Thermo Products chx-3 75n, 100n, 125n operation manual Heat input rate in BTUH =

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

5.To obtain an accurate manifold gas pressure reading, the main burner must be cycled on and off several times to stabilize the gas control valve pressure regulator diaphragm.

6.Allow the burner to operate for at least 3 minutes before taking gas pressure readings.

7.Using a pressure gauge, measure the burner manifold gas pressure.

8.If checking the input rate by measuring burner manifold pressure, skip to step 12. If measuring the input rate using a gas meter, proceed to step 9.

9.Using a clock (or watch) capable of measuring time in seconds, carefully clock the gas meter to determine the time for one (1) complete revolution of the gas meter dial or reel. At least one (1) cubic foot of gas flow should be measured. Use Table 6 to determine the main burner gas flow rate in cubic feet per hour (CFH).

NOTICE: Some gas meters will require more than one (1) cubic foot of gas pass through the meter for reasons of accuracy. When more than one (1) cubic foot of gas is consumed, divide the total time by the number of cubic feet for comparison to the figures in Table 6.

10.Compare actual heat input rate with our recommended input (printed on the furnace rating label). To convert the rating label input rate (given in BTUH) to the equivalent gas flowrate (in CFH), use the following formula:

	Heat input rate (in BTUH ) =
	⎛	BTU		⎞	⋅ Fuel gas flowrate (in CFH )
	⎜	BTU		⎟
	⎜		3	⎟
	Fuel gas higher heating value ⎜in	ft	3	⎟
	⎝	ft		⎠

	or,
	Fuel gas flowrate (in CFH ) =	Heat input rate (in BTUH )
	Fuel gas flowrate (in CFH ) =	⎛	BTU		⎞
		⎛			⎞
		⎜			⎟
		⎜		3	⎟
		Fuel gas higher heating value ⎜in	ft	3	⎟
		⎝	ft		⎠

11.If the measured input rate is above, or below, the rating label value by more than 2%, adjust the manifold gas pressure using the gas control valve pressure regulator to obtain the input rating within a ± 2% range. Refer to steps 12(a) through 12(d).

12.If the gas pressure is not within the specified low fire manifold pressure range (refer to Table 5), use the following procedure to adjust the low fire, gas pressure regulator to match the specified low fire manifold pressure.

a. Remove the regulator cover screw from the gas valve. Refer to Figure 23.

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Contents MODELS FOR USE WITH NATURAL GAS OR LP GAS PROPANE CHX3-75N CDX3-75N CHX3-100N CDX3-100NCHX3-125N CDX3-125N INSTALLATION AND OPERATION MANUALI. 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 CDX3 SERIES INSTALLATION PARTS PACKAGES – CHX3-75 INSTALLATION PARTS PACKAGES – CDX3-75 Grounding instructions III. GENERAL INSTALLATION B. FURNACE LOCATION B1. CDX3 HORIZONTAL APPLICATIONFigure 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 •near soffit vents, crawl space vents, or other areas where condensate or water vapor could create a nuisance, hazard, or cause property damage, and 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 Applications Applications leading away from the furnace must be composed of 3-inchdiameter PVC pipe and pipe fittings only. Refer to item E in Figure 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 Figure2. CDX3 MODELS: COUNTERFLOWS Figure L. WIRING Table 4A S7 DIP Switch Switch SettingsOptions Time2-StageBlower Settings from factory Table 4C IV. STARTING THE UNIT A. SEQUENCE OF OPERATIONS FLAME MUST BE DETECTED IF THERMOSTAT W2 CONTACTS ARE CLOSED OTHERWISE B. INITIAL START UP OPERATING INSTRUCTIONSC. Measuring And Adjusting Heat Input Rate Observe the following precautions when measuringA.Burner manifold pressure with a pressure gauge 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 = Figure 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 CHECK FOR 24 VOLTS Appendix –AReplacement Parts List Page Page Page Appendix – B Wiring Diagrams