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Armstrong Air Allied A98USMV Service Manual

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SERVICE MANUAL
A98USMV Gas Furnace
This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in manuals, be alert to
the potential for personal injury or death.
A98USMV
series
units
horizontal right and left) gas furnaces equipped with
variable capacity gas valve, variable speed combustion
air inducer and variable speed indoor blower motor.
All models are designed only for direct vent (dual pipe)
venting system. A98USMV units are available in heating
capacities from 66,000 to 132,000 Btuh (19.3 to 38.6 kW)
and cooling applications from 2 to 5 tons (7.0 kW to 17.5
kW). Refer to Technical Specifications for proper sizing.
Units are factory-equipped for use with natural gas. Kits
are available for conversion to LPG operation. A98USMV
models include a variable capacity integrated control that
can be used with Allied Air Comfort Sync Wi-Fi
as part of a communicating comfort system. All A98USMV
units meet the California Nitrogen Oxides (NOx) Standards
and California Seasonal Efficiency requirements.
All specifications in this manual are subject to change.
Procedures outlined in this manual are presented as
recommendations only and do not supersede or replace
local or state codes. In the absence of local or state codes,
the guidelines and procedures outlined in this manual
(except where noted) are recommendations only and do
not constitute code.
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer (or
equivalent), service agency or the gas supplier.
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves
and protective clothing.
508420-01
are
high-efficiency
thermostat
®
WARNING
CAUTION
upflow,
Technical Specifications - A98USMV...........................2
Parts Arrangement.......................................................7
Unit Components .........................................................8
Configuring Unit Size Codes .....................................16
Placement and Installation ........................................36
Joint Cementing Procedure .......................................37
Venting Practices .......................................................38
Vent Piping Guidelines ..............................................40
Condensate Piping ....................................................50
Start-Up .....................................................................55
Heating System Service Checks ...............................56
Typical Operating Characteristics ..............................60
Maintenance ..............................................................61
Wiring and Sequence of Operation ...........................64
...................................................................................67
...................................................................................70
*P508420-01*
Issue 2346

Table of Contents

®
WARNING
Electric shock hazard.
Can cause injury or death. Before attempting
to perform any service or maintenance,
turn the electrical power to unit OFF at
disconnect switch(es). Unit may have
multiple power supplies.
(P) 508420-01
Page 1 of 75

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  • Page 1: Table Of Contents

    SERVICE MANUAL A98USMV Gas Furnace This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in manuals, be alert to the potential for personal injury or death. A98USMV series units high-efficiency upflow, horizontal right and left) gas furnaces equipped with Table of Contents...

  • Page 2: Technical Specifications - A98Usmv

    Technical Specifications - A98USMV MODEL NUMBER GUIDE A 98 U S M V 11 0 C 20 S - 01 A = Flagship Numeric Code 98 = 98% Efficiency S = Stainless Steel Heat Exchanger U = Upflow/Horizontal 8 = 3 Ton add on cooling D = Downflow 12 = 3 Ton add on cooling 16 = 4 Ton add on cooling...
  • Page 3 BLOWER PERFORMANCE: BOTTOM INLET Heating Cooling Motor Temp CFM @ 0" - 0.8" w.c. CFM @ 0" - 0.8" w.c. Blower Cooling Speed Model Size Rise Size Stages Adjustment 100% Medium Medium High (hp) F° Input Input Input High Default +15% 1128 +10%...
  • Page 4 BLOWER PERFORMANCE: SIDE INLET Heating Cooling Motor Temp CFM @ 0" - 0.8" w.c. CFM @ 0" - 0.8" w.c. Blower Cooling Speed Model Size Rise Size Stages Adjustment 100% Medium Medium High (hp) F° Input Input Input High Default +15% 1093 +10%...
  • Page 5 BLOWER PERFORMANCE: SIDE INLET WITH RETURN AIR BASE Heating Cooling Motor Temp CFM @ 0" - 0.8" w.c. CFM @ 0" - 0.8" w.c. Blower Cooling Speed Model Size Rise Size Stages Adjustment 100% Medium Medium High (hp) F° Input Input Input High...
  • Page 6 ACCESSORY LIST Catalog Number Description External Filter Rack Kits 1.841018 1 pack (16 x 25) 1.841039 10 pack (16 x 25) Natural to LP Kits 68W77 Modulating 97/98% (including gas valve) 68W77 High Altitude > 7500 ft. Return Air Base 68W62 17.5"...

