Thermo Products CDX3-75N Diagnostic Features, Power must be disconnected before servicing

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All installations and services must be performed by qualified service personnel.

memory, the LED will flash two green flashes. The control will flash the most recent error first and the oldest error last (last in first out). There will be 2 seconds between codes. Solid LED error codes will not be displayed.

DIAGNOSTIC FEATURES

The 50V51 control used on this furnace continuously monitors its operation and the operation of the system.

If the sensed failure is in the system (external to the control), the red LED will flash in the following flash- pause sequences to indicate failure status (each flash will last approximately 0.25 seconds, and each pause will last approximately 2 seconds):

Red LED Flash (DS1)

1 - flame sensed when no flame should be present 2 - pressure switch stuck closed / inducer error

3 - 1st stage pressure switch stuck open / inducer error 4 - open limit switch

5 - open rollout / aux limit

6 - pressure switch cycle lockout

7 - external lockout (retries)

8 - external lockout (recycles)

9 - grounding or reversed polarity

10 - gas flow with no call for heat

11 - limit switch open – blower failure

12 - ignitor failure

Solid - internal GV error, micro, and frequency check

3 double - 2nd stage pressure switch stuck open / inducer error

The LED will also flash once at power-up.

Amber LED Flash (DS1)

1 – normal call for first stage heat

2 – normal call for second stage heat

3 – W2 present with no W1

4 – Y present with no G call Rapid – low flame sense current

Green LED indicator (DS2) is present to obtain an estimate of the air flow rate (in CFM) produced by the house air blower. This LED cycles regularly by providing a constant light, followed by a sequence of flashes. Each flash can be translated to programmed CFM by using the following:

1 flash per 100(programmed) CFM

: Power must be disconnected before servicing.

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Contents MODELS OR LP GAS PROPANE CDX3-75N CDX3-100N CDX3-125NTWO STAGE CONDENSING GAS FURNACE I. SAFETY INFORMATION This and the previous page contain reproductions of the various warning and instruction labels placed on the Thermo Pride Two Stage Condensing Gas Furnaces. Please read and comply with the contents of these labels 1.A windows be opened The CHX3/CDX3 furnace models are sealed combustion design, which does not require an air shutter adjustment air shutters are not used for proper flame characteristics. Burner box access cover must always be secured with all screws in place and tightened before operating furnace INDEX SECTIONBEGINNING PAGE II. FURNACE SPECIFICATIONS CHX3 SERIES CDX3 SERIES INSTALLATION PARTS PACKAGES - CHX3-75 INSTALLATION PARTS PACKAGES - CDX3-75 Grounding instructions III. GENERAL INSTALLATION B. FURNACE LOCATION B1. CDX3 HORIZONTAL APPLICATIONPage PVC Pipe Designation Maximum Quantity of Elbows E.Direct Venting Through a Sidewall Outside Combustion Air Intake RH viewc.The vent terminal shall not be located Page E1. Single-PipeSidewall Venting Option 5.Optional Direct Vent Terminations Install these optional kits according to the instructions provided with each kit. The location and clearance requirements are identical to those of the standard vent terminations described in this manual 1.Figures 6B, 7, and 8 follow depicting typical exhaust vent and air intake connections for the furnace model series CHX3 and the CDX3, respectively, as well as a list of required parts to correctly install each system Page Applications Figure 9 Typical Internal Vent Piping Arrangement for theFurnace Model Series CHX3 3. Connecting The Combustion Air Intake Piping I.CONDENSATE DRAIN LINE AND TRAP ASSEMBLY Figure 14. TRAP ASSEMBLY MOUNTED ON CHX3Figure 15. TRAP ASSEMBLY MOUNTED ON CDX3 2.Determine on which side of furnace the condensate disposal line is to be run NOTICE On CHX3/CDX3’s this must be the same side as the flue outlet or bottom of unit. Attach the condensate trap to the furnace casing using the #8x3/4” sheet metal screws provided in the parts package. Pilot holes are provided on both sides of the casing for mounting J. GENERAL GAS PIPING J1. REQUIREMENTS AND SIZING OF DUCT WORK Figure 18A TABLE 2A K. FILTERS 1. CHX3 MODELS HIGHBOYS 2. CDX3 MODELS COUNTERFLOWSPage L. WIRING Table 4A Options S7 DIP SwitchSwitch Settings Time2-StageBlower Settings from factory Table 4C IV. STARTING THE UNIT A. SEQUENCE OF OPERATIONS IF NOT IF THERMOSTAT W2 CONTACTS ARE CLOSED OTHERWISE B. INITIAL START UP OPERATING INSTRUCTIONSA.Burner manifold pressure with a pressure gauge C. Measuring And Adjusting Heat Input RateObserve the following precautions when measuring B.Gas flowrate by clocking gas meterNOTICE A U-tubemanometer, measuring pressure in inches of water column, is recommended for all gas pressure measurements. However, an aneroid pressure gauge, in good working condition, capable of reading pressure changes of 0.05 in. W.G., or less, that was recently calibrated within the last year, is a satisfactory alternate. These two 2 devices will be considered as equivalent and interchangeable. Either device is referred to below as a “pressure gauge” Heat input rate in BTUH = Page 21.Go to Checkout Procedure below Checking The Burner FlameCheckout Procedure TABLE 6 - CONVERTING GAS FLOW RATE D. FURNACE CHECKOUT PROCEDURE V. INSTALLERS INSTRUCTIONS TO USERFigure VI. TROUBLESHOOTING DIAGNOSTIC FEATURES Power must be disconnected before servicingTROUBLESHOOTING GUIDE IS INDUCER RUNNING ON LOW SPEED? YES DOES THE HOT DO BURNERS STAY LIT PAST PROOF OF FLAME CHECK? REPLACE THE 50V51-843CONTROL DOESBURNERSHUT OFF Appendix -AReplacement Parts List Page Page Page Appendix - B Wiring Diagrams