ICP N9MP1, N9MP2, T9MPD, H9MPD, C9MPD Service Manual
MULTI POSITION
SINGLE STAGE
GAS FURNACES
N9MP1, N9MP2 & *9MPD
This manual supports condensing gas furnaces manufactured in 2001
Manufactured by:
ã 2001 International Comfort Products Corporation (USA)
“A1 & A2”
Part Number
440 08 2001 02
4/2002
N9MP1 -- Indoor combustion air (1 pipe only)
N9MP2 -- Direct Vent ONLY (2 pipe only)
*9MPD -- Dual Certified Venting (1 or 2 pipes)
* Denotes Brand (T, C or H)
Single 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. BURNERS 7................................................................
8. L.P. PRESSURE SWITCH 7...................................................
9. HIGH ALTITUDE OPERATION 7...............................................
10. CHECKING TEMPERATURE RISE 8..........................................
11. ROOM THERMOSTATS 8....................................................
12. CONTROL WIRING 9.......................................................
13. TWINNING KITS 10..........................................................
14. LIMIT SWITCHES 10.........................................................
15. PRESSURE SWITCHES 12...................................................
16. VENT/COMBUSTION AIR PIPING 14..........................................
17. STANDARD VENT TERMINATION 14..........................................
18. CONCENTRIC VENT TERMINATION 16........................................
19. EXHAUST BLOWER 17......................................................
20. CONDENSATE DRAIN TRAP 17...............................................
21. HONEYWELL ST9160B FAN TIMER/FURNACE CONTROL 18....................
22. ST9160B TESTING SEQUENCE 19............................................
23. ST9160B -- UNIQUE CONTROL FUNCTIONS/RESPONSES 19...................
24. HONEYWELL SV9541M GAS VALVE/IGNITION SYSTEM 20.....................
25. HONEYWELL SV9541M SYSTEM OPERATION 20..............................
26. CHECKING FLAME CURRENT 21.............................................
27. CAPACITORS 22............................................................
28. BLOWER ASSEMBLY 22.....................................................
29. BLOWER ROTATION 23......................................................
30. HEAT EXCHANGER REMOVAL/REPLACEMENT 44.............................
SV9541M “SMART VALVE” -- Sequence of Operation 45.............................
SV9541M “SMART VALVE” -- Trouble shooting 47...................................
SV9541M “SMART VALVE” -- Electrical Variation 49.................................
WIRING DIAGRAM 50...........................................................
TECHNICAL SERVICE DATA (N9MP1 or 2) 52......................................
TECHNICAL SERVICE DATA (*9MPD/A1) 54......................................
TECHNICAL SERVICE DATA (*9MPD/A2) 55......................................
BLOWER PERFORMANCE DATA (N9MP1 or 2 & *9MPD) 56.........................
APPENDIX OF HELPFUL INFORMATION 57.......................................
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 our new multi--position furnaces,
both Direct Vent (2 pipe Only), Indoor combustion (1 pipe
Only) and Dual Certified (1 or 2 pipe) models. The overall operation of all of these models is essentially the same.
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.
Single Stage Multi Position Furnace
!
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 suchrepairs to 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.
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
and/or service procedures.
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
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.
* 9 MP D 075 B 12 A 1
Brand Identifier Engineering Rev.
T=Tempstar Denotes minor changes
C = Comfortmaker Marketing Digit
H=Heil Denotes minor change
A = Arcoaire
X = Evaluation Cooling Airflow
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
MP = Multiposition, Upflow/Downflow/Horizontal Cabinet Width
Major Design Feature B = 15.5² Wide
1 = One (Single) Pipe N = Single Stage F = 19.1² Wide
2=TwoPipe P=PVCVent J = 22.8² Wide
D = 1 or 2 Pipe T = Two Stage L = 24.5² Wide
L = Low NOx V = Variable Speed Input (Nominal MBTUH)
440 08 2001 02
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Single Stage Multi Position Furnace
Service
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Figure 1
Gas Valve/Ignition Module
Component Locations for Four Position Furnaces
Furnace Vent Pipe
Manual Gas Valve
Vent Drain Fitting
Diagnostic Light
Combustion Air
5
Blower
/8² OD Vent Pipe
Drain Hose
3
/4² OD Transition Box
Drain Hose
Door Interlock Switch
Fan/Delay Control
Vent Pipe
Grommet
Rating Plate
Air Intake Pipe
(Dual Certified or Direct
Vent Model)
Primary Heat Exchanger
Secondary Heat Exchanger
Pressure Switch
Plastic Transition Box
Circulating Air Blower
dwg 25--23--29a
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 maintaining the surface area of the heat exchanger 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 secondary combustion airflows at right angles
to the burner flame, making it likely to “pull” the flame
off a ribbon or slotted port type burner.