  • Page 7: Parts Arrangement

    Parts Arrangement BURNER BOX ASSEMBLY PRESSURE SWITCHES HEAT EXCHANGER VARIABLE CAPACITY PRIMARY LIMIT GAS VALVE VARIABLE SPEED COMBUSTION AIR INDUCER BAG ASSEMBLIES (shipping location) COLD END HEADER ACCESS PANEL VARIABLE SPEED BLOWER MOTOR SHIPPING BLOCK (-135 UNITS ONLY) CONTROL BOX (includes variable capacity integrated control transformer, circuit breaker and door switch) Figure 1.

  • Page 8: Unit Components

    Circuit Breaker (CB8) Unit Components A 24V circuit breaker is also located in the control box. The switch provides overcurrent protection to the transformer A98USMV unit components are shown in Figure 1. (T1). The breaker is rated 3A at 32V. If the current exceeds The gas valve, combustion air inducer and burners can this limit the breaker will trip and all unit operation will be accessed by removing the access panel.
  • Page 9 Thermostat Selection Modes Pin # Function See Table 3 for DIP switch settings Not Used High Fire Pressure Switch The control can be made to operate in three modes: variable capacity, three-stage timed or two-stage. The variable Rollout Switch In capacity and two-stage modes are only operational with Ground a two-stage thermostat.
  • Page 10 NEUTRAL TERMINALS COMBUSTION AIR INDUCER CONNECTOR IGNITOR CONNECTOR FLAME SENSE DIAGNOSTIC LINE VOLTAGE PUSH BUTTON TERMINALS DIP SWITCHES INDOOR BLOWER CONNECTOR OUTDOOR AIR SENSOR TERMINALS 7-SEGMENT DIAGNOSTIC LED W915 Y1 TO Y2 DISCHARGE AIR SENSOR W951 R TO O TERMINALS W914 R TO DS FACTORY TEST W915...
  • Page 11 Figure 5. Integrated Control Configuration Guide 508420-01 Issue 2346 Page 11 of 75...
  • Page 12 Operation Thermostat Switch 1 Switch 2 Switch 3 Variable Capacity Heat Two-Stage (35% to 100%) 2nd Stage Delay OF = 7 minutes Three-Stage Heat Single-Stage ON = 12 minutes (35%, 70%, 100%) 3rd Stage Delay 10 minutes fixed Two-Stage Heat Two-Stage (W1 70%, W2 100%) Table 3.
  • Page 13 will continue to operate as normal. This mode is used to Ramping Option C check motor operation. • Motor runs at 100% until demand is satisfied. • Once demand is met, motor runs at 100% for 45 Adjustment Switch 10 Switch 11 seconds then ramps down to stop.
  • Page 14 +15% Airflow Determination Identify blower speed adjustment points at low and high fire Airflow will lie on straight line between these two points and will fall within +7.5% the shaded area as shown EXAMPLE -7.5% at low fire +7.5% at high fire Nominal High Fire -7.5%...
  • Page 15 • Initiate furnace ignition sequence and move to and Soft Disable hold mid-fire rate by applying a jumper to R and W2. Soft disabling is when thermostat finds a device on the • Apply then remove the jumper from R to W1 and W2 BUS that it does not recognize and the thermostat sends to change the firing rate from low fire to mid fire and a the device a message to be in soft disabling mode until...

