COMFORT-AIRE Century GUH97M Service Manual
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COMFORT-AIRE Century GUH97M Service Manual

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SERVICE MANUAL
GUH97M 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.
GUH97M
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. GUH97M 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. GUH97M
models include a variable capacity integrated control that
can
be
used
with
thermostat. All GUH97M units meet the California
Nitrogen
Oxides
(NOx)
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.
WARNING
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.
CAUTION
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.
508146-01
are
high-efficiency
Comfort-Aire/Century
Standard
Standards
and
California
upflow,
Technical Specifications - GUH97M.............................2
Parts Arrangement.......................................................7
Unit Components .........................................................8
Configuring Unit Size Codes .....................................16
Placement and Installation ........................................31
Joint Cementing Procedure .......................................32
Venting Practices .......................................................33
Vent Piping Guidelines ..............................................35
Condensate Piping ....................................................45
Start-Up .....................................................................50
Heating System Service Checks ...............................51
Typical Operating Characteristics ..............................55
Maintenance ..............................................................56
Wiring and Sequence of Operation ...........................59
Thermostat.................................................................59
Chart..........................................................................65
*P508146-01*
Issue 2051

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) 508146-01
Page 1 of 70

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Summary of Contents for COMFORT-AIRE Century GUH97M

  • Page 1: Table Of Contents

    LPG operation. GUH97M Condensate Piping ............45 models include a variable capacity integrated control that Start-Up ..............50 used with Comfort-Aire/Century Standard Heating System Service Checks .......51 thermostat. All GUH97M units meet the California Typical Operating Characteristics ......55 Nitrogen...

  • Page 2: Technical Specifications - Guh97M

    Technical Specifications - GUH97M MODEL NUMBER GUIDE 0 0 7 7 0 0 B B 3 M REV CODE G = GAS FURNACE REVISION CONFIGURATION NOM. CFM X 100 UH = UPFLOW/HORIZONTAL 3 TON ADD ON COOLING DD = DOWNFLOW 4 TON ADD ON COOLING 5 TON ADD ON COOLING AFUE...
  • Page 3 BLOWER PERFORMANCE DATA: BOTTOM INLET Heating Cooling CFM @ 0" - 0.5" w.c. CFM @ 0" - 0.8" w.c. Motor Temp Speed Size Blower Rise 100% Cooling Adjust- Medium Medium High Model (hp) Size F° Input Input Input Stages ment High Default +15%...
  • Page 4 BLOWER PERFORMANCE DATA: SIDE INLET Heating Cooling CFM @ 0" - 0.5" w.c. CFM @ 0" - 0.8" w.c. Motor Speed Size Blower Temp Rise 100% Cooling Adjust- Medium Medium High Model (hp) Size F° Input Input Input Stages ment High Default +15%...
  • Page 5 BLOWER PERFORMANCE DATA: SIDE INLET WITH RETURN AIR BASE Heating Cooling CFM @ 0" - 0.5" w.c. CFM @ 0" - 0.8" w.c. Motor Speed Size Blower Temp Rise 100% Cooling Adjust- Medium Medium High Model (hp) Size F° Input Input Input Stages...
  • Page 6 ACCESSORY LIST CATALOG NUMBER DESCRIPTION External Filter Rack Kits AEFR1 1 pack (16 x 25) AEFR10 10 pack (16 x 25) Natural to LP Kits 68W77 Modulating 97% (includes gas valve) Return Air Base 68W62 17.5" B Width 68W63 21.0" C Width 68W64 24.5"...

  • Page 7: Parts Arrangement

    Parts Arrangement Figure 1. 508146-01 Issue 2051 Page 7 of 70...