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. 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.
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Single 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.
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.
CHECKING GROUNDING AND POLARITY
7. A pressure switch (Air Proving Switch) is used as a
safety device that prevents the ignition system from firing the furnace until it senses that a proper draft has
been established through the furnace.
Polarity may be verified as follows:
1. Turn the power supply “ON”.
2. Using a Vo lt m e t e r check for voltage between the Hot
(Black) and Neutral (White) wire of supply circuit.
POLARITY
CORRECT POLARITY of the line voltage supply to all furnaces is also required for safety reasons.
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 lt a g e.(ifzero
volts is read, there is no ground, or polarity is reversed.)
Figure 2
NOTE: Junction Box can
be mounted to either the
left or right side.
Electrical Connections
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.
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.
440 08 2001 02
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4
Single Stage Multi Position Furnace
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
Typ ical Gas Valve HoneywellFigure 4
Pilot Pressure
Adjustment (Hid-
den)
On\Off
Switch
Diagnostic Light
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.
NATURAL GAS
OUTLET
Manifold Pressure
Adjustment
dwg 25--23--31a
INLET
Manual
10--12--96
Figure 3
Service
Typical Interlock Switch
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.
Table 1 Gas Pressures Below 2000¢¢¢¢
Gas
Type
Natural 7² 14² 4.5² 3.5²
· With Propane gas, the rated input is obtained when the
· If Propane gas has a different BTU content, orifices
· Measured input can NOT exceed rated input.
· Any majorchange in gas flow requires changing burner
Recommended Max. Min.
LP 11² 14² 11² 10²
BTU content is 2,500 BTU per cubic foot and manifold
pressure set at 10²²²² W.C.
MUST be changed by licensed Propane installer.
orifice size.
Supply Pressure
Important Note:
Manifold
Pressure
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.
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,
!
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.
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440 08 2001 02
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Manual
Single Stage Multi Position Furnace
Figure 5
Pressure Connections
Typical "U" Tube
Manometer
MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS
Gas Pressure Testing Devices
3
2
1
0
1
2
3
0
INCHES OF WATER
510
MAGNEHELIC
MAX. PRESSURE 15 PSIG
15
1. Connect a manometer or Magnehelic gauge (0-- 12²
W.C. range) to the pressure tap on the “OUTLET” side
of the gas valve.
2. Turn gas “ON”, fire the furnace, and remove adjustment cover (screw--cap).
3. Turn adjustment screw clockwise (IN) to INCREASE
pressure, and counterclockwise (OUT) to DECREASE
pressure.
4. At altitudes BELOW 2,000¢¢¢¢ set manifold pressure to
3.5² W.C. for Natural Gas, and 10² W.C. for L.P. Gas.
5. For Natural Gas units ABOVE 2,000¢¢¢¢, set manifold
pressure according to TABLE 2.
6. For L.P. Gas units ABOVE 2,000¢¢¢¢, insure that orifice
size has been changed (per “National Fuel Gas Code”
-- Appendix “F”) if gas supply has not already been de-rated for altitude by the gas supplier .
7. For ALL UNITS ABOVE 8,000¢, contact the factory for
SPECIFIC de--rating information.
CHECKING MANIFOLD PRESSURE
Table 2 NATURAL GAS
eatValue
Btu/Cu.Ft.
800 3.5 3.5 3.5 3.5 3.5 3.5 3.5
850 3.5 3.5 3.5 3.5 3.5 3.5 3.5
900 3.5 3.5 3.5 3.5 3.5 3.5 3.4
950 3.5 3.5 3.5 3.5 3.3 3.2 3.1
1000 3.5 3.4 3.3 3.2 3.0 2.9 2.8
1050 3.2 3.1 3.0 2.9 2.7 2.6 2.5
1100 2.9 2.8 2.7 2.6 2.5 2.4 2.3
Orifice Size #42 #42 #42 #42 #42 #42 #42
0--1999
(²²²²××××wc)
2000--2999
(²²²²××××wc)
3000--3999
(²²²²××××wc)
“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.