  • Page 16: Configuring Unit Size Codes

    Configuring Unit Size Codes Power-Up - Number displayed by integrated control represents unit size code (furnace model and capacity). If three horizontal bars are displayed followed by continuous E203, furnace control does not recognize unit size code. Configure per the following: Turn room thermostat to OFF.
  • Page 17 Code Diagnostic Codes / Status of Equipment Action Required to Clear and Recover Idle mode (Decimal blinks at 1 Hertz - 0.5 • seconds ON, 0.5 seconds OFF). Cubic feet per minute (cfm) setting for indoor blower (1 second ON, 0.5 seconds OFF) / cfm setting for current mode displayed.
  • Page 18 Code Diagnostic Codes / Status of Equipment Action Required to Clear and Recover E180 Outdoor air temperature sensor failure. Only Compare outdoor sensor resistance to temperature resistance charts shown if shorted or out of range (Communicating in unit installation instructions. Replace sensor pack if necessary. At systems only) beginning of (any) configuration, furnace or air handler control will sense outdoor air and discharge air temperature sensor(s) If detected (reading...
  • Page 19 Code Diagnostic Codes / Status of Equipment Action Required to Clear and Recover E240 Low flame current - Run mode- Refer to Check micro-amperes of flame sensor using control diagnostics or field troubleshooting installed mode. Clean or replace sensor. Measure voltage of neutral to ground to ensure good unit ground.
  • Page 20 Code Diagnostic Codes / Status of Equipment Action Required to Clear and Recover E311 Heat rate reduced to match indoor blower airflow. Warning Only. Furnace blower in cutback mode due to restricted airflow. Reduce firing rate every 60 seconds to match available CFM. Check filter and duct system.
  • Page 21 Operating Sequence System Demand System Response Thermostat Relative Humidity Blower Demand System Step Compressor Comments Condition (COOL) Status Stage NO CALL FOR DEHUMIDIFICATION Compressor and indoor Normal Operation Acceptable 24 VAC High 100% blower follow thermostat demand BASIC MODE (only active on a Y1 thermostat demand) Normal Operation Acceptable 24 VAC...
  • Page 22 Operating Sequence System Demand System Response Thermostat Demand Relative Humidity Blower System Step Compressor Comments Condition (COOL) Status Stage Stage NO CALL FOR DEHUMIDIFICATION Normal Operation Acceptable Compressor and indoor - Y1 blower follow thermostat Normal Operation demand Acceptable High 100% - Y2 ROOM THERMOSTAT CALLS FOR FIRST STAGE COOLING...

  • Page 23: Indoor Blower Motor

    Indoor Blower Motor A solid-state controller is permanently attached to the motor. The controller is primarily an A.C. to D.C. converter. Converted D.C. power is used to drive the motor. The controller contains a microprocessor which monitors varying conditions inside the motor (such as motor workload).
  • Page 24 Remove Blower from Unit Motor Start-Up 1. Remove unit access panels, control box, bolts and When B3 begins start-up, the motor gently vibrates back wiring jackplugs. and forth for a moment. This is normal. During this time the electronic controller is determining the exact position 2.
  • Page 25 P48 5 Pin P48 5 Pin P49 4 Pin SHAFT SHAFT P49 4 Pin MOTOR with INTEGRATED MOTOR with INTEGRATED CONTROLLER CONTROLLER J48 5 Pin J49 4 Pin P48 5 Pin P49 4 Pin J49 4 Pin Control Connector J48 5 Pin Line Voltage Connector J48 Connector 120v Figure 9.

  • Page 26: Heating Components

    Troubleshooting Motor Windings TEST B Ensure that motor windings are not damaged by performing Use an ohmmeter to measure the motor phase-to-phase the following tests: resistance by checking these combinations of the the 3-pin motor plug. For the purpose of this test, start at either end NOTE: If your ohm meter is not an auto-ranging type, set of the connector as lead 1.
  • Page 27 Flame Rollout Switches that is precisely matched to the burner input. Burners can be removed as a one piece assembly for service. If burner Flame rollout switch S47 is a high temperature limit located assembly has been removed, it is critical to align center inside the burner box.
  • Page 28 Primary Limit Control (S10) Figure 15 shows the primary limit (S10) used on A98USMV DANGER units located in the heating vestibule panel. When excess Danger of explosion. heat is sensed in the heat exchanger, the limit will open. Once the limit opens, the furnace control energizes the There are circumstances in which odorant supply air blower and de-energizes the gas valve.
  • Page 29 Finally, the switch interrupts the combustion process if • Venting conditions change (affecting high and low the condensate drainage system becomes blocked to the pressure switch operation) point the condensate level builds up in the cold end header • Ramp down low fire switch check failed (calibration will box/ secondary coil or vent system.
  • Page 30 5. If low pressure switch opens turn off inducer. No further The CAI is installed on the cold end header box. The cold action. end header box is a single piece made of hard plastic. The box has an internal channel where the combustion 6.