  • 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 GUH97M 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 this limit the breaker will trip and all unit operation will can 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 COMBUSTION TERMINALS AIR INDUCER CONNECTOR IGNITOR CONNECTOR FLAME SENSE DIAGNOSTIC LINE VOLTAGE PUSH BUTTON TERMINALS DIP SWITCHES ON-BOARD LINKS OUTDOOR AIR INDOOR SENSOR BLOWER TERMINALS 7-SEGMENT CONNECTOR DIAGNOSTIC LED W915 Y1 TO Y2 DISCHARGE AIR SENSOR W951 R TO O TERMINALS W914 R TO DS FACTORY TEST...
  • Page 11 Figure 5. Integrated Control Configuration Guide 508146-01 Issue 2051 Page 11 of 70...
  • Page 12 Operation Thermostat Switch 1 Switch 2 Switch 3 Variable Capacity Heat Two-Stage (40% to 100%) 2nd Stage Delay OF = 7 minutes Three-Stage Heat Single-Stage ON = 12 minutes (40%, 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 B3, refer to blower cfm regardless of motor rpm. IMPORTANT Initial Power Up Earlier ECM motors used on other Comfort-Aire/ When line voltage is applied to B3, there will be a large Century furnace models are not interchangeable with inrush of power lasting less than 1/4 second.
  • 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 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 The low fire pressure switch LPG change over kits are available from Comfort-Aire/ provides this function. Century. Kits include burner orifices and an LP 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 Measuring Pressure Differential (Figure 18) the CAI to the box must also be replaced. Checks of pressure differential can aid in troubleshooting. Comfort-Aire/Century provides a kit (10L34) if necessary. Set Point Set Point When measuring the pressure differential, readings...

  • Page 31: 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 32: 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 33: Venting Practices

    Exhaust Piping (Figure 22 and Figure 23) 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 22 and Figure 23) The GUH97M furnace may be installed only in direct vent applications.
  • Page 34 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 35: Vent Piping Guidelines

    Vent Piping Guidelines Exhaust Pipe 12” Min. 12” Max. NOTE: Comfort-Aire/Century has approved the use of Horizontal DuraVent® and Centrotherm manufactured vent pipe and Gas Furnace terminations as an option to PVC. When using the PolyPro® by DuraVent or InnoFlue® by Centrotherm venting system the vent pipe requirements stated in the unit installation instruction –...
  • Page 36 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 37 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 38 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 39 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 GUH97M is then classified as a direct vent, For Canadian Installations Only: Category 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 40 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 41 ‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of two sides beneath the floor. Comfort-Aire/Century recommends avoiding this location if possible. Figure 27. Vent Termination Clearances Direct Vent Installations...
  • Page 42 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 43 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 44 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 45: 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 46 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 47 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 43.
  • Page 48 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 49 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 50: 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 51: 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 52 (available as Comfort-Aire/ Century part 10L34) to assist in measurement. Seconds for One Revolution 1. Remove the threaded plug from the outlet side of the Natural gas valve and install a field-provided barbed fitting.
  • Page 53 Gas Valve Field Installed Figure 49. Manifold Pressure Measurement Negative Port Positive Port Red and Black Tubing or Red Tubing - Black Tubing + Gas Valve Field Installed Measuring Device Figure 50. Operating Signal (Delta P) Measurement 508146-01 Issue 2051 Page 53 of 70...
  • Page 54 Proper Combustion High Altitude Furnace should operate minimum 15 minutes with correct NOTE: In Canada, certification f or i nstallations at 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 55: Typical Operating Characteristics

    External Static Pressure Typical Operating Characteristics 1. Tap locations shown in Figure 51. 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 56: 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 57 Condensate Hose Screens (Figure 52) 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 58 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 59: Wiring And Sequence Of Operation

    Wiring and Sequence of Operation Figure 53. 508146-01 Issue 2051 Page 59 of 70...
  • Page 60 Sequence of Operation 7. When the demand for first- and second-stage heat is satisfied, the gas valve is de-energized and the NOTE: The ignition control thermostat selection DIP switch field-selected indoor blower off delay begins. The is factory-set in the “TWO-STAGE” position. combustion air inducer begins a 20-second post-purge period.
  • Page 61 Applications Using a Two-Stage Thermostat C - Heating Sequence -- Control Thermostat Selection DIP switch in “Two-Stage” Position (Factory Setting) 1. On a call for heat, thermostat first-stage contacts close sending a signal to the integrated control. The integrated control runs a self-diagnostic program and checks high temperature limit switches for normally closed contacts and pressure switches for normally open contacts.

  • Page 62: 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 63 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 64 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 Capable of 2- stage gas heat Intact...

  • Page 65: 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 66 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 67 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 68 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 69 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 70 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?

This manual is also suitable for:

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