3. Time how many seconds it takes the smallest (normally 1 cfh) dial on the gas meter to make one complete
revolution.
Elevation Above Sea Level
4000--4999
(²²²²××××wc)
5000--5999
(²²²²××××wc)
6000--6999
(²²²²××××wc)
4. Calculate input rate by using ACTUAL BTU content of
gas in formula shown in example.
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
7000--7999
(²²²²××××wc)
BTU Per
Hour
440 08 2001 02
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Single Stage Multi Position Furnace
7. 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 compartment 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. See page 6 for further information on manifold pressure
adjustments.
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.
8. L.P. PRESSURE SWITCH
Models converted to operate on L.P. Gas will be installed
with an L.P. Pressure Switch. If so equipped, the switch will
be located in the gas supply line (in a “Tee” fitting), just ahead
of the gas valve.
Figure 6
Figure 7
Service
Main Burner
Burner Face
Typical L.P . Pressure Switch
Manual
10--10--78
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 (vent) 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
power to the gas valve.
On some models, it is located (electrically) between the Furnace (vent) pressure switch and the gas Valve.
+
0.6² W.C. interrupting
9. 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.
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 (Page *), and pressure switches (Page **) to obtain specific information for you
particular installation altitude.
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440 08 2001 02
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10. CHECKING TEMPERATURE RISE
Single Stage Multi Position Furnace
Figure 8
Thermometer:
Return Air Temp.
Return
Air Flow
Checking Temperature Rise
Supply
Air Flow
Thermometer;
Supply Air Temp.
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.
ALLOWABLE TEMPERATURE RISE ALL
MODELS
Model
50 Mbtu 35°F--65°F
75, 100 & 125 Mbtu 40°F--70°F
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
Solution: Increase Blower Speed
Range
°
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.
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.
440 08 2001 02
8
Figure 9
THERMOSTAT
5 ft.
Thermostat Location
DRAFTS
SUN
SHIELD
LIGHT
Single Stage Multi Position Furnace
Service
Manual
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.
Figure 10
Measuring Current Draw
The best method to obtain the required setting for the heat
anticipator, is to measure the actual current draw in the control 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.
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.
If an ammeter is not available, a setting of 0.30 amps may
be used for models equipped with the HONEYWELL
SV9541M 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.
W
Amps
R
Subbase
Ammeter
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 malfunctions.
Control wiring that is either too long, undersized, or improperly connected (be it simply loose, or on the wrong terminal)
can in fact be the source of many equipment problems.
ALWAYS check to make sure that the control wiring is connected to the proper terminal(s) of the equipment and thermostat you are using. Remember, also, that the thermostat
terminals are not always identified alike by different thermostat manufacturers. Connections MUST be clean and tight
to insure trouble--free operation.
For years, installers have run a wire from the “Y” terminal of
the room thermostat and connected it directly to the contact
on coil of a condensing unit. (not making any connection to
the furnace with this wiring. Then, run the low voltage “Common” wire from the condensing unit back to the “C” terminal
of the furnace.
With the HONEYWELL ST9160B electronic Fan Timer/Furnace Control, 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:
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440 08 2001 02
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Single Stage Multi Position Furnace
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
13. TWINNING KITS
Some installations may require a Heating capacity or Airflow
capabilities greater than a single furnace of this series can
provide.. When this is necessary, furnaces may be installed
in a “Twinned” configuration.
The T winning Kit allows the two (2) furnaces to be controlled
by the same room thermostat. When Twinned, the circulating (conditioned air) blowers of BOTH furnaces will operate
14. 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 limit switches are used on
all models.
NOTE: All limit switch es 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, before the furnace can resume proper operation.
COOLING speed on a call for cooling from the thermostat.
(The HEATING speed will be energized instead via the “G”
terminal)
simultaneously.
Models equipped with a HONEYWELL ST9160B series Fan
Timer/Furnace Control may be twinned using a model
NAHA003WK01 twinning kit.
To assist troubleshooting efforts of “Twinned” installations,
“TYPICAL” control wiring diagrams are provided on pages **
through **.
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.)
!
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:
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
Figure 11
Typical Limit Switch
440 08 2001 02
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Single Stage Multi Position Furnace
Service
Manual
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.
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 LIMIT
A “Normally Closed” switch (wired in series with the Main
Limit switch) mounted on the burner box.