  • Page 31: Comfort Sync Wi-Fi ® Thermostat (If Applicable)

    Comfort Sync Wi-Fi Thermostat (if applicable) ® DATS (Optional) OATS (Optional) Communicating Communicating Outdoor Unit Indoor Unit Smart Hub Display Subbase Figure 19. Comfort Sync A3 with Communicating Indoor and Outdoor Units DATS (Optional) OATS (Optional) SETUP NOTES: CUT Y1-Y2 ON-BOARD MUNICATING) CUT R-O ON-BOARD LINK FOR OUTDOOR HEAT...
  • Page 32 DATS (Optional) OATS (Optional) SETUP NOTE: CUT Y1-Y2 ON-BOARD LINK FOR 2-STAGE OUTDOOR UNITS (NON-COMMUNICATING) Smart Hub Display Subbase 24VAC Outdoor Unit Communicating (1 - or 2-Stage Indoor Unit Air Conditioner) Figure 21. Comfort Sync A3, Communicating Indoor Unit with 24VAC Air Conditioner Communicating Outdoor Unit If jumber is present between...
  • Page 33 Indoor Unit Controller Outdoor Unit Smart Hub HD Display Subbase 12VDC COM BUS ACC1 ACC2 R i+ I- C +12V -12V Single wire Single wire to indoor unit to bundle terminal “C”. wire to indoor Single wire terminal “C”. to terminal “C”. Unused wires Unused wires Unused wires...
  • Page 34 24VAC UV Light Applications: In any Allied communicating system, the indoor unit will FURNACE (IFC) OR AIR HANDLER (AHC) NOT have adequate power to to run the 24VAC UV light application. An additional transformer will be required. UV light wiring connections are independent of the HVAC system operation CHARGE AIR SENSOR (refer to UV light installation instruction.
  • Page 35 Communicating Indoor Unit HRV/ERV Terminal Block Smart Hub Display Subbase Wire Jumper required between ON and RED terminals. ACC1 is always low-stage for single- and two-stage ventilators. Figure 27. Comfort Sync A3 with Ventilation (Fresh Air Damper, ERV and HRV) 508420-01 Issue 2346 Page 35 of 75...

  • Page 36: Placement And Installation

    Canadian Applications Only - Pipe, fittings, primer and Placement and Installation solvent cement used to vent (exhaust) this appliance must be certified to ULC S636 and supplied by a single All pipe, fittings, primer and solvent cement must conform manufacturer as part of an approved vent (exhaust) with American National Standard Institute and the American system.

  • Page 37: Joint Cementing Procedure

    STANDARD CONCENTRIC Outdoor Outdoor Exhaust 1-1/2” 2” 3” Exhaust Flush VENT Accelerator Concentric Concentric Concentric Accelerator Mount Kit PIPE (Dia. X Length) Unit (Dia. X Length) DIA. (in.) 71M80 69M29 60L46 1-1/2” X 12” 2” X 12” 51W11 * or 44W93+ +44W92++ +44W92++ 1-1/2...

  • Page 38: Venting Practices

    Exhaust Piping (Figure 29 and Figure 30) Venting Practices Route piping to outside of structure. Continue with installation following instructions given in piping termination section. SCHEDULE 40 PVC - 5' all other pipe* - 3' Intake Piping (Figure 29 and Figure 30) The A98USMV furnace may be installed only in direct vent applications.
  • Page 39 EXHAUST INTAKE 2” INTAKE EXHAUST 2” 2” 2” 2” 2” *2” *2” 070 Only 1-1/2” TRANSITION 2” 6” MINIMUM DO NOT transition from smaller to larger pipe in horizontal runs of exhaust pipe. * When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.

