum from 8² to 18² for cold climates (sustained temperatures below 0 ° F).
15. VENT/COMBUSTION AIR PIPING
Vent and combustion air piping are an extremely important
part of the total furnace installation. Improperly installed or
inadequately sized vent and/or combustion air piping can be
the source of many perceived furnace problems.
For example, most problems associated with pressure
switch operation can normally be traced to short comings in
the vent and/or combustion air piping. Anytime these type
25--23--33
* Increase minimum from 8² to 18² for cold climates (sustained temperatures
below 0°F).
25--23--33a
problems arise, a thorough inspection of the vent and/or
combustion air piping should be conducted.
ALL MODELS require a vent (exhaust) pipe to carry flue
products to the outside of the structure.
Direct VENT (ONLY) models require a combustion air inlet
to bring in all air for combustion from outside the structure.
440 08 2002 02
13
Service
Manual
Two- Stage Multi Position Furnace
DUAL CERTIFIED models require a combustion air inlet
pipe to bring in all air for combustion from outside the structure only when installed as a Direct Vent Furnace (I.E. Two
Pipe Installation)
16. STANDARD VENT TERMINATION
Vent/Combustion Air Piping Charts
Single Piping Chart
Tab l e 4
50,000 & 75,000 Btuh Furnaces
40¢ & (5) 90° elbows with 2² PVC pipe
100,000 & 125,000 Btuh Furnace
40¢ & (5) 90° elbows with 3² PVC pipe
Elbows are DWV Long Radius Type for 2² and 3² vents.
If more than five elbows are required, reduce the length of both
the inlet and exhaust pipes 5¢ for each additional elbow used.
NOTE: It is allowable to use larger diameter pipe and fitting than
shown in the tables but not smaller diameters than shown.
Dual Piping Chart
Tab l e 5
50,000 & 75,000 Btuh Furnaces
40¢ & (5) 90° elbows with 2² PVC pipe
100,000 & 125,000 Btuh Furnace
40¢ & (5) 90° elbows with 3² PVC pipe
Elbows are DWV Long Radius Type for 2² and 3² vents.
If more than five elbows are required, reduce the length of both
the inlet and exhaust pipes 5¢ (1.5m) for each additional elbow
used.
* Feet of pipe is whichever pipe run is the longest, either inlet or
outlet side.
Figure 15
Pipe Diameter Table
Single Piping ONLY
Pipe Diameter Table
Dual Piping ONLY
Standard Termination
Rooftop Termination
B
Consult the appropriate Venting tables and/or piping chart
for the model (series) you are servicing.
Figure 16
Inlet is optional on
Dual Certified models
Figure 17
12²²²² Min. Grade
or Snow Level
Dimension “A” is touching or 2² maximum separation.
Figure 18
Sidewall Termination 12² or More
Above Snow Level or Grade Level
8² *
MIN.
20’
MAX
*18² Minimum for cold climates
(substained below 0° F)
Concentric Vent and Combustion-Air Roof Termination
Exhaust
Combustion
Air
“A”
Concentric Vent and Combustion-Air Sidewall Termination
25-- 00--05F
Inlet is optional on
Dual Certified models
A
A
A=12² Above roof or snow accumulation level
B=8² Min., 20¢ Maximum, except in areas with extreme
cold temperatures (sustained below 0°F), the 18² Min.
440 08 2002 02
25-- 00--06
14
1²²²² Maximum
Combustion Air
Exhaust
Ven t
Dimension “A” is touching or 2² maximum separation.
(TYP.)
Ven t
“A”
25--22--02d
Two- Stage Multi Position Furnace
Service
Manual
Figure 19
“A”
Inlet
12²²²² Min. Grade
or Snow Level
Dimension “A” is touching or 2² maximum separation.
Figure 20
18²²²² Min. for Cold Climates
(Sustained Below 0°°°° F)
Exhaust
Sidewall Inlet Vent and Exhaust-Air Termination
Exhaust
8²²²² Min.
20¢¢¢¢ Max.
18²²²² Min. for
Cold Climates
(Sustained Below 0°°°° F)
“A”
8²²²² Min.
Sidewall Inlet Vent and Exhaust--Air
Termination with Exterior Risers
8²²²² Min.
8²²²² Min.
20¢¢¢¢ Max.
12²²²² Min.
Grade or
Inlet
Snow Level
Figure 22
FRONT VIEW
Recommended Alternate Installation for Sustained Cold Weather
(--0°°°° F & below)
OVERHANG
12²²²² MIN.