This switch may be of the manual type, depending upon the
particular model and/or family. Different temperature
(OPENING) settings are also used on different models.
When replacing this switch, be absolutely certain the correct
one is used.
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
ST9160 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.
AUXILIARY LIMIT SWITCHES
All models are equipped with one (1) additional (AUXILIARY)
limit switch mounted on the blower deck. Its purpose is to
monitor return air temperature, and interrupt burner operation when a temperature is sensed which could result in the
filter surface(s) exceeding allowable temperatures. Depending upon the particular model, the combustion blower, and/or
circulating blower may be energized continuously while the
auxiliary limit switch remains open.
This control is an “Automatic” reset control which will reset
itself when the temperature drops to a safe level. See the
Tech. Service Data Sheet for the model you are servicing, to
obtain its specific auxiliary limit switch setting.
Figure 12
Typical Roll Out Limit Switch
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.
11
440 08 2001 02
Service
²
W.C
1
8+0.1
0
W.C
Manual
15. PRESSURE SWITCHES
Single Stage Multi Position Furnace
Transition Pressure Switch
This switch is designed to monitor a blockage of the condensate drain line. It uses a single tap (port) “Normally Open”
pressure switch (wired in series with the furnace air proving
(pressure) switch. The switch “Closes” at a (negative) pressure setting for the switch associated with that particular
model furnace (See unit specitications).
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.
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.
Figure 13
Pressure Switches
Blower
Transition
HIGH ALTITUDE PRESSURE SWITCHES - ALL
MODELS
--1.40
Max.
Close
²
Open Part #
--
--1.
.
²
--
.
Model
Upflow
Downflow
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.
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 le 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:
25--23--72
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Single Stage Multi Position Furnace
0Mb
M
b
100Mb
1
25M
b
Tab l e 3 APPROXIMATE OPERATING PRESSURES (²²²² OF W.C.)
Model Vent Length @Blower @ Transition
5
75
tu
tu
tu
tu
Short -- (5¢ No. Elbows) --1.80 --2.60
Long -- (40¢ +590° Elbows) --1.30 --2.30
Short -- (5¢ No. Elbows) --1.80 --2.60
Long -- (40¢ +590° Elbows) --1.30 --2.30
Short -- (5¢ No. Elbows) --1.80 --2.60
Long -- (40¢ +590° Elbows) --1.70 --2.50
Short -- (5¢ No. Elbows) --1.80 --2.60
Long -- (40¢ +590° Elbows) --1.70 --2.50
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.)
2. Leak (lack of restriction) on the Inlet side of the combustion blower.
Figure 14
UPFLOW
*8²²²² Min.
20¢¢¢¢ Max.
in same
atmospheric zone
Vent Pipes MUST be
supported Horizontal-
ly and Vertically
Typical Vent/Combustion Air Piping Installation
Aluminum or non--rusting shield recommended.
(See Vent Termination Shielding for dimensions).
Inlet Pipe
(not used
on
Single Pipe
models)
DISCHARGE AIR
Coupling on ends of exhaust pipe. Total pipe &
coupling outside structure = 8²²²²
*8²²²² 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
(not used on
Single Pipe
models)
Vent Pipes MUST
be supported
Horizontally and
Vertically
See Vent Termination Shielding
in Vent Section.
*8²²²² Min.
20¢¢¢¢ Max.
in same
atmospheric
zone
Coupling on inside
and outside of wall to
restrain vent pipe
8² Min.
*8²²²² Min.
20¢¢¢¢ Max.
in same
atmospheric zone
* Increase minimum from 8²
0 °°°° F).
² to 18²²²² for cold climates (sustained temperatures below
²²
25--23--33
13
* Increase minimum from 8²²²² to 18²²²² for cold climates (sustained temperatures
below 0°°°°F).
25--23--33a
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Service
Manual
16. VENT/COMBUSTION AIR PIPING
Single Stage Multi Position Furnace
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
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
17. STANDARD VENT TERMINATION
Vent/Combustion Air Piping Charts
Dual Certified Models ONLY - Non- Direct Vent
Installation
Single Piping Chart
Tab l e 4
50,000 & 75,000 Btuh Furnaces
40¢ & (5) 90° elbows with 2² PVC pipe or
70¢ & (5) 90° elbows with 3² PVC pipe or
70¢ & (5) 90° elbows with 3² PVC pipe
40¢ & (5) 90° elbows with 3² PVC pipe
Elbows are DWVLong 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.