  • Page 40: Vent Piping Guidelines

    Vent Piping Guidelines Exhaust Pipe 12” Min. 12” Max. NOTE: Allied Air has approved the use of DuraVent ® Horizontal Centrotherm manufactured vent pipe and terminations as Gas Furnace an option to PVC. When using the PolyPro by DuraVent ® or InnoFlue by Centrotherm venting system the vent ®...
  • Page 41 Use the following steps to correctly size vent pipe diameter. 070, 090, Furnace capacity? 110 or 135 btuh Standard or Which termination? Concentric? See Table 20 Which needs most Intake or elbows? Exhaust? How many? 1-1/2”, 2”, Desired pipe size? 2-1/2”...
  • Page 42 Maximum Allowable Intake or Exhaust Vent Length (feet) Standard Termination at Elevation 0 - 4,500 ft 1-1/2” Pipe 2” Pipe 2-1/2” Pipe 3” Pipe Number of 90° Elbows Model Model Model Model Used Standard Termination at Elevation 4,501 - 10,000 ft 1-1/2”...
  • Page 43 Maximum Allowable Intake or Exhaust Vent Length (feet) Concentric Termination at Elevation 0 - 4,500 ft 1-1/2” Pipe 2” Pipe 2-1/2” Pipe 3” Pipe Number of 90° Elbows Model Model Model Model Used Concentric Termination Elevation 4,501 - 10,000 ft 1-1/2”...
  • Page 44 General Guidelines for Vent Terminations In Direct Vent applications, combustion air is taken from IMPORTANT outdoors and the flue gases are discharged to the outdoors. The A98USMV is then classified as a direct vent, Category For Canadian Installations Only: IV gas furnace. In accordance to CSA International B149 installation codes, the minimum allowed distance between the In Direct Vent applications, the vent termination is limited...
  • Page 45 Maximum Allowable Vent Pipe Length without Insulation in Unconditioned Space for Winter Design Temperatures Modulating High Efficiency Furnace Winter Design Temperatures ºF Vent Pipe (ºC) Diameter 1-1/2 in. 32 to 21 2 in. (0 to -6) 2-1/2 in. 3 in. 1-1/2 in.
  • Page 46 VENT TERMINATION CLEARANCES FOR DIRECT VENT INSTALLATIONS IN THE USA AND CANADA INSIDE CORNER DETAIL Fixed Operable Fixed Closed Closed Operable AREA WHERE TERMINAL AIR SUPPLY INLET VENT TERMINAL IS NOT PERMITTED US Installations Canadian Installations Clearance above grade, veranda, 12 inches (305mm) or 12 inches (305mm) 12 inches (305mm) or 12 inches (305mm) porch, deck or balcony...
  • Page 47 Details of Intake and Exhaust Piping 2. Intake and exhaust pipes should be placed as close together as possible at termination end (refer to Terminations for Direct Vent Installations illustrations). Maximum separation is 3” (76MM) NOTE: In Direct Vent installations, combustion air is taken on roof terminations and 6”...
  • Page 48 6. On field-supplied terminations, a minimum distance STRAIGHT-CUT OR between the end of the exhaust pipe and the end of ANGLE-CUT IN DIRECTION OF ROOF SLOPE * the intake pipe without a termination elbow is 8” and a minimum distance of 6” with a termination elbow. See 3”...
  • Page 49 FIELD FABRICATED WALL TERMINATION NOTE − FIELD−PROVIDED REDUCER MAY BE 2” (51mm) 3” (76mm) REQUIRED TO ADAPT Vent Pipe Vent Pipe LARGER VENT PIPE SIZE TO TERMINATION A− Minimum clearance above grade or average 12” (305 mm) 12” (305 mm) snow accumulation B−...

  • Page 50: Condensate Piping

    1. Determine which side condensate piping will exit the Condensate Piping unit, location of trap, field-provided fittings and length of PVC pipe required to reach available drain. This unit is designed for either right- or left-side exit of 2. For furnaces with a 1/2” drain connection use a 3/8 condensate piping in upflow applications.
  • Page 51 line should be routed within the conditioned space to avoid freezing of condensate and blockage of drain line. If this is not possible, a heat cable kit may be used on the condensate trap and line. Heating cable kit is available in various lengths;...
  • Page 52 Evaporator drain From Evaporator Coil line required Field Provided Vent 1” min. 2” max. above (Trap at coil is optional) condensate drain. Field-Provided Vent (1” min. to 2” Max.above condensate drain connection) Furnace Condensate Condensate Drain Condensate Drain Connection Optional Overflow Switch Figure 50.
  • Page 53 Optional Condensate Drain Connection Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) 90° Street Elbow 3/4 inch PVC (not furnished) Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) Condensate Drain Connection In Unit 1 (25 mm) Min. Vent 2 (50 mm) Max.
  • Page 54 Optional Condensate Drain Connection Adapter 1/2 inch slip X 1/2 inch mpt (Not Furnished) 90° Street Elbow 1/2 inch PVC (Not Furnished) Adapter 1/2 inch slip X 1/2 inch mpt (Not Furnished) Condensate Drain Connection In Unit 1 (25 mm) Min. Vent 2 (50 mm) Max.