EXHAUST
90°°°°
INLET
12²²²² MIN. Ground Level
OR Snow Level
SIDE VIEW
12²²²² MIN.
25--23 --73
Figure 21
18²²²² Min. for Cold Climates
12²²²² Min.
Grade or
Snow Level
“A”
“A”
Dimension “A” is touching or 2² maximum separation.
Rooftop Inlet Vent and Exhaust-Air Termination
(Sustained Below 0°°°° F)
Inlet
8²²²² Min.
20¢¢¢¢ Max.
Exhaust
Same Joist
Space
25--22--43
440 08 2002 02
15
Service
Manual
17. CONCENTRIC VENT TERMINATION
Two- Stage Multi Position Furnace
Vent/Combustion Air Piping Charts
Concentric Termination Kit NAHA001CV
Tab l e 6
NAHA002CV -- 35¢ & (4) 90° elbows with 2² PVC pipe
NAHA001CV -- 35¢ & (4) 90° elbows with 3² PVC pipe
1. Do not include the field supplied 45° elbow in the total elbow
count.
2. If more than four elbows are required, reduce the length of
both the inlet and the exhaust pipes five feet for each
additional elbow used.
3. Elbows are DWV long radius type for 2
Figure 23
& NAHA002VC Venting Table Dual Piping
ONLY
50,000 & 75,000 Btuh Furnaces
100,000 & 125,000 Btuh Furnace
² and 3² vents.
Concentric Vent Roof Installation
Vent
Combustion
Air
Roof Boot/
Flashing
(Field Supplied)
Maintain 12² min. clearance
above highest anticipated
snow level. Max. of 24²
above roof.
Figure 24
3² x2² Bushings or
1
/2² Bushings
3² x2
If 3² vent not used
(Field supplied)
Vent
Combustion
Air
Note:
Securing strap must be field installed to prevent movement of termination kit in side wall.
Concentric Vent Sidewall
Attachment
Strap
(Field Supplied)
45° Elbow
(Field Supplied)
Combustion
Air
Vent
Flush to
1² max.
25-- 22--02
Support
(Field Supplied)
45° Elbow
(Field Supplied)
Vent
Combustion
Air
Note:
Support must be field installed to secure termination kit to structure.
25-- 22--02
440 08 2002 02
16
Two- Stage Multi Position Furnace
18. EXHAUST BLOWER
Figure 25
Exhaust Blower
Service
Manual
Always check the current “Technical Support Manual” for
part nos.
Vent Fitting
&Clamps
90° Elbow
Vent Pipe
(Side panel exit)
Vent Fitting
&Clamps
DRAIN SIDE VIEW
C
L
Rotate
downward
20° to 30°
Vent Pipe (Top panel exit)
Rubber Coupling & Clamps
Blower
25-- 23--35
19. CONDENSATE DRAIN TRAP
This furnace removes both sensible and latent heat from the
products of combustion. Removal of the latent heat results in
condensation of the water vapor. The condensate is removed from the furnace through the drains in the plastic transition and the vent fitting. The drains connect to the externally mounted condensate drain trap on the left or right side of
the furnace. Refer to Figure 26.
The condensate drain trap supplied with the furnace MUST
be used. The drain line between the condensate drain trap
and the drain location must be constructed of
CPVC pipe.
The drain line must maintain a
1
/4² per foot downward slope
toward the drain.
3
/4² PVC or
Figure 26 External Drain Trap
Vent Pipe
(Side panel exit)
Vent Drain Connection
Drain Line
(hidden)
Vent Drain
OLD
Transition
Box Drain
DO NOT trap the drain line in any other location than at the
condensate drain trap supplied with the furnace.
If possible DO NOT route the drain line where it may freeze.
The drain line must terminate at an inside drain to prevent
freezing of the condensate and possible property damage.
1. A condensate sump pump MUST be used if required
by local codes, or if no indoor floor drain is available.
The condensate pump must be approved for use with
acidic condensate.
2. A plugged condensate drain line or a failed condensate
pump will allow condensate to spill. If the furnace is
installed where a condensate spill could cause damage, it is recommended that an auxiliary safety switch
be installed to prevent operation of the equipment in
the event of pump failure or plugged drain line. If used,
an auxiliary safety switch should be installed in the R
circuit (low voltage) ONLY.
17
NEW
25--23--63
440 08 2002 02
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