All Series (Models) - Direct Vent Installation
Tab l e 5
50,000 & 75,000 Btuh Furnaces
40¢ & (5) 90° elbows with 2² PVC pipe or
70¢ & (5) 90° elbows with 3² PVC pipe or
70¢ & (5) 90° elbows with 3² PVC pipe
40¢ & (5) 90° elbows with 3² PVC pipe
Elbows are DWVLong Radius Type for 2² and
3
² ven ts.
Pipe Diameter Table
Single Piping ONLY
100,000 Btuh Furnace
125,000 Btuh Furnace
Dual Piping Chart
Pipe Diameter Table
Dual Piping ONLY
100,000 Btuh Furnace
125,000 Btuh Furnace
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.
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)
Consult the appropriate Venting tables and/or piping chart
for the model (series) you are servicing.
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, eitherinlet or
outlet side.
Figure 15
Inlet is optional on
Dual Certified models
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.
Figure 16
Inlet is optional on
Dual Certified models
Standard Termination
Rooftop Termination
B
A
A
25--00--06
Sidewall Termination12² or More
Above Snow Level or Grade Level
8²²²² *
MIN.
20’
MAX
*18² Minimum for cold climates
(substained below 0° F)
25--00--05F
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Single Stage Multi Position Furnace
Service
Manual
Figure 17
12²²²² Min.
Grade or
Snow Level
Dimension “A” is touching or 2² maximum separation.
Figure 18
Combustion
Concentric Vent and Combustion-
Air Roof Termination
Exhaust
Combustion
Air
Concentric Vent and Combustion-Air Sidewall Termination
Air
“A”
1²²²² Maximum
(TYP.)
Ven t
Figure 20
18²²²² Min. for Cold Climates
(Sustained Below 0°°°° F)
Exhaust
Figure 21
18²²²² Min. for Cold Climates
(Sustained Below 0°°°° F)
Sidewall Inlet Vent and Exhaust--Air
Termination with Exterior Risers
8²²²²
Inlet
Min.
12²²²² Min.
Grade or
Snow Level
8²²²² Min.
20¢¢¢¢ Max.
“A”
“A”
Dimension “A” is touching or 2² maximum separation.
Rooftop Inlet Vent and Exhaust--Air
Termination
Inlet
8²²²² Min.
20¢¢¢¢ Max.
Dimension “A” is touching or 2² maximum separation.
Figure 19
Inlet
12²²²² Min. Grade
or Snow Level
“A”
Ven t
Exhaust
25-- 22- -02d
Sidewall Inlet Vent and Exhaust--Air
Termination
“A”
Ex-
haust
“A”
8²²²² Min.
20¢¢¢¢ Max.
18²²²² Min. for
Cold Climates
(Sustained Below 0°°°° F)
Dimension “A” is touching or 2² maximum separation.
8²²²²
Min.
12²²²² Min.
Grade or
Snow Level
Exhaust
25-- 22- -43
15
440 08 2001 02
Service
Manual
Single Stage Multi Position Furnace
Figure 22
FRONT VIEW
Recommended Alternate Installation for Sustained Cold Weather
(--0°°°° F & below)
OVERHANG
12²²²² MIN.
EXHAUST
90°°°°
INLET
12² MIN. Ground
Level
OR Snow Level
SIDE VIEW
12²
25--23--73
Same Joist
Space
18. CONCENTRIC VENT TERMINATION
Vent/Combustion Air Piping Charts
Concentric Termination Kit NAHA001CV
Tab l e 6
NAHA002CV -- 35¢ & (4) 90° elbows with 2² PVC pipe
NAHA001CV -- 65¢ & (4) 90° elbows with 3² PVC pipe
NAHA001CV -- 65¢ & (4) 90° elbows with 3² 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 2² and 3² vents.
& NAHA002VC Venting Table Dual Piping
ONLY
50,000 & 75,000 Btuh Furnaces
100,000 Btuh Furnace
125,000 Btuh Furnace
Figure 23
Roof Boot/
Flashing
(Field Supplied)
Concentric Vent Roof Installation
Vent
Combustion
Air
Vent
Maintain 12² min. clearance
above highest anticipated
snow level. Max. of 24² above
roof.
Support
(Field Supplied)
45° Elbow
(Field Supplied)
440 08 2001 02
Note:
Support must be field installed to secure termination kit to structure.
16
Combustion Air
25--22--02
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