  • Page 55: Start-Up

    Each time the thermostat calls for heat, the burners will Start-Up automatically light The ignitor does not get hot when there is no call for heat on units with an ignition system. Preliminary and Seasonal Checks Priming Condensate Trap 1. Inspect electrical wiring, both field and factory installed The condensate trap should be primed with water prior for loose connections.

  • Page 56: Heating System Service Checks

    4. This furnace is equipped with an ignition device which off power to unit. All access panels and covers must be in automatically lights the burners. Do not try to light the place and secured. burners by hand. 5. Remove the upper access panel. Heating System Service Checks 6.
  • Page 57 Operating Pressure Signal (Delta P) When checking piping connections for gas leaks, use preferred means. Kitchen detergents can cause harmful Measurement (Figure 57) corrosion on various metals used in gas piping. Use of a Operating pressure signal can be taken while the specialty Gas Leak Detector is strongly recommended.
  • Page 58 Gas Valve Field Installed Figure 56. Manifold Pressure Measurement Negative Port Positive Port Red and Black Tubing or Red Tubing - Black Tubing + Gas Valve Field Installed Measuring Device Figure 57. Operating Signal (Delta P) Measurement Page 58 of 75 Issue 2346 508420-01...

  • Page 59: Proper Combustion

    Proper Combustion High Altitude Furnace should operate minimum 15 minutes with correct NOTE: In Canada, certification installations manifold pressure and gas flow rate before checking elevations over 4500 feet (1372 m) is the jurisdiction of combustion. Take combustion sample beyond the flue local authorities.

  • Page 60: Typical Operating Characteristics

    External Static Pressure Typical Operating Characteristics 1. Tap locations shown in Figure 58. Blower Operation and Adjustment 1. Blower operation is dependent on thermostat control system. 2. Generally, blower operation is set at thermostat subbase fan switch. With fan switch in ON position, blower operates continuously.

  • Page 61: Maintenance

    Filter Size Maintenance Furnace Cabinet Width Side Return Bottom Return 17-1/2” 16 x 25 x 1 (1) 16 x 25 x 1 (1) 21” 20 x 25 x 1 (1) WARNING 24-1/2” 16 x 25 x 1 (2) 24 x 25 x 1 (1) ELECTRICAL SHOCK, FIRE, OR EXPLOSION Table 31.
  • Page 62 Condensate Hose Screens (Figure 59) 10. Disconnect condensate drain tubing from flue collar. Remove screws that secures the flue collar into place. Check the condensate hose screens for blockage and Remove flue collar. It may be necessary to cut the clean if necessary.

  • Page 63: Cleaning The Burner Assembly

    Cleaning the Burner Assembly 30. Reinstall pressure switches and reconnect pressure switch wiring. 1. Turn off electrical and gas power supplies to furnace. Remove upper and lower furnace access panels. 31. Carefully connect combustion air pressure switch hosing from pressure switches to proper stubs on cold 2.

  • Page 64: Wiring And Sequence Of Operation

    Wiring and Sequence of Operation BLACK WHITE BLACK WHITE GN/YLW WHITE WHITE WHT/ PINK FLAME SENSOR FLAME SENSE BLACK CIRC WHITE BLACK 120V YELLOW BLUE BLUE RO(OUT) BROWN BROWN RO(IN) BLUE BLUE S102 PURPLE (HI) PINK S128 (LO) PINK YELLOW ORANGE AUTO Figure 60.
  • Page 65 Sequence of Operation 7. When the demand for high fire (second stage) heat is satisfied, the gas valve is de-energized and the The integrated control initiates a pressure switch field selected indoor blower off delay begins. The calibration at the initial unit start-up on a call for heat. The combustion air inducer begins a 20 second post purge ignition control will also initiate a calibration any time main period.
  • Page 66 7. When the demand for first and second stage heat is satisfied, the gas valve is de-energized and the field selected indoor blower OFF delay begins. The combustion air inducer begins a 20 second post-purge period. 8. When the combustion air post-purge period is complete, the inducer is de-energized.

  • Page 67: Field Wiring Applications With Conventional Thermostat

    Field Wiring Applications with Conventional Thermostat DIP Switch Settings and On-Board Links W915 W914 W951 Thermostat Wiring Connections DIP Switch 1 (Y1 to Y2) (DS to R) (O to R) Two-Stage Cooling Dehumidification Heat Pumps CONTROL OUTDOOR T'STAT TERM. STRIP UNIT 1 Heat / 1 Cool NOTE:...
  • Page 68 DIP Switch Settings and On-Board Links W915 W914 W951 Thermostat Wiring Connections DIP Switch 1 (Y1 to Y2) (DS to R) (O to R) Two-Stage Cooling Dehumidification Heat Pumps CONTROL OUTDOOR T'STAT TERM. STRIP UNIT 2 Heat / 2 Cool Intact Intact CONTROL...
  • Page 69 DIP Switch Settings and On-Board Links W915 W914 W951 Thermostat Wiring Connections DIP Switch 1 (Y1 to Y2) (DS to R) (O to R) Two-Stage Cooling Dehumidification Heat Pumps CONTROL T'STAT TERM. STRIP HEAT PUMP 67M41** Dual Fuel Single- Stage Heat Pump Comfort Sync thermostat w/dual Intact...

  • Page 70: Sequence Of Operation And Troubleshooting Flow Chart

    Sequence of Operation and Troubleshooting Flow Chart Safety Check Verify There Is No Main Burner Flame After Indoor blower OFF Heat OFF Delay (Low Heat Speed) Combustion Air Limit Limit Indoor Blower De−Energize Error Code Inducer On Switch Closes Within 3 Gas Valve Flashes ON (100%)
  • Page 71 2 Stage Thermostat 1st Call for High Fire? 2nd Stage Recognition Delay (30 Seconds) Combustion Air Inducer ON (100% Rate Speed) High Pressure Switch Increase Combustion Error Code Wait 5 Closes Within Air Inducer Speed Flashes Minutes 10 Seconds? if Not at 100% Rate Speed Adjust Indoor Blower to...
  • Page 72 RUN MODE (2 STAGE THEREMOSTAT) RUN MODE (SINGLE STAGE THERMOSTAT) 1ST OR 2ND STAGE CALL FOR HEAT ALL ALL INPUTS MONITORED (LIMIT, PRESSURE, INPUTS MONITORED (LIMIT, PRESSURE, CALL FOR HEAT / COOL, FLAME LEVEL) CALL FOR HEAT / COOL, FLAME LEVEL) 2nd Stage Heat 2nd Stage Call for Heat...
  • Page 73 Safety Check Verify There Is No Main Burner Flame Indoor Blower OFF After Heat OFF Delay (Low Heat Speed) Indoor Blower Limit Limit De−Energize Error Code Combustion Air Switch Closes Within 3 Gas Valve Flashes (100% Speed) Inducer ON Closed? Minutes? (100%) Indoor Blower OFF...
  • Page 74 1st Stage Cooling Request Received Energize 1st Stage Cooling Contactor (Compressor & Fan) Indoor Blower On After 2−second delay Energize Indoor Blower (Per Ramping Profile) 1st Stage 2nd Stage Cooling Request Cooling Still Active? Request? Energize 2nd Stage Energize Indoor Blower Cooling Contactor (High Cooling mode) (Compressor &...
  • Page 75 Call for Continuous Blower Indoor Blower On (Speed Determined by Dip Switch settings) Request Maintain Indoor for Cooling Go to Call for Cooling Blower at set speed Received? Go to Call for Heat - 2 Stage Thermostat Request Maintain Indoor for Heat Blower at set speed Received